“We are what we eat.” We’ve all heard this common expression and may think of it in nutritional and biological terms: for example the way that the chicken or beans we consume are turned into muscle tissues. However, this simple phrase has a deeper meaning: Food production, food culture, and organization of food transport and consumption loom very largely in the way that our society "is". These food-related activities also strongly impact the earth's fundamental surface processes and ecosystems. So, we are what we eat, but in a societal as well as an individual sense. This wider vision of food as a driving presence within society is increasingly relevant as groups and individuals like you become more interested in the ramifications of their food for themselves and for the environment. This course is designed to provide you with the tools to understand the combined environmental and human dimensions of food production and consumption. To do so we must start with some simple questions and reflect a bit on how we can address them.

Figure 1.1.1. The above image of a food festival in the United Kingdom captures both the excitement food creates in our culture, the varied cultural influences leading to different types of street food, and behind the scenes, the pathways of production and transportation that keep food moving to consumers' plates at all times.

Credit Helen (Afeitar), used with permission, Flickr: Liverpool food festival, Creative Commons (CC BY 2.0)

Where does our food come from? And, how can we make our food supply more sustainable? These two questions may seem simple, but they lead us to a range of considerations that are covered through the remainder of this course. As we consider these questions in each module, we'll explore a model of food systems as human systems in interaction with natural systems, or coupled human-natural systems (Fig. 1.1.2). As the name suggests, the concept of Coupled Human-Natural Systems (CHNS) tries to describe two major components that are involved in the production and consumption of food. The first component is the natural world and a set of interacting natural factors. Some of you may know the term ecosystem, and ecosystems developed from interacting natural components such as water, soils, plants, and animals (e.g. Fig. 1.2.1 in module 1.2) are the context for most food production. Throughout the course, we may also refer to the elements and processes of ecosystems as the earth system and earth system processes, or simply as the environment. These natural systems are a basic foundation of the food supply that we will learn more about in modules four through six (Environmental Dynamics and Drivers). The continued productivity of natural systems is evaluated as being crucial to sustainability, as you will see in the short reading below.

On the other hand, the two questions posed above involve the role of people, both as individuals in groups such as communities, institutions (including colleges and universities, farm and food processing businesses, and farmer organizations, for example) and political units such as countries. To introduce this dimension we often refer to this globally as the "human system" within a coupled human-natural system (Fig. 1.1.2.; a complete definition of human and natural systems are given in Module 1.2). Within the human system, factors such as styles of farming and food choices, tastes, economic inequality, and farmer and scientific knowledge that inform humans' management of ecosystem emerge from human cultural, social, economic, and political influences.

Figure 1.1.2. A simple illustration of coupled human and natural systems with reference to food production. The list of human (households: urban and rural, businesses, governments, knowledge and science, diet and food traditions, belief systems) and natural system components (water, atmosphere, soils, plants and animals, biodiversity) on each side of the diagram is not exhaustive, and the diagram will be revisited throughout the course. The reciprocal arrows represent the mutual effects of each subsystem on the other, and are highly schematic, although they can denote specific impacts or feedbacks that will be addressed in module 1.2 and beyond.

Credit: Steven Vanek, adapted from the National Science Foundation (NSF)

The end result of these interactions between human and natural systems are what we call a food system, which has has also been called an "environment-food system" (see the introductory reading on the next page) with "environment" pointing to the natural components and the "food system" pointing to the human organization needed to produce, transport, and deliver food to consumers, along with a host of cultural, regulatory, and other aspects of human society that relate to food. In terms of geography, the interactions of environment-food systems exhibit a huge range of variation across the world. As we all know this variation exists between countries, so that food and farming types can be associated with “Chinese food,” “French food,” “Peruvian food”, or scores of other examples. Farming and food also vary a great deal among regions within a country and sometimes even among local places, as we know if we compare a large dairy or grain farm with a fresh vegetable farm serving local markets here in the United States. Understanding the geographic variations of environment-food interactions is key to recognizing their increased relevance and importance to people and places.

Introductory Reading Assignment:

1. Read the brief section (pp 1-7) of Colin Sage's book "Environment and Food", entitled "Why Environment and Food?" (see the assignments page). The author explains why we are interested in considering food's relationship to the environment (the latter is what we are also calling "natural systems"). He presents a provocative and critical account of our relation to food in modern societies (human systems) and the need to think about food production and consumption patterns in relation to the environment.
2. As you read, try to identify three to five main points of the reading, which is always a good practice when you read in this course and other courses.
3. After reading the assignment, continue reading below and see whether your perceptions of this author's analysis agree with the main arguments we have noted below. You may have noted similar points, or additional ones not noted here.

Consult AFTER Reading:

First, consider the list below of some of the main ideas in the reading. Do these roughly agree with your list of main points? You may have identified additional points in the reading.

1. The essential need of humans to eat has defined the relation of all societies to food production and the environment through history.
2. Transformation of food production systems in the last 100 years has dramatically changed diets and societies' impact on the environment:
   • Yields have increased with industrial methods and food for many in the world has become more available.
   • However, diets have worsened in many cases so that human nutrition has suffered.
   • Inequality in access to food based on wealth and poverty of consumers has continued.
3. Negative impacts on the environment have multiplied, which is expressed in the large amounts of water needed to produce food, the strong dependence of food production on fossil fuels, and the contribution of food production to CO₂ methane, and other greenhouse gas emissions that cause climate change.
4. A sustainable food system, which is increasingly the vision promoted by some food producers and consumers, involves reducing fossil fuel use in food production, cutting waste of food in transport and consumption, and increasing the just distribution of food to consumers at all levels of wealth.

We can also think of the way that these main points fit into a diagram, sometimes called a concept map, like the one that is drawn here. As part of the final assignment or summative assessment for module 1, and in the capstone assignment for the entire course, you will be drawing concept maps of a food system example. This diagram may get you started on visualizing human and natural components of food systems and their interaction. You'll note that a concept map can start from a very preliminary drawing or rough draft (like this one), and gradually be reorganized as you learn more about a topic use an organizational principle like the coupled human-natural systems concept we present in this course.

Text description of the Figure 1.1.3 image.

The image is a hand-drawn concept map illustrating the interaction between human systems and natural systems within the context of food systems and sustainability. On the left side, labeled “Human System” in pink, several interconnected elements are shown: Sustainable food movements (with goals such as protecting resources, reducing waste, and promoting social equity), fossil fuels, farmers, food companies and retailers, agricultural and food system science, and modern consumers. Arrows indicate flows of products and relationships among these components, such as farmers providing products to companies and consumers, and fossil fuels influencing production. Additional notes highlight social challenges like need income, poor are left out, and issues of diet inequality, child labor, and poverty. On the right side, labeled “Natural System” in green, a box titled Environment lists key elements: landscapes, soil, fresh water, biological diversity, and livestock. Surrounding this are concerns such as climate change and greenhouse gases, as well as the need for healthier food. The diagram uses arrows and annotations to show how human activities impact natural resources and vice versa, emphasizing the complexity of food systems and the interplay between environmental sustainability, social equity, and economic factors.

Credit: Steven Vanek

After reading Colin Sage's brief introduction to the modern-day issues surrounding environment and food, you should be aware of the fact that food production by human societies has transformed the earth's natural systems. In fact, it is very difficult to understate the enormous impact that food production to support human societies has had on the surface of our planet as the earth's population has grown. Here are some of them:

• Humans have replaced permanent forests and wild grasslands with farm fields that allow much higher rates of soil erosion where the soil is not covered year-round. This has led to trillions of tons of soil being washed into rivers, lakes, and oceans, where it is unavailable as a key resource for food production.
• The expansion of farming and grazing has contributed to the reduction and elimination of wild forest and grassland species of plants and animals: the loss of earth's biodiversity.
• In some cases, previously unproductive dryland areas have been made highly productive through the movement of irrigation water into desert areas, allowing the expansion of human settlements.
• In other cases, elimination of forest in favor of farmland has contributed to the expansion of desert areas and worsening droughts.
• Humans have intensively fertilized cropland to make it more productive with manures and chemical fertilizers, leading to excesses of nutrients and pollution in many of the world's waterways.
• Farming and the other human activities that support modern food systems are major contributors to changes in earth's climate linked to increasing greenhouse gas concentrations in the atmosphere.

One term that is used to summarize these human impacts within the history of the earth is the Anthropocene, from Anthropos (human) and cene, a suffix used within the geologic timescale to denote the recent past. The Anthropocene has been proposed as a new geologic epoch because of the profound and unprecedented human alteration of earth's natural systems that we point to above. Scientists researching the Anthropocene tend to agree that it was the beginnings of agriculture that probably marked the onset of the Anthropocene. We will introduce you to the history of agriculture in Module 2. The concept of sustainable food systems that Colin Sage points to in the introductory reading are currently a major topic of debate and discussion in human societies and are a consequence of the sustainability issues that are a key feature of the Anthropocene. The idea of sustainable food systems is also a major topic of this course, and you will be asked to contribute to this discussion in your capstone project. The term Anthropocene helps us to appreciate the epochal change of the extent and degree of these changes. Yet these changes do not suggest or imply that all is lost, or that all cropping and livestock-raising are pervasively damaging to the environment. As you’ll see throughout this course there are already well-developed options worth considering and pursuing in order to expand sustainable environment-food systems.

Studies of the changes in the type of ecosystems that cover different areas of the earth or land cover (e.g. crop fields versus forest versus desert) allow us to appreciate the impact on earth during the Anthropocene (Fig. 1.1.4 below). We can see in the bar chart reflecting changes over time in land cover that farmed and grazed areas involved in food production for rising populations have expanded from less than 10% of earth's usable (ice-free) surface in the 1700s to over 50% in 2000, a stupendous change considering the size of earth's land area (similar expansion of human influence in food production in earth's ocean fisheries has also occurred).

Figure 1.1.4. A graph showing the global allocation of the ice-free land area, on all five continents, to human land use versus wild (bottom stippled bar section) across three centuries from 1700 to 2000, during the rapid expansion of human population in the Anthropocene.

Click for a text description of Figure 1.1.4

(Approximate estimate of the percentages of global allocation in ice-free land area)

Year 1700:

• Wild (uninhabited) ≈ 49%
• Seminatural (e.g. inhabited forests) ≈ 45%
• Rangeland (grazed livestock, non-cropped) ≈ 1.5%
• Cropland ≈ 3%
• Villages ≈ 0.25
• Urban ≈ 0.25%

Year 1800:

• Wild (uninhabited) ≈ 45%
• Seminatural (e.g. inhabited forests) ≈ 45%
• Rangeland (grazed livestock, non-cropped) ≈ 5%
• Cropland ≈ 3%
• Villages ≈ 1.5%
• Urban ≈ 0.5%

Year 1900:

• Wild (uninhabited) ≈ 35%
• Seminatural (e.g. inhabited forests) ≈ 35%
• Rangeland (grazed livestock, non-cropped) ≈ 19.5%
• Cropland ≈ 8%
• Villages ≈ 1.75%
• Urban ≈ 0.75%

Year 2000:

• Wild (uninhabited) ≈ 24.5%
• Seminatural (e.g. inhabited forests) ≈ 20%
• Rangeland (grazed livestock, non-cropped) ≈ 32%
• Cropland ≈ 14%
• Villages ≈ 8.5%
• Urban ≈ 1%

Credit: Steven Vanek, adapted from Ellis et. al. 2010. Anthropogenic transformation of the biomes, 1700-2000; Global Ecol. Biogeogr 19, 589–606.

Similarly important is that the Anthropocene, or the "human recent history of the earth" if we translate the word slightly, brings to our attention to not only the changes in natural systems or the environment but also the significant alterations of the human dimension of human-natural systems related to food. It’s safe to say that for nearly all of us this human dimension is significantly different than it was for our grandparents or even our parents. Some basic examples can be used to illustrate this trend. In the United States, for example, the population of farmers has continued to shrink. It is now less than 4 percent of the national population. At present this fraction, though generally declining worldwide, is somewhat higher in European countries and much higher in Asia and Africa. The continued importance of food-growing agriculture among large sectors of the populations in Africa and Asia, for example, creates different patterns of livelihoods (Fig 1.1.5a) and landscapes (Fig. 1.1.5b).

Figure 1.1.5a.Farmer Cleaning Soybeans, Malawi

Credit: Max Orenstein; used with permission.

Figure 1.1.5b. Rice-growing landscape, Vietnam. This photo illustrates the intensive interactions that exist between human habitation and farming communities in the background and food production which occupies the entire foreground.

Credit: Tommy Chiu, used with permission under a creative commons license.

One important point: familiarity with environment-food systems through immediate experience among human populations, including you and your fellow learners in this course, is presumably at an all-time low. It’s also an interesting reflection on the human dimension of the Anthropocene. Other statistics could be quoted to show related trends. For example, the average amount of time being spent on food preparation is roughly one-quarter the standard allocation of time devoted to this activity 40-50 years ago. This course takes these statistics as a challenge and opportunity since environment-food interactions are both less-known than previously and, at the same time, have a very high level of importance to the environment and society.

The guided reading in this module on concerns around "Environment and Food" and our consideration of the Anthropocene as an era defined by the dramatic expansion of food production on earth's surface lead us naturally to the concept of sustainability, which is a common term in much of our discourse in the present day, in many different settings from the coffee shop and classroom, to dinner tables and company boardrooms, to government offices. As we think about the increasingly obvious impacts of our food system on the global environment and on the social dynamics of global society, we are concerned that this food system needs to (a) be part of society and communities with adequate opportunities for all and just relationships among people and (b) not compromise the future productivity and health of earth's many different environments. As part of the introductory work of this first module, we ought to consider a definition of sustainability that is broad enough to encompass both human and natural systems, and geographic scales from communities to single farming communities to the worldwide reach of food production and transport in the modern global food system. We present below in figure 1.1.6 one relatively common definition of sustainability as a "three-legged stool" (we will return to this concept later in Module 10 when we return to food systems).

Figure 1.1.6. Three-legged Stool of Sustainability

Click for a text description of the three-legged stool of sustainability image.

A green three-legged stool. The seat is labeled Sustainable Food System. One leg is labeled Environment, one leg is labeled Community, and the third is labeled Economy. There is a list for each as follows. Environment: reduce pollution and waste, use renewable energy, conservation, restoration. Community and Social Sustainability: good working conditions, health care, education, community, and culture; Economy: employment, profitable enterprises, infrastructure, fair trade, security.

Credit: Steven Vanek, based on multiple sources and common sustainability concepts

In the model of the three-legged stool, environmental sustainability reflects protecting the future functioning, biodiversity, and overall health of earth's managed and wild ecosystems. Community and social sustainability reflect the maintenance or improvement of personal and community well-being into the future, versus relations of violence and injustice within and among communities. In the case of food systems, this reflects especially the just distribution of food and food security among all sectors of society, the just treatment of food producers and the rights of consumers to healthy food, and the expression of cultural food preferences. Economic sustainability within food systems has often been conceptualized as relationships of financial and supply chains that support sufficient prosperity for food producers and the economic access of consumers to food at affordable prices.

Dividing the concepts of sustainability into three parts of an integrated whole allows us to think about food production practices or food distribution networks, for example, are sustainable in different aspects. Excessive water use or fossil fuel consumption, for example, are aspects of environmental sustainability challenges in food systems considered further on in this course. Meanwhile, issues of food access, poverty, and displacement from war, and their impacts on human communities and their food security are issues that combine social and economic sustainability, which will also be considered by this course. The three-legged stool is a simple, if sometimes imperfect, way to combine the considerations of sustainability into a unified whole. As you consider the sustainability challenges at the end of module one and in your capstone project, you may be able to use these three different concepts along with the concepts in the guided reading to describe the sustainability challenges of some food system examples. You may want to ask yourself, is this practice or situation environmentally sustainable? socially sustainable? economically sustainable?

Individuals, Communities, and Organizations Taking Action on Sustainability: Information Resources on Real-World Efforts

The interest in the sustainability of environment-food systems, as we've just defined them -- see the "three-legged stool" on the previous page -- has skyrocketed in recent years. A brief sampling of these issues involves the following:

• Health and Nutrition concerns over the nutritional quality and nutrient content of food and food-producing environmental systems
• Food security among approximately 1.1 billion persons around the world with low income and other limitations that do not allow them to access sufficient food.
• The need to design food and agricultural systems that can respond successfully to climate change.

We aim that this course will allow you as a learner to this rapidly expanding suite of interests while it offers background and the capacity to understand better and more fully these issues. You will pursue this aim through the readings and evaluations in this course, and also in completing a capstone project on the food system of a particular region.

One way to begin learning about this expanding interest is to consider the activities of individuals, communities, and governments as well as organizations ranging from nonprofits to international and global groups. In the case of individuals and communities, much interest is being generated by local food initiatives, such as farmers’ markets, and other local groups of producers and consumers seeking to improve environment-food systems. A variety of government agencies in the United States and other countries have also become increasingly involved in environment-food issues.

The United States Department of Agriculture, for example, now offers a focus on environment-food issues such as responses to climate change and dietary guidelines in its range of research and science activities. The USDA website also includes the compilation of data through its different research services that you will use in this course.

The United Nation’s Food and Agriculture Organization (FAO), which is based in Rome, Italy, is one of a number of international organizations focused on environment-food issues. It addresses nearly all the topics raised in the course, as well as many others. The statistical branch of the FAO, known as FAOSTATS, is an important source of information on the international dimension of issues involving food and the environment.

Numerous non-profit organizations are involved in environment-food issues in the United States and in other countries. One of these organizations in the U.S., which is called Food Tank, periodically provides the lists of other organizations that it considers leaders in environment-food issues. In 2014, for example, Food Tank named the "101 Organizations to Watch in 2014”. This interesting list, complete with brief descriptions, includes a number of both well-known and lesser-known groups active in environment-food issues. Other organizations have greatly expanded their environment-food focus. National Geographic, for example, now has a major focus on environment-food issues. Its website includes an important section on food and water within the organization’s initiative on EarthPulse: A Visual Guide to Global Trends. This section includes a number of excellent global maps of environmental and food conditions, challenges, and potential solutions.

These resources may be a help to you as you consider not just the learning resources we present in this text, but the real efforts to promote environmental, social, and economic sustainability in food systems, which you will address in the final section of the course and in your capstone project.

Instructions

Look over Food Tank's "101 organizations to Watch in 2014".

Choose one organization from this website that treats the combination of environment-and-food issues. You'll need to be selective since some of the organizations specialize in food-related issues but have little emphasis on environmental one. Also, read the assignment from Colin Sage, pp. 1-8 on "Introduction: Why environment and food?" in Environment and Development that is one of the required readings for this module (see the assignments page)

Then,

1. Write a brief overview description of the organization you chose from the Foodtank website, its summary goals in relation to the environment and food issues - distinct from the more detailed description of issues and factors below, funding source or sources, location and scope (local, national, and/or global), longevity (including when it was founded), and what you perceive as its intended audience and/or client or target population.
2. After addressing these overview questions for the organization, continue and address briefly the following two questions where you can draw on the assigned reading from C. Sage:
   • What factors or issues of importance to environment-food systems does it address - a more complete elaboration of its summary goals in the previous overview? (1 paragraph)
   • How is sustainability defined and addressed by this organization? (1 paragraph)

Your writing should be between one and one and a half pages long, and no longer than two pages. When appropriate, you can relate the work of this organization to the other material in this introductory module regarding multidisciplinary approaches or the concept of the Anthropocene. Be sure to describe what types of environmental and food issues are being addressed by this organization, as well as the wider factors and sustainability questions.

Submitting Your Assignment

Please submit your assignment in Module 1 Formative Assessment in Canvas.

Grading Information and Rubric

Your assignment will be evaluated based on the following rubric. The maximum grade for the assignment is 25 points.

What defines a system?

In this course, we will refer to the term "system" repeatedly, so it is worthwhile to think about how systems are defined. A basic definition of a system is "a set of components and their relationships". Rather than dwelling on this definition in the abstract, it's probably best to immediately think of how the definition applies to real examples from this course. An ecosystem is a type of system you may have heard of, in which the components are living things like plants, animals, and microbes plus a habitat formed of natural, urban, and agricultural environments, and all the relationships among these component parts, with an emphasis on the interactions between the living parts of the system and their interactions, for example, food webs in which plants feed herbivores and herbivores feed carnivores. A food system, as we have just begun to see so far, consists of food production components like farms, farm fields, and orchards, along with livestock; food distribution chains including shipping companies and supermarkets, and consumers like you and your classmates, with myriad other components like regulatory agencies, weather and climate, and soils. In the case of food systems we have already pointed out how these can be considered as human-natural (alternatively, human-environment) systems, where it can help to see the system as composed of interacting human components (societies, companies, households, farm families) and natural components like water, soils, crop varieties, livestock, and agricultural ecosystems.

Fig. 1.2.1. A simplified diagram of a typical ecosystem. Ecosystems are a common system type analyzed by geoscientists, ecologists, and agroecologists. The black rectangular outline is one way to define a boundary for the ecosystem, where climate and sunlight fall outside the system but provide resources and define the conditions under which the ecosystem develops. This diagram can also be considered a type of concept map where for example 'sun', 'plants', and 'climate' are components, and the arrows connecting the components are relationships in the system. These relationships are now labeled as either flows (of energy, food, nutrients) or causal links, like the way that dead plants and animals end up feeding soil microbes, or the ecosystem affects the climate over time. You may be able to see how this simplified diagram could represent a far more complex system containing hundreds of plant and animal species and thousands of types of microbes, interacting in complex ways with each other and the environment. Keep this diagram in mind as a possible example when you think about completing your preliminary concept map of a regional food system at the end of unit 1.

Click for a text description of the ecosystem image.

A diagram of a typical ecosystem. Soil resources is on the bottom. The sun is at the top. There is a black line (ecosystem boundary) drawn around four boxes and the soil. The four boxes are carnivores (including humans), herbivores (including humans), plants, and microbes. Lines from carnivores, herbivores, and plants go to microbes and say "feed". There are "feed" lines from plants to herbivores and herbivores to carnivores. A line from the sun to inside the ecosystem boundary says, "sunlight energy for plants". A line from soil resources to microbes says, "supply nutrients, water, habitat. A line from microbes to soil resources says, "replenish and cycle nutrients". A line from soil resources to plants says, "supply nutrients and water stored in soils". Lines from plants to microbes and plants to soil resources say, "replenish organic matter". Outside the ecosystem boundary is "climatic conditions". A line from climatic conditions to the ecosystem says, "provides basic conditions, rainwater". A line from the ecosystem to climatic conditions says, "impacts on climate change".

Credit: Steven Vanek

Behavior of Complex Systems

Systems that contain a large number of components interacting in multiple ways (like an ecosystem, above, or the human-natural food systems elsewhere in this text) are often said to be complex. The word "complex" may have an obvious and general meaning from daily use (you may be thinking "of course it is complex! there are lots of components and relationships!") but geoscientists, ecologists, and social scientists mean something specific here: they are referring to ways that different complex systems, from ocean food webs to the global climate system, to the ecosystem of a dairy farm, display common types of behavior related to their complexity. Here are some of these types of behaviors:

• Positive and negative feedback: the change in a property of the system results in an amplification (positive feedback) or dampening (negative feedback) of that change. A recently considered example of positive feedback would be that as the arctic ocean loses sea ice with global warming, the ocean begins to absorb more sunlight due to its darker color, which accelerates the rate of sea ice melting.
• Many strongly interdependent variables: this property results in multiple causes leading to observed outputs, with unobserved properties of the system sometimes having larger impacts than we might expect.
• Resilience: Resilience will be discussed later in the course, but you can think of it here as a sort of self-regulation of complex systems in which they often tend to resist changes in a self-organized way, like the way your body attempts to always maintain a temperature of 37 C. Sometimes complex systems maintain themselves until they are pushed beyond a breaking point, after which they may change rapidly to another type of behavior.
• Unexpected and "emergent" behavior: one consequence of the above three properties is that complex systems can display unexpected outcomes, driven by positive feedbacks and unexpected relationships or unobserved variables. Sometimes this is referred to as "emergent" behavior when we sense that it would have been impossible to predict the behavior of the system even if we knew the "rules" that govern each component part.

To these more formal definitions of complex systems, we should add one more feature that we will reinforce throughout the course in describing food systems that combine human and natural systems, which is that drivers and impacts often cross the boundary between human or social systems and environmental or natural systems (recall Fig. 1.1.2). Our policies, traditions, and culture have impacts on earth's natural systems, and the earth's natural systems affect the types of human systems that develop, while changes in natural systems can cause changes in policies, traditions, and culture.

For more information on complex systems properties with further examples, see Developing Student Understanding of Complex Systems in Geosciences, from the On the Cutting Edge program.

On the next page, we'll see an interesting example of complex system behavior related to the food system in India.

The Indian Vulture Crisis: An Example of Complex Systems Behavior

The "Indian Vulture Crisis" may or not be a familiar term to you, but it is important enough to the history of modern India that it has involved dozens of research experts as well as major changes in wildlife, human health, and government policies, and now has its own Wikipedia page (Indian vulture crisis) that you can browse. It is also an interesting example of complex systems behavior that involves food systems and unintended consequences of veterinary care for animals. The main causal links are outlined below in figure 1.2.2, and the narrative of the crisis goes as follows:

Beef cattle are hugely important to Indian food systems even though they are usually not consumed by adherents of the majority Hindu religion (however, Indian Christians and Muslims, for example, do consume beef). Cattle are also widely used as dairy animals (think: yogurt and clarified butter as important parts of Indian cuisine) and are even more important as traction animals (oxen) to till soil for all-important food crops by small-scale farmers across India. Because of their importance and to treat inflammation and fevers in cattle, in the 1990s the drug diclofenac was put into widespread use across India. However, timed with the release of this medication, a precipitous drop in the population of Indian vultures began, which became the fastest collapse of a bird population ever recorded. Vultures are not valued in many parts of the world, but scavenging by vultures was the main way that dead animal carcasses were cleared from Indian communities, especially in the case of beef cattle where the meat is not consumed. It was not until the 2000s that the cause of vulture population collapse was discovered to be the diclofenac medicine administered to cattle, which is extremely toxic to vultures eating dead carcasses. However, the consequences of this population collapse did not end with the solving of the mystery of the vulture population collapse, which was already a tragic and unforeseen consequence. Rather, the fact that vultures are a key part of a complex system resulted in further unforeseen consequences in both human and natural parts of the Indian food system. A few of these are shown in figure 1.2.2 below: first, since vultures are in fact an ideal scavenger that creates a "dead end" for human pathogens in rotting carcasses, and since they were no longer present, water supplies suffered greater contamination from carcasses that took months instead of weeks to rot, leading to greater human illness. Second, populations of rats and dogs, which are less effective carcass scavengers, expanded in response to these carcasses and the lack of competition from vultures, which resulted in dramatic increases in rabies (and other diseases) due to larger dog and rat populations and human contact with wild dogs. This is significant since more than half of the world's human rabies deaths occur in India. Finally, the vulture crisis even had implications for religious rituals in India: people of the Parsi faith, who practice an open-air "sky burial" of their dead where the body is consumed by vultures, were forced to abandon the practice because of hygiene concerns when human bodies took months instead of weeks to decompose. A final consequence of these problems was that the drug diclofenac was banned from use in India, Nepal, and Pakistan in hopes of helping vulture populations to revive. This final turn of events is an example of the human system responding to the unforeseen consequences. Additionally, alternatives to these drugs have been developed for veterinary use that have no toxicity to vultures.

Figure 1.2.2. Diagram of the causal chain leading to the Indian Vulture Crisis. This crisis contains several examples of complex system behavior and unforeseen consequences.

Click for a text description of the causal chain image.

A diagram using boxes to show the causal chain leading to the Indian Vulture Crisis. Box 1: Cattle as essential milk and traction animals in the food system. An arrow goes from box 1 to box 2: Veterinary use of diclofenac (diclofenac highly toxic to vultures). An arrow goes from Box 2 to Box 3: Collapse of vulture populations. From box 3 there are two arrows. One leads to a comment box that says, "Banning of diclofenac and alternative developed in India, Nepal, and Pakistan." The second arrow from box 3 leads to box 4: Crisis of unconsumed carcasses. A comment box that says, "vultures as honored, efficient, and most sanitary practical method of carcass disposal", also has an arrow to box 4. From box 4 there are three arrows pointing towards comment boxes as follows: dogs and rat populations expand; lack of vultures for ritual consumption of bodies in Parsi faith; contamination of drinking water in rural areas. There is also an arrow from, dogs and rat populations expand, to a comment box that says, greater incidence of rabies.

Credit: Steven Vanek

Note the properties of complex systems and human-natural systems exhibited by this example. Farmers sought mainly to protect their cattle from inflammation and speed healing in service of the food system, while pharmaceutical companies sought to profit from a widespread market for an effective medication. The additional, cascading effects of the human invention diclofenac, however, were dramatic, far-ranging, and in some cases unexpected, because of the many interacting parts in the food systems and ecosystems of Indian rural areas: cattle, groundwater, wild dogs, and human pathogens like rabies. The crisis eventually provoked responses from the human system, with impacts on human burial practices among the Parsi, laws banning diclofenac, and development of alternative medications. The search for sustainability in food systems, like those you will think about for your capstone regions, involves designing and choosing adequate human responses to complex system behavior.

Complex Systems and Interdisciplinarity

One final note on this example is to point out that to fully understand the Indian vulture crisis a large number of different disciplines were brought to bear: we need cultural knowledge about the beliefs and practical usefulness of both cattle and vultures in India. We also need biological knowledge about drug toxicity to wildlife, pathogens, groundwater contamination by microbes, and rat and dog populations. We also need policy expertise to think about transitioning food systems to less toxic alternatives to current practices. And all of these disciplines needed to be brought together in an integrated whole to assemble the diagram shown in figure 1.2.2. The purpose of this text and this course on food systems is to help you to develop some of the skills needed for this sort of interdisciplinary analysis of human-environment or human-natural systems.

Food System Examples from Household Gardens to Communities and Global Food Systems

Some of you in this course, perhaps even many of you, have had the experience of growing herbs or vegetables (Fig. 1.2.3) or keeping chickens for eggs or animals for meat. Although dwarfed by the enormous dimensions of the global food system, home food production is still a significant part of the food consumed by billions of earth's inhabitants. In other cases, small-scale fishing and hunting provide highly nutrient-dense foods, and coexist with modernized and industrial food systems, as any fishers and hunters in the class may be able to attest. These experiences of food production for personal or family consumption show natural-human interactions in a very simple way. To grow vegetables or hunt or raise animals means bringing together natural factors (seed, animal breeds, soil, water, fishing and hunting ranges, etc.) and also human factors (e.g. knowledge of plants, livestock, or wild animals, government policies) to gain access to food, as well as food storage and preparation, markets for tools and seeds, or human-built infrastructures like a garden fence or a chicken coop. This same interaction between natural and human factors is evident at a larger scale in the photo in Figure 1.2.4, which shows a landscape that has been transformed by a human community for food production.

Figure 1.2.3. This diverse home garden includes lettuce, kale, beans, sweet corn, peppers, squash, carrots, and garlic, among other crops. During the growing season, it offsets food expenses in an urban setting and offers extremely fresh food as well as an excellent way to recycle kitchen wastes as compost.

Credit: Steven Vanek

Fig. 1.2.4. Landscape near Acobamba, Huancavelica, Peru. This Peruvian landscape has been almost completely transformed for food (and firewood) production.

Credit: Steven Vanek

Beyond these experiences of auto-sufficient food production and consumption, however, most of humanity also currently depends on global and local versions of the food system which features a web of suppliers, producers, transporters, and marketers that supply all of us as food consumers. Compared to gardening, catching trout, or keeping chickens, these food systems together form a far more complex version of the interactions between natural and human factors that produce and transport the food that we then consume as part of global and local food systems.

One way of viewing these regional and global food systems is that they can be divided by the type of activity in relation to food, and dividing them into components of food production, food transport, and food consumption (Fig. 1.2.5). Like other diagrams we've seen so far, this diagram can be considered a concept map showing relationships between the different components of a food system. The main arrows show the flow of food through the system from the managed natural environments used to produce food and the end result of nutrition and health outcomes. There are some unseen or implicit relationships here as well, like the way that farming practices, technology, communication and education, and other attributes of human societies support the functioning of a food system, and are included in the outer system boundary.

Figure 1.2.5. A simplified diagram of food system components, depicting a linear progression of production, transportation, and consumption of food. It’s helpful to think of this more linear version in conjunction with the interacting natural and human and systems in figure 1.2.6 to remember that food systems are not just linear conveyor belts delivering outcomes.

Click for a text description of the food system component image.

Simplified diagram of food system components. The diagram is within a circle. At the top, is the heading, Natural Resources, and Environments. From here is an arrow pointing directly below to an oval with the word, Production. From Production, there is an arrow pointing directly below to another oval with the word, Transport. From Transport, there is an arrow pointing directly below to a final oval with the word, Consumption. From the consumption oval, an arrow leads direction below it to Nutrition and Health Outcomes. On the left side of the circle are the following items listed from top to bottom: Farming Practices and Agroecology; Food Processing; Policy support; and Food Preparation. On the right side of the circle are the following items listed from top to bottom: Technology and Infrastructure; Crop and Livestock Breeding and Biodiversity and Communication and Education.

Credit: Figure adapted from Combs et al., 1996.

In addition to this more linear or "conveyer belt" portrayal of food systems delivering nutrition from natural resources, we may also be interested in thinking about the dramatic impacts humans have made on earth systems during the Anthropocene, discussed in module 1.1. In that light, we know that these natural systems may either be sustained or degraded by management, an important response that either maintains or undermines the entire food system. For this purpose, we may be interested in a food system diagram that makes the interactions among human and natural systems very explicit. Below in figure 1.2.6 is a version of a Coupled Human-Natural Systems diagram -- again, a concept map of sorts -- developed by an interdisciplinary group of social and environmental scientists (Liu et al. 2007) to represent the human-environment interactions in food systems.

Figure 1.2.6. A food system as a Coupled Human-Natural System, a way of considering food systems that will be explored throughout the course. This more detailed presentation compared to that in module 1.1 shows that both human systems (communities, regions, food supply chains) and natural systems (agroecosystems, landscapes, water bodies) have internal interactions. Human systems also organize and modify natural systems to produce food, and natural systems respond via feedbacks (food provision, aggradation or degradation depending on the human modification and management of the natural systems.

Click for a text description of the Human Natural Coupling image.

A coupled human-natural system. Heading at the top says, Human to natural coupling: Human systems reorganize natural systems to produce food: e.g. gardens, farms, fisheries, managed forests. Below this heading are two boxes, side by side. On the left is a box with the heading, Human System. Outside of the box is a descriptor that says, human system internal interactions. There are two lists inside the box on the left. The first list is Farms, farming households; food policies; food distribution companies, consumers. The second list is management knowledge for farming, herding, hunting, fishing, etc.; local and national governments; agriculture input companies. Inside this box are arrows indicating a continuous relationship among the listed items. On the right side is a box with the heading, Natural System. Outside the box is a descriptor that says, natural system internal interactions. There are two lists inside the box. The first list is plants and animals (crops, livestock, pests, wild species); soils. The second list is the climate system and water. Below the two boxes is the heading Natural to Human Coupling: Altered ecosystems respond with food production, degradation, sustained production. There are arrows around the entire diagram indicating the continuous relationship among all items.

Credit: Steven Vanek and Karl Zimmerer; modified from the National Science Foundation.

This diagram highlights internal interactions within both the natural and human components of the food system. The natural components of food systems shown here are those we will tackle first in the first part of the course, while the latter half of the course will address the human system aspects of food systems and human-environment interactions shown as the large arrows connecting these two major components. As we saw in comparing home garden production, smallholder production landscapes and global food production chains above, food systems and their components are highly varied. However many similarities apply across the different components, actors, and environments of the food system:

• Food systems modify the natural environment and capture the productivity of the earth’s natural systems to supply food to human populations. Globally they create huge changes in the earth’s surface and its natural populations and processes.
• As portrayed in Figure 1.2.6, despite their complexity, food systems often involve coupling between human management and the response of natural systems. As pointed out by author Colin Sage in Module 1.1, the response of natural systems to human management can create sustainability challenges in food systems.
• Food systems involve the production, transportation, distribution, and consumption of food (Figure 1.2.5). The scale of these three processes can differ among food systems, which can be local, regional, and global.
• Food systems are examples of complex systems: they involve many interacting human and natural components, as well as important variability, for example, droughts, soil erosion, population changes, and migration, and changing policies. All of these affect the natural and human systems and can disrupt simple cause and effect relationships, in spite of the large-scale drivers and feedbacks shown in figure 1.2.6.

Knowledge Check

Summative Assessment: Concept Mapping and Assessment of Food Systems

First, download the worksheet to understand and complete the assessment. This assignment will require you to draw on your reading of this online text from module one, as well as several options for case studies where we have provided brief descriptions and audiovisual resources (radio clips, videos, photos) that describe these systems. You will accomplish two parts of an assignment that will not only evaluate the learning objectives for module one but will also give you practice in skills you will need to complete your capstone project. These two parts are:

1. Draw a concept map of the system that distinguishes between human and natural components or sections of the system (an example is given below)
2. Fill in a table that identifies some key components, relationships, and sustainability concerns for this system.

You will complete this assignment for your choice of two food system examples, as described in the detailed instructions below. You will first read, then draw a concept map, and then fill in a table with short responses.

Instructions

1. Choose ONE national to global food system example and ONE local to regional food system example from the options that follow this assignment page in the text (see links in outline view at right, or the link to the next page at the bottom of this page). National to global food system examples are Pennsylvania Dairy, Colorado Beef Production, and Peruvian Asparagus, while local to regional examples are the Peruvian smallholder production and New York City greenmarkets examples. Read the descriptions of the system, which may include photos, videos, audio clips, or visiting other websites. Completely read through the description of the two systems you have chosen (one national/global and one local/regional), including these external links before continuing on to the following steps (though you may certainly return to the descriptions as needed). You are welcome to consult other resources online regarding the system you have chosen since that is a skill that will be helpful when embarking on data gathering for your capstone project.
2. Using a sheet of paper, or composing in PowerPoint, develop a concept map of only ONE of the systems you chose, subject to the following guidelines:
   1. Title your concept map with the name of the system you are describing (among the five described on the following pages) and put your name on the diagram.
   2. Before you begin your concept map, draw a vertical line in your diagram to distinguish between Human and Natural components of the system to right and left, drawing on Fig. 1.2.6, 1.2.7 below, and 1.1.3 (the last one is the concept map example from the guided introductory reading by Colin Sage). However, you do not need to make your diagram look like the highly schematic diagrams in the text of the previous pages (see rather Fig. 1.2.7 below) -- you should include components that are discussed in the examples on the following pages, and connect them in the way that makes sense to you.
   3. Your concept map should be legible, but it does not need to be extremely neat since it reflects a first attempt to characterize a system. Additional components and relationships will occur to you as you draw, and you may need to squeeze them in. Therefore, leave space as you begin your diagram. If you feel your map becoming too hard to understand, please do compose a second "clean" copy.
   4. Remember that systems are defined as components and the relationships between them. If you are having trouble thinking of what to draw, think what the components are in the system (these can be boxes or ovals), and then how they are related (these may be labeled arrows)
   5. Below in Fig. 1.2.7 is an example of a concept map drawn from a food production system producing field crops (wheat, oats, barley, soybeans) and hogs for pork in Western France. Material for this concept map is drawn from Billen et al., 2012, "Localising the nitrogen footprint of the Paris food supply"¹

Text description of the Figure 1.2.7 image.

The image is a hand-drawn concept map illustrating the interaction between human systems and natural systems in global food production and distribution. The diagram is divided into two sections: Human (labeled in red on the left) and Natural (labeled in green on the right). On the human side, key elements include European consumers, global shipping, farm management knowledge, and food processing and distribution companies, which are linked to products such as meat products and baked goods. Arrows show relationships such as government regulation for food safety and the role of companies in supplying consumers. On the natural side, components include soybean farms (Brazil), good climate for farming, pigs and pig farms, crops and crop farms (wheat, oats, barley), and good soils and flat land. Environmental concerns are noted, such as overuse of manure and fertilizer pollution, and the impact on rivers, estuaries, and coastlines, with an emphasis on regulation of water pollution. The map uses arrows to demonstrate how natural resources and farming conditions support agricultural production, which then connects to human systems through shipping, processing, and consumption. This visual emphasizes the complex interdependence between environmental factors and human activities in sustaining global food systems.

Credit: Steven Vanek

3. Fill in the table on the worksheet with short answer responses regarding the two food systems you have chosen. The worksheet asks for responses in the following areas:
   1. Identify two natural components of the food system.
   2. Identify three human components of the food system.
   3. Tell how products from the system are transported to markets or to households for consumption.
   4. Name one sustainability challenge for the system, and state whether it represents a challenge in the area of environmental, social, or economic sustainability.

Once complete, use the worksheet as a guide to complete the Summative Assessment quiz. 

Hunting and gathering activities were the primary way for humans to feed themselves from their natural environments for over 90% of human history. Gathering plant products, such as seeds, nuts, and leaves, is considered to have been the primary activity in these early human-natural food systems, with hunting mostly secondary. The mix of hunting-gathering activities and the tools used varied according to the environment. Among many hunter-gatherer groups worldwide fire was one of the most important tools and was used widely. Fire was used by these human social systems to transform natural systems in habitats ranging from grasslands and open forests, such as those of Africa, Asia, Europe, and North America, to those of denser forests that included the Amazon rain forest of South America. One importance of fire was that it helped enable hunter-gatherers to “domesticate the landscape” so that it yielded more of the desired plants through gathering and the sought-after animals through hunting.

Fire also was and is crucial in enabling humans to cook food. Cooking rendered animals and many plants into forms that humans were significantly more able to digest. The capacity to cook foods through the use of fire----which was obtained through gathering and hunting---may have arisen as long ago as 1.8 – 1.9 million years ago at about the same general time as the emergence of our ancestral species Homo erectus on the continent of Africa. (Homo erectus subsequently evolved to Homo sapiens, our own species, about 200,000 years ago). These early humans were able to extract significantly more energy from food as a result of cooking. In short, cooking enabled through the use of fire, produced chemical compounds in food that were more digestible and energy-dense. While the changes and challenges of human diets and nutrition continued to evolve---they are a focus of Module 3 —this early shift to cooking through the use of fire was one of the most influential in our history.

Hunter-gatherer peoples are assumed to have used thousands of different types of plant species and, at the least, hundreds of different animal species. In many cases, the impact on the environment or natural systems was only slight or moderate, since population densities were low and their use of the environment was dispersed. Populations were relatively small and technology was fairly rudimentary. In a few cases, environmental impacts were significant, such as the use of fire as discussed above. Hunting pressure also could have led to significant environmental impacts. It is hypothesized that hunting by groups in North America contributed to the extinction of approximately two-thirds of large mammal species at the end of the last Ice Age around 10,000-12,000 years ago. The human role in this extinction episode, referred to as the Pleistocene Overkill Hypothesis, was combined with the effects of other changes. Climate and vegetation changes in particular also impacted the populations of these large mammals and made them more vulnerable to hunting pressure.

We know less about the societies and social structure (human systems) of these groups. However, work with recent and present-day hunter-gatherers suggests they had high levels of egalitarianism since livelihood responsibilities are widely shared and not easily controlled by single individuals or small groups within these groups. One thing we do now know is that hunter-gatherers have been related to agricultural peoples in a number of ways. A first and obvious way is that in the history of human groups and food systems, "we" were all hunter-gatherers once, and across a wide range of environments agriculturalists emerged from hunting and gathering in their origin. Another is that hunter-gatherers sometimes coexist with agriculturalists and may even have conducted rudimentary trade. Last, there are even cases of hunting and gathering emerging from agricultural groups. In Africa and South America, for example, the Bantu or Bushmen (in southern Africa) and the Gi (in present-day Brazil) are thought to have been agriculturalists prior to assuming hunter-gatherer lifestyles. These changes presumably owed to lessening population densities and the opportunity for more feasible livelihoods through hunting and gathering given the circumstances these peoples faced. This re-emergence of hunting and gathering is an excellent example of the sort of human natural-coupling we consider in this module and apply to the history of food systems: the social factor of lessening population densities, and perhaps something the re-emergence of more wild ecosystems in natural landscapes, allowed these agriculturalists to re-adopt hunting and gathering, with consequent changes in the natural systems.

The origins of agriculture as the predominant mode of food production were dependent on the domestication of plants and animals. Domestication refers to the evolution of plants and animals into types that humans cultivate or raise; conversely domesticated types can no longer exist in the wild. Domestication and the social and environmental transformation that accompanied them are closely related to the Anthropocene and represent one of the most pivotal experiences ever, both of earth’s environments and in our history and evolution as a species. Domestication has been and is widely studied by interdisciplinary environmental and agricultural fields as well as various disciplines such as archaeology, biology, geography, genetics, and agronomy.

A couple of common definitions of domestication will help to underscore the importance of this concept. In a 1995 book on The Emergence of Agriculture, the archaeologist Bruce Smith defines domestication as “the human creation of a new form of plant or animal---one that is definitely different from its wild relatives and extant wild relatives”. In 2002 in the scientific journal Nature the geographer, Jared Diamond writes that an animal or plant domesticate is “bred in captivity [or in a field] and thereby modified from its wild ancestors in ways making it more valuable to humans its reproduction and food supply [nutrients in the case of plant domesticates]” (page 700). In other words, plant and animal domesticates have lost most or all the capacity to reproduce long-term populations in the wild---thus making domesticated populations of plants or animals different than ones that have been simply tamed or brought into cultivation on a one-time basis as single organisms. Expanding beyond these definitions, you can read more about domestication at National Geographic: domestication.

Figure 2.1.1. Grains and ears of the wild ancestor of maize, teosinte, domesticated in the area of present-day Mexico about 6000 years ago (left), a comparison of the plant and seedstalk of teosinte and modern maize (center), and size comparison of teosinte and maize ears (right). Note the relatively large seeds of teosinte that may have called attention to early plant domesticators as a useful species for a staple food, and the true size comparison of the two ears at far right that shows the dramatic increase in size accomplished through domestication and breeding.

Credit: Teosinte photo (left), Matt Lavin; Teosinte/Maize comparison diagram (center), Biosciences for farming in Africa (B4FA); size comparison photo (right), Hugh Iltis.

A great deal is now known about the nature of domestication and its timing, in addition to the place of origin of many domesticated crops and animals (covered on the next page). Illustrating the multiple disciplines needed to understand the history of food systems, this information owes to evidence and analysis in archaeology; biology, ecology, and agronomy; geography; anthropology; and genetics. For one, the domesticates in general, and our most important domesticated crops and animals in particular---such as wheat, rice, corn (maize), barley, potatoes, sorghum, cattle, pigs, and sheep, are recognized to have evolved from wild plants and animals that were selected, gathered, and brought back to camp by hunter-gatherers. Second, while a broad spectrum of wild plant and animal foods were being gathered and hunted prior to domestication the origins of agriculture represented a bottleneck. The effect of this bottleneck was that the number of major domesticates that became available to humans numbered in the several dozens, but not the thousands. Third, well-established demonstration of the actual dates of domestication varied from 8,000 - 10,000 years ago in the Near East (the Fertile Crescent of present-day Iraq, Turkey, Iran, and Syria) and China to the broad window of 4,000-8,000 years ago in several of the other world regions discussed next.

Domestication of plants and animals has been framed by many experts in terms of a " domestication syndrome" which refers to a set of traits or "syndrome" that are common to domesticates. Syndrome traits are ones that should be easy to remember because these traits confer usefulness to humans. In plants, for example, wild relatives may have shattering seed pods, where a seed is dropped on the ground as it ripens, while domesticates generally keep their seed on the plant to give humans greater convenience in harvesting. There are also dramatic increases in seed and inflorescence size in many plant domesticates in relation to wild relatives (e.g.. Fig. 2.1.1), as well as decreases in bitter or toxic substances that make food crops generally more appealing and nutritious to humans (and sometimes to wild herbivores as well, which then become pests!). Plant domesticates are generally less sensitive to day length as a requirement for flowering and reproduction, which means they complete their life cycles and produce grain and other products in a more predictable way for humans, and tend to have greater vigor as seedlings than wild relatives, which also follows from their larger seeds. In animals, the greater docility of animal pets and livestock, and traits such as floppy ears and general juvenile-type behavior of domesticated dogs are oft-cited examples of domestication syndrome. See if you can identify examples of these traits in the website presentation of domestication cited in the text above.

Just as for the dates and historical processes that led to domestication, the sites of plant and animal domestication are known from a similar interdisciplinary mix of perspectives, from archaeology to genetics. The map in Figure 2.1.2 and Table 1 show current knowledge of seven important areas of early agriculture where the world’s major crops and animals were domesticated. The question of crop and livestock origins and movements presented in this module is still an active and interesting area of research and more remains to be discovered. Most important of these areas was the Fertile Crescent of the Tigris-Euphrates river system and surrounding uplands in Southwest Asia---present-day Turkey, Iran, Iraq, and Syria. This region was responsible for the domestication of several major crops (wheat, barley, oats) and almost all the major domesticated animals (cattle, sheep, goats, pigs) that are incorporated today into major food systems worldwide (for the definition of food system see module 1.2). Like other areas it also included domesticated plants in particular that were significant components of local food systems and diets---such as bitter vetch and chickpeas—that did not become major global staples. China, which we identify as a single geographic area, was responsible for the domestication of rice, soybeans, millet, and several other domesticates that included tree crops such as the peach. Pigs were domesticated independently in China, meaning the pig population there that evolved to domesticated forms was separate from that of the Fertile Crescent. It is likely that China contained two separate areas of major importance in our global overview: the Yangtze River basin and the Wei (Yellow) River valley.

Four other major world regions were also vitally important as sites of early agriculture and in the domestication of major crops and animals. Southeast Asia including New Guinea and the Pacific Islands is an expansive geographic area where staples such as various species of yam, citrus, bananas, and sugar cane were domesticated (see Table 1). A significant size region of sub-Saharan Africa was also quite important, contributing crops such as sorghum, coffee, and species of millet other than the ones domesticated in East Asia (see Table 1). Geographically this area of sub-Saharan Africa includes the savanna areas of West Africa as well as the highlands of Ethiopia and Kenya. Locally within this region, such domesticates as teff and fonio, a pair of grain crops, became highly regarded foodstuffs.

Figure 2.1.2. Map of the crop centers of origin as described by botanist and breeder Nikolai Vavilov: (1) Mexico-Guatemala, (2) Peru-Ecuador-Bolivia, (2A) Southern Chile, (2B) Southern Brazil, (3) Mediterranean, (4) Middle East, (5) Ethiopia, (6) Central Asia, (7) Indo-Burma, (7A) Siam-Malaya-Java, (8) China and Korea.

Credit: Wikimedia Commons: Vavilov-center (Creative Commons CC BY 3.0)

In South America, the combination of the Andes mountains and the Amazon basin was an important area of early agriculture and domestication that included potatoes, sweet potatoes, peanuts, and manioc (or cassava). The Andes and Amazon also included many locally important domesticates such as quinoa and acai (the fruit of the acai palm) that recently have gained popularity as elements of global food systems. The area of Mexico (extending to the U.S. Southwest and southern Arizona in particular) and Central America is also important. This area’s contributions included corn (also known as maize) and domesticated species of bean, chili pepper, and squash in addition to the turkey. Eastern North America was also an important area of early agriculture though most domesticates there did not become familiar items in major contemporary food systems. Sunflower did though become relatively important and some of the domesticated plants of the northern parts of North America, such as cranberry and so-called Indian rice, did become moderately important foods.

At this juncture, it’s important to note some important points for understanding the environment-food interactions that arise from our discussion thus far of hunting-gathering, domestication, and early agriculture. This geographic and historical context highlights the importance of the independent establishment of early agriculture through domestication in multiple geographic areas across diverse world regions. Our description of current knowledge emphasizes the importance of seven world geographic areas, but other variants of this accounting are possible. Crop origin areas could potentially be more numerous, for example, if we counted additional distinct sub-areas of China, Sub-Saharan Africa, and South America. It is interesting that the major modern population centers, the Eastern United States and Northern Europe, seem to have been less important than other world regions in the domestication of the major staple grains and vegetables. As noted above, the question of crop origins and the relations of humans to crops via domestication, breeding, and knowledge of how to cultivate crops remains an active and fascinating area of research.

Our description also highlights the domestication of a handful of specific species of major crops (approximately 100 species) and major animal domesticates (14 species). These domesticated species are the same ones we still recognize today as the most valuable cornerstones of our current food systems as well as being central elements in their environmental impacts. When local crops and livestock are added the numbers of these domesticates is significantly higher (upwards of 500 species). Still, the number of species in this new agricultural biota paled in comparison to the thousands of species that have been the basis of human livelihoods in hunter-gatherer systems. In other words, early agriculture meant that humans narrowed their focus on a select group of species in the biotic world, namely the ones that were most productive and could be most feasibly and effectively produced and consumed. In doing so, humans intensified the level of interaction, knowledge, and cultural importance of these crop species as a fundamental human-natural relationship at the base of food systems from prehistory to the present day.

In a variety of subsequent units of this course, we will be considering the diversity of crops and animals in agriculture as we explore the agroecology and geosystems of food production (Section II) and the role of human-environment interactions amid such challenges as climate change, food security, human health, and environmental sustainability (Section III). In this module, we keep our focus on early agriculture and domestication. Our present focus will also require that we use the model of Coupled Natural-Human Systems (CNHS) through the remainder of Module 2.1 followed by continuation and expansion of this focus in the next module (Module 2.2) where we discuss a few of the major historical transformations leading to the world’s current situation with regard to the environment and food (Module 2.2).

The Coupled Natural-Human Systems, which we introduced in Module one, can be used as a framework to explain domestication events and early agriculture in the history of food systems. This framework is sometimes used to think about the "why" question of domestication, for example, "why did human and natural systems come together at a particular time in different parts of the world, including the middle east, so that plants were domesticated and agriculture started?; Why not earlier, and why not later?". The framework can also be used to explore the history of food systems after domestication, which is the subject of module 2.2.

Review and Definitions: Drivers, Feedbacks, and Coevolution

You probably recall from module 1.2 that systems are assemblages of components and the relations between them. Two basic relations that can occur within systems, and that you likely included in your concept map of a food system example (summative evaluation 1.2) were those of a driver and a feedback relation. As you may already suspect, drivers are those processes or changes that can be said to impel or cause changes in other parts of a system, somewhat like a volume knob that causes the volume of music to increase in a room. In the example of the Pleistocene overkill hypothesis from module 2.1, for example, human hunting is thought of (hypothesized) as a dominant human system driver that eliminates the possibility of hunter-gatherers to easily find food, so that they may have been forced to develop early forms of agriculture. Excessive hunting is the driver, and collapsing prey animal populations, and eventually, domestication are responses. Meanwhile, feedback processes are those that can be said to be self-strengthening or self-damping (see module 1.2), and in the case of domestication, also may involve multi-driver processes where a response to a driver is another process that serves to strengthen both processes (positive feedback) or diminish the change (negative feedback). For example, as you will see in the next module, a common dynamic around the emergence of agriculture could be the coming together of excessive hunting, changing climate with worsening conditions for both wild game and crops, and the expansion of human settlements that may have also degraded the land. This combination of human and natural drivers could all tend to drive increased areas under cultivation to deal with the lack of food from hunting, and later the lack of food from soil degradation. A positive feedback emerges when the expansion of agriculture itself begins to change the climate, further eliminate prey, or reduce food availability from soil degradation. These processes would be thus said to interact as a positive feedback on domestication and the emergence and continuing expansion of agriculture. The diagram below (fig. 2.1.3) shows these potential drivers and feedback processes. the basic-level illustration shows the coupling of these two systems.

Figure 2.1.3 General Diagram of Coupled Natural-Human Systems (CNHS) illustrating potential drivers and feedback processes from human to natural systems and from natural to human systems (blue ovals show examples of these processes). It is understood from module 1 that the human and natural systems themselves consist of multiple social and environmental components, but are represented as solid blocks here for simplicity.

Click for a text description of the Human Natural System image.

Diagram of coupled natural-human systems. At the top of the diagram is the heading "Human to natural drivers and feedbacks: Human system causes changes in the natural system and strengthens existing changes". At the bottom of the diagram is the heading "Natural to Human drivers and feedbacks: Natural system causes change in the human system and strengthens existing changes". From Human System, the arrow flows to an oval with the following items inside: Hunting, Domestication, Fire, Expansion of land under tillage and food crops, City building. There is another arrow from Natural System to an oval with the following items inside: Long-term drought or rainfall increases, Climate warming or cooling, Collapse of wildfire or plant populations. The arrows represent a continuous relationship.

Credit: adapted by Karl Zimmerer and Steven Vanek from a diagram designed by the National Science Foundation Coupled Natural-Human Systems Program

In Figure 2.1.3, then, the human factors that can change the environment we will refer to as “Human Drivers” or “Human Responses” of the CNHS model. The environmental factors that influence humans are referred to as “Environmental Drivers” or “Environmental Feedbacks.” As illustrated below with examples, the CNHS model describes the combined, interlocked changes of human behaviors and societies, on the one hand, and environmental systems including the plants and animals under domestication, on the other hand. This model is also referred to as a coevolutionary model since the drivers and feedbacks, including intentional and unintentional changes, influence subsequent states and the resulting development of the human-environment food system.

An initial, specific example: Why did agriculture emerge at the end of the ice age?

Before using these diagrams in Module 2.2 to explain the history of food systems (including the summative assessment which asks you to diagram some of these relationships yourselves), we'll illustrate the concept of drivers, feedbacks, and the coevolutionary emergence of food systems using a very specific diagram about the emergence of agriculture in Fig. 2.

Figure 2.1.4 Specific example of a coupled human-natural system in a transition from hunting and gathering to domestication and early agriculture, showing what are thought to be a dominant driver (climate change) and a human response that created positive feedbacks in strengthening the transition to agriculture (densification and social organization of human settlements near water sources)

Click for a text description of the Human Natural System image.

Specific examples of coupled natural-human systems. At the top of the diagram is the heading "Human to natural drivers and feedbacks: Human system causes changes in the natural system and strengthens existing changes". At the bottom of the diagram is the heading "Natural to Human drivers and feedbacks: Natural system causes change in the human system and strengthens existing changes". An arrow from Natural System to an oval with the following: 1. Change to warmer climates and more seasonal precipitation, including vegetation changes (late Pleistocene and early Holocene, i.e. end of ice ages). From Human System, the arrow flows to an oval with the following: 2. Increase in the size and density of human population near water and increased social complexity and demand for agricultural products. The arrows represent a continuous relationship.

Credit: National Science Foundation Coupled Natural-Human Systems Program

The "story" of this diagram is as follows: First, climate change is one of the main environmental drivers that influenced early agriculture and domestication. At the end of the Pleistocene, the geologic epoch that ended with the last Ice Age, there was a worldwide shift toward warmer, drier, and less predictable climates relative to the preceding glacial period (Fig. 2.1.4, oval (1)). This climate shift that began in the Late Pleistocene resulted from entirely natural factors. Hunter-gatherer populations are documented to have been significantly influenced by this climate change. For example, many hunter-gatherer populations responded to this climate change by increasing the size and density of human populations near water sources such as river channels and oases (Figure 2.1.4, oval (2)). This climate change also led to the evolution of larger seed size within plants themselves (especially those plants known as annuals that grow each year from seed), which are summarized as part of the vegetation changes noted in Fig. 2.1.4. It may have also selected for annual plants being more apparent parts of natural environments in dry climates these humans inhabited, since surviving only one season as an annual plant, and setting seed that survives a dry period is one evolutionary response in plants to dry climates (see module 6 for the concept of annual and perennial life cycles). The driving factor of climate change thus led to responses in plants and human societies that are hypothesized to have acted as drivers for domestication and early agriculture. The driver of climate change is also thought to have concentrated the populations of the ancestors of domesticated animals. Their concentrated populations would have better-enabled humans to take the first steps toward animal domestication. Recognizing the importance of climate change we single it out as the main driver in Figure 2.1.4, though doubtless there were other interacting drivers.

Influential Human Drivers included such factors as population (demographic) pressure and socioeconomic demands for food and organization of food distribution were also highly important in contributing to the domestication of plants and animals and the rise of early agriculture (Figure 2.1.4, oval (2)). This pair of factors is also referred to as human to natural drivers, as shown in the diagram. The influence of human demographic pressure was felt through the fact that settlements were becoming more permanently established and densely populated toward the end of the Pleistocene. People in these settlements would have been inclined to bring wild plants with good harvest and eating qualities into closer proximity, and thus take the first steps toward agriculture.

Socioeconomic factors are also considered important as Human Drivers in early agriculture and domestication. As hunter-gatherer groups became more permanently settled in the Late Pleistocene they evolved into more socially and economically complex groups. Socioeconomic complexity is generally associated with the demands for more agricultural production in order to support a non-agricultural segment of the population as well as for the use of the ruling groups within these societies. The emergence of this social organization, and higher population density, combined with the ability to feed larger populations with newly domesticated grains, are plausible as a powerful positive feedback that served to continue and strengthen the course of domestication and agriculture. Continued climate change associated with the expansion of farmed areas, and potentially soil degradation from farming that necessitated even larger land areas and/or more productive domesticated crops (see module 5), would have been additional feedback forces that strengthened the emergence of agriculture. Therefore, drivers and feedbacks are one way to answer the "when and why" questions around the start of agriculture, as a coevolution of human society with changing climate and vegetation. The concepts of drivers, feedbacks and coevolution will be further explored in module 2.2, to explain other stages and transitions in the history of food systems.

From the Origins of Agriculture to Challenges and Opportunities for the Future of Food 

Introduction

The development of agriculture as part of food systems in the Anthropocene began with domestication and has continued across millennia among diverse peoples inhabiting a wide variety of the earth’s environments (e.g. the Mediterranean region, the Indus River Valley; southern South America; the Congo River basin; the Island now called Sumatra, and many other highly varied landscapes). The history of agriculture also includes the present: domesticated plants and animals, as well as agricultural management, continues to change. In module 2.2 we will divide an overview of this complex history into four general periods:

1. Domestication/Early farming (10,000 BP-4,000 BP);
2. Independent States, Small Groups, World Trade, and Global Colonial Empires (4,000 BP – 1800/1900 CE);
3. Modern Industrial Agriculture (1800/1900 CE – Present);
4. Recent Quasi-Parallel Agricultural Types and Possible Next Phase (2000 – Present): Agroecological Modernization (e.g., Organic) and Local Environment-Food Systems.

Each of these categories lumps together a lot of variation with regard to the specifics of agriculture and coupled human-natural food systems, and if you have the chance to read in more detail about these phases of the Anthropocene, you'll find a significant and interesting amount of variation among different places and time periods (see the additional readings at the end of the unit).

To continue describing the environment-food systems of each of these four periods, we recall that in module 2.1 we described the long period of hunter-gatherer activities and environment-food systems, which comprised well over 90% of the history of humans as a cultural species. We also looked at plausible drivers and feedbacks in the origins of agriculture and domestication. Here in Module 2.2. We’ll pick up the thread of the environmental and social transformations represented by agricultural origins and domestication. We note that early agriculture, and perhaps a later stage of agricultural development marked the transition to the Anthropocene epoch in which humans became a dominant force in transforming earth's surface and natural systems (see module 1 regarding the Anthropocene).

Key terms and concepts for the history and development of food systems

After its first origins, agriculture spread worldwide through a process known as spatial diffusion. The spatial diffusion of agriculture involved individuals and groups of people gaining access to the ideas, information, and materials of agriculture and other innovations through physical relocation and social interactions. Spatial diffusion can occur through local individual-level human observation and the exchanges of goods and information as well as long-distance trade and organized activities (e.g. group-level decisions to adopt a new planting technology). A brief description and examples of spatial diffusion in early agriculture are given in Table 2.2.1. While agriculture was developed independently in each of the different world geographic areas roughly corresponding to centers of crop domestication (Module 2.1, Figure 2.NN), agriculture then spread widely out of these early centers in a way that was highly influential. Agriculture's diffusion from the Near East to Europe, for example, transformed a wide range of environments and societies. As discussed more below, the spread of crops themselves was often transformative for the environment-food systems to which these domesticates arrived. For example, all the major cuisines we know today rely on food ingredients that were made available as the result of spatial diffusion For example, foods originally from Mexico, such as tomatoes, chili peppers, and maize transformed environment-food systems globally beginning in the 1500s, spreading as far as Africa, India, and China.

The geographic spread of agriculture created both similarities and differences across space and time. On the one hand, sharing the same food crops and sometimes agricultural techniques created commonalities among environment-food systems. The current environment-food system of the country of Peru, for example, is rooted to a large degree in the connections that were forged through spatial diffusion during the Inca Empire that ruled between roughly 1400 and 1532 of the Common Era (CE). On the other hand, differences in environment-food systems also evolved over time as crops and food were subject to the human and natural system influences in each new site to which agriculture spread. One of the main reasons for these differences was the role of people in adapting agriculture to different environments and sociocultural systems.

A few concepts in addition to spatial diffusion are central to understanding the spread of agriculture and its importance, and we introduce them here. These concepts -- adaptation, agrodiversity, and niche construction -- are briefly described with examples in Table 2.2.1, and the term Anthropocene is also reviewed from the standpoint of its relation to early agriculture. The first of these, adaptation, refers broadly to the way in which humans use technical and social skills and strategies to respond to the newness or changes of environmental and/or human systems (e.g. droughts, hillier topography or increased rainfall as crops moved to new areas, climate change). Adaptation and adaptive capacity of human society are a major focus of Module 11.

The use of agrodiversity was also vital to the spread of early agriculture. Agrodiversity is described by the geographer Harold Brookfield and the anthropologist Christine Padoch as human management of the diversity of environments in agriculture and food-growing. Brookfield and Padoch use agrodiversity to describe indigenous farming practices among native peoples, but all knowledgeable farmers actively make use of agrodiversity, even if the technologies may differ greatly. Managing diverse agricultural environments was essential since early farmers produced domesticated plants and animals under new and different conditions. The third concept is that of niche construction, meaning that agriculturalists (and hunter-gatherers) shaped food-growing environments (“niches”) through constructing fields and all kinds of other activities. As a result, adaptation occurring across the wide geographic and historical evolution of environment-food systems involves responses to a range of factors that include both natural ones and those resulting from human activities.

The development of agriculture through the four periods mentioned above has resulted and continues to incur, a wide range of both environmental and social impacts that will be mentioned in the following pages of this module. Environmentally these impacts have altered the biogeophysical systems of our planet, including the land, water, atmosphere, and biodiversity of the earth. As mentioned the idea of the Anthropocene epoch---a distinct geologic epoch defined by drastic human modifications of the earth’s environmental systems---is often tied to agricultural activities. Global environmental sustainability, whether the earth’s systems are operating within limits that will enable long-term functioning, is fundamentally influenced through agriculture, as you’ll see in this module and all the ones to follow.

We will start our historical summary of environment-food systems by describing domestication and early farming (10,000 BP – 4,000 BP). Widespread environmental and social impacts occurred during this period. New agricultural ecosystems were created and spread along with the use of domesticated plants and animals. These agroecosystems contained distinctive species and populations of plants and animals including domesticates, as well as characteristic insects, mammals, soil biota, and uncultivated plants (such as weeds). In many places, agroecosystems were increasingly established in areas that previously had supported tree cover. During this period in the Near East, China, and Europe, for example, clearing for agriculture led to increased deforestation.

As part of this survey, we ask you to read the short and provocative article by Jared Diamond on the impacts of the diffusion of early agriculture. This should prompt a lot of thinking on your part about the way that the emergence of agriculture affected human societies that we describe further below.

Impacts of domestication and early agriculture were notable not just for natural systems but also on human systems. Both a population explosion and a technology explosion occurred in conjunction with early agriculture. The early farming societies grew in the size of their populations and the use of diverse tools and technologies, including ones that no longer needed to be transported as part of highly mobile hunter-gatherer lifestyles. The growth of population was made possible by the increased productivity of food per unit of land area. Impacts on human health and disease were also notable in this period, though they were not entirely positive. As Jared Diamond points out in the required reading above, there were negative impacts on human health traced to larger settlements and denser human populations (e.g. highly infectious “crowd diseases” such as measles and bubonic plague) and also infectious disease involving transmission from domesticated animals (measles, tuberculosis, influenza). Nutritional stress also ironically increased, with life expectancy actually decreased following domestication and the early development of agriculture.

These negative impacts on humans have led Diamond to refer to agriculture provocatively as “The Worst Mistake in the History of the Human Race”. This title is purposefully provocative, and by way of understanding this "mistake", we should realize that early farmers’ switching to agriculture may have become the most viable option in many places. Agriculture becoming the principal livelihood option would have occurred as local hunted-gathered food sources were overexploited and/or required by population pressure. By the end of this period, the evolution of more complex societies also meant the development of deep class divisions. There the social phenomena of deepened class divisions must also be seen as a product, in part, of the evolution of agriculture. In addition, changing social arrangements from agriculture would tend to create a positive feedback (see the end of module 2.1), along with other factors, in maintaining and deepening the pathway of society towards a greater embrace of an agriculture-based food system.

The model of Coupled Natural-Human Systems (CNHS) can be used to reflect on the above impacts through the integrated perspective of human-environment interactions. Here we can highlight a couple of these interactions. First, widespread deforestation occurred as a result of early agriculture. In addition to changing land cover and ecosystems, it has been postulated that the extent of this deforestation at this time was significant enough to release considerable carbon dioxide (CO₂) and thus to define the beginning of the Anthropocene epoch. As mentioned below other scientists argue the Anthropocene was created more recently. This scientific debate about the Anthropocene epoch has been productive in our understanding of human dynamics and impacts with respect to the environment.

Humans are presumed to have responded to deforestation by increasing their reliance on agriculture, since the removal of forest cover would have reduced the productivity of hunting-gathering activities, creating a second positive feedback that would have deepened the transition to agriculture. The second form of human-environment interaction involved the selection of a relatively small fraction of utilizable plants and animals that become the cornerstones of early agriculture. Since these plant and animal domesticates produced well relative to others, they became relied upon by early farmers, also acting as positive feedback towards the adoption of an agricultural lifestyle. The legacy of this initial selection of certain types of plants and animals demonstrates the important role of contingency and positive feedbacks, whereby initial decisions were amplified and exerted a lasting influence on the Coupled Natural-Human Systems of agriculture. The concepts of feedback are considered further in the subsequent pages and in this Module’s Summative Assessment.

The second period of our rapid historical survey encompasses independent states, societies based on small groups, world trade, and global colonial empires and covers roughly 5,000 years between 3,000 BP and 1800/1900 CE. Both positive and negative environmental and social impacts were associated with this period. We can use the coupled system model to illustrate two examples of this period’s characteristic forms of environment-society interactions. The Inca Empire in the Andes Mountains of western South America (from present-day Colombia to Argentina) offers a good example of an independent state with pronounced environmental and social impacts of its agriculture. Ruling from approximately 1400-1532 the Inca state oversaw the building and maintenance of extensive agricultural field terraces and irrigation canals (Figure 2.2.1). These terraces and canals produced sustainable landscapes in the tropical mountain environments of the Andes.

Figure 2.2.1. Terraces and related irrigation works built by the Inca and other early, large-scale agricultural societies are a dramatic example of the transformation of the earth's surface for sustained food production.

Credit: Phil Romans, Flickr (Creative Commons CC BY-NC-ND 2.0)

From the perspective of coupled natural-human systems (CNHS), the terraces and canals of the Inca produced sought-after foods and symbolized Inca imperial power, thus contributing further to Inca capacity to extend these sustainability-enhancing earthworks. The Inca state eventually established terraces and other large-scale agricultural and food transportation works (storage facilities, improved riverbank fields, roads, and bridges) that extended over much of the area of their empire. Environmental impacts of these terraces and other earthworks were beneficial since they stabilized mountain agricultural environments and enabled higher levels of food-growing per unit land area without major damage. Still, we need to remind ourselves that early independent states, such as the Inca, also created environmental problems and often were marked by large social inequalities between rulers and commoners. In other words, just as today, the environment-food systems of non-European peoples could and did attain high levels of sophistication while, at the same time, they were often wracked by significant issues with both environmental and social sustainability (see module 1 for definitions from the "three-legged stool" of sustainability. Similarly important for us to note is that some Inca terraces and canals continue to exist and are still used today as they are in Peru so that they still create a sustainable contribution to food systems at a local scale.

A second example of environmental and social impacts resulting from this period of agricultural diffusion and trade in world history comes from the world trade system established by global colonial empires involving major European powers between 1400 and 1800 (such as the Spanish, British, and French colonial empires). A well-known example of social and environmental impacts from this time period is the exporting of crops and livestock, along with related elements of European environment-food systems, on many areas of the world by these empires. Examples included wheat, sugar cane, alfalfa, cattle, and sheep. These crops and livestock had not originated in Europe but had already diffused there during earlier history, and were common in Europe at the time these empires were expanding. These components of new European colonial environment-food systems were mutually reinforcing, since for example the forage crop alfalfa and introduced European grasses were highly conducive to expanding the raising of cattle and sheep and making new sources of animal food products available to human populations. There were thus reinforcing (positive) feedbacks between the way that these crop species such as alfalfa and grasses were able to "remake" environments and make them more hospitable for European livestock. Sugar cane is another crop that is notorious for remaking the landscapes and social relations in the Caribbean, South America, and the United States, through plantation agriculture and slavery. The case of pasture species and livestock is considered further in this module's summative assessment.

The third major period in our broad historical summary is modern industrial agriculture, which is the predominant environment-food system today, though it coexists with a significant sector of smallholder agriculture that has incorporated modern industrial techniques to a greater and lesser extent.

Modern agriculture arose in the 1800s and 1900s through a variety of developments in agriculture and in the processing and business of foods. “Industrial” in this description refers to the major role of factory-type processes that are principally large-scale and involve the defining role of technological inputs such as large amounts of freshwater use, chemical fertilizer, pesticides, and “improved” seed that delivers high-yield responses to the other inputs. Industrial is also an appropriate term since this environment-food system has narrowed concentration on a few species of crops and livestock. “Modern” is important in this description since distinct foodways and consumption practices---many based on foods that are highly processed, relatively inexpensive, easy-to-prepare convenience items---that are integral to this environment-food system. Modern is also an important term since it’s estimated this predominant system is based on more changes in the past 100 years than occurred over several hundred and maybe even thousands of years previously.

In much of the world, the advent of the modern environment-food system was provided through the Green Revolution beginning in the 1940s and 1950s. The Green Revolution used science and technology to develop modern crops and agricultural production systems for the countries of Asia, Africa, and Latin America. While it has evolved considerably, the approach of the Green Revolution continues to be used today. The worldwide influence of the Green Revolution suggests one additional term to describe this type of environment-food system, which is “global.” The development of this system, as well as its inputs and impacts, is global in scope. The global characteristics of today’s predominant environment-food system will be evident throughout this module and the others in this course as we place emphasis on the global scale of environmental and social impacts, which relates to the concept of the Anthropocene. In fact, if we consider the bar graphs of the relative areas of wild versus managed land (crops and livestock) globally presented in module 1 (Figure 1.1.4) we can see why some experts prefer to think of modern industrial agriculture, and the related expansion of human populations, as the defining period of the Anthropocene.

Figure 2.2.2. Modern industrial agriculture is a culmination of social and technological processes beginning in the 1800s that sought to increase yields of agriculture for growing human populations by applying fossil fuel energy, mechanization, and advanced crop breeding methods. This photo of a modern grain variety being harvested encapsulates this transformation towards modern agriculture in many ways: the large area of a single grain variety, likely bred and sold by a modern corporation; the extreme mechanical efficiency and speed of grain flowing off the field into a wagon for storage and sales; the need for diesel fuel and associated carbon dioxide emissions to drive the powerful machinery, whose power and efficiency reduces the workforce needed for agriculture.

Credit: Alan Harrison, used with permission from Flickr under a creative commons license

A wide range and mix of environmental and social impacts are associated with modern industrial agriculture. Agricultural mechanization has coincided with a major reduction in the agricultural workforce. In the United States, for example, less than 2% of the population is estimated to be directly employed in agriculture. In the 1870s and 1880s, by contrast, this estimate was 60-80% of the U.S. population. Environmental impacts and human-environment interactions have also been strongly influenced by the widespread use of fossil fuels in modern industrial agriculture.

Fossil fuel use is the foundation for many modern agricultural technologies ranging from tractors and farm machinery (Fig. 2.2.2) to fertilizers and pesticides as well as the energy costs of processing and the large number of “food miles” typically involved in transportation. As the result, energy issues along with greenhouse gas emissions have become a major concern with modern industrial agriculture----as discussed in subsequent modules.

One example of human-environment interaction will suffice in this section since modern industrial agriculture will be examined in detail in many of the modules that follow. (Modules 6, 7, and 8, which focus on agroecology, feature excellent and far more extensive examples.) The widespread use of pesticides and the creation of pesticide-dependent crops and cropping systems are a defining characteristic of this agriculture worldwide. The development of these synthetic products for protecting crops, and potentially the increase in yields associated with solving, if temporarily, a pest problem. Meanwhile, the populations of agricultural pests continue to evolve resistance in response to these applications, an example considered further in module 8. As a result, it is essential that these modern industrial crops and cropping systems (including the use of pesticides) be constantly developed in order to gain a new advantage against the most recently evolved pests.This innovation process in agricultural technology for crops is another example of a positive feedback driving the further industrialization of agriculture.

In recent history (since 2000) significant new directions have entered the spectrum of existing environment-food systems. The future of food will depend on these newer systems, in addition to modern industrial agriculture that was introduced on the previous page. The new directions---which we refer to here as “ecological modernization” and “alternative community-based food systems”---are a response to concerns over environmental sustainability, human health, and food safety in addition to the attempt to reinvigorate rural society and address social justice issues, a concept we introduced in module 1 as "social sustainability". Each of these new directions also has its own environmental and social impacts. These impacts are introduced here and then taken up again in module 10.1 when we consider them as "global" and "local community" variants of new, alternative food system types. In both these new directions, a major role is taken by ecological methods and techniques replacing to a significant degree the use of synthetic chemicals. Substantial success can be seen in some cases: for example, organically certified lettuce and carrots with reduced use of synthetic pesticides now account for more than 10% of the land producing these crops in the United States.

Social changes---remember we use this term broadly to refer to economic impacts as well---vary widely in the environment-food systems associated with ecological modernization. Large corporations as well as a substantial number of large family-managed farms, for example, predominate in the large-scale sector of organic agriculture and organic food production and distribution, where these companies and large farms occupy a "quasi-parallel" role to their role in supporting modern industrial food production (previous page). We and other authors describe their style of adoption of organic production techniques as ecological modernization because they seek environmentally sustainable methods as relatively interchangeable replacements for synthetic chemical inputs in modern agriculture (previous page). Ecological modernization also retains modern forms of organization, for example, large scale and efficiency of cropping and shipping of food, corporate management, and sales through mass outlets such as supermarkets. Food distribution companies in this system can offer organic foods at lower prices in the case of fresh vegetables and fruits. This advantage is significant since affordability is a major issue among potential consumers of organic food, and such "corporate organic" foods may be more accessible at the present for a larger proportion of the population. Others argue that issues of cost and accessibility resulting from transitions towards organic and other more ecologically-based ways of managing agriculture merely reflect the artificially low financial, environmental, and social costs of comparable products from the modern industrial food system, for example, the carbon dioxide emitted in the manufacture of fertilizers and pesticides (see module 10). In any case, the rules, regulations, and preferences of human systems designed to foster organic agriculture (such as organic certification and labeling) may be effective in improving the natural system, though the feedbacks to human systems may be ones mostly supporting large agribusiness through positive feedback effects introduced in Module 2.1.

Take for example the case of organic produce such as lettuce and carrots where natural conditions in climatically optimum growing areas (e.g., organic vegetable-growing areas in California) favor the capacity of large corporations and family farms able to access the high-quality land, resource systems (such as water), and deal with the regulatory tasks associated with large-scale national markets. The large scale of these corporate actors becomes a positive feedback driver which strengthens the transition towards this "ecological modernization" mode of a new food production system. This case is considered further in this Module’s Summative Assessment.

“Alternative community-based food networks” is a term that is applied to various smaller though increasingly important types of environment-food systems. We use this term to focus on local environment-food systems. Proponents and activists supporting these types of environment-food systems center much of their attention on the process known as re-localization. This process brings food producers into closer contact with consumers. Local farmers' markets, where farmers sell food directly to consumers, are an example of re-localization. Local environment-food systems are seen as an alternative to the concentrated corporate control of environment-food systems. A major goal of re-localization is supporting small- and medium-scale farmers, including the majority of family-owned farms, as a means of reinvigorating rural life among a range of small businesses---not just a larger number of farms but also the corresponding number of small business that support and benefit rural areas. This interest in “alternative food systems” is committed to increasing the percentage of the “food dollar” that goes directly to farmers. This percentage is estimated currently at 8-10% in modern industrial environment-food systems where a large share of the food dollar goes to food processors and farm input suppliers. For this reason, the local food emphasis in alternative food movements is also sometimes referred to as an emphasis on short food supply chains exemplified by farmers' markets or regional sourcing of food in supermarkets and restaurants. These alternative food systems are presented further in Module 10.

Instructions

Download the worksheet to understand and complete the assessment. You will submit the answers from the worksheet to the Module 2 Summative Assessment in Canvas.

The first part of the worksheet presents a more detailed version of the interaction of human and natural systems at the onset of agriculture at the end of the last ice age, presented at the end of Module 2.1. This is to provide you an example in the use of these diagrams to think about changes in food systems over human history, and it is shown below here as well.

Fig. 2.2.3. Example of human and natural system drivers around domestication in human food systems, to guide responses in the two other examples in the assessment.

Click for a text description of the Human Natural System image

Heading at the top says, Human to natural drivers and feedbacks: Human system causes changes in the natural system and strengthens existing changes. At the bottom is the heading Natural to Human drivers and feedbacks: Natural system causes changes in the human system and strengthens existing changes. From Human System on the left, an arrow leads to the following items: Humans settle near to water sources in higher population densities, Increase in social complexity, Humans notice and make use of large-seeded wild plants and animals near water for domestication, Increased need for food, Deforestation, and disturbed soils. From Natural system, an arrow flows to the following items: Warmer/drier climates with more seasonal precipitation, Larger seed size in wild plants, Potential domesticated animals drawn to water sources near to humans, Good niches for crops around human settlements. The arrows represent a continuous flow between Human and Natural systems.

Credit: Steven Vanek, adapted from the National Science Foundation

Further instructions for the assignment are given in the worksheet. You will need to fill in four questions on the worksheet, some of which have multiple parts.

Completing Your Assignment

Please use this completed worksheet as a guide for taking the Summative Assessment quiz. You do not need to submit your worksheet. 

Energy: Requirements and Function

Carbohydrates (starches and sugars), fat, and protein within food can all function as sources of energy when they are metabolized to carbon dioxide and water in respiration processes in all of our body’s cells. This energy fuels everything from the production of neurotransmitters in our brains to the muscle contractions required to shoot a basketball or weave a basket. The energy content of food is expressed as “calories” (“calories” are in reality kcal or kilocalories as defined in chemistry; 1 kcal will heat one liter of water one degree C). Energy-dense foods with high caloric content are generally those with high carbohydrate, protein, or fat content - for example, pasta, bread, oatmeal, grits, and other cooked whole grains and porridges consumed around the world as staples; plant oils or animal lard present in cooked foods, or meat and cheese. It is interesting to note that gram for gram, fats contain over twice the energy density of carbohydrates or protein: about 9 kcal per gram for fats versus only about 4 kcal per gram for carbohydrates and protein. We’ll address the further role of high-quality fats as a nutrient, rather than just an energy source on a page further on.

Energy Sources: Diet and Food System Aspects

Current U.S. Department of Agriculture (USDA) and other major nutritional guidelines promote the idea of accessing calories via a predominance of whole grains (e.g.. whole wheat and oats and flours made from these, brown rice) as these whole grains contain a mixture of carbohydrates, proteins, and indigestible fiber, as well as vitamins. These non-caloric contributions to nutrition are also important as discussed in the pages below, and combine well with the caloric content of food to produce better health outcomes. Calories are a fundamental consideration within nutrition because a negative calorie balance (calories consumed minus those expended in human sedentary activities and exercise) along with shortages of other associated food components described below leads to weight loss and faltering growth in children, including childhood stunting and permanent harm to a person’s developmental potential. By contrast, large excesses in a calorie balance over time lead to weight gain that is linked at a population level to increased rates of heart disease and diabetes. These diet-related diseases increasingly afflict populations in industrialized economies and urban populations worldwide with access to abundant, though often less healthy, food choices. Diet-related diseases as part of food systems will be taken up again in module 3.2.

Protein: Requirements and Function

The second main component conceptualized by nutritionists as a key ingredient of a healthy diet is protein, which is used in many different ways to build up and repair human tissues. Proteins are basically chains of component parts called amino acids, and it is these amino acids that are the basic “currency” of protein nutrition. Twenty amino acids are common in foods, and of these nine[1] are essential because humans cannot synthesize them from other nutrient molecules. Meat, fish, and eggs are animal-based and protein-dense foods that contain the complete profile of amino acids, basically because we are eating products that are very similar in composition to our own body tissues. In addition, some grains such as quinoa and buckwheat contain complete protein, while most legumes (peas, beans, soybeans, bean sprouts, products made from these) are high in proteins in a way that complements grains in the diet.

Protein Sources: Diet and Food System Aspects

For people who do not eat meat (a vegetarian diet) or who avoid all animal-based foods (vegan diets), the full complement of amino acids are accessed by eating milk and egg products or by eating a diversity of plant-based foods with proteins such as whole grains, nuts, and legumes. Legumes are particularly protein-dense and important in addressing the lack of amino acids in other plant-based foods. The combination of rice and beans is an oft-cited example of the complementarity of amino acids for a complete amino acid profile. Eating a wide range of plant-based foods is an excellent strategy to access the full complement of essential amino acids, as well as the diversity of mineral, vitamin, and fiber needs discussed on the next pages. Many of the most problematic diets are those that are highly monotonous due to poverty and/or inadequate knowledge about diet, with an excess or a sole dependence on a single starch source without legumes or animal products, or overconsumption of processed foods in comparison to fresh plant and whole-grain foods. Where only a single grain is eaten, deficiencies of certain amino acids can result.

[1] These are phenylalanine, tryptophan, methionine, lysine, leucine, isoleucine, valine, and threonine, which you can find in many introductory nutrition texts or resources online, if further interested. A ninth amino acid, histidine, is important in child growth and may also be vital to tissue repair, while another, arginine is essential for some growth stages and can usually be synthesized by healthy adults.

In addition to the daily requirements for energy and protein, vitamins and minerals are required in relatively small amounts as part of a proper diet to ensure proper functioning and health and are especially important for childhood development. Vitamins and minerals deficiencies can lead to “hidden hunger”, where energy and protein needs are being met but the lack of vitamins and minerals prevents adequate development and health of child rent and saps the productive capacity of adults, for example via iron-deficiency anemia (see below). There are a large number of essential vitamin and mineral components in foods. In this module, we focus on a few that frequently pose major challenges within food systems. If you are interested, full details on the roles of many nutrients can be found in the excellent online text from the Food and Agriculture Organization (FAO) of the United Nations, Human Nutrition in the Developing World. This module's formative assessment may also point to other vitamins and minerals that can become deficient in diets.

Calcium

Although it is important for other functions, calcium is emblematic in its role in proper bone growth and maintenance. It is especially important for women to consume adequate calcium throughout life, and higher intakes of calcium from childhood on are associated with lower rates of osteoporosis and stronger bones later in life. Vitamin D is also essential for the proper absorption of calcium so that a vitamin D deficiency can lead to calcium deficiency. Dairy products and small fish that are consumed whole (so that fine bones are eaten) are highly calcium-dense foods around the world. Grains are low in calcium but are consumed in such volumes that they often contribute substantial calcium to diets. As is true for many other nutrients, women who are breastfeeding a child have an especially high calcium need because they export calcium in their breast milk to help grow the bones of a developing infant.

Iron

Iron is most important as an ingredient in hemoglobin that causes the red color of blood, and the role of red blood cells in carrying oxygen. Iron deficiency thus leads to anemia from a lack of red blood cells, including shortness of breath and overall weakness. Women require more iron than men because of blood loss in menstruation, and pregnant and lactating women require especially high amounts of iron as they expand their blood supply and provide for a growing fetus. During lactation or breastfeeding, mothers pass substantial amounts of iron to their growing infants, so that iron need for women is also high during the period when mothers are nursing their children. When shortage arises during pregnancy or lactation, a woman’s iron stores tend to be sacrificed to the benefit of the child, which can leave a mother who lacks adequate food due to poverty with acute iron deficiency and anemia that greatly complicates other daily activities such as economically important work. The best sources of iron in foods are meat, fish, eggs, green leafy vegetables, and whole grains. Cooking food cast iron utensils is also an easy way to supplement iron in food.

Zinc

Zinc is an essential mineral that is important in a large number of human cellular enzyme processes. It is important for proper tissue growth, cell division, wound healing, and the functioning of the immune system, among other functions. As such it is very important for children’s health, growth, and development. Zinc is an example of a nutrient that is often used to fortify processed foods and is also naturally present in a wide variety of foods such as red meat, poultry, beans, nuts, and whole grains. One goal of plant breeders recently has been to breed or identify traditional varieties of whole grains and potatoes that are high in zinc and iron. This way of enhancing diets by way of the properties of crop plants is called a biofortification strategy. Because these staple foods are usually present even in the most rudimentary diets associated with extreme poverty, biofortification can be an effective strategy to ease access to these important mineral nutrients in the most vulnerable populations.

Vitamin A

Vitamin A or retinol (linked to the word ‘retina’ or part of the eye) is famous for the popularized connection between eating carrots and good eyesight. Vitamin A deficiency is the cause of reduced vision in dim light, called night blindness, as well as a broad correlation to increased infant mortality in children from a variety of causes. True vitamin A is not in fact directly present in carrots and other dark green or pigmented vegetables (collards, squash, sweet potatoes, tomatoes, and even yellow maize) but is readily synthesized in the body from the orange pigment (beta-carotene) that these plant sources contain. True retinol is found in eggs as well as meat and fish products. Like zinc, vitamin A is another crucial nutrient for growth and development that can become deficient in the diets of children and other vulnerable groups (Figure 3.1.2), and has been targeted as a priority for resource-poor populations around the world through the promotion of orange-fleshed sweet potato, other orange vegetables, and yellow maize within smallholder diets and "golden rice" as a genetically engineered innovation in maize varieties that was developed to address vitamin A deficiency. While not all biofortification approaches utilize genetic engineering, golden rice is a further example of a biofortification strategy.

Figure 3.1.2. Prevalence of Vitamin A deficiency around the world, with colors indicating the percentage of children affected. Many of the areas with "no data" are in fact areas where per-capita incomes are high enough that consumers are assumed to be eating enough animal products and vitamin-A-containing vegetables to avoid deficiency. The map shows that prevalence rates in Mexico, Africa, South Asia, East Asia, and the Pacific are highest, reaching up to 80 percent. The rates of deficiency in China, Central America, and South America reach up to 20 percent.

Credit: Steven Vanek, based on data from Bassett & Winter-Nelson, 2010, Atlas of Human Nutrition

Vitamin C

Vitamin C is not a major deficiency challenge worldwide, though in the 1700s vitamin C deficiency was linked to the disorder scurvy in sailors due to highly monotonous diets. Rather it is presented here because of its iconic association with fresh fruits and vegetables, especially citrus fruit but also potatoes, bananas, spinach, collards, cabbage, and many of the weeds that are consumed around the world as leafy vegetables. True deficiency is thus uncommon in most diets around the world, though vitamin C’s role as an antioxidant and health-promoting vitamin that “cleans up” harmful free radicals in the body has been promoted. Also, vitamin C is an excellent example of a positive interaction between nutrients. Vitamin C promotes iron absorption. Since most plant sources of iron are much less available than so-called heme iron in animal iron sources, fruits and vegetables with vitamin C in the same meal with plant-based sources of iron are an excellent way for people that eat meat-free diets (or just individual meals without meat) to absorb sufficient iron.

A number of other vitamins and minerals are essential, and in general, the way that a food system can work to provide these to human populations is to make a wide variety of plant-based foods as well as a few meat options, available to consumers. As we will see soon, this is in contrast to what certain sectors of the food system often make available to consumers. Some of these important vitamins and minerals are Vitamin C, Vitamin D, the B-complex vitamins, potassium, and magnesium, and you may see these arise as concerns in the formative assessment below.

A complete description of vitamins, minerals, and other diet components in an accessible format can be found in the online book from the FAO, Human Nutrition in the Developing World.

You may be familiar with the idea that fats are perhaps "delicious yet harmful" for most humans, and to be consumed in moderation (see the balanced plate in figure 3.1.1). Recently there has been increased attention focused on the role that “good fats” play in health and development, in addition to the awareness that most diets in more affluent areas of the world contain excessive fat, especially saturated fats of animal origin. Unsaturated fatty acids of plant origin are generally considered essential healthy nutrients, and there is evidence that fatty acids derived from plant sources and fish are important in promoting better neural development and nerve function. For consumers that tend to face food-insecure conditions, also, fats are a highly concentrated energy (calorie) source and therefore a valuable addition to a diet. Where calories are already in excess such as in many urban diets around the world and particularly in the industrialized first world, the calorie content is not a benefit of high-fat diets. Recently it has been found that excessively processed or hydrogenated fats often included in processed foods (trans-fats) are harmful to health, and so labeling now specifies the trans-fat content of foods. For example, you can find the trans-fat content of diets in the diet tool used with this module's formative assessment.

Fat in foods as a case study of shifting paradigms in nutrition

(this section is adapted from a contribution by Human Geographer Mark Blumler at Binghamton University)

Most of us have probably absorbed the current overall thinking that fat in diets needs to be treated with caution, that it is synonymous with "divine" or "sinful" food in a joking way, or perhaps that there is something suspect about fat. Because of evolving in limited nutrition environments, most humans are primed to take in fats and other high-calorie foods as a nutritional bonanza and store it away in an evolutionarily "thrifty" way to confront future calorie shortage. However, western nutrition scientists’ beliefs regarding different types of fat in diets have undergone drastic fluctuations over the past century (Table 3.1) that may potentially shake our confidence in exactly what is known about "good" and "bad" in nutritional terms. The advice coming out of the nutritional science community, as filtered through government proclamations such as the food pyramid, have also caused enormous changes in the American diet, which have benefited some such as the vegetable oil processing industry, while hurting others such as cattle ranchers and the beef lobby.

To recap this sometimes bewildering history: around the 1960s, scientists discovered a relationship between cholesterol and cardiovascular disease and noticed that saturated fats have more cholesterol than other oils. Consequently, there was a big push to replace butter with margarine and to cut back on the consumption of red meats, lard, and other animal fats. Initially, it was believed that polyunsaturated fats such as safflower oil are most heart-healthy and so there was a major promotion of such oils. Later, interest developed in the “Mediterranean diet” because of the presence of many very old people in Mediterranean Europe, and nutritionists came to believe that monounsaturated fats such as in olive oil were best for us. Polyunsaturated oils, on the other hand, were increasingly shown to be not beneficial. Meanwhile, further research showed that cholesterol in the blood does not correlate with cholesterol in the diet, undermining the assumption that saturated fats are unhealthy. Trans fats, high in margarine and other processed fatty foods, were shown to be very inimical to heart health. Also, fish oils were recognized as being high in omega 3 fatty acids, which are deficient in the typical American diet today. Recently, butter has been officially accepted as “good” fat, reversing a half-century of denigration of its nutritional value. While other saturated fats are not yet accepted, there is nothing to distinguish butter from the others that would explain how it could be “good” and the others “bad”.

It is interesting to compare these shifting attitudes against traditional diets: The Japanese have the longest life span of any nation. Within Japan, the longest-lived are Okinawans. On Okinawa the only fat used for cooking is lard (of course, being on an island Okinawans also consume considerable fish oil although they do not cook with it). So, what is going on here? Why can science and scientists not "make up their minds" about fat in diets? Are findings on diet overly influenced by lobbying groups of major food industries, as some have charged for the case of margarine or dairy fats?

The story of fat recommendations illustrates the nature of science, that it proceeds piece by piece, and also seems to have a penchant for identifying single causes that are later shown in the context of a complex system to be overly simplistic. Each research finding, such as that cholesterol is associated with cardiovascular disease, may have been correct. But that gave rise to recommendations that were wrong, because other facts, such as that dietary cholesterol does not correlate with blood cholesterol, were not yet known. Given that many of us would like to eat healthy diets and may also believe that science should guide better nutritional policy, there is a need for principles that emerge from current science to inform dietary recommendations, rather than the confusion that is perhaps caused by this tangled story about the history fats in nutrition. In the summary below, we try to provide some ballpark recommendations regarding fats, other dietary constituents, and lifestyle choices. They summarize many of the same principles from the "balanced plate" at the beginning of this module or the "healthy plate" from the USDA and other nutritional recommendations of government organizations.

Summary: Fat consumption within a healthy diet and lifestyle

• Diets very high in fat in the absence of fiber and sufficient fruits, vegetables, and whole grains are probably not very healthy within the range of choices of modern consumers.
• Eliminating fats in favor of simple (i.e. non-whole grain) carbohydrates to promote "low-fat dieting approaches" was probably a bad idea.
• Plant-based fats and fish oils, on the whole, seem to contain more health-promoting properties than exclusive reliance on animal-based fat. However, some recent large studies have shown little significant correlation between saturated fat consumption (like those found in meats) and chronic diseases like heart disease, although these diseases are definitely thought of as diet-linked.
• Whole grains of many different types are good, as is a preponderance of fruits and vegetables in the diet.
• Much of this seems to be leading us back towards the principles of more traditional unprocessed food diets without a preponderance of meat (which has benefits for the water use related to a diet as well, as you will see next in module 4 regarding water and food).
• Lifestyles should encompass diet and exercise, but this exercise does not need to be high-intensity for it to have a really positive effect on well-being and health.
• Pay attention to upcoming research and advice from research communities regarding diet, but resist taking them to extremes unless there is robust evidence over the long term, and place them in the context of more traditional knowledge and the other principles we've addressed in this module.

The Importance of Fiber Overall and for the Gut Microbiome

In addition to these nutrients that contribute to particular functions within the human body, fiber is the mostly undigestible component of food that moves through the human digestive tract but also provides remarkable benefits. Undigestible cell wall components of plant foods (fruit membranes, bean and grain seed hulls, most of the plant cell wall, etc.) are examples of dietary fiber. In addition to its famous role in avoiding constipation by moving masses of foodstuffs through the digestive tract as a bulking agent, fiber helps to feed beneficial gut bacteria that produce beneficial substances. Over the last few decades fiber consumption associated with the benefits of avoiding certain cancers, heart disease, and diabetes. Emerging knowledge regarding fiber highlights the role played by the gut microbiome --many billions of non-human cells that inhabit our digestive tract in promoting human health and avoiding disease. These cells are more in number than the human cells in our body, due to the small size of bacteria compared to human cells. Much like the other areas of nutrition described here, the importance of fiber links directly to the importance of eating a varied diet with whole grains, legumes, fruits, and vegetables. It is interesting to view fiber and these microbes not as a direct nutrient for human life processes, but as a "helper nutrient" or "catalyst" for human nutrition. Dietary fiber is relatively inert as a source of protein, minerals, or vitamins, but helps our digestive system do its job.

Food insecurity, or the inability to access sufficient, culturally appropriate food for adequate nutrition, is a major problem for the poorest segments of the world’s population, the 1 billion or so people who live on less than two dollars per day (Food Security and Insecurity are more fully addressed in module 11). These poorest members of society often face chronic malnutrition, which some call undernutrition to distinguish it from nutrition diseases of overconsumption or poor food choices, which are considered malnutrition of a different type. Undernutrition is sometimes coupled with nutrition-related illnesses and long work hours in paid employment or smallholder agriculture on small and/or degraded land bases that often accompany poorer farms in rural areas. Undernutrition represents a failure of human societies and food systems to create access to a minimum standard of diet quality that can allow all human beings to live to their potential. In addition, the difficulty posed by undernutrition may fall disproportionately on the most vulnerable members of society: women, children, and the disabled and elderly. A particular burden is faced by caregivers of children (women, and increasingly grandparents) to both provide adequate care and feeding and take on the role of earning money to farm or buy food.

Organizations who work with these populations have worked to identify barriers to better care and feeding practices because it has been recognized that if the allocation of food within households is not equitable, simply increasing farm production or access to food can sometimes fail to increase consumption of healthy foods by vulnerable groups in households. Increasing the direct involvement and knowledge of parents and other caregivers in nutrition practices, and focusing attention on children under five years of age can help to improve nutrition outcomes and child growth in many poor households. These aspects of care, feeding, nutrition, and harmonization with local culture are important parts of food security referred to as the utilization component (this will be further addressed in module 11.2). As an example of the sort of trade-off that can occur between agricultural and nutrition goals in improving livelihoods, agricultural methods that are introduced to improve soil quality or increase agricultural income can be labor-intensive and must take care not to place undue additional time burdens on caregivers, who may then neglect the care and nutrition needs of children.

The challenges of chronic malnutrition are often linked in rural food-producing households to small land bases and/or degraded soils, which is of concern to us because it is a highly problematic case that links human system factors in the form of poverty, and natural system factors in the form of the degradation of earth's ecosystems. As will be described further in module 10.2, the coupling of malnutrition and soil degradation can form a ‘poverty trap’ for rural households, where unproductive soils demand large amounts of labor for small yields, with limited alternative options for food production or employment because of inequality -- or lack of social sustainability -- in the local and global human system. In this way, degraded soils have particular bearing on malnutrition because of the additional work and expenditure of calories required to coax yields from degraded land, which both deepens issues of food deficit and malnutrition, and can translate to expansion of the land area under degrading practices, or contribute to continued production at the lowest level that soil will allow. These factors can trap households in poverty. Such a situation can also translate into the migration of a smallholder household in search of more lucrative activities, which often means a dramatic change in diet towards more urban and processed foods, even if it changes the overall income possibilities of a family and can be considered as an adaptive response to food shortage and vulnerability.

A second major issue facing modern food systems is chronic diet-related disease that results from calorie overconsumption, often linked to increasing rates of obesity in societies around the world. The major chronic conditions related to calorie overconsumption are heart disease and type II or “old-age” (later onset) diabetes (see Fig. 3.2.1 for a global map of diabetes incidence). These have been called “diseases of affluence” because they tend to increase in prevalence as countries increase in material wealth, with a combined increase in meat and calorie availability along with more sedentary jobs and lifestyles.

Figure 3.2.1. Percent of the population affected by diabetes by country, including Type II or old-age onset diabetes. Note that diabetes is more common in middle and high-income countries. It is, however, increasing in developing countries as diets change with increasing incomes and urbanization. The map shows that North America, most of South America, Europe, Northern, and Western Asia, and Australia, have incidences of diabetes of at least 5% and up to more than 10%. Whereas, most of Africa, Central Asia, Southeast Asia, and the Pacific have incidences of 2.5% or less.

Credit: Steven Vanek, based on data in Millstone and Lang 2013, The Atlas of Food.

The dominant role of the globalized, corporate food system in these societies (see module 10.1 for the typology of food systems) means that processed foods (e.g. mass-produced “non-food” snacks and sweetened beverages, prepared frozen meals, fast food, pasta) occupy a larger and large part of the diet of typical consumers in these societies. To save cost and maintain demand, processed fats, sugar, and salt, are used as low-cost ingredients in these foods (e.g. corn syrup, oil by-product from the cattle and cotton industries) As has been described by food writers such as Michael Pollan, the prevalence of these diet choices means that consumers eat a large proportion of “empty calories” without fiber, high-quality fats, sufficient vitamins, and minerals, or in some cases adequate protein. Although high-calorie and fatty restaurant foods have been common for generations, at a whole food system level the prevalence of these foods, and the way they have been normalized in such concepts as “the American diet” (which upwardly mobile consumers in many other countries aspire to) are of great concern because they provide a dominant range of food choices that are not consistent with human health. This is especially so as consumers become more urban and many (though not all) expend fewer calories in manual labor related to farming. The increased prevalence of calorie excess has produced increasing rates of obesity in North America and Europe. (Fig. 3.2.2 below)

Figure 3.2.2. The prevalence of obesity in the United States at the county level. The map shows that the prevalence of obesity in the U.S. is highest in Alaska and the southern and southeastern states. It is the lowest in the western states.

Credit: Max Masnick based on U.S. Centers for Disease Control data, 2008. Used with permission as a public-domain image.

The “double burden”: chronic diseases in poor economies: Moreover, the term “diseases of affluence” is misleading because it is, in fact, poor people in industrialized countries as well as the developing world that face the greatest impact of these diseases. Empty calories are often very cheap calories for poorer sectors around the world, so the consumption of processed or dominantly carbohydrate diets with insufficient whole grains, fruits, and vegetables is more common among the poor. In addition, poorer households often are less able to pay for the expensive consequences of these diseases in the middle-aged and elderly (e.g. insulin provision for diabetics, the consequences of heart attack and stroke in the elderly). Ironically the same poorer sectors in poorer parts of the world and even within the United States can simultaneously face the issues of “traditional malnutrition” (i.e undernutrition, insufficient consumption of vitamins, iron, zinc, calories), especially among children and women, as well as diseases of overconsumption of empty calories. This ironic pairing of food system dysfunction has been called the “double burden” on developing countries by food policy experts. It also acts, at a national level, to reduce the overall income of a country by impairing the productivity of its human population (Figure 3.2.3, below).

Figure 3.2.3. The economic impact of chronic diseases around the world estimated as the total income sacrificed by different countries between 2005 and 2015 to impaired productivity and costs to populations and government from chronic diseases like diabetes, heart disease, and conditions resulting from stroke.

Click for a text description of the economic impact of chronic diseases image

The image is a bar chart illustrating foregone total national income (in billion dollars) across several countries, likely due to chronic diseases or related economic impacts. The horizontal axis lists the countries: Brazil, Canada, China, India, Nigeria, Pakistan, Russian Federation, United Kingdom, and Tanzania. The vertical axis represents income loss in billions of dollars, ranging from 0 to 600. Each country has a vertical orange bar indicating its estimated foregone income. China shows the highest value, approaching 550 billion dollars, followed by the Russian Federation at around 300 billion dollars and India at approximately 225 billion dollars. Other countries, including Brazil, Canada, Pakistan, United Kingdom, and Nigeria, display much smaller losses, generally below 50 billion dollars, while Tanzania has the lowest value, close to zero. The chart visually emphasizes the disproportionate economic burden among nations, with China experiencing the most significant impact compared to others.

Credit: Steven Vanek, adapted from data in World Health Organization (WHO), 2005, Rethinking "Diseases of Affluence": the Economic Impact of Chronic Disease

Food deserts: Within industrialized countries, food system analysts have noted that the marketing model of the globalized food system has focused on suburban supermarkets that are able to capture profits from middle and high-income consumers. This model is profitable for food distribution companies but has the effect of not adequately serving either inner-city poor populations and the rural poor, who face difficulties in physically getting to distant supermarkets. Fast food and high-priced, smaller food markets with a preponderance of processed and unhealthy foods are the only food options in many poorer parts of the United States and other industrialized countries. These areas of low food access for healthy, reasonably priced foods are called food deserts. You will explore these more with a mapping tool in the summative assessment for this module.

Although the modern globalized food system is highly dynamic and able to move enormous quantities of food and generate economic activity at a huge scale in response to global demand, the issues of poor diets, malnutrition and constrained food access we have described here are sobering issues that human societies need to confront. From the earliest days of civilization, food has been at once (1) a fundamental human requirement and human right; (2)a source of livelihood and a business as well as (3) the common property of cultures and ethnicities. The rise of a globalized food system, however, has brought new patterns into play because food has become an increasingly fiscalized commodity and experience.“Fiscalized” means that the provision of a fast food item, a food service delivery to a restaurant, or a supermarket buying experience (vs. a traditional regional open-air market, for example) are increasingly not only interactions among farmers, truckers, shopkeepers, and consuming households. Instead, the activities of production, distribution, and consumption within food systems become more and more integrated into the trade and investment patterns of the global economy. Food production, trade, and sales have been absorbed into the purview of profit-driven corporations that seek maximum value for stockholders. These stockholders are in turn citizens, organizations, and even governments that also participate by profiting from the functioning of the global system, demonstrating the involvement of common citizens in this system as well. Food activists, policymakers, and advocates of concepts like “agriculture of the middle” (see module 10.1) have argued that this new corporate character of the food system increasingly creates a food system that has an incentive to ignore important values like food access equity, just treatment of producers and workers, healthy diets, and environmental sustainability as the elements of the three "legs" of sustainability (see Module 1). However, reform movements within the globalized food system also demonstrate that it is able to pay attention to human nutrition goals and environmental sustainability.

In fact, the food system is not a completely unfettered capitalist enterprise.& Examining any food packaging shows the degree to which food is subject to regulation and oversight by the government. Food safety scares and health inspections of restaurants show the close attention paid to the acute impact (if not always the chronic impact over time) of unhealthy food. Education efforts promoting healthy choices in diet and exercise are regularly heard from both government organizations and private advocacy organizations: for example, state cooperative extension agencies, universities, and public service announcements. The efforts to label calories on restaurant menus and the movement of food service companies and local restaurants towards healthy options in menus show the growing awareness and movement of food demand towards healthy options. And many supermarket chains are making substantial efforts to include more local and regionally produced foods and promote healthy diets and nutrition as part of the communication to consumers.

In part, these changes show the changing awareness of the problems in the modern “American diet” among the public, brought on by food activists and authors about the food system. And on-the-ground marketing initiatives for values-based value chains such as those promoted by local and regional food system advocates include improving access to healthier foods like whole grains, fruits, and vegetables. For middle- and higher-income consumers with access to the abundance of foods in typical supermarkets and farmer’s markets around the world, this can incentivize better choices about well-rounded diets. In many cases, these healthier diets also include less reliance on meat because of its water footprint and adverse impacts on health when eaten in excess. One essential question, however, is how these efforts to improve food choices and access can expand their reach to poorer consumers and those who live in food deserts, either by improving geographic access, low-cost alternatives, or income opportunities to these consumers. You’ll explore this question of food equity more in the summative assessment for this module, regarding food deserts and examples of organizations in your capstone regions that are promoting healthy food choices and production.

At the end of module 2, you read about alternative food systems and the relocalization of food production and distribution as one of the emerging future proposals in the history of food. These efforts, which will be revisited in a typology of current food systems in module 10, are an important source of ideas and initiatives to increase sustainable food production methods and equitable relations between consumers and producers. Local and regional food systems and initiatives have been promoted as ways to retain economic benefits and jobs within regional contexts. Organic and sustainable production methods often form a part of these movements and seek to reduce the environmental impacts of food production. Organic food is, in fact, a documented way to reduce exposure to pesticide residues in foods, which is of concern to many consumers. Food such as fruits and vegetables, which is fresher when it is consumed, which can be the case for locally produced food, is also likely to have a greater content of vitamins and other health-promoting components. However, others have pointed out that at a global level, the optimal freshness of produce, or a complete absence of pesticides, can be of smaller benefit to health in the overall food supply than would be, say, orienting diets away from processed fats or towards greater vegetable consumption or plant-based oils. This more incremental approach suggests that it is important to target low-hanging fruit like availability of lower-cost vegetables and higher-fiber diets to more of the worlds' population, rather than just playing up potential benefits from foods that are local or produced with fewer or no pesticides. It is also important to point out that there can be much confusion among consumers on whether all organic food is locally produced (it's not) or whether local food is always organically produced (also not true).

In summary, given the much smaller size of these local and alternative food initiatives in comparison to the global food system, and also the scale of the problems of malnutrition and unhealthy diets, it may be important to put potential benefits of local and/or organically produced foods in the context of the overall challenges of the food system. For example, in the case of an urban food desert where only low dietary quality processed foods are available, increasing the availability of vegetables, fruits, and whole grains consumed using a number of strategies may be a more viable food system strategy to pursue than promoting locally or organically produced foods as a sole strategy. These multiple strategies could, in fact, rely on greater supermarket access and food streams from the globalized food system along with seasonal access to farmers' markets for local produce. Home and community gardens can also complement and reinforce strategies for healthy eating. In addition, organizations of farmers using organic and other more sustainable methods have often acted as important allies in local food system settings for promoting healthier diets. As we will see throughout this course, the nutrition and sustainability outcomes emerging from the interacting parts of the food system are complex, and we can't always go with a single alternative to provide the best outcomes.

Required Video: Putting local alternative food systems in context

Please view this short video from the "Feeding the nine billion" project of Professor Evan Fraser at the University of Guelph. He argues for the importance of local, alternative food systems but also acknowledges the issues of scale that make global food systems an important aspect of diet and nutrition for the foreseeable future. This is not just about nutrition -- he is also reviewing many of the themes of food and sustainability we will be covering in the course and the relationships between human and natural systems as part of feeding humanity.

Video: Feeding Nine Billion Video 5: Local Food Systems by Dr. Evan Fraser (5:19)

By now you may be forming the correct impression that a better diet and nutrition around the world is a matter of finding a “happy medium” for consumers between food shortage on the one hand, and excessive consumption of unhealthy foods on the other hand. That is, consumers in poorer sectors and societies eat too little fruits, vegetables, high-quality fats and proteins and in the worst case even insufficient calories. Meanwhile, wealthier consumers and even some of the urban poor eat excessive quantities of low-quality calories and fats in relation to relatively sedentary lifestyles. The results are serious chronic malnutrition (undernutrition and nutrient deficiencies, specifically) at one end of the diet spectrum and chronic diseases such as heart disease and diabetes at the overconsumption end of the same spectrum. In addition, a high-meat diet and millions of acres in crops to feed beef cattle and pigs creates a water-consuming and polluting food sector of the economy to support these diets, as seen in previous modules. Therefore, increasingly there has been a movement to unite concerns about the environmental impacts of food with the problematic diet and nutrition outcomes from modern high meat and processed food diets. The reading below from food columnist Michael Pollan addresses these principles for a happy medium in diets.

One example of a "happy medium": the demitarian diet concept

In order to address the need for this "happy medium", a number of scientists and activists globally have enunciated the interesting principle of the demitarian diet¹, in which consumers commit to reducing their consumption of meat products, short of adopting vegan and vegetarian diets. The prefix demi- comes from French for “half” and reflects the principle that consumers in high-income societies and sectors need to at least halve their consumption of meats, to produce better health and environmental impacts, especially the impacts on nitrogen pollution and greenhouse gases from fossil fuels in agriculture (more on this in the following modules). The demitarian diet and its proponents are primarily focused on the environmental sustainability of first-world diets. Nevertheless, we can extend this concept to the third world to say that populations eating diets of poverty will receive benefit from increasing their intake of legumes, fish, meat, vegetables, and other high-quality nutrient sources. Populations at risk from undernutrition may see dramatic positive effects from even slight increases in consumption of these high-quality foods that are often lacking in circumstances of poverty. This is because even small quantities of meat, eggs, and other animal products along with legumes, fruits, and nuts, can be very high-density sources of protein, Iron, Zinc, Vitamin A, and high-quality fats. Because of this nutrient-density, animal protein (e.g. poultry, fish, eggs) as well as legume crops (e.g. bean, pigeon pea), vegetables (e.g. sweet potato, collards, carrots), and fruits (e.g. papaya, mango, avocado) therefore feature prominently in nutrition interventions of government and other organizations.

In order to understand why growing food uses so much water, we need to explore the process of evaporation. Evaporation is a hydrologic process that we're all quite familiar with, even if you aren't aware of it. Think about hanging clothes out to dry on the clothesline, or blow-drying your hair. Both of those involve the movement of water from its liquid form to its vapor or gaseous form that we call water vapor, or in other words, both involve the evaporation of water.

In what weather conditions do your clothes dry faster? A hot, dry, windy day, or a cool, cloudy, rainy day? Why do you use a blow drier to dry your hair? Water evaporates faster if the temperature is higher, the air is dry, and if there's wind. The same is true outside in the natural environment. Evaporation rates are generally higher in hot, dry, and windy climates.

The rate at which water evaporates from any surface, whether from a lake's surface or through the stomata on a plant's leaf, is influenced by climatic and weather conditions, which include the solar radiation, temperature, relative humidity, and wind (and other meteorological factors). Evaporation rates are higher at higher temperatures because as temperature increases, the amount of energy necessary for evaporation decreases. In sunny, warm weather the loss of water by evaporation is greater than in cloudy and cool weather. Humidity, or water vapor content of the air, also has an effect on evaporation. The lower the relative humidity, the drier the air, and the higher the evaporation rate. The more humid the air, the closer the air is to saturation, and less evaporation can occur. Also, warm air can “hold” a higher concentration of water vapor, so you can think of there being more room for more water vapor to be stored in warmer air than in colder air. Wind moving over a water or land surface can also carry away water vapor, essentially drying the air, which leads to increased evaporation rates. So, sunny, hot, dry, windy conditions produce higher evaporation rates. We will see that the same factors - temperature, humidity, and wind - will affect how much water plants use, which contributes to how much water we use to produce our food!

Evaporation requires a lot of energy and that energy is provided by solar radiation. The maps below (Figure 4.1.1) illustrate the spatial patterns of solar radiation and of annual evaporation rates in the United States. Notice how the amount of solar radiation available for evaporation varies across the US. Solar radiation also varies with the season and weather conditions. Note that annual evaporation rates are given in inches per year. For example, Denver, Colorado in the lake evaporation map is right on the line between the 30-40 inches and 40-50 inches per year of lake evaporation, so let's say 40 inches per year. On average, if you had a swimming pool in Denver, and you never added water and it didn't rain into your pool, the water level in your pool would drop by 40 inches in a year. Explore the maps and answer the questions below.

Text description of the Figure 4.1.1a image.

The image is a color-coded map of the United States, including insets for Hawaii, Alaska, and Puerto Rico, showing daily solar radiation in langleys. The main map uses a gradient of colors from light yellow to dark red to represent increasing solar radiation levels. The legend on the right explains the ranges: 230–250, 250–300, 300–350, 350–400, 400–450, 450–500, and 500–550 langleys. The lightest shades, indicating the lowest solar radiation (230–250), appear in the northern states such as Washington, Montana, and the upper Midwest. Darker shades, representing higher solar radiation (500–550), dominate the southwestern U.S., particularly Arizona, New Mexico, and southern Nevada. The Southeast, including Florida and Texas, shows moderately high values (400–500). Hawaii and Puerto Rico are shaded in dark red, indicating very high solar radiation, while Alaska shows mostly light colors, reflecting low solar radiation levels. The map emphasizes regional variation in solar energy potential, with the Southwest and tropical territories receiving the most sunlight compared to northern and coastal regions.

Credit: Data from U.S. Department of Commerce, 1968). From Hanson 1991.

Text description of the Figure 4.1.1b image.

The image is a color-coded map of the United States showing annual lake evaporation in inches. The map uses a gradient of colors to represent different evaporation ranges, as explained in the legend on the right: 10–20 inches (dark blue), 20–30 (medium blue), 30–40 (light blue), 40–50 (yellow), 50–60 (light orange), 60–70 (orange), 70–80 (red-orange), and 80+ inches (dark red). The northern and northeastern states, as well as much of the Midwest and Pacific Northwest, are shaded in blue tones, indicating low evaporation rates between 10 and 40 inches annually. Central regions, including parts of the Great Plains, show yellow and light orange areas, representing moderate evaporation of 40–60 inches. The southwestern U.S., particularly Nevada, Arizona, and southern California, is shaded in red and dark red, signifying the highest evaporation rates exceeding 80 inches per year. This pattern reflects the influence of climate and geography, with arid regions experiencing significantly higher evaporation compared to cooler, wetter areas in the north and east.

Credit: Data from U.S. Department of Commerce, 1968). From Hanson 1991.

Why do we need so much water for agriculture? Plants use a lot of water!

Plants need water to grow! Plants are about 80-95% water and need water for multiple reasons as they grow including for photosynthesis, for cooling, and to transport minerals and nutrients from the soil and into the plant.

"We can grow food without fossil fuels, but we cannot grow food without water."
 

We can't grow plants, including fruits, vegetables, and grains, without water. Plants provide food for both us and for the animals we eat. So, we also can't grow cows, chickens, or pigs without water. Water is essential to growing corn as well as cows!

Agriculture is the world's greatest consumer of our water resources. Globally about 70% of human water use is for irrigation of crops. In arid regions, irrigation can comprise more than 80% of a region's water consumption.

The movement of water from the soil into a plant's roots and through the plant is driven by an evaporative process called transpiration. Transpiration is just the evaporation of water through tiny holes in a plant's leaves called stomata. Transpiration is a very important process in the growth and development of a plant.

Water is an essential input into the photosynthesis reaction (Figure 4.1.2), which converts sunlight, carbon dioxide, and water into carbohydrates that we and other animals can eat for energy. Also, as the water vapor moves out of the plant's stomata via transpiration (Figure 4.1.2), carbon dioxide can enter the plant. The transpiration of water vapor out of the open stomata allows carbon dioxide (another essential component of photosynthesis) to move into the plant. Transpiration also cools the plant and creates an upward movement of water through the plant. The figure below (Figure 4.1.2) shows the photosynthesis reaction and the movement of water out of the plant's stomata via transpiration.

As water transpires or evaporates through the plant's stomata, water is pumped up from the soil through the roots and into the plant. That water carries with it, minerals and nutrients from the soil that are essential for plant growth. We'll talk quite a bit more about nutrients later in this module and future modules.

Figure 4.1.2 Photosynthesis and transpiration

Click for a text description of the photosynthesis and transpiration image

This drawing shows the sunlight shining down on a flower. The roots of the flower are in the soil and there is water in the soil. Carbon dioxide is going into the flower. Water vapor and oxygen are being released from the flower (Transpiration). The chemical formula for photosynthesis is shown as 6 CO₂ (Carbon Dioxide) + 6 H₂O (Water) an arrow representing light leads to C₆H₁₂O₆ (Sugar) + 6 O₂ (Oxygen).

Credit: Wikimedia Commons: Photosynthesis (Creative Commons CC BY-SA 3.0)

How much water does a crop need?

The amount of water that a crop uses includes the water that is transpired by the plant and the water that is stored in the tissue of the plant from the process of photosynthesis. The water stored in the plant's tissue is a tiny fraction (<5%) of the total amount of water used by the plant. So, the water use of a crop is considered to be equal to the water transpired or evaporated by the plant.

Since a majority of the water used by the crop is the water that is transpired by the plant, we measure the water use of a plant or crop as the rate of evapotranspiration or ET, which is the process by which liquid water moves from the soil or plants to vapor form in the atmosphere. ET is comprised of two evaporative processes, as illustrated in figure 4.1.3 below: evaporation of water from soil and transpiration of water from plants' leaves. ET is an important part of the hydrologic cycle as it is the pathway by which water moves from the earth's surface into the atmosphere.

Remember, evaporation rates are affected by solar radiation, temperature, relative humidity, and the wind. ET, which includes evaporation from soils and transpiration from plants, is also evaporative, so the ET rate is also affected by solar radiation, temperature, relative humidity, and the wind. This tells us that crop water use will also be affected by solar radiation, temperature, relative humidity, and the wind! More water evaporates from plants and soils in conditions of higher air temperature, low humidity, strong solar energy, and strong wind speeds.

The transpiration portion of ET gets a little more complicated because the structure, age, and health of the plant, as well as other plant factors, can also affect the rate of transpiration. For example, desert plants are adapted to transpire at slower rates than plants adapted for more humid environments. Some desert plants keep their stomata closed during the day to reduce transpiration during the heat of a dry desert day. Plant adaptations to conserve moisture include wilting to reduce transpiration. Also, small leaves, silvery reflective leaves, and hairy leaves all reduce transpiration by reducing evaporation.

In summary, the amount of water that a crop needs is measured by the ET rate of a crop. The ET rate includes water that is transpired or evaporated through the plant. And, the ET rate varies depending on climatic conditions, plant characteristics, and soil conditions.

Figure 4.1.3. Evapotranspiration includes evaporation from soil and transpiration from leaves.

Click for a text description of the evapotranspiration image

Diagram of Evapotranspiration. At the bottom is soil and below that, available soil water. In the soil are two plants with roots extending into the soil water. There are lines coming up from the soil representing evaporation from the soil. Lines from the plants represent transpiration from leaves. There is a line drawn around all of this, with the sun outside and humidity and temperature flowing in. An arrow from transpiration and evaporation leads to evapotranspiration.

Credit: Figure drawn by Gigi Richard, adapted from Bates, R.L. & J.A.Jackson, Glossary of Geology, Second Edition, American Geology Institute, 1980

Crop water use varies

If the ET rate of a crop determines the water use of that crop, we could expect water use of a single crop to vary in similar spatial patterns to evaporation rates. For example, if evaporation rates are very high in Arizona because of the hot, dry climate, you would expect ET rates to be higher for a given crop in that climate. ET is measured by the average depth of water that the crop uses, which is a function of the plant and of the weather conditions in the area. In cool, wet conditions, the plant will require less water, but under hot, dry conditions, the same plant will require more water.

Figure 4.1.4 shows a range of typical water use for crops in California. The graph shows how much water needs to be applied as irrigation to grow different crops. Notice how some crops, like alfalfa, almonds, pistachios, rice, and pasture grass can require four feet or more of water application. Other crops, like grapes, beans, and grains only require about one to two feet of water.

If we moved the plants in Figure 4.1.4 to a cooler and more humid climate, the rate of evaporation would be less and the crop water demand would decline as well. In a hot dry climate, you need to apply more water to the plant to keep it healthy and growing because more water is evaporating from both the soil and through the stomata on the plants’ leaves, so the plant is pulling more water out of the soil via its roots to replace the water transpiring from its leaves.

Figure 4.1.4. Water use of California crops, as measured by water application depth. Note: The range shown reflects the first and third quartile of the water application depth for the period 1998-2010, and the white line within that range reflects the median application depth during that period.

Credit: California Agricultural Water Use: Key Background Information, by Heather Cooley, Pacific Institute.

Where do plants get their water?

The source of water for most land plants is precipitation that infiltrates or soaks into the soil, but precipitation varies dramatically geographically. For example, we know that Florida gets a lot more precipitation per year than Arizona. Figure 4.1.5 below shows the average annual precipitation across the United States and around the globe. Notice on the map of the U.S. that the dark orange colors represent areas that get less than ten inches of precipitation per year. And, the darkest green to blue regions receive more than 100 inches or more than eight feet of precipitation per year!

Climate, including the temperature of a region and the amount of precipitation, plays an important role in determining what types of plants can grow in a particular area. Think about what types of plants you might see in a high water resource region versus a low water resource region. A low resource region with respect to water receives lower precipitation, so would have desert-like vegetation, whereas a higher resource region for water would have lusher native vegetation, such as the forests of the eastern US.

Regions that receive enough precipitation to grow crops without irrigation (i.e., those areas shaded green on the map below) would be considered high resource areas with respect to water. A high-resource region is more likely to be a more resilient food production region. In contrast, a low resource region with respect to water would be regions on the map below in the orange-shaded colors. In these regions, extra effort is needed to provide enough water for crops, such as through the development of an irrigation system.

Compare the crop water use values in Figure 4.1.6 with the average annual precipitation in Figure 4.1.5 and you'll see that there are parts of the US where there isn't enough precipitation to grow many crops. In fact, there is a rough line running down the center of the US at about the 100th meridian that separates regions that get more than about 20 inches of rain per year from regions that get less than 20 inches of rain per year. On the map in Figure 4.1.5, this line is evident between the orange-colored areas and the green-colored areas. Generally, west of the 100th meridian there is insufficient precipitation to grow many crops. If a crop's consumptive water use or ET is greater than the amount of precipitation, then irrigation of the crop is necessary to achieve high yields.

Figure 4.1.5. a) Average annual precipitation in the United States 1961-1990 and b) Mean annual Global Precipitation (1961-1990)

Credit a) USGS: The National Map and b)Terrascope: Rainwater Harvesting

Figure 4.1.6. Water use of California crops, as measured by water application depth. Note: The range shown reflects the first and third quartile of the water application depth for the period 1998-2010, and the white line within that range reflects the median application depth during that period.

Credit: California Agriculture Water Use: Key Background Information by Heather Cooley, Pacific Institute.

How can we grow crops when there is insufficient precipitation?

In regions where precipitation is insufficient to grow crops, farmers turn to other sources of water to irrigate their crops. Irrigation is the artificial application of water to the soil to assist in the growth of agricultural crops and other vegetation in dry areas and during periods of inadequate rainfall. These sources of water can be from either surface or groundwater. Surface water sources include rivers and lakes, and diversion of water from surface water sources often requires dams and networks of irrigation canals, ditches, and pipelines. These diversions structures and the resulting depletion in river flow can have significant impacts on our river systems, which will be covered in the next part of this module. The pumping of water for irrigation from aquifers also has impacts, which are also discussed in the next part of this module.

Water use for irrigation comprised about 80-90 percent of U.S. consumptive water use in 2005, with about three-quarters of the irrigated acreage being in the western-most contiguous states (from USDA Economic Research Service). For example, in the state of Colorado, irrigation comprised 89% of total water withdrawals in 2010 (Figure 4.1.7). Irrigated agriculture is also very important economically, accounting for 55 percent of the total value of crop sales in the US in 2007 (from USDA Economic Research Service). Globally only about 18 percent of cropland is irrigated, but that land produces 40 percent of the world's food and about 50 percent by value (Jones 2010).

Figure 4.1.7. Colorado Total water withdrawals by water-use category

Click for a text description of the Colorado Total water withdrawals image

A pie chart of Colorado total water withdrawals by water-use category in 2010 shows that almost 89% percent of water withdrawals were from irrigation. The remaining percentages are as follows (approximately): 8% public water supply, 1.18% industrial, 1.11% aquaculture, .70% thermoelectric power, .34% domestic fresh, .33% livestock, .26% mining.

Credit: Data from Maupin, M. A., Kenny, J.F., Hutson, S.S., Lovelace, J.K., Barber, N.L., and Linsey, K.S., 2014, Estimated use of water in the United States in 2010: U.S. Geological Survey Circular 1405, 56 pp.

Activate Your Learning

In this activity, you will employ geoscience ways of thinking and skills (spatial thinking and interpretation of the spatial data to characterize specific regions for the geographic facility).

Figure 4.1.1. Mean annual lake evaporation in the conterminous United States, 1946-55.

Credit: Data from U.S. Department of Commerce, 1968. From Hanson 1991.

The amount of water used for irrigation varies depending on the climate and on the crop being grown, and it also depends on the irrigation technique used. Just like in your garden or home landscaping there are more or less efficient sprinklers. In many parts of the world flood or surface, irrigation is still used where water flows across a field and soaks into the soil.

Surface or flood irrigation is the least efficient manner of irrigation. When a field is flooded, more water than is needed by the plant is applied to the field and water evaporates, seeps into the ground, and percolates down to the groundwater, where it can be out of reach of the plant's roots. Another problem with flood irrigation is that the water is not always applied evenly to all plants. Some plants might get too much water, and others get too little. On the other hand, flood irrigation tends to use the least energy of any irrigation system.

Furrow irrigation (Figure 4.1.8) is another type of surface irrigation in which water is directed through gated pipe or siphon tubes into furrows between rows of plants. When using furrow irrigation, water is lost to surface runoff, groundwater, and evaporation, and it can be challenging to get water evenly to an entire field.

Figure 4.1.8. Furrow irrigation of an onion field in the Uncompahgre Valley, CO.

Credits: Perry Cabot

More efficient methods of irrigation include drip irrigation (Figure 4.1.9) sprinklers (such as center pivots, Figure 4.1.10), and micro-spray (Figure 4.1.11) irrigation. All of these methods, while more efficient, also require significant investments in equipment, pipes, infrastructure (e.g., pumps Figure 4.1.9) and energy. In addition to the high cost, some soil types, irrigation networks, field sizes, and crops pose greater challenges to the implementation of more efficient methods of irrigation. For example, in the Grand Valley of western Colorado, the irrigation network is entirely gravity-fed, meaning that farmers can easily flood and furrow irrigate without the use of pumps. In addition, the fields are small and the soils are very clayey, all of which make using center pivots for row crops particularly challenging and expensive. But, in the same valley, the peach orchards have successfully used micro-spray and drip systems. A major advantage of more efficient irrigation in addition to reduced water consumption is that crop yields are often higher because the water can be applied more directly to the plant when water is needed.

Figure 4.1.9. Filtration and pumps for a drip irrigation system for onion and bean crops in the Uncompahgre Valley, CO.

Credit: Gigi Richard

Figure 4.1.10. a) Center pivot sprinkler irrigation on an alfalfa crop in the San Luis Valley, CO and b) a hay crop for cattle feed in the Uncompahgre Valley, CO.

Credit: Gigi Richard

Figure 4.1.11. Micro-spray irrigation at a peach orchard in the Grand Valley, CO.

Credit: Gigi Richard

Activate Your Learning

Table 4.1.1 presents data on the top 15 irrigated states in the United States. You can see how many acres of land are irrigated in each state, and how much water is used for irrigation of both surface water and groundwater. Consider the relationship between the amount of irrigated land in a state, the type of irrigation used and the amount of water used.

An acre-foot is a unit of measure for large volumes of water and is the volume of water required to cover one acre of land to a depth of one foot (325,851 gallons). Imagine a football field, including the end zones, one foot deep in water.

How much water do you eat?

Water is essential to growing food and every bite of food we consume required water to grow, process, and transport. The water necessary to grow, process, and transport food is often referred to as virtual water or embedded water. Virtual water is the entire amount of water required to produce all of the products we use, including our mobile phones and cotton t-shirts. But a global assessment of virtual water reveals that the majority of water that we consume is in the food we eat. If we total up all of the virtual water embedded in everything we use and eat, we can estimate our total water footprint. Water footprints can be used to provide insights into how much water is used every day in all of our activities including producing our food. For example, Figure 4.1.12 shows the amount of water used per person around the globe associated with wheat consumption. When you eat food imported from another region, you are eating the water of that region. The apple from New Zealand, grapes from Chile, and lettuce from California all required water to grow and by consuming those products you’re "eating" that virtual water. The concepts of virtual water and water footprints can be powerful tools for businesses and governments to understand their water-related risks and for planning purposes (water footprint network).

Text description of the Figure 4.1.12 image.

The image is a color-coded world map illustrating total water footprint per capita (m³/year/cap) across different countries. The legend on the left shows seven categories represented by colors: 0–25 (bright yellow), 25–50 (light yellow), 50–100 (orange-yellow), 100–200 (orange), 200–500 (dark orange), 500–1000 (red), and 1000–2500 (dark red). Countries in North America, Europe, Russia, and Australia are shaded in red or dark red, indicating the highest water footprints, often exceeding 500 m³/year per person, with Australia reaching the darkest shade (1000–2500). Many African nations and parts of South Asia are in yellow or light orange, showing lower footprints between 0–100 m³/year per person. South America and parts of East Asia display mixed values, ranging from orange to red. This map highlights stark regional differences in water consumption, with developed nations generally having much higher per capita water footprints compared to developing regions.

Credit: Figure from Hoekstra, A.Y. and M.M. Mekonnen, 2012, The Water Footprint of Humanity, Proceedings of the National Academy of Sciences, vol. 109, no. 9.

Check Your Understanding

Scroll through this infographic explaining virtual water and then answer the questions below.

Instructions

Please download the worksheet below for detailed instructions.

• Download Module 4 Formative Assessment Activity Worksheet

You will perform three activities in this assessment:

1. Watch the video below, Turning water into food, and answer the questions on the worksheet as you watch the video
2. Visit the water footprint calculator website, compare how your water footprint changes with varying levels of meat consumption, and answer questions on the worksheet. This portion of the assessment will be included in the weekly discussion and not included in the assessment quiz.
3. Perform a comparison of the virtual water embedded in different food products and answer questions on the worksheet.

Video: Turning water into food, Bruce Bugbee | TEDxUSU (16:32)

Submitting Your Assignment

Please submit your assignment in Module 4 Formative Assessment in Canvas.

The storage and redistribution of water by dams, diversions, and canals has been a key element in the development of civilizations. Large-scale water control systems, such as on the Nile in Egypt or the Colorado River in the southwestern U.S. make it possible to support large cities and millions of hectares of agricultural land. As the population grows and water diversions increase, serious questions are being raised about the environmental costs of these large water management systems.

Agricultural water withdrawals are placing significant pressure on water resources in water-scarce regions around the globe (Figure 4.2.2). If more than 20 percent of a region's renewable water resources are withdrawn, the region is in a state of water scarcity and the water resources of the region are under substantial pressure. If the withdrawal rises to 40 percent or more, then the situation is considered critical and evidence of stress on the functions of ecosystems becomes apparent. More than 40% of the world's rural population lives in river basins that are physically water-scarce and some regions, such as parts of the Middle East, Northern Africa, and Central Asia, are already withdrawing water in excess of critical thresholds (FAO 2011).

In order to divert water from rivers, diversion structures or dams are usually constructed and create both positive and negative effects on the diverted river system. Dams can provide a multitude of benefits beyond their contribution to storage and diversion for agricultural uses. Dams can contribute to flood control, produce hydroelectric power, and create recreational opportunities on reservoirs. Negative impacts of dams and agricultural diversions include:

• Habitat fragmentation – blocks fish passage
• Reduction in streamflow downstream, which then results in changes in sediment transport, and in floodplain flooding
• Changes in water temperature downstream from a dam
• Evaporation losses from reservoirs in hot, dry climates
• Dislocation of people
• Sedimentation behind dam fills in reservoirs with sediment and reduces their useful lifespan

Figure 4.2.2. Global Distribution of Physical Water Scarcity by Major River Basin (FAO 2011)

Click for a text description of the global distribution of physical water scarcity image

The image is a world map showing the global distribution of water scarcity risk, categorized into three levels: Low (light yellow), Moderate (orange), and High (dark red). Most regions across North America, South America, Europe, and parts of Asia are shaded in light yellow, indicating low water scarcity risk. However, significant areas in North Africa, the Middle East, South Asia (including India and Pakistan), and parts of East Asia are shaded in dark red, representing high water scarcity risk. Moderate-risk areas, shown in orange, include regions in southern Europe, parts of Africa, and sections of South America and Australia. The map highlights that water scarcity is most severe in arid and semi-arid regions, particularly across the Middle East and North Africa, while temperate and tropical regions generally face lower risk. This visualization underscores the uneven global distribution of water stress, with implications for resource management and sustainability planning.

Credit: © FAO 2011 The State of the World's Land and Water Resources for Food and Agriculture (SOLAW)

Where surface water supplies are insufficient, groundwater is often used for irrigation (Figure 4.2.3). Agriculture uses about 70% of the groundwater pumped for human use globally and about 53% of the groundwater pumped in the US (USGS: Groundwater use in the United States). In some parts of the world, groundwater is pumped at a faster rate than natural processes recharge the stored underground water. Groundwater use where pumping exceeds recharge is non-renewable and unsustainable.

Another problem that may occur in some aquifers with excessive groundwater pumping is a compaction of the aquifer and subsidence of the ground surface. When the water is pumped from the pore spaces in the aquifer, the pore spaces compress. The compression of millions of tiny pore spaces in hundreds of meters of aquifer material manifests on the surface as subsidence. The ground elevation actually decreases. Subsidence from groundwater pumping is irreversible and leaves the aquifer in a condition where it cannot be recharged to previous levels.

Our reliance on and depletion of groundwater resources is becoming a global concern as aquifers are being pumped at unsustainable rates in the US (Figure 4.2.4) and all over the world. Enhanced irrigation efficiencies and conservation measures are being implemented when possible to prolong the life of some aquifers. Unfortunately, groundwater is often the water resource that we turn to in times of drought or when other surface-water resources have been depleted. For example, in California during the recent drought, farmers drilled wells and used groundwater to save their crops when surface water resources were not available.

Figure 4.2.3. Groundwater withdrawals, by State, 2005

Click for a text description of the groundwater withdrawals image

This map of the U.S. shows total groundwater withdraws by state, in millions of gallons per day. California has the highest at 20,000 - 60,000. Nebraska follows at 10,000 - 20,000. Texas and Arkansas are 5,000 - 10,000, Mississippi, Florida, Colorado, Kansas, Arizona, Oregon, and Idaho are each 2,000 - 5,000. The rest of the country is 0 - 2000.

Credit: USGS: Groundwater use in the United States

Figure 4.2.4. Map of the United States (excluding Alaska) showing cumulative groundwater depletion, 1900 through 2008, in 40 assessed aquifer systems or subareas. Colors are hatched in the Dakota aquifer where the aquifer overlaps with other aquifers having different values of depletion.

Credit: USGS: Groundwater depletion

Knowledge Check

Runoff from agricultural areas is often not captured in a pipe and discharged into a waterway; rather it reaches streams in a dispersed manner, often via sub-surface pathways, and is referred to as non-point source pollution. In other words, the pollutants do not discharge into a stream or river from a distinct point, such as from a pipe. Agricultural runoff may pick up chemicals or manure that were applied to the crop, carry away exposed soil and the associated organic matter, and leach materials from the soil, such as salts, nutrients or heavy metals like selenium. The application of irrigation water can make some agricultural pollution problems worse. In addition, runoff from animal feeding operations can also contribute to pollution from agricultural activities.

The critical water quality issues linked to agricultural activities include:

• Fertilizers – nutrients (nitrogen and phosphorus)
  • Eutrophication – dead zones
• Pesticides
• Soil erosion
• Animal Feeding Operations
  • Organic matter
  • Nutrients
• Irrigation and return flows
  • Salinity
  • Selenium

Check Your Understanding

Flow Depletion and Salinity

The Colorado River in the southwestern U.S. is an excellent case study of a river that is highly utilized for irrigation and agriculture. A majority of the Colorado River’s drainage basin has an arid or semi-arid climate and receives less than 20 inches of rain per year (Figure 4.2.5), and yet the Colorado River provides water for nearly 40 million people (including the cities of Los Angeles, San Diego, Phoenix, Las Vegas, and Denver) and irrigates 2.2 million hectares (5.5 million acres) of farmland, producing 15 percent of U.S. crops and 13 percent of livestock (USBR 2012). Much of the irrigated land is not within the boundaries of the drainage basin, so the water is exported from the basin via canals and tunnels and does not return to the Colorado River (Figure 4.2.6).

The net results of all of these uses of Colorado River water (80 percent of which are agricultural) in both the U.S. and Mexico are that the Colorado River no longer reaches the sea, the delta is a dry mudflat, and the water that flows into Mexico is so salty as a result of agricultural return flows that the U.S. government spends millions of dollars per year to remove salt from the Colorado River.

Many farmers in the Colorado River basin are working to use Colorado River water more efficiently to grow our food and food for the animals that we eat. Watch the video below and answer the questions to learn more about farming in the Colorado River basin.

Figure 4.2.5. Average annual precipitation of the Colorado River basin. Data are United States Average Annual Precipitation, 1961-1990 published by Spatial Climate Analysis Service, Oregon State University; USDA - NRCS National Water and Climate Center, Portland, Oregon; USDA - NRCS National Cartography and Geospatial Center, Fort Worth, Texas.

Credit: Map by Gigi Richard

Figure 4.2.6. Map of the Colorado River basin showing areas outside of the basin using Colorado River water

Credit: USBR 2012

Check your Understanding

Watch the following video then answer the questions below

Video: Resilient: Soil, water and the new stewards of the American West (10:13)

Dead Zone in the Gulf of Mexico

Agricultural runoff can contribute pollutants to natural waters, such as rivers, lakes, and the ocean, that can have serious ecological and economic impacts, such as the creation of areas with low levels of dissolved oxygen called dead zones caused by pollution from fertilizers. Nutrients, such as nitrogen and phosphorus, are elements that are essential for plant growth and are applied on farmland as fertilizers to increase the productivity of agricultural crops. The runoff of nutrients (nitrogen and phosphorus) from fertilizers and manure applied to farmland contributes to the development of hypoxic zones or dead zones in the receiving waters through the process of eutrophication (Figure 4.2.7).

Figure 4.2.7. Eutrophication

Credit: EPA: Mississippi River/Gulf of Mexico Hypoxia Task Force

Watch the following videos from NOAA’s National Ocean Service that show how dead zones are formed and explain the dead zone in the Gulf of Mexico:

• Video: Happening Now: Dead Zones in the Gulf 2017 (2:33) (Transcript)
• Video: Hypoxia (3:51) (Text description - video has no narration, just on screen text)

The nutrients that make our crops grow better also fertilize phytoplankton in lakes and the ocean. Phytoplankton are microscopic organisms that photosynthesize just like our food crops. With more nitrogen and phosphorus available to them, they grow and multiply. When the phytoplankton dies, decomposers eat them. The decomposers also grow and multiply. As they’re eating all of the abundant phytoplankton, they use up the available oxygen in the water. The lack of oxygen forces mobile organisms to leave the area and kills the organisms that can’t leave and need oxygen. The zone of low oxygen levels is called a hypoxic or dead zone. Streams flowing through watersheds where agriculture is the primary land use exhibit the highest concentrations of nitrogen (Figure 4.2.8).

Figure 4.2.8. Nitrogen concentrations in streams draining watersheds with different land uses

Credit: Dubrovsky and Hamilton 2010, The Quality of Our Nation’s Waters, Nutrients in the Nation’s Streams and Groundwater: National Findings and Implications

The Mississippi River is the largest river basin in North America (Figure 4.2.9), the third largest in the world, and drains more than 40 percent of the land area of the conterminous U.S., 58 percent of which is very productive farmland (Goolsby and Battaglin, 2000). Nutrient concentrations in the lower Mississippi River have increased markedly since the 1950s along with increased use of nitrogen and phosphorus fertilizers (Figure 4.2.10). When the Mississippi River’s nutrient-laden water reaches the Gulf of Mexico, it fertilizes the marine phytoplankton. These microscopic photosynthesizing organisms reproduce and grow vigorously. When the phytoplankton die, they decompose. The organisms that eat the dead phytoplankton use up much of the oxygen in the Gulf’s water resulting in hypoxic conditions. The resulting region of low oxygen content is referred to as a dead zone or hypoxic zone. The dead zone in the Gulf of Mexico at the mouth of the Mississippi River has grown dramatically and in some years encompasses an area the size of the state of Connecticut (~5,500 square miles) or larger. Hypoxic waters can cause stress and even cause the death of marine organisms, which in turn can affect commercial fishery harvests and the health of ecosystems.

Figure 4.2.9. The Mississippi and Atchafalaya River Basin and the hypoxic zone in the Gulf of Mexico

Credit: USGS Factbook - Nitrogen in the Mississippi Basin-Estimating Sources and Predicting Flux to the Gulf of Mexico

Figure 4.2.10. Nitrogen inputs and population from 1940-2010

Credit: USGS: Trends in Nutrients and Pesticides in the Nation's Rivers and Streams

What can be done to reduce the size of the dead zone?

The dead zone in the Gulf of Mexico is primarily a result of runoff of nutrients from fertilizers and manure applied to agricultural land in the Mississippi River basin. Runoff from farms carries nutrients with the water as it drains to the Mississippi River, which ultimately flows to the Gulf of Mexico. If a number of nutrients reaching the Gulf of Mexico can be reduced, then the dead zone will begin the shrink.

Since 2008, the Hypoxia Task Force, led by the U.S. Environmental Protection Agency and consisting of five federal agencies and 12 states, has been working to implement policies and regulations with the aim of reducing the size of the dead zone in the Gulf of Mexico. Many of the strategies for reducing nutrient loading target agricultural practices including (USEPA, The Sources and Solutions: Agriculture).

• Nutrient management: The application of fertilizers can vary in amount, timing, and method with varying impacts on water quality. Better management of nutrient application can reduce nutrient runoff to streams.
• Cover Crops: Planting of certain grasses, grains, or clovers, called cover crops can recycle excess nutrients and reduce soil erosion, keeping nutrients out of surface waterways.
• Buffers: Planting trees, shrubs, and grass around fields, especially those that border water bodies, can help by absorbing or filtering out nutrients before they reach a water body.
• Conservation tillage: Reducing how often fields are tilled reduces erosion and soil compaction, builds soil organic matter, and reduces runoff.
• Managing livestock waste: Keeping animals and their waste out of streams, rivers, and lakes keep nitrogen and phosphorus out of the water and restores stream banks.
• Drainage water management: Reducing nutrient loadings that drain from agricultural fields helps prevent degradation of the water in local streams and lakes.

Watch the following video from the US Department of Agriculture about strategies to reduce nutrient loading into the Mississippi River:

Video: Preventing Runoff Into The Mississippi River (1:44)

EPA website about nutrient pollution and some solutions to nutrient pollution: The Sources and Solutions: Agriculture

Figure 4.2.11. Size of the Gulf of Mexico hypoxic zone in mid-summer.

Credit: Data source: Nancy N. Rabalais, LUMCON, and R. Eugene Turner, LSU. Funding sources: NOAA Center for Sponsored Coastal Ocean Research and U.S. EPA Gulf of Mexico Program. From Gulf of Mexico Ecosystems & Hypoxia Assessment (NGOMEX).

Figure 4.2.12. Annual Total Nitrogen loads to the Gulf of Mexico

Credit: Mississippi River Gulf of Mexico Watershed Nutrient Task Force, 2013.

Figure 4.2.13. Annual total phosphorus loads to the Gulf of Mexico

Credit: Mississippi River Gulf of Mexico Watershed Nutrient Task Force, 2013.

We may be used to referring to soil as “dirt”, as in “my keys fell in the dirt somewhere” or “after planting the garden we had dirt all over our hands” but the way in which soil supports food production far more complex than a smear of clay on our hands. One way to define this difference in perspective is to think about the biological and chemical complexity in soil, and the fact that soils are not just brown, powdery handfuls of dirt but occupy a grand scale in the natural systems that underlie food systems. Soil is the "skin of the earth", layers that ascend from bedrock and supply water and nutrients to the fields and forests that make up the terrestrial biosphere. Soils are ecosystems in their own right, within mineral layers that form part of the earth’s surface. Soils can be as shallow as ten centimeters and as deep as many tens of meters.

An interesting exercise is to think of a single term or concept that describes how soils work and what they are. For example, if we were seeking an acronym to describe soil and market it as the marvelous thing that it is¹ —and if we lacked time to think of a catchier name – we might think up the acronym “PaBAMOM” which nevertheless is a pretty good summary of what soil is: a “Porous and Biologically Active Mineral-Organic Matrix”. It’s a good summary because it defines the unique properties of soils (see Figure 5.1.1 below):

1. Porous (full of open spaces or pores), at a range of pore sizes from well below a micron (10^-6 m or 0.0001 cm) to many centimeters, and therefore able to store water and transmit it to deeper earth layers, and host organisms as diverse as bacteria, plant roots, and prairie dogs. This porosity arises not only from the inherent sizes of particles in soil but is also a result of soil organisms and roots that generate aggregation of the soil from clay and silt particles into crumbs and clods that may be familiar to from typical garden soil. This biologically generated aggregation is sometimes referred to as structure, which is seen in figure 5.1.1 as the overall arrangement of pores and aggregates, and in the notion that soil is a matrix (point five below). The ideas of aggregation and structure will be revisited in this module and in module 7.
2. Soil is phenomenally biologically active and biologically diverse, especially in microbes, which makes it able to perform many useful functions. For example, soil microbes are able to "recycle" or decompose materials like wood, wheat straw, and bean roots into energy for themselves and other soil biotas; various other types of microbes also draw or fix nitrogen out of the air to feed plants, detoxify the soil from organic pollutants, or perform myriad other beneficial services -- and other not so beneficial processes such as diseases.
3. Soil is mineral, formed from the breakdown and chemical processing of the earth’s rock crust into sand, silt, and clay, each with its own ability to store water based on the size of pores they create and unique chemical roles in further processing and breakdown of soil materials. Usually, the mineral part is most of the solid (non-pore) part of soil (Figure 5.1, top pie chart)
4. Soil is also organic, containing bits of organic (carbon-containing) remnants of plants and animals, some of which become stabilized until they last hundreds and even thousands of years as part of the soil. In the current efforts to promote carbon sequestration to alleviate (mitigate) climate change, it is worth noting that the amount of carbon stored in these bits of soil organic matter globally easily exceeds the total carbon stock in all of the planet’s forests.
5. Lastly, it is a matrix, which means that at least as important as the particles, aggregates, and pores of the soil are the organisms and processes that occur on and in these particles and pores (Fig. 3.1, bottom). This matrix hosts a highly complex ecosystem that winds its way through the millions of pores, roots, fungal hyphae, insects, and other organisms in soil. And here we are referring to the complex system concept we presented in module one: soil has many interacting parts with overlapping interactions, the ability to produce unexpectedly stable or unstable outcomes, and contains processes that can produce positive and negative feedbacks. One important example of this type of behavior is the range of soil productivity “behavior” of soils over time, including the ability of some soils to sustain moderate to high levels of productivity over years or decades (they resist change through processes of negative feedback), and then collapse in terms of food production as the interlocking, complex systems fueled by organic constituents and biological processes are dismantled (positive feedbacks operate to drive them towards degradation). Soils can then be similarly resilient in terms of remaining unproductive until the complex systems can be rebuilt through soil restoration practices.

Fig. 5.1.1. Top: pie chart showing the typical physical composition of most soils used in food production; Bottom: Basic cross-section of approximately 20 mm wide of soil as a porous, biologically active mineral-organic matrix. Red arrows show non-living components while purple arrows show biological components. Large macropores resulting from good soil structure allow adequate drainage and air entry to a soil for biological activity, while smaller mesopores and micropores hold water at varying degrees of availability for plant roots. Macrofauna such as earthworms (>2mm approximate dimension) are also very important but would occupy too much of the diagram to show.

Credit: Steven Vanek, adapted from Steven Fonte.

So, soil is not dirt. It is porous and complex, it covers almost every land surface on the planet (ice caps, glaciers, and bare rock are exceptions), and it is a ubiquitous, critical resource that is heavily coupled to human societies for their food production and in need of protection. It’s not dirt, it’s a PaBAMOM!

^1. We don’t have to do this marketing job (phew!) because the existence and value of soils are so often taken for granted. Recently, economists have been working on estimating the implicit worth of the services performed for society by a single hectare (100 m x 100 m) of soil, and the amounts can range into tens of thousands of dollars per year depending on soils’ properties and the way they are used.

Support, Water, and Nutrients

Before examining other basic soil functions, it is helpful and will avoid possible confusion, to understand the basics of how soils support the needs of crops, which in turn support the food needs of humans and their livestock. Firstly, soils provide a physical means of support and attachment for crops – analogous to the foundation of a house. Second, most water used by plants is drawn up through roots from the pores in soils that provide vital buffering of the water supply that arrives at crops either from rainstorms or applied as irrigation by humans. Third, as crops grow and build their many parts by photosynthesizing carbon out of the air (see module 6, next, for more on this) they gain most of the mineral nutrients they need (chemical elements) they need² from soils, for example by taking up potassium or calcium that started out as part of primary minerals in earth’s crust, or nitrogen in organic matter that came originally from fertilizer or the earth’s atmosphere. The adaptation of crop plants domesticated by human farmers (and other plants) to soils, and the adaptation of the soil ecosystem to plants as their primary source of food mean that soils usually fulfill these roles admirably well.

² The elements needed by plants other than Carbon (from the air) and Hydrogen/Oxygen (from water) in rough order of concentration are Potassium, Nitrogen, Phosphorus, Calcium, Magnesium, Sulfur, Iron, Manganese, Zinc, Boron, Copper, Molybdenum, and Cobalt (for some plants). Other elements are taken up into plants in a passive way without being essential, such as Sodium, Silicon, or Arsenic.

How do soils form in different places?

Soil Formation Factors

Soils around the world have different properties that affect their ability to supply nutrients and water to support food production, and these differences result from different factors that vary from place to place. For example, the age of a soil -- the time over which rainfall, plants, and microbes have been able to alter rocks in the earth's crust via weathering-- varies greatly, from just a few years where soil has been recently deposited by glaciers or rivers to millions of years in the Amazon or Congo River Basins. A soil's age plus the type of rock it is made from gives it different properties as a key resource for food systems. Knowing some basics of soil formation helps us to understand the soil resources that farmers use when they engage in food production. Below are some of the most important factors that contribute to creating a soil:

1. Climate: climate has a big influence on soils over the long term because water from rain and warm temperatures will promote weathering, which is the dissolution of rock particles and liberating of nutrients that proceed in soils with the help of plant roots and microbes. Weathering requires rainfall and is initially a positive process that replenishes these solubilized nutrients in soils year after year and helps plants to access nutrients. However, over the long run (thousands to millions of years) and in rainy climates, rainwater passing through a soil (leaching) leaves acid-producing elements in the soil like aluminum and hydrogen ions and carries away more of the nutrients that foster a neutral pH (e.g. calcium, magnesium, potassium; see the next page on soil properties for a discussion on soil pH). Old soils in rainy areas, therefore, tend to be more acidic, while dry-region soils tend to be neutral or alkaline in pH. Acid soils can make it difficult for many crops to grow. Meanwhile, dry climate soils retain nutrients gained in weathering of rock -- a good thing -- but may lack plant cover because of dry conditions. A lack of plant cover leaves the soil unprotected from damage by soil erosion and means that dry climate soils often lack dead plant material (residues) to enrich the soil with organic matter. Both dry and wet climate soils have advantages as well as challenges that must be addressed by human knowledge in managing them well so that they are protected as valuable resources.
2. Parent material: soils form through the gradual modification of an original raw material like rock, ash, or river sediments. The nature of this raw material is very important. Granite rock (magma that hardened under the earth) versus shale (old, compressed seabed sediments) produce very different soils. An important example of parent material influencing soils with consequences for human food production are soils made from limestone or calcium and magnesium carbonates. These rocks strongly resist the process of acidification by rainfall and leaching described above. Limestone soils maintain their neutral level of acidity (or pH) even after thousands of years of weathering, and thus can better maintain their productivity. An example of this parent material influence is the Great Valley in Pennsylvania, USA, where the Amish reside. These Pennsylvania soils are considered some of the most productive soils in the U.S. even after hundreds of years of farming. Pockets of other limestone soils the world over are similarly productive over the long term. In summary, as part of learning about a food production systems of a region, it can be helpful to consider the types of rock that occur in that region, which you may want to consider for your capstone regions.
3. Soil age: the time that a soil has been exposed to weathering processes from climate, and the time over which vegetation has been able to contribute dead organic material, are important influences on a soil. Very young soils are often shallow and have little organic matter. In a rainy climate, young (e.g. 1000 years) to medium aged (e.g. 100,000 years) soils may be inherently very fertile because rainfall and weathering have not yet removed their nutrients. Old soils are usually deep and may be fertile or infertile depending on the parent material and long-term climatic conditions. Soils in previously glaciated regions such as the northern U.S. and Europe are usually thought of as young because glaciers recently (~10,000 years ago) left fresh sediments made from ground up rock materials.
4. Soil slopes, relief, and soil depth: Steep slopes in mountains and hilly regions cause soils to be eroded quickly by rainfall unless soils are covered by throughout the year by crops or forest. These hilly and mountain regions may also have young soils, and the combination of young soils and erosion can make for soils that are quite thin. Meanwhile, flat valley areas are where the eroded soil is likely to accumulate, so soils will be deep. Along with the water holding capacity and the nutrient content of a soil, soil depth determines how much soil "space" or soil volume a crop's roots can explore for nutrients and water. Soil depth is an important and often overlooked determinant of crop productivity of soils. Moreover, these large-scale "mountain versus valley" differences can be mirrored within a single field, with small differences in topography creating differences in drainage, depth, and other soil properties that dramatically affect soil productivity within ten to twenty meters distance.

A Summary of Soil Formation: The Global Soils Map

These four factors along with the vegetation, microbes, and animals at a site, create different types of soils the world over. A basic global mapping of these soil types is given below in Fig. 5.1.2 We've attached some soil taxonomic names (for soil orders, categories used by soil taxonomists) to these basic soil types for those who are familiar with some of the terminology of soil classification. We should emphasize that understanding these orders is not essential to your understanding of food production and food systems, as long as you understand how the basic processes of soil formation described above, and the properties of soils described on the next page, contribute to the overall productivity of a soil. You should think about how the soil formation processes affect crop production in your capstone regions of your final project, and you should be able to find resources on how soils were formed in any place in the United States and around the world.

Text description of the Figure 5.1.2 image.

The image is a color-coded world map showing a simplified global soil scheme based on USDA soil orders. The map uses multiple colors to represent different soil types and their distribution across continents. The legend at the bottom explains four main categories:

1. Dominant global soils arranged along a precipitation gradient (wet to dry):
   • Dark green: Old, highly weathered soils in hot, rainy climates (Oxisols, Ultisols).
   • Light green: Highly fertile soils in temperate regions (Entisols, Inceptisols, Alfisols).
   • Yellow: Dry climate soils developed under scrub vegetation (Aridisols).
   • Brown: Soils with high nutrient status in semi-arid regions (Mollisols).
2. Soils developed on special parent materials:
   • Pink: Soils from volcanic ash with high phosphorus retention (Andisols).
   • Blue: Soils from long weathering of sediments, highly fertile but poorly drained (Vertisols).
3. Boreal and cold region soils:
   • Purple: Soils under boreal forests with low pH and nutrients (Spodosols).
   • Gray: Soils dominated by freezing temperatures (Gelisol).
4. Non-vegetated areas:
   • White: Shifting sand.
   • Light gray: Ice-covered regions.

The map shows tropical regions like the Amazon and Congo Basin in dark green, indicating highly weathered soils, while temperate agricultural zones in North America and Europe appear in light green and brown, representing fertile soils. Arid regions such as the Sahara and Middle East are yellow, signifying desert soils. Boreal zones in Canada and Russia are purple, and polar regions are gray for ice coverage. This visualization highlights global soil diversity and its correlation with climate and vegetation.

Credit: Steven Vanek based on USDA world soils map.

Formation and Management Affect a Soil's Productivity

Another important point is that soil formation processes described above largely determine only the initial state of a soil as this passes into human management as part of a coupled human-natural food system. Human management can have equally large effects as soil formation on productivity, either upgrading productivity or destroying it. The best management protects the soil from erosion, replenishes its nutrients and organic matter, and in some ways continues the process of soil formation in a positive way. We'll describe these best practices as part of a systems approach to soil management in module 7. Inadequate human management can be said to "mine" the soil, only subtracting and never re-adding nutrients, and allowing rainfall and wind to carry away layers of topsoil.

The next page adds to this description of soil formation by focusing in on the basic properties that affect food production on soils, like acidity and pH which is discussed above.

Nutrients, pH, Soil Water, Erosion, and Salinization

In growing crops for food, farmers around the world deal with local soil properties that we started to describe on the previous page. These properties can either be a positive resource for crop production or limitations that are confronted using management methods carried out by farmers. The first of these, a soil's nutrient status, is described in more detail in module 5.2. Regarding nutrients is only important to emphasize here that most nutrients taken up by plants (other than CO₂ gas) come to plant roots from the soil, and that the supply of these nutrients often has to do with the amount of dead plant remains, manure, or other organic matter that is returned to the soil by farmers, as well as fertilizers that are put into soils to directly boost crop growth. Here are the other major soil properties that farmers pay attention to in order to sustain the production of food and forage crops:

Soil pH or Acidity: Near Neutral is Best

Most crops prefer soils that have a pH between 5 and 8, mildly acidic to mildly alkaline (to understand these pH figures, remember that water solutions can be either acidic or basic (alkaline), and that pH 7 is neutral, vinegar has a pH of about 2.5, and baking soda in water creates a pH of about 8). As discussed above under the climate and parent material sections describing soil formation, soils in rainy regions tend to become more acidic over time.& Soils with too low a pH will have trouble growing abundant food or feed for animals. Farmers manage soils with low pH by adding ground up limestone (lime) and other basic (that is, acid-neutralizing) materials like wood ash to their soils. As an alternative, farmers sometimes adapt to soil pH by choosing or even creating crops or crop varieties that have adapted to low pH, acidic soils. For example, potatoes do well in high elevation, acidic soils of the Andes and other areas around the world. Alfalfa for livestock does better in neutral and alkaline soils while clovers for animal food grow better in more acidic soils.

Soil Water Holding Capacity and Drainage: Deep, Loamy, and Loose is Best

Module 4 described the importance of water for food production and the way that humans go to great lengths to provide irrigation water to crops in some regions. Soil properties also play a role in the amount of water that can be stored in soils (for days to weeks) that is then available to crops. A soil that holds more water for crops is more valuable to a farmer compared to a soil that runs out of water quickly. Among the properties that create water storage in soils is soil depth or thickness, where a deep soil is basically a larger water tank for plant roots to access than a thin soil. The proportions of fine particles (clay) versus coarse particles (sand) in a soil, called soil texture, also influence the water available to plants: Neither pure clay nor pure sand hold much plant-available water because clay holds the water too tightly in very small pores (less than 1 micron or 0.001 mm, or smaller than most bacteria) while sand drains too rapidly because of its large pores and leaves very little water. Therefore an even mix of sand, clay, and medium-sized silt particles hold the maximum amount of plant-available water. This soil type is known as loamy, which for many farmers is synonymous with “productive”. In addition to these soil properties, farmers try to maintain good soil structure (also called "tilth"), which is the aggregation of soil particles into crumb-like structures, that help to further increase the ability of soils to retain water. Soil aggregation or structure, and its multiple benefits for food production are further described in Module 7 on soil quality.

Clayey soils, and soils that have been compacted by livestock or farm machinery ("tight" vs. "loose" soils), can also have problems allowing enough water to drain through them (poor drainage), which can lead to an oversupply of water and a shortage of air in soil pores (refer back to figure 5.1.1 and the roughly equal proportion of air and water in pores of an agricultural soil). Too much water and too little air in a soil lead to low oxygen in the soil and an inability for roots and soil microbes to function in providing nutrients and water to plants. Part of good tilth, described above, is maintaining a loose structure of the soil.

In the face of these important soil properties for water storage, farmers seek out appropriate soils with sufficient moisture (e.g. deep and loamy, see Figs. 5.1.3 and 5.1.4) but also adequate drainage. Food producers also modify and maintain the moisture conditions of soils, through irrigation but also through maintaining good soil aggregation or tilth (see modules 5.2 and 7), and by avoiding compaction of soils that also leads to poor drainage and soils that are effectively shallower because roots cannot reach down through compacted soils to reach deeper water.

Fig. 5.1.3. The shallow soil with an oat crop is in a mountainous region that has likely suffered erosion, and features of the bedrock can be seen within 50 cm of the surface (yellow line), where the soil becomes much poorer. The total volume available to store nutrients and water in this soil is low. A pick axe head is shown for scale.

Credit: Steven Vanek

Fig. 5.1.4. This loamy, deep soil is likely in a flatter region and has an organic-matter rich layer that extends to about 40 cm below the surface and water storage capability to beyond one-meter depth (numbers on tape are cm), an excellent nutrient and water resource for food production.

Credit: Stan Buol, North Carolina State University Soil Science, on Flickr Creative Commons (CC BY 2.0)

Salinization and Dry Climates: Hold the salt

Dry climate soils have less rainfall to leach them of minerals. They can, therefore, be high in nutrients, but also carry risks of harmful salts building up as rainfall does not carry these away either. Salt-affected soils may either be too salty to farm at all or may carry a risk that if irrigation water is too high in salts or applied in insufficient amounts to continually “re-rinse” the soil of salts, then salts can build up in soils until crops will not grow. The way that arid soils are managed is a key part of the human knowledge of food production in dry regions.

Relief and Erosion: Don't Let Soil Wash Down the Hill

Soil slope and relief are described on the previous page as creating higher risks of erosion (Fig. 5.1.5). To address this limitation food producers have either (a) not farmed vulnerable sloped land with annual crops, leaving them in the forest, tree crops, and year-round grass cover and other vegetation that holds soils on slopes; (b) built terraces and patterned their crops and field divisions along the contours of fields (Fig. 5.1.6). Terracing and terraced landscapes can be seen from Peru to Southeast Asia to Greece and Rwanda. Nevertheless, while sloped soils have been seen as the Achilles heel of environmental sustainability in mountain areas, the extreme elevation differences present in mountain areas can also be seen as a benefit to these food systems. The benefits arise because soils with very different elevation-determined climates and soil properties in close proximity, which allows for the production of a greater variety of crops. The simultaneous production in the same communities of cold- and acid soil tolerant bitter potatoes and heat-loving maize and sugar cane in lower, more neutral soils in the Peruvian Andes is an example of this benefit in high-relief mountain regions.

Fig. 5.1.5. Soil erosion in a mountain landscape

Credit: Steven Vanek

Fig. 5.1.6. Terracing in a mountain landscape.

Credit: Quinn Comendent, used with permission under a creative commons license.

Soil Health: Understanding Soils as an Integrated Whole for Food Production

We hope that you are beginning to appreciate that appropriate management of soils is emphatically about integrating management principles like the ones presented here as human responses, along with an understanding of the basic properties of soils, and also the nutrient flows presented next in module 5.2. Soils are very much a complex system, and managing them for food production and environmental sustainability means that we must understand the multiple components and interactions of this system. The way in which this is accomplished has been summarized as the concept of Soil Health, which involves multiple components that are more fully addressed in module 7. Soil health is an aspiration of effective management and means that management has maintained or promoted properties like nutrient availability, beneficial physical structure, and diversity of functionally important and 'health-promoting' microbes and fauna in soils along with sufficient organic matter to feed the soil ecosystem. These integrated properties then allow production to avoid soil degradation, produce sufficient amount of food and livelihoods, and preserve biodiversity in soils as well as other significant ecosystem services like buffering of river flows and storage of carbon from the atmosphere.

³ This is not always true; Molybdenum, Sulfur, Boron and other micronutrients are sometimes found to limit plants, but the complexity of analyzing these is beyond the scope of this survey course.

Soil scientists have done an enormous amount of work in mapping the patterns of soil at a global level. The most current and detailed effort comes out of mapping work from the Food and Agriculture Organization of the United Nations, now an independent agency that is known as the International Soil Resource Information Centre (ISRIC), and is based on classifying a set of diagnostic types of topsoil layers that occur in different climates, landscape ages, and vegetation types. The details of this system⁵ are beyond the scope of this course, however, and to summarize the introduction to global soil fertility in this unit we present a simplified version of the United States Department of Agriculture (USDA) system that is still in wide use by soils practitioners in the United States. The USDA system lines up very well with the ISRIC system at this simplified level and allows understanding of the broad strokes of soil nutrient geography in the way we have presented it (Figure 3.8).

Text description of the Figure 5.1.2 image.

The image is a color-coded world map showing a simplified global soil scheme based on USDA soil orders. The map uses multiple colors to represent different soil types and their distribution across continents. The legend at the bottom explains four main categories:

1. Dominant global soils arranged along a precipitation gradient (wet to dry):
   • Dark green: Old, highly weathered soils in hot, rainy climates (Oxisols, Ultisols).
   • Light green: Highly fertile soils in temperate regions (Entisols, Inceptisols, Alfisols).
   • Yellow: Dry climate soils developed under scrub vegetation (Aridisols).
   • Brown: Soils with high nutrient status in semi-arid regions (Mollisols).
2. Soils developed on special parent materials:
   • Pink: Soils from volcanic ash with high phosphorus retention (Andisols).
   • Blue: Soils from long weathering of sediments, highly fertile but poorly drained (Vertisols).
3. Boreal and cold region soils:
   • Purple: Soils under boreal forests with low pH and nutrients (Spodosols).
   • Gray: Soils dominated by freezing temperatures (Gelisol).
4. Non-vegetated areas:
   • White: Shifting sand.
   • Light gray: Ice-covered regions.

The map shows tropical regions like the Amazon and Congo Basin in dark green, indicating highly weathered soils, while temperate agricultural zones in North America and Europe appear in light green and brown, representing fertile soils. Arid regions such as the Sahara and Middle East are yellow, signifying desert soils. Boreal zones in Canada and Russia are purple, and polar regions are gray for ice coverage. This visualization highlights global soil diversity and its correlation with climate and vegetation.

Credit: Steven Vanek based on USDA world soils map.

This simplified map is intended to serve as a resource for your other learning in the course on how food systems may respond to the opportunities and limitations of soils, and also summarizes the learning in this module about how soils result from an interaction of parent material, time, climate, vegetation, and other factors. For example, you’ll notice that just four very broad summarized types (See section 1 of the soils key, “Dominant global soils” in Fig. 3.8) cover the vast majority of the earth’s surface, and can be organized into a rough typology of precipitation from wet to dry, along with their age and vegetation types (e.g. tropical and subtropical forests; other forest types; grasslands, and desert vegetation). Soils formed by temperate grasslands have been hugely important in recent history because once humans developed steel plows that were sufficiently strong to til prairie soils, these Mollisols could be farmed and became the breadbaskets of the modern era (e.g. the U.S. and Canadian Great Plains, the Ukraine, the Argentinian pampas). There are also small pockets of soils globally that depend strongly on their original parent material. Andisols or volcanic ash soils are an excellent example of this: although their global extent is minuscule and even invisible on our map (Fig. 3.8) at this scale, they often occur in areas with high population densities such as Ecuador, Japan, and Rwanda. The high densities of population are not an accident but occur exactly because these soils have high fertility potential and have become extremely important in these local food systems. The simplified global soils map is also a way to spatially conceptualize a number of key limiting factors in soils that food producers must face: acidic, P-retaining soils in highly weathered tropical and subtropical soils, P retention in volcanic soils, and the risk of salinization of soil in dry climate soils.

In addition, it is worth noting that the broad swaths of soil of young to moderate age and with moderate to high fertility (light green in our map) may be the dominant type of soil in the world and also includes many areas that are critical in terms of the sustainability outcomes for human-natural systems in relation to soils. Because these tend to be “medium-everything” soils (medium age, medium fertility, medium depth, medium pH, medium moisture, etc.) they do not actively dissuade human systems from occupying them with high population densities or intensity of management and production, especially as the global population increases. However these soils are often easily degraded, and so sustainable methods are especially important to guarantee future food production.

⁵ Nevertheless, you may peruse this impressive global resource and the soil horizon definitions at ISRIC.

In module four, and in your education previous to this course, you've learned about the water cycle, in which water evaporates from bodies of water, condenses into clouds, and then is returned as rain to drain again into groundwater, lakes, and oceans. Each of the major crop nutrients, and most chemical elements on the earth's surface, has a similar cycle in which the nutrient is transported and transformed from one place to another, spending time in different 'pools', analogous to the division of water into lakes, rivers, clouds, rain, and the ocean. Just as rainwater and groundwater may be of more immediate use to crop plants than the ocean, different pools of the same nutrient differ in availability to plants. For example, most soils hold a tremendous amount of nitrogen in large organic molecules, but only the smaller soluble pool, and some smaller molecular forms of N, are directly available to plants. The way that soil nutrients move through the earth system, including within food production systems, is called nutrient cycling. The objective of this module is for you to understand the main features of nitrogen (N) and phosphorus (P) cycling in human-managed soils. Earth scientists sometimes use the term "biogeochemical cycling" to emphasize that each nutrient’s cycle represents the geological and atmospheric sources of the nutrients, the biology of organisms that often transform nutrients from one form to another, and the chemical nature and interactions of each element.

As an example of biogeochemical cycling, think of the important element carbon (C). Carbon has a chemical nature that allows it to be a fundamental molecular building block for all living things. In addition, there is an impressive atmospheric pool (a sort of geologic pool) of non-organic carbon dioxide. Interacting with this atmospheric pool, green plants and algae play a fundamental role in turning atmospheric CO₂ into biological organic carbon in living things and the remains of living things, such as plants, that fall back into the soil. Scientists refer to this large set of interacting parts with geological, biological, and chemical attributes, earth's system that "processes" and recycles carbon in a certain sense, as the biogeochemical C cycle. Another example is phosphorus (P), which will be described in more detail on the following pages: The earth’s crust is the primary source of all P, which is then weathered by geological and biological processes and also in human fertilizer factories, held or retained strongly by soil clay minerals after application by farmers, and eventually occupies a key role in every living thing as one of the elements within the DNA molecules encoding our genes. It’s essential to realize that humanity and human systems are now major players within these nutrient cycles including C, P, and nitrogen. We can see this in activities such as mining (and eventually threatened depletion) of phosphorus sources for fertilizers or fixing of large amounts of nitrogen for fertilizers with a massive expenditure of energy and emission of carbon dioxide through the use of oil and gas.

The proper management of soil nutrients in soils for human food production boils down to a simple requirement: the need to replace nutrients that are "subtracted" from soil during production. These subtractions occur as nutrients are taken up by crops from the soil and then exported as food products in crops and livestock. Nutrients can also be lost to soil erosion and in dissolved forms, by drainage of water from the soil (called leaching). The goal of incorporating manure, plant material, and chemical fertilizers by farmers is to add back these subtracted nutrients. In the case of soil erosion, the idea is to avoid such losses completely by protecting soils. Human-managed fields and farms can be compared to nutrient bank accounts, where withdrawals must be balanced by deposits, and where it is better to have a substantial balance than a minuscule balance. Natural systems like forests or prairies lose some nutrients as does a farm field, but to a comparatively minor degree (fig 5.2.1 below). The need for humans to replenish nutrients is much greater in any managed system like a crop field or pasture than in unmanaged forests or grasslands. This is especially true in intensive production systems of crops or animal forages, for example, the corn, vegetable, and hay fields and pastured rangelands that are typical in agriculture of the United States and around the world. In systems where soils are tilled to grow annual crops on hillsides, the combined exported nutrients in food and those lost to erosion can quickly rob a soil of most of its nutrients. Protecting a soil from these losses, and regenerating the nutrients lost by adding crop residues (straw, cornstalks, other stems, and roots), manure, and fertilizer materials (ash, phosphate rock, bone, chemical fertilizers) are therefore important strategies used by food producers to sustain production. We’ll devote more focus to the important role of crop species, crop rotations, tillage, and soil erosion as part of agroecosystems in modules 6 and 7. For now, we want to understand the basics of these principles of soil regeneration.

Fig. 5.2.1: Nutrient cycling (biogeochemical cycling) in a closed natural ecosystem (left) and a crop production system (right) in which humans must replace exported nutrients from soils through the use of plant residues, manure, and other soil fertility inputs. The magnitude of soil nutrient losses in flows such as erosion, leaching, and nitrogen gas emissions from soils tends to also be greater in the cropped system than the losses from soils found in natural systems. The relationships of crop management to nutrient cycling will recur in greater detail in Module 7 with the concept of an agroecosystem.

Credit: Steven Vanek

Soil Organic Matter as a Soil "Master Variable"

In addition to individual nutrients like N, P, potassium (K) and calcium, an overarching aspect of soil depletion and regeneration by human food producers is the important role played by soil organic matter (SOM) and the potential to either to deplete or sustain organic matter in soils (recall figure 5.1.1 and the fact that organic material is one of the key solid components of soil). In particular, concerns about soil organic matter (SOM) center on the large amounts of organic carbon in large molecules of SOM. This soil organic carbon (SOC) both feeds microbes in soil, allowing them to perform nutrient cycling functions and also contributes positively to soil properties. SOC is not a plant nutrient that comes from soil. In fact, it actually comes originally from the atmosphere in the form of plant remains that contain carbon fixed by plants (roots, leaves, manure, rotting wood, etc.) and accompanies N, P, and other nutrients that were in the plants. SOC within soil organic matter plays so many important roles in soil function and soil fertility that it should be considered a “master variable” explaining soil productivity, along with soil pH, soil depth, and soil drainage. Among its other functions, SOM promotes soil storage of crop-available water, is a major food source for soil microbes that perform beneficial roles in soil, and fosters the availability of many nutrients by holding them in moderately available form or decomposing to release them in soils. In addition, by far the largest pool of nitrogen in soils is held in N atoms within many types and sizes of soil organic molecules, and also within the bodies of soil microbes.

In many food production systems where the soil is plowed (also called tilling or tillage), SOM is in fact depleted by oxidation (a “slow burn”, like iron rusting) when soils are broken apart by plows, hoes, and other implements. Therefore, an important part of soil regeneration by human food production systems is not just replacing nutrients in a pure chemical form like fertilizers, but also maintaining overall soil function with soil organic matter. Therefore, in most parts of the world farmers have developed ways of reincorporating the roots and stems of plants (crop residues) as well as manure made by animals from the forage crops fed to them. These sources of plant carbon sustain SOM over the long term and feed microbes. These ways of sustaining the nutrients and organic matter of soils are depicted with a coupled human-natural systems diagram below (Fig 5.2.2) as a type of feedback loop in which human systems respond to soil degradation by incorporating organic matter like residues, compost, and manure.

The following brief reading assignment further illustrates the important functions of organic matter.

Activate Your Learning

The following exercise asks you to use graphical data based on real soils to make conclusions about the important role of SOM in the water-holding capacity of soils. Along with the materials in module 4 on water and food production, and the systems approach to soil management in module 7, these concepts should help you to appreciate the role of SOM in fostering the environmentally sustainable production of food, as well as resilient systems (see module 10) that can deal with drought stress.

Fig. 5.2.2. Storage of crop-available water associated with the texture of soil (sandiness, clayiness) and its level of organic matter (SOM)

Credit: Steven Vanek, based on data from Hudson, B.D. 1994. "Soil organic matter and available water capacity. Journal of Soil and Water Conservation 49: 180-194.

Examine Fig. 5.2.2, which draws on about sixty soils analyzed in a publication that related the water-holding capacity of soils to their organic matter content. The graph summarizes that data as the height of three columns on a bar graph. The height represents the amount of water stored in each soil, imagined as a depth of water in mm covering the soil at its surface (this is also how irrigation managers imagine applying water to soils, as the mm of rainfall they have replaced with irrigation). Each column represents a type of soil, from a coarse-textured sand on the left to a "heavy" or clayey soil on the right. The stacked colors on the graph represent the way that organic matter is able to improve the water-holding capacity of soils. Answer the following questions.

Nitrogen (N) is one of the most important nutrients for plant growth and crop production, along with phosphorus (P) considered on the next page. Nitrogen is important because it is used by plants to create proteins, which include the enzymes and building blocks of their photosynthetic "machinery". In fact, nitrogen in some ways underlies the green color of plants and vegetated areas on the earth's surface, because of the green, N-containing chlorophyll proteins (enzymes) used in photosynthesis (see module 4), which along with the other photosynthetic enzymes is one of the major uses of nitrogen within plants. These plant proteins become animals protein when plants are fed to livestock, or when we eat plants. The ubiquitous nature of nitrogen for the protein needs of the earth's biosphere explains why N is such an important nutrient for plant growth. Nitrogen is, therefore, a key element in the entire food system and interacts very strongly with human management. One indication of nitrogen's importance to the food system is that humans currently expend more energy on creating N fertilizers for food production by taking N₂ out of the atmosphere in fertilizer factories (Fig. 5.2.3) than is spent on any other nutrient.

This module focuses on the subject of nutrient cycling, and below in figure 5.2.3, we present a basic diagram of the nitrogen cycle. Your initial impression of the diagram may be its relative complexity compared to the water cycle, for instance. This is true: the N cycle is complex, starting with the fact that it involves gas, solid, and liquid forms: gaseous N in the atmosphere, solid forms of N in soils and plants, and N dissolved in water in the soil and in earth's waterways (you may remember the problem of N pollution in waterways from module 4). To simplify this and take away the key concepts which should be your goal in this module (entire courses can be taught on the N cycle), we will present the basic pathway of N from the atmosphere into plants, soils, and water, which will complement the caption for the N cycling diagram below. Please refer to Figure 5.2.3 throughout this description. First, N exists in an enormous reserve as 78% of the earth's atmosphere (top left of Fig. 5.2.3). Creating usable forms of nitrogen requires that this N₂ gas is "fixed" in the same way that plants fix carbon into their carbonaceous stems and leaves. Legume plants like beans, peas, and alfalfa host bacteria in their roots in nodules that are able to fix N₂ gas (more on legumes as an important crop family in module 6). Nitrogen then moves directly into legume plants' tissues as proteins. In parallel to this biological fixation of N, humans have designed industrial methods to fix N in factories, using energy from petroleum and natural gas, and creating soluble nitrogen chemicals that are applied to soil, where they dissolve in soil water to become part of the pool of soil soluble N that is available to plants. This pool of soluble N (light green oval within the soil N pool below) is also called inorganic N to contrast it from organic N in proteins, crop residues, and soil organic matter. Inorganic N taken up by plants, plus the N fixed by legumes, is then used to grow crops and eventually produce crop- and livestock-based food products. Meanwhile, organic "waste" products from growing crops like straw, cornstalks, and roots, plus animal manures which are undigested plants, are not "waste" at all but are a hugely important organic source of N and other nutrients that are recycled to soil (brown arrows in Fig. 5.2.3). These organic soil inputs applied by farmers help to maintain soil organic matter (SOM; see previous pages and the assigned reading on soil organic matter) including the largest pool of soil N within SOM and soil microbes. Soil organic matter can be decomposed by microbes, liberating additional amounts of N to the inorganic N pool. µbes also can take up soil inorganic N, reversing the effects of SOM decomposition.

Figure 5.2.3 Main features of nitrogen (N) cycling in food production systems. The diagram shows the multiple forms of N in soils and food production. Despite its complexity, the diagram can be more simply considered in four parts: (1) a large atmospheric pool of N at upper left, which is used to make chemical fertilizer in factories, and also by legumes to directly absorb N from the air for their own protein needs; (2) A soil pool which includes a predominant pool of organic N in large organic molecules (Soil Organic Matter or SOM) and microbes, as well as a fluctuating pool of inorganic N that is soluble in water (nitrate and ammonium ions); (3) The crops at the center of the diagram that are a main focus of human food production, and draw nitrogen from the pool of inorganic N in soil as well as from the atmosphere (in the case of legumes) and (4) Crop and livestock nitrogen exports from soil of nitrogen that then move through the food system to consumers. The very important return of crop residues and manure N to the soil N pool should also be noted (brown arrows). In addition, N can be lost from the soil in ways that are not productive (red arrows): as gases back to the atmosphere, including N₂O, a potent greenhouse gas; as leaching losses of nitrate in rainfall into waterways, and as erosion of soil particles that include soil organic N that move out of agricultural fields, eventually becoming sediments in waterways and estuaries.

Credit: Steven Vanek

So far the N cycle may appear a relatively neat and ingenious system (albeit quite complex!). However, it is important to highlight the ways that it can become problematic under human management, indicated by the red "loss" arrows in Fig. 5.2.3. First, when the soluble N pool in soil is large, for example after fertilizer or manure is applied, and abundant water moves through the soil, like during a rain event, excessive soil N can move into waterways causing pollution and coastal dead zones (this is covered in some detail in module four, and again in this module's summative assessment). This process is called leaching of soil soluble N. Second, when erosion occurs, soils can also lose large amounts of their N "bank account" through erosion, because solid organic matter particles are rapidly eroded from soils in hilly areas when soil is not protected by plant cover or stabilized by plant roots. Lastly, soils can lose nitrogen back to the atmosphere through the processes of gaseous loss, where dissolved nitrogen becomes N-containing gases that diffuse back to the atmosphere. If you have ever caught a whiff of ammonia from a bottle of ammonia cleaning solution (dissolved ammonium that becomes ammonia gas) you know how N can move from a solution like that in a wet soil into the air. The most serious of these gas loss pathways is nitrous oxide (N₂O) which is of concern because it is a potent greenhouse gas that contributes to global warming.

All of these loss pathways create the impetus for farmers and the food systems that support them, to manage nitrogen in an efficient and non-polluting way. The idea that highly productive farming systems with annual crops, manures, and fertilizers can completely eliminate N losses is actually quite challenging. This is because the N cycle has so many participants (humans, plants, microbes, livestock) interacting in complex ways (note: a complex system!), and because nitrogen is inherently "flighty" and "leaky", never staying put and always in transformation, with some forms so easily lost from soils to rivers, lakes, and the atmosphere. Nevertheless, there is much room for improvement that can also serve to save money and energy for food producers, and avoid the pollution costs to downstream ecosystems and food producers (for example, fishing communities affected by dead zones, see module 4). Two of these are (1) increasing the efficiency of timing and amounts of N fertilizer and manures to better match only what is needed by crops and (2) including crops and other plant components on farms that help to recycle soluble N from deeper in the soil and in downslope areas before it reaches waterways. Both of these strategies are addressed in the following modules on crops and systems approaches to soil management (modules 6 and 7). In addition, if N is not replenished in soils after it is exported as food products or suffers these losses, crops can face N insufficiency, which is a major issue for poorer farmers around the world. The summative assessment for this module focuses on these twin issues of nutrient deficiency and excess.

Basics of The Phosphorus Cycle in Food Production

In an analogous way to the nitrogen (N) cycle on the previous page, we will present the basics of the phosphorus (P) cycle related to food production (refer to figure 5.2.4 below in this section) You'll note that the P cycle is a good deal simpler than the N cycle. For example, there is no gaseous form of P as there is for N, so the atmosphere does not participate in the P cycle. Also, leaching of soluble P is not a major issue as it is for soluble soil N. To begin the description of the P cycle, the large reserve of "primary" P that is accessed by plants and fertilizer production for agriculture is not the atmosphere (as it is for N), but rather so-called phosphate rocks (or rock phosphate) in the crust of the earth, which are mined like other minerals. These rocks are ground up and treated in fertilizer factories to make the phosphate (PO₄^-) in them water-soluble so that phosphate can be directly taken up by plants from the small pool of soluble phosphorus in soils. In addition to this industrial process that supplies P to plant roots, there are small amounts of soluble P that are continually released by weathering (see Module 5.1) of grains of rock phosphate that form a small part of most soils. These plant-available forms of P from fertilizers and weathering are taken up by plants and pass into the food system when crops are harvested for food products or are fed to livestock. Just as for N (figure 5.2.3), crop residues and manures with organic P are recycled to the soil and are an essential way of replenishing soil organic P supplies. Also, decomposition of soil organic P that liberates soluble P, and uptake of P into the bodies of microbes, link the organic P pool in soil organic matter (SOM) with the small amount of soluble P in soils.

Fig. 5.2.4. Diagram of phosphorus (P) cycling relevant to food systems, drawn in an analogous way to the N cycle in figure 5.2.3. This diagram can be thought of as four main areas: (1) Phosphate rock deposits that are used to produce phosphorus fertilizers (along with "native" grains of rock phosphate in soils, see below); (2) Soil P, which is divided into a larger organic P pool and a relatively minuscule pool of soluble P, and also contains relatively unavailable forms called "retained P" held on soil minerals like clays; (3) Phosphorus in plants, which includes all tissues and the energetic machinery of plants; (4) Crop and livestock P exports to the food system. Note that there are multiple flows into and out of soils of P, and also fractions and internal cycling within soils from one form of P to another. In addition to the rock phosphates that are mined and turned into fertilizer, many soils also have their own mineral P supplies in the form of small rock grains that contain rock phosphate. These amounts are small but can be sufficient in wild ecosystems (Fig. 5.2.1) under normal weathering processes that release nutrients in most soils (see module 5.1 for a description of weathering). The different fractions of soil P represented by the shapes in the soil box are not necessarily in proportion to their relative size; also the relative amounts in different pools varies considerably among different soils.

Credit: Steven Vanek

P retention in soils and management responses: "clingy P" versus "flighty N"

One difference between the cycling of P vs. N in soils is the fact that most soils have ways of chemically capturing and holding soluble P in forms that can become very unavailable to plants. The clay mineral fraction of soils is especially active in retaining P, especially so for the clays that occur in tropical soils (you may be familiar with rusty or yellow-colored clays, made from iron oxides, in warmer areas of the United States and the world). This is called soil retention or fixation of P. In a soil that retains P strongly, less than five percent of the P in applied fertilizer, which enters in a soluble form very suited for plant uptake, is ever available for crops. The rest is quickly locked away by reactions with soil clay minerals. Soil scientists call this process P fixation or P retention, and a global map of estimated P retention has been made (Figure 5.2.5) that summarizes how phosphorus can become limiting to food production, which is a serious problem in many tropical soils. One comparison that may be helpful in remembering the way that soil locks away phosphorus is to contrast it to the behavior of soil N. While soil N is "flighty" or "leaky" with multiple forms and loss pathways, soil P tends to be the "clingy" opposite of soil N -- the issue is not that it is held too loosely in soils but rather that it is held too tightly.

To address the challenge of retained P, farmers may resort to continually supplying fertilizers and manures to crops, often in quantities that greatly exceed crop demand. Nevertheless, additions of organic matter also tend to make retained or fixed P more available, combined with the use of crop species that can better take up fixed forms of P, so that P is moved from the retained, unavailable fraction of P to organic forms in crop and microbial biomass that are eventually recycled into available soluble forms. Certain plant-symbiotic soil microbes, especially mycorrhizal fungi, are particularly efficient at helping plants to access these less soluble forms of soil P. In addition to these soil management measures, first farmers, and now formal plant breeders have developed crop varieties that are more efficient in taking up some of retained P that is locked away in soil.

Fig. 5.2.5. Global map of soil P retention potential. Old and very old soils in warm-climate areas, as well as leached soils under cold-climate conifer vegetation, tend to exhibit the highest rates of soil P retention. These soils can make applied P fertilizers very unavailable to crops. In response, farmers can apply lime to raise the pH of these often acid soils, or continually re-supply P via fertilizers (which can be very inefficient if most of this fertilizer is quickly made unavailable); or add P in organic forms that become solubilized by decomposition and can directly feed plant roots before P is fixed. In practice, all of these approaches are used.

Image Credit: United States Department of Agriculture, Natural Resource Conservation Service

Soil Erosion and P

As can be seen in Fig. 5.2.4, erosion of particles of soil that contain organic and retained P is the major pathway of phosphorus loss from soils (red arrow in Fig. 5.2.4), in contrast to P export for useful purposes in crop- and livestock-based foods. Along with maintaining the availability of soil P with regard to P retention, protecting soils against erosion is an excellent way to protect the ability of soils to supply P for food production. This main message will be taken up in the summative assessment for this module, and again in Module 7.

Soil Nutrients: The Sustainability Issues of Shortage and Surplus

Both N and P are distinctive in possessing extremes of surplus and shortages across the variety of food production systems around the globe. For poorer small-scale farmers, who number more than two billion globally, the means to effectively replenish the nutrients exported by crops, or detain the nutrients removed by erosion on sloping land can be beyond the reach of their financial means or labor power, or simply not sufficiently part of their knowledge systems. Deficits of nitrogen and phosphorus in soils ensue, complicated by soils that may have a high degree of P retention, and low organic matter levels that decrease the overall soil quality by retaining less water and crusting easily, aspects that will be emphasized in the following modules. Applying the "bank account" analogy of soil nutrients introduced at the beginning of this module, after constant withdrawals the "soil bank account" begins to run such a low balance that overall functioning of soil productivity, and with it the livelihood of a smallholder household, are impaired. This can lead to a downward spiral of soil productivity (see the assigned reading for this module) that links issues of environmental, social, and economic sustainability.

Fig. 5.2.5. The concept of the downward or vicious cycle of soil nutrients and organic matter as a driver of soil productivity (brown spiral), and a "virtuous cycle" alternative (green spiral) where the maintenance of soil nutrients and soil quality broadly with organic matter, allows for better livelihoods and reinvestment in soils with nutrients. We will revisit this diagram in module 10 when talking about sustainable food systems.

Credit: Steven Vanek

Another feature of human-natural interactions for soil nutrients is the aspect of surplus exhibited by a "leaky" or "flighty" nutrient like nitrogen. This has been compounded by the development of the large-scale human capacity to add surplus nutrients to farm fields for food production. It's important to realize that prior to N fertilizers, bacterial nodules on the roots of legume crops (see Fig. 5.2.3 and the coverage of legumes in module 6) were the major way that N entered soils from the atmosphere, including the soils used for food production. Farmers before about 1900 relied exclusively on legume crops, as well as animal (and human!) manures derived from legumes and other crops as the principal way of regenerating the nitrogen in soil organic matter. These materials incorporated to soils decompose and release N that was used by crops. Since 1913, when N fertilizer production from the atmosphere was developed as a factory process, humanity has deployed greater and greater amounts of fossil fuel energy to fix greater and greater amounts of atmospheric N₂ into soluble forms to feed crops. A startling fact is that humans now fix more atmospheric nitrogen than do legumes. This has buoyed the overall productivity of human food systems beyond what might have occurred without such fertilizers and is credited by many with avoiding widespread hunger (or dramatically expanding the population carrying capacity of earth’s human-natural systems, depending slightly on the perspective that is taken).

As has been noted in module 4, there have been unforeseen consequences of this trend towards greater fertilizer use that have become more evident in recent years. First, the share of CO₂ greenhouse gas emissions from fertilizer production has become a primary contributor to the overall impact of agriculture on global warming. Another is that fertilizers, in combination with a profit-minded vision of soil fertility that did not incorporate a view of the whole human-environment system, bred a highly “chemical” vision of soils that neglected the important role of soil organic matter and the physical and biological qualities of soil. This resulted in unforeseen negative impacts as farmers over-applied nutrients at a local scale to guarantee the highest yields possible, thereby polluting watersheds, and allowing farmers to lose sight of the important role of soil organic matter outlined in this module. In a more subtle way, there has been an increasing focus in plant breeding and globalized seed systems on varieties that respond well to soluble fertilizers, which many argue have favored the expansion of more industrial modes of food production to the financial detriment of smaller and more sustainable food producers. If you recall the narration of agricultural history in module 2, you will recognize that this is an example of niche construction, in which a modern, chemical-intensive niche has been created for specially bred modern varieties along with fertilizers and other chemical inputs. Nevertheless, many of these problems associated with an exclusive reliance on nitrogen fertilizers and chemical fertilizers are now recognized by researchers and policymakers. Current approaches to soil the world over have placed renewed emphasis on the importance of organic matter and a more economical use of nitrogen fertilizers.

In the summative evaluation for this module, you will explore these “surplus and shortage” issues of sustainability for Nitrogen and Phosphorus, which are emblematic of present-day and future sustainability challenges in the area of nutrients cycling.

Plants need light, water, nutrients, an optimal temperature range, and carbon dioxide for growth. In a natural environment, the availability of plant resources is determined by the:

• soil fertility, soil depth, and soil drainage

• climate: the seasonal temperature and precipitation distribution
• competition with other plants, herbivory by other organisms, and pathogens
• the frequency of environmental disturbances (for example from fire, floods, and herbivory).

In some environments, nutrients, light, and water, are readily available and temperatures and the length of the growing season are sufficient for most annual crops to complete their lifecycle; we will refer to these as high resource environments for crop production. High resource environments tend to have soils that are fertile, well-drained, deep, and generally level, as well as growing seasons with temperatures and precipitation that are optimal for most plant growth. In general, in environments where competition for resources among plants is low, annual plants with more rapid growth rates tend to dominate (Lambers et al, 1998). Consequently, humans tend to cultivate annual plants with high growth rates in high-resource environments.

By contrast, in low-resource environments plant growth may be limited due to soil features and/or climatic conditions. Soils may be sloped, with limited fertility, depth, and drainage; and/or the growing season may be short due to extended dry seasons and/or long winters (with temperatures at or below freezing). In natural ecosystems, resources can be limited due to competition among plants, such as in a forest or grassland where established plants limit the light, water, and nutrients for new seedlings. And in these environments where resources are limited, plants with slower growth rates and perennial life cycles tend to succeed (Lambers et al, 1998), and perennials are often the primary crops that humans cultivate in resource-limited environments. 

Annual plants grow, produce seeds, and die within one year. In general, annual plants evolved in environments where light, water, and nutrients were available, and they could consistently reproduce in one year or less. Where resource availability is high, plants that can germinate and grow rapidly have a competitive advantage capturing light, nutrients, and water over slower growing plants and are more likely to reproduce. To ensure the survival of their offspring, annuals allocate the majority of their growth to seeds (often contained in fruit); and they tend to produce many seeds.

Human selection of annual crop plants typically further selected for large seeds and/or fruit. Some examples of annual crop plants are corn, wheat, oats, peppers, and beans (see photos). What are some other examples of annual crop plants?

Figure 6.1.1: Cornfield

Credit: Heather Karsten

Figure 6.1.2: Wheatfield

Credit: Heather Karsten

Figure 6.1.3: Corn Grain

Credit: Heather Karstena

Figure 6.1.4: Peppers

Credit: pixabay

Figure 6.1.5: Beans

Credit: pixabay

Annual crop plants are generally categorized into one of the three seasons that falls in the middle of their plant growth life cycle: spring, summer, or winter. For instance, summer annuals are generally planted in late spring, grow and develop through summer, and complete their lifecycle by late summer or autumn. Winter annuals are generally planted in early autumn and germinate and grow in autumn. Depending on how cold the winter is where they are cultivated, winter annuals may grow slowly in winter or become dormant until spring. In spring, they grow, flower, and produce seed by early to mid-summer (See Figure 6.1, Annual Crop Types). After an annual crop is harvested, in some regions farmers may be able to plant another crop, such as a winter annual crop after a spring annual crop, this is referred to as double-cropping (cultivating two crops in one year). If only one crop is cultivated in a season, the soil may be left exposed until the next growing season. Leaving crop residue on the soil can reduce erosion, but planting another crop with live plant roots and aboveground vegetation provides better soil protection against water and wind erosion. Alternatively, a cover crop may be planted after the harvested crop to protect the soil from erosion and provide other benefits until the next crop is planted. Cover crops are typically annual crops that can establish quickly; you will learn more about cover crops in Module 7.

Figure 6.1.6: Annual seasonal crop types with their approximate growing seasons in Northeastern US

Click for a text description of the Annual Seasonal Crop Types image.

The image is a chart titled “Annual Crop Types” in bold green text at the top. Below the title, there is a horizontal timeline spanning from January (Jan) to December (Dec), with each month abbreviated and arranged in order from left to right. The chart visually represents three categories of annual crops—Spring annual, Winter annual, and Summer annual—using colored arrows to indicate their growing periods throughout the year.

• Spring annual is shown in blue with an arrow starting around April and ending around July, indicating that these crops are typically grown during late spring to mid-summer.
• Winter annual is represented in purple with two arrows:
  • The first arrow starts around February and ends around June, showing crops planted in late winter and harvested in early summer.
  • The second arrow starts around September and continues through December, indicating crops planted in fall and continuing into winter.
• Summer annual is shown in orange, with an arrow starting around May and ending around September, representing crops grown during the warm summer months.

Below the timeline, there is a legend listing examples of crops for each category:

• Spring annual (blue text): oats, spring barley, spring canola, peas, leafy greens, broccoli.
• Winter annual (purple text): winter wheat & barley, cereal rye, hairy vetch, crimson clover, triticale, winter canola.
• Summer annual (orange text): corn, soybeans, sorghum, peppers, string beans, cucumber, summer squash, eggplants.

The overall design uses color coding (blue, purple, orange) to clearly distinguish the crop types and their respective growing seasons. The background is white, and the text is in black except for the colored crop names and arrows, which match their category colors.

Credit: Heather Karsten

Biennials are plants that live and reproduce in two years, and at the other end of the life-cycle spectrum are perennial plants that live for 3 or more years. Perennials evolved in environments where resources were limited often due to competition with other plants and their growth rates tend to be slower than annual plants (Lambers et al, 1998). In these resource-limited environments, often plants cannot germinate from seed and reproduce by seed within one year. Therefore, to increase their opportunities for successful reproduction, perennials evolved ways to grow and survive for multiple years to successfully produce offspring. Perennial crops are typically cultivated in environments that may also have a climatic limitation such as a short growing season or dry climate, or where a plant's ability to access resources may be limited due to frequent disturbance such as grazing.

To survive for multiple years, perennials allocate a high proportion of their growth to vegetative plant parts that enable them to access limited resources and live longer. For instance, they often invest in extensive and deep root systems to access water and nutrients, or in tall and wide-reaching aboveground stems and shoots to compete for light, such as bush and tree trunks and branches. Perennials also store reserves to regrow after growth-limiting conditions such as drought, freezing winters, or disturbance such as grazing. Carbohydrates, fat, and protein are stored in stems and roots, or modified stems such as tubers, bulbs, rhizomes, and stolons. In many plant species, these storage organs can produce root and shoot buds that can grow into independent offspring or clonal plants; this is called vegetative reproduction. Although most perennials reproduce both through seed and vegetative reproduction, in resource-limited environments where plant competition is high, the large storage organs and their reserves offer vegetative offspring plants a competitive advantage over starting from seed.

Perennial Crops

Humans have cultivated and selected perennial crop plants for their vegetative plant parts, storage organs, fruit, and seeds. For instance, the leaves and stems are the primary plant parts harvested from perennial forage crops (crops in which most of the aboveground plant material is grazed or fed to animals). Horticultural perennial crops that are harvested for stems and leaves include asparagus, rhubarb, and herbs. And in some cases, a perennial crop's storage organs are harvested each year, limiting the plant's ability to complete its perennial lifecycle and effectively reducing its cultivated lifecycle to an annual. Examples of such crops perennial crops that are cultivated as annuals include potato, sweet potato, and taro, Tree, shrub, and vine food crops managed as perennial crops are typically cultivated for their fruit and seeds, such as apples, stone fruit (ex. peach, plum), plantains, nuts, berries, and grapes (see photos below).

Figure 6.1.7. Perennial alfalfa field in Pennsylvania.

Credit: Heather Karsten

Figure 6.1.8. Apple orchard in Washington. Entomologist Brad Higbee (left) with Jerry Wattman, manager of this apple orchard near West Parker Heights, Washington.

Credit: Scott Bauer of USDA

Figure 6.1.9. Potatoes in a supermarket in Lima, Peru.

Credit: Heather Karsten

Figure 6.1.10. Perennial tree crops at an open-air market in Peru.

Credit: Heather Karsten

Figure 6.1.11. Foreground: Perennial grassland grazed by Angus cattle in western Montana, where precipitation and high daytime temperatures in summer limit plant growth. In the background, perennial grasses and broadleaf plants including shrubs and trees on the foothills of the mountain range have deep roots to access soil moisture that also help reduce soil erosion.

Credit: Heather Karsten

Figure. 6.1.12. Rangeland in Southwest Utah where precipitation and high temperatures limit plant growth

Credit: Heather Karsten

Figure 6.1.13. Alfalfa roots

Credit: Kulbhushan Grover

Annual plants are typically cultivated in high-resource environments and regions with:

• climates that have sufficient precipitation and temperatures for plants to complete their life cycle each year
• soils that soils tend to be relatively flat and well-drained, and are not prone to erosion when they are tilled or planted to an annual crop each year
• high fertility soil

Annual crops produce grain and fruit crops within one growing season. Grain crops are typically a concentrated source of carbohydrates, protein, and sometimes fat, that can be cost-effectively stored and transported long distances, enhancing their market options and utility. Grain and oilseed annual crops are often processed for multiple uses and markets. For instance, oil is extracted from soybean for industrial and human uses, and the remaining meal is high in protein that is used for both human food products and livestock feed.

If conditions are not ideal for annual crops, farmers sometimes use management practices or technologies to improve conditions for crop growth such as irrigation to compensate for the lack of precipitation or black plastic to warm the soil in environments where temperatures may limit plant growth.

Regions, where perennial crops dominate the landscape, tend to have soil or climatic limitations such as steep or hilly slopes that are prone to erosion, shallow or poorly drained soils, soil nutrient limitations; limited precipitation and soil moisture availability, short growing seasons, or temperatures outside of optimal plant growth temperatures. In these environments, farmers may produce annual crops that are adapted to the environment, such as spring or winter wheat that grow during the cooler season or drought-tolerant annuals such as sorghum and pearl millet. Or farmers may use technologies and management practices, particularly for high-value crops, to improve conditions for crop growth such as tile drains, irrigation or season extension technologies.

See illustration and comparison of plant life cycles, the time and forms of reproduction. Can you name a specific crop plant example for each type of plant life cycle?

Text description of the Figure 6.1.14 image.

The image is a black-and-white diagram titled “Figure 1. Weed life cycles” and illustrates the growth and reproduction patterns of four types of weeds—Perennial, Biennial, Winter Annual, and Summer Annual—across the months of the year. Each life cycle is represented by a horizontal timeline labeled from January to December, with sketches of plant stages and seed dispersal points.

• Perennial weeds show continuous growth throughout the year, with mature plants appearing in spring and summer, and seeds dispersed in late summer and early fall. These plants persist year after year.
• Biennial weeds germinate in the first year, grow vegetatively, and then flower and produce seeds in the second year, typically during summer.
• Winter annual weeds germinate in fall, overwinter as small plants, and then grow rapidly in spring, producing seeds by early summer before dying.
• Summer annual weeds germinate in spring, grow through summer, and produce seeds in late summer or early fall, completing their life cycle within one year.

The diagram uses simple line drawings to depict stages such as seedlings, mature plants, and seed dispersal, providing a clear visual comparison of how different weed types align with seasonal changes.

Credit: Bellinder, R. R.; R. A. Kline, D. T. Warholic. 1963. Weed control for the Home Garden. Cornell Cooperative Extension Bulletin 216. Figure 1, Pg. 6.

Because perennials allocate a high proportion of their growth to vegetative structures and regrow for many years, they can: i. protect soil from erosion; ii. return organic matter (carbon-based materials that originated from living organisms) to the soil, providing multiple soil health benefits; and iii. remove carbon dioxide from the atmosphere, potentially sequestering (storing) carbon in the soil or aboveground plant biomass. Forests, for example, sequester carbon above-ground in trees and in below-ground root systems.

Perennial grasses, in particular, have dense, fibrous roots that protect soil from erosion well and are valuable plants for soil conservation. In addition, over the years, some perennial roots and aboveground plant tissues die when environmental conditions limit growth (ex. drought, winter, grazing), and accumulate organic matter and nutrients in the soil. The majority of the most fertile and deep agricultural soils of the world were formed under natural perennial grasslands, whose deep root systems accumulated organic matter in the soil which contributed many beneficial soil properties, as well as carbon sequestration. Some annual crops can also contribute to conserving soil and add organic matter to the soil if a large portion of the crop residue is left on the soil surface, such as corn stalks left on a field after the grain is harvested.

Figure 6.1.15. Perennial grass roots, belowground rhizomes, and aboveground plant tissues provide year-round protection from soil erosion on a sloping field in Pennsylvania, while also providing forage for ruminant dairy cows during the spring, summer and autumn months.

Credit: Heather Karsten

Figure 6.1.16. Some cool-season perennial grasses with rhizomes indicated by the red arrows.

Credit: Maria Carlassare

Figure 6.1.17. Perennial grass mowed and drying for hay harvest on a steeply sloped field in Pennsylvania.

Credit: Heather Karsten

Figure 6.1.18. Sheep moving to high mountain pastures in the New Zealand South Island of where perennial grasses and legumes protect the soil from erosion on steep slopes and the perennial life cycle is adapted to the short growing season.

Credit: Heather Karsten

Plants that have similar flowers, reproductive structures, other characteristics, and are evolutionarily related, are grouped into plant families (See Figure 2). Species in the same plant family tend to have similar growth characteristics, nutrient needs, and often the same pests (pathogens, herbivores). Planting crops from different plant families on a farm and the landscape; and rotating crops of different plant families over time can interrupt the crop pest life cycles, particularly insect pests, and pathogens, and reduce yield losses due to pests. Increasing plant family diversity can also provide other agrobiodiversity benefits including, diverse seasonal growth and adaptation to weather stresses such as frosts, and drought; different soil nutrient needs, as well as producing diverse foods that provide for human nutritional needs.

Figure 6.2.1: The Plant Family Tree

Click for a text description of Figure 6.2.1.

The Plant Family Tree

1. Ancestral Green Algae
   1. Modern Green Algae - single and multicellular algae
      1. Volvox Spirogyra
   2. Seedless Non-vascular - plants with no veins and no seeds
      1. Liverworts
      2. True Mosses
   3. Seedless Vascular - plants with veins and NO seeds
      1. Selaginella
      2. Quillworts
      3. Club Mosses
      4. Whisk Ferns
      5. Adder's Tongue
      6. Water Ferns
      7. Royal Ferns
      8. Horsetails
      9. Climbing Ferns
      10. Tree Ferns
      11. Common Fern
   4. Gymnosperms - Plants with cones
      1. Ephedra
      2. Welwitschia
      3. Firs
      4. Pines
      5. Ginkgo
      6. Cycad
      7. Yew
      8. Sequoia
      9. Cypress
      10. Podocarpus
      11. Monkey Puzzle
   5. Angiosperms - Flowering Plants
      1. Dicots
         1. Euphorbs
         2. Violets
         3. Willows
         4. Mustard
         5. Papaya
         6. Cacao
         7. Mallow
         8. Maples
         9. sumacs
         10. Citrus
         11. Roses
         12. Elms
         13. Hopes
         14. Mulberries/figs
         15. Beans
         16. Begonias
         17. Cucumbers
         18. Oaks
         19. Walnuts
         20. Birch
         21. Coffee
         22. Milkweeds
         23. Gentians
         24. Morning Glories
         25. Tomatoes
         26. Scrophs/Snapdragons
         27. African Violets
         28. Holly
         29. Olive
         30. Mints/Verbena
         31. Ginseng
         32. Carrots
         33. Sunflowers
         34. Pawpaw
         35. Magnolia
         36. Laurel
         37. Pepper
         38. Poppies
         39. Grapes
         40. Buttercup
         41. Eucalyptus
         42. Evening Primrose
         43. Geraniums
         44. Sedum
         45. Peonies
         46. Currants
         47. Sycamore
         48. Star Anise
         49. Water Lilies
         50. Sundew
         51. Mistletoe
         52. Carnations
         53. Beets
         54. Cacti
         55. Portulaca
         56. Blueberries
         57. Impatiens
      2. Monocots
         1. Amborella
         2. Aroids
         3. Yams
         4. Lilles
         5. Iris
         6. Palms
         7. Pineapple
         8. Sedges
         9. Dayflowers
         10. Bananas
         11. Gingers
         12. Cannas
         13. Grasses
         14. Orchids
         15. Asparagus
         16. Agave
         17. Amaryllis
         18. Onions
         19. Daylillies
         20. Aloe

Credit: The U. S. Botanic Garden and the National Museum of Natural History, Department of Botany, Smithsonian Institution.

The Fabaceae/Leguminosae, commonly called the Legume plant family, is important for soil nitrogen management in agriculture and for soil, human and animal nutrition. Legume plants can form a mutualistic, symbiotic association with Rhizobium bacteria which inhabit legume roots in small growths or nodules in the roots (seed images in the video listed below). The rhizobia bacteria have enzymes that can take up nitrogen from the atmosphere and they share the “fixed nitrogen” with their legume host plant. Nitrogen is an important nutrient for the plants and animals, it is a critical element in amino acids and proteins, genetic material and many other important plant and animal compounds. Legume grains crops, also called pulses are high in protein, such as many species of beans, lentils, peas, and peanuts. Most of their plant nitrogen is harvested in grain, although there is some in crop residues that can increase soil nitrogen content. Perennial legume crops are typically grown as forage crops for their high protein for animals. Because they allocate a large portion of their growth to vegetative plant parts and storage organs, perennial legumes also return a significant quantity of nitrogen to the soil, enhancing soil fertility for non-legumes crops grown in association or in rotation with legumes.

Watch the following NRCS video about legumes and legume research.

Video: The Science of Soil Health: Understanding the Value of Legumes and Nitrogen-Fixing Microbes (2:30)

In addition to characterizing plants by their taxonomic plant family, crop plants are also classified as either cool season or warm season, referring to the range of temperatures that are optimum for their growth. Examples of cool-season agronomic crops include wheat, oats, barley, rye, canola, and many forage grasses are called cool-season grasses, such as perennial ryegrass, timothy, orchardgrass, tall fescue, smooth bromegrass, and the bluegrasses. Warm-season agronomic crops include corn or maize, sorghum, sugarcane, millet, peanut, cotton, soybeans, and switchgrass.

In addition, plants are classified by the type of photosynthetic pathway that they have.

Plant Photosynthesis, Transpiration, and Response to Changing Climatic Conditions

Plants require light, water, and carbon dioxide (CO₂) in their chloroplasts, where they create sugars for energy through photosynthesis. The chemical equation for photosynthesis is:

6 CO₂+ 6 H₂O → C₆H₁₂O₆+ 6 O₂

Carbon dioxide (CO₂) enters plants through stomata, which are openings on the surface of the leaf that are controlled by two guard cells. The guard cells open in response to environmental cues, such as light and the presence of water in the plant.

Figure 6.2.2: Stomate on a Tomato leaf

Credit: Wikimedia Commons, Tomato leaf stomate, Public Domain

Water (H₂O) enters the plant from the soil through the roots bringing with it important plant nutrients in solution.

Transpiration or the evaporation of water from plant contributes to a “negative water potential.” The negative water potential creates a driving force that moves water against the force of gravity, from the roots, through plant tissues in xylem cells to leaves, where it exits through the leaf stomata. Since the concentration of water is typically higher inside the plant than outside the plant, water moves along a diffusion gradient out through the stomata. Transpiration is also an important process for cooling the plant. When water evaporates or liquid water molecules are converted to a gas, energy is required to break the strong hydrogen bonds between water molecules, this absorption of energy cools the plant. This is similar to when your body perspires, the liquid water molecules absorb energy and evaporate, leaving your skin cooler.

Figure 6.2.3: Picture of water molecules leaving stomata - side view

Credit: USDA National Institute of Food and Agriculture, found at Plant & Soil Sciences eLibrary

Carbon dioxide (CO₂) also diffuses into the plant through the stomata, because the concentration of carbon dioxide is higher outside of the plant than inside the plant, where carbon dioxide concentration is lower due to plant photosynthesis fixing the carbon dioxide into sugars. To conduct photosynthesis, plants must open their leaf stomata to allow carbon dioxide to enter, which also creates the openings for water to exit the plant. If water becomes limited such as in drought conditions, plants generally reduce the degree of stomatal opening (also called “stomatal conductance”) or close their stomata completely; limiting carbon dioxide availability in the plant.

Credit: ASU School of Life Sciences, Snacking on Sunlight

The majority of plants and crop plants are C3 plants, referring to the fact that the first carbon compound produced during photosynthesis contains three carbon atoms. Under high temperature and light, however, oxygen has a high affinity for the photosynthetic enzyme Rubisco. Oxygen can bind to Rubisco instead of carbon dioxide, and through a process called photorespiration, oxygen reduces C3 plant photosynthetic efficiency and water use efficiency. In environments with high temperature and light, that tend to have soil moisture limitations, some plants evolved C4 photosynthesis. A unique leaf anatomy and biochemistry enables C4 plants to bind carbon dioxide when it enters the leaf and produces a 4-carbon compound that transfers and concentrates carbon dioxide in specific cells around the Rubisco enzyme, significantly improving the plant’s photosynthetic and water use efficiency. As a result in high light and temperature environments, C4 plants tend to be more productive than C3 plants. Examples of C4 plants include corn, sorghum, sugarcane, millet, and switchgrass. However, the C4 anatomical and biochemical adaptations require additional plant energy and resources than C3 photosynthesis, and so in cooler environments, C3 plants are typically more photosynthetically efficient and productive.

Since carbon dioxide is the gas that plants need for photosynthesis, researchers have studied how the elevated CO₂ concentrations impact C4 and C3 plant growth and crop yields. Although C3 plants are not as adapted to warm temperatures as C4 plants, photosynthesis of C3 plants is limited by carbon dioxide; and as one would expect research has shown that C3 plants have benefitted from increased carbon dioxide concentrations with increased growth and yields (Taub, 2010). By contrast, with their adaptations, C4 plants are not as limited by carbon dioxide, and under elevated carbon dioxide levels, the growth of C4 plants did not increase as much as C3 plants. In field studies with elevated carbon dioxide levels, yields of C4 plants were also not higher (Taub, 2010). In addition, if soil nitrogen was limited, C3 plant response to elevated CO₂ concentration was reduced or crop plant nitrogen or protein content was reduced compared to plants grown in high soil N conditions (Taub, 2010). These results suggest that crops will likely require higher soil nutrient availability to benefit from elevated atmospheric carbon dioxide concentrations. For more optional reading information about C3 and C4 plant response to elevated carbon dioxide concentrations, see the following summary of research that is also listed in the additional reading list, Effects of Rising Atmospheric Concentrations of Carbon Dioxide on Plants.

Other Drought Tolerant Crop Plant Traits

Some additional plant traits that help plants tolerate drought and heat stress include deep root systems (typical of perennials) and/or thick leaves with waxes that reduce water loss and the rate of transpiration. In addition, some plants roll their leaves to reduce the surface area for solar radiation reception and heating, and some reduce their stomatal conductance more (water loss) more than others.

Temperature

Elevated temperatures projected with climate change can have multiple impacts on plant growing conditions. Climate change may lengthen growing seasons in some regions, although day lengths will not change. As planting dates are altered with longer growing seasons, crops may also be exposed to high temperature, moisture stress, and risk of frost. Elevated temperatures may also increase evaporation of water from the soil, reducing soil water availability. Higher temperatures are not necessarily ideal for yield, even if the temperatures are below a plants’ optimal temperature. At elevated temperatures, plants grow faster which tends to, one, reduce the amount of the time for photosynthesis and growth, resulting in smaller plants, and two, reduce the time for grain fill, reducing yield, particularly if nighttime temperatures are high (Hattfield et al., 2009). High temperatures can also reduce pollen viability, be lethal to pollen. The multiple effects of high temperatures on plant physiological process and soil moisture likely explain why research has found that grain development and yield are often reduced when temperatures are elevated (Hattfield et al., 2009).

Many factors that are projected to change with climate change could influence plant growth. These include carbon dioxide concentration, temperature, precipitation, and soil moisture, and ozone concentrations in the lower atmosphere.

Socio-economic Factors

In addition to the climate and soil resources for crop production, many socioeconomic factors influence which crops farmers chose to cultivate, including production costs, domestic and international market demand; and government policies that subsidize agricultural producers, and reduce trade barriers or export costs. As discussed in Module 3, the protein, energy, fat, vitamins, and micro-nutrients of crops for human nutrition are one predictor of the market value of a crop. However some food crops are highly valued and cultivated for their cultural and culinary qualities, such as flavor (ex. chilies, vanilla, coffee, wine grapes); and their high economic value often reflects high production and processing costs, as well as market demand for their unique culinary and cultural properties.

Some crops are cultivated for non-human food uses such as livestock feed, biofuel, fiber, industrial oil and starch, and medicinal uses. Crop processing often creates by-products that can be used for other purposes, adding market value. For example, when oil is extracted from oilseeds such as soybean, the soybean meal by-product is high in protein and sold for livestock feed or added to human food products. And for crops that are cultivated on many acres often with support from government policies, the consistent, abundant supply of these commodity crops has contributed to the development of multiple processing technologies, uses, and markets. To better understand factors that contribute to the production of commodity crops, we will now examine two case studies of corn and sugarcane.

Understanding Agricultural Commodities: Two Agricultural Crops Case Studies 

In the following two agricultural crop case studies, you will have the opportunity to apply your understanding of crop plant life cycles, classification systems, and crop adaption to climatic conditions to understand how plant ecological features and human socioeconomic factors influence which crops are some of the major crops produced in the world.

Recall in module 5, we examined how soils, climate, and markets play major roles in determining which crops farmers cultivate. In many cases, farmers cultivate multiple crops of more than one life-cycle because the diversity provides multiple benefits, such as soil conservation, interruption of pest lifecycles, diverse nutritional household requirements, and reduced market risk. In this module, we examine some ways that farmers cultivate crops in sequence and define some of the terms for this crop sequencing.

A sole crop refers to planting one crop in a field at a time. Recall from Module 5, the seasonal crop types (Figure 7.1.1) and note that different seasonal crops could be planted in succession. A monoculture refers to planting the same crop year after year in sequence (See Figure 7.1.2). By contrast in a crop rotation, different crops are planted in sequence within a year or over a number of years, such as shown in Figures 7.1.3a and 7.1.3b. When two crops are planted and harvested in one season or slightly more than one season, the system is referred to as double cropping, as illustrated in Figure 7.1.4. Where growing seasons are long and/or crop life cycles are short (ex. leafy greens), three crops may be planted in sequence within a season, as a triple-crop.

Figure 7.1.1: Crop Term: Seasonal Types and Example Crops

Credit: Heather Karsten

Figure 7.1.2: Monoculture

Credit: Heather Karsten

Figure 7.1.3a: Simple Summer Annual Crop Rotation

Credit: Heather Karsten

Figure 7.1.3b: Dairy Perennial - Annual Crop Rotation

Credit: Heather Karsten

Figure 7.1.4: Double-cropped annual crops

Credit: Heather Karsten

Crop rotations and double cropping can provide many soil conservation and soil health benefits that are discussed in the reading assignment at the end of this page, and in Module 7.2. Crop rotations can provide additional pest control benefits particularly when crops from different plant families are rotated, as different families typically are not hosts of the same insect pest species and crop pathogens. Integrating crops of different seasonal types and life cycles in a crop rotation also interrupts weed life cycles by alternating the time when crops are germinating and vulnerable to weed competition. Rotating annual crops with perennial forage crops that are harvested a couple of times in a growing season also interrupts annual weed life cycles, because most annual weeds don't survive the frequent forage crop harvests.

When all or most of a crop is grazed or harvested for feed for ruminant livestock, such as dairy and beef cattle or sheep, the crop is referred to as a forage crop. Examples of forage crops include hay and pasture crops, as well as silage that can be produced from perennial crops and most grain crops. For instance, silage from alfalfa, perennial grass species, corn, oat, and rye is made when most of the aboveground plant material (leaves, stems and grain in the case of grain crops) is harvested and fermented in a storage structure called a silo or airtight structure. To preserve the silage, air is precluded from the storage structure and microbes on the plant material initially feed on the crop tissues, deplete oxygen in the storage structure, and produce acidic byproducts that decrease the pH of the forage. This acidic environment without oxygen prevents additional micro-organisms from growing, effectively "pickling", and preserving the forage.

Figure 7.1.5: Airtight upright silo

Credit: Heather Karsten

Figure 7.1.6: Bunker silos are packed tightly with heavy equipment and covered with plastic to keep out air and moisture.

The bunker silo on the right is uncovered because the silage is being removed to feed to dairy cattle.

Credit: Heather Karsten

Intercrops are two or more crops that are planted together in a field at the same time or to be planted close in time and overlap for some or all of their life cycle. Intercrops may provide a range of benefits including: i. improving soil fertility, ii. increasing crop diversity and iii. reducing pest pressure. The mixtures also often produce higher yield and crop quality. There are multiple types of intercrops that vary in their spatial arrangement.

Strip intercrops are wide strips with multiple rows of one crop, that are alternated on the field with strips of one or more different crop(s). Strip intercrops are typically planted on the field contour with crops of different life cycles that protect soil from erosion throughout the year.  For instance, strips of corn may be alternated with strips of perennial forage grasses that can reduce soil erosion across the field when the corn isn't growing. Or, as in the photo below, winter wheat provided live plant coverage on portions of the field in spring, prior to corn and soybean were planted. In mid-summer, corn and soybean provide live coverage after wheat is harvested; and in fall, winter wheat will be growing on some strips after corn and soybean are harvested. Having strips of different crop species can also reduce the spread of insect pests and crop pathogens compared to cultivating one crop on the entire field. 

Figure 7.1.7. Strip intercrop: Alternating strips of corn, soybean and winter wheat planted on the contour.

Credit: Heather Karsten

Row intercrops alternate rows of different crop species, usually every other row or every two rows.

Figure 7.1.8. Row intercrop: Alternating rows of onion and hairy vetch. Hairy vetch is a winter annual legume that is mowed frequently to reduce competition with the onions. In this system, hairy vetch is planted to provide soil protection, suppress weeds, and add nitrogen to the soil.

Credit: Heather Karsten

Mixture intercrops tend to be combined randomly when planted; such as grass and legume forage mixtures. Intercrops of different crop species (ex. native tuber mixtures) or different varieties of a crop species (ex. rice) are sometimes planted to reduce pathogen and insect pest infestations. Crop rotation and intercropping increase agrobiodiversity across an agricultural landscape, providing multiple potential agroecosystem benefits, such as i. reducing the risk of crop loss to pests and climatic stresses (ex. frosts, floods, and drought), ii. providing habitat for beneficial organisms such as pollinators and pest predators, and iii. enhancing the diversity of nutritional crops for farmers and markets. Further, integrating crops from the grass family tends to promote soil structure, while legumes enhance soil nitrogen, and integrating perennial crops protects the soil from erosion and builds soil organic matter and soil biological activity because perennials allocate a high proportion of their growth to storage organs. For instance, the photos below illustrate how both intercropping and crop rotation enhance agrobiodiversity in the high Andes of Peru.

Figure 7.1.9. Pasture intercrop of four perennial forage crops: tall fescue, orchardgrass, Kentucky bluegrass, and white clover.

Credit: Heather Karsten

Figure 7.1.10. Four major native tuber crops: Maca, Oca, Ulluco, and Mashua at the CIP International Potato Center in Lima, Peru.

Credit: Heather Karsten

Figure 7.1.11. Example High Altitude Andean Crop Rotation from Peru

Credit: Heather Karsten

Figure 7.1.12: Sheep grazing perennial pastures that are typically rotated to annual crops: potato, native tuber crops, legumes, and small grains before rotating back to perennial pasture.

Credit: Heather Karsten

Figure 7.1.13. Agrobiodiversity is high across the high altitude Andean landscape due to crop rotation and genotypic diversity within fields.

Credit: Heather Karsten

Figure 7.1.14. Diversity of potato and native tuber crops in a grocery store in Lima, Peru

Credit: Heather Karsten

Cover Crop: A cover crop is planted after a crop that is harvested and is terminated before the subsequent crop is planted. Cover crops tend to be annual crops that they can quickly establish after a harvested crop to protect the soil from erosion and provide other benefits including i. to add organic matter to the soil; ii. to scavenge nutrients and prevent nutrients from leaching out of the topsoil (also called a catch crop); iii. to support soil organisms in the root zone, iv. to suppress weeds, and v. to provide habitat for aboveground beneficial organisms, such as insects that predate on crop pests or weed seeds. Leguminous cover crops also add nitrogen to the soil when they are terminated and returned to the soil and are therefore often referred to as green manure crops. Cover crops are also sometimes referred to as "catch crops" because they can take up and retain nitrogen and other nutrients that might otherwise leach out of the rooting zone and be lost to deeper soil profiles, and potentially to groundwater.

Cover Crop Intercrops

Because cover crop species have different plant traits that provide different cropping system benefits, often two or more species of cover crops are planted together as a cover crop intercrop or cover crop mixture. For instance, small grains that scavenge nitrogen well and have fibrous roots that bind soil particles and promote soil structure are often mixed with tap-rooted legumes that fix nitrogen. Some cover crop mixtures combine plant species that establish quickly in the late summer or early fall but don't typically survive the winter, such as oats or deep-rooted radish species. Non-winter hardy species are sometimes combined with winter-hardy species such as hairy vetch, cereal rye or annual ryegrass that survive the winter and provide cover in early spring.

Figure 7.1.15. Annual crimson clover and winter wheat cover crop intercrop photographed in spring.

Credit: Heather Karsten

Figure 7.1.16. Cover crop intercrop of annual cereal rye and hairy vetch (a legume) photographed in spring.

Credit: Heather Karsten

As discussed in Module 5, soil is a complex matrix of minerals, air, water, organic matter, and living organisms. Historically, the emphasis in agriculture has been on reducing soil erosion. But since the 1990s, soil scientists and conservationists have recognized and described multiple valuable properties and ecosystem functions of soil that are referred to as indicators of soil quality or soil health. In 1997, the Soil Science Society of America's Ad Hoc Committee on Soil Quality (S-581) defined Soil Quality as:

"the capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation" (Karlen et al., 1997).

Indicators or measures of soil quality describe a soil's biological, chemical and physical properties. In addition to the soil chemical properties such as nutrient content and pH, additional indicators of soil quality include a soil’s:

• Organic matter content. Organic matter stores carbon can release nutrients, support soil biological activity, buffer soil pH, hold plant nutrients, and increase a soil's water-holding capacity
• Biological activity in the soil. Soil organisms can provide multiple benefits such as nutrient cycling, secreting sticky polysaccharides that help bind together soil particles and increase soil porosity and predation, and suppression of plant pests such as plant pathogens and weed seeds.
• Soil structure and porosity. Soils with good structure and porosity can support water and air infiltration and resist compaction. Water stable aggregates are an important physical indicator of soil health. Water stable aggregates contain soil mineral particles such as sand, silt, and clay that are typically held together by a combination of binding materials including fine root hairs, soil fungal hyphae (fungal filaments), and sticky polysaccharides that are exuded from soil microorganisms. Because they are stable when wet (during or after a precipitation event) they maintain soil pores that can contain and allow air and water to infiltrate the soil, reducing water and soil run-off. Water stable aggregates can also protect organic matter from degradation and soil microorganisms from predatory micro-organisms.

Figure 7.1.17: Plant roots, fungal hyphae, and microbial polysaccharide exudates contribute to binding soil mineral particles together into soil macroaggregates, creating macropores between them.

Credit: Illustration by Heather Karsten

Read

Chapter 1 (Healthy Soil) and Chapter 2 (Organic Matter: What it is and Why it’s so important?) from the book that you downloaded: Building Soils for Better Crops. Edition 3. Sustainable Agriculture Network, USDA. Beltsville, MD.

Then watch the following video about soil biology and list four kinds of soil organisms and how they influence soil.: The Living Kingdoms Beneath our Feet. (USDA NRCS).

Video: International Year of Soils July: The Living Kingdoms Beneath Our Feet (2:08)

In addition to exposing soil to wind and water erosion, tillage can alter the physical structure, distribution of organic matter, and biological activity of soil. At the depth where the plow impacts the soil, a layer of soil compaction can develop (a plow pan), limiting water infiltration and plant rooting depth. Under tillage, crop residues, roots and root hairs, and their associated fungal hyphae are disturbed and more decomposed in the plow layer. By contrast, when roots, fine roots, and fungal hyphae are not disturbed and decomposed as rapidly, there are more channels that water, air, earthworms, and roots can move through, and soil aggregation is enhanced. Below is a schematic comparing the root zone profile of a conventionally tilled soil to a no-till soil.

Figure 7.2.1: Steps Toward a Successful Transition to No-Till.

Credit: S. W. Duiker and J.C. Myers. 2005 Penn State University.

Watch the three videos below, from USDA NRCS about soil tillage and soil health.

Video 1: The Science of Soil Health: What Happens When You Till? USDA NRCS (3:05)

Video 2: The Science of Soil Health: Nightcrawlers and Soil Water Flow. USDA NRCS (3:05)

Video 3: The Science of Soil Health: Compaction USDA NRCS (4:26)

Humans have developed many different ways to prepare the soil to plant crops, with the primary goal of achieving good seed to soil contact to keep seeds moist as they germinate and grow. There are some benefits of tillage. For instance, tillage enables the farmer to bury or mix-in crop residues that insulate the soil and keep it moist and cool which can delay crop seed germination in cool environments. By burying the insulating crop residues, solar radiation can warm the soil more quickly. Tillage can also terminate weeds, cover crops or perennials, and bury weed seeds and crop residues that may harbor pathogens and insect seeds; tillage also mixes in soil amendments, such as fertilizer and animal manures.

In conventional tillage systems, primary tillage equipment such as the moldboard plow or a rototiller inverts the soil. A second tillage event or plow is often used afterward to break up large soil clods into smaller particles, with the goal of improving seed to soil contact. See photos below.

Figure 7.2.2: Moldboard plow

Credit: Heather Karsten

Figure 7.2.3: Soil inverted and crop residue buried by a moldboard plow.

Credit: Heather Karsten

Figure 7.2.4. Disk plow breaking up soil clods in a secondary tillage operation

Credit: Heather Karsten

Removing or mixing-in crop residue leaves the soil exposed and prone to wind and water erosion, as well as soil moisture loss. Tilling crop residue into the soil also makes residues more accessible to soil organisms and incorporates oxygen into the soil, increasing the decomposition rate of the residues and decreasing organic matter content at the soil surface and plow layers. Tillage also disrupts soil organisms, particularly mycorrhizal fungi, and soil physical properties such as water stable aggregates.

Conservation tillage or minimum tillage is another soil preparation method designed to reduce soil erosion by reducing disturbance and leaving some plant residue (at least 30%) on the surface. The soil is not inverted, but the surface is disturbed and often a high proportion of crop residues are mixed in with tillage equipment such as a disk plow or a chisel plow.

No-till or Direct-seeding is designed to eliminate tillage, by cutting a slit in the surface and placing the seed in the slit. In addition to minimizing crop residue disturbance, the crop is planted in one pass across the field, thereby reducing erosion, labor, and fuel needed to prepare a field and plant the crop.

Figure 7.2.5. No-till drill. A coulter wheel cuts a slit in the ground, a tube drops the seed into the slit and press wheels follow behind to cover the slit with soil.

Credit: Heather Karsten

Figure 7.2.6. The no-till drill causes very little disturbance of the soil and crop residue.

Credit: Heather Karsten

Some hurdles to no-till adoption As discussed earlier, there are a number of reasons that farmers till the soil. For instance, conventional tillage can terminate perennials, cover crops, and weeds prior to planting the subsequent crop. Without conventional tillage, farmers typically use herbicides to terminate the previous perennial or cover crop and control weeds. In cool environments, crop residues can harbor pathogen and insect pests, and insulate soil, which can slow soil warming in spring and delay crop emergence. These factors can reduce crop yield, particularly if farmers don't rotate crops to interrupt pest life cycles. In addition, although farmers typically need less tillage equipment to plant with no-till, there is an initial cost associated with purchasing no-till equipment for farmers who use conventional or conservation tillage equipment. And with new equipment, farmers need to learn how to adjust no-till planters to ensure that seed is planted at the optimal depth. Consequently, no-till planters are typically heavier to cut through crop residues and place seeds at a sufficient depth for good seed to soil contact.

Zone or strip tillage When soils have high crop residue and/or are high in organic matter, or are not well-drained, soils can remain cool and delay seed germination. Zone tillage or strip tillage incorporates the insulating crop residue in a narrow zone or strip of soil where the seed is placed. Residue between the seed planting zones is not disturbed or removed. Removing the soil insulating layer increases the rate of soil drying and warming in close proximity to the seed, promoting earlier seed germination compared to soil with residue left intact.

Figure 7.2.7: A field prepared with zone tillage or strip tillage that removes residue in a narrow zone where the seed is planted.

Credit: Heather Karsten

Soil conservation practices are most effective when they reduce soil disturbance or tillage and also maintain live plants in the soil.

As discussed in Module 5, perennials provide year-round live plant cover that protects soil from erosion; and their live and large root systems support rhizosphere activity and return organic matter to the soil all year. To provide continuous live roots for soil conservation and soil health, perennial crops can be rotated with annual crops, and double crops and cover crops can be integrated into annual cropping systems. Recall that in Module 7.1, a dairy crop rotation of corn-alfalfa was shown in Fig. 7.1.3b, and double cropping in Fig.7.1.4. The photos below also illustrate examples of how year-round cropping provides multiple agroecosystem benefits.

In addition, consider how managing crops and soils for soil conservation and health can enhance agricultural resilience and adaption to climate change. For instance, by increasing soil organic matter content, agricultural soil can: i. contribute to carbon sequestration (removing carbon dioxide from the atmosphere and storing it in soil), ii. improve soil structure and porosity and enhance water infiltration and water content in soil, and iii. store and cycle nutrients. Perennial crop production and double-cropping can utilize potentially longer growing seasons; provide more year-round protection of soil from erosion, and planting and harvesting crops at multiple times of the year can reduce the risk of extreme weather events or irregular weather interfering with cropping activities.

Figure 7.2.8: When annual crops such as corn and soybeans have completed their lifecycle in autumn, perennial forages such as alfalfa and perennial grasses and winter annuals such as winter wheat are alive, protecting the soil and supporting soil organisms in their root zones.

Credit: Heather Karsten

Figure 7.2.9: Double-cropped winter canola provides live soil cover in fall and early spring.

Credit: Heather Karsten

Figure 7.2.10: Winter rye cover crop in March protects the soil from erosion, produces organic matter to return to the soil, takes up soil nutrients such as Nitrogen, suppresses weeds and provides habitat for below ground and aboveground organisms such as beetles that eat weed seeds and crop insect pests.

Credit: Heather Karsten

For more discussion of a crop-soil system management approach, watch the three short videos below from NRCS about the benefits of cover crops on soil health.

Video 1: The Science of Soil Health: Using Cover Crops to Soak up Nutrients for the Next Crop USDA NRCS (3:08)

Video 2: The Science of Soil Health: Without Carrot or Stick USDA NRCS (2:39)

Video 3: The Science of Soil Health: Cover Crops and Moisture USDA NRCS (3:26)

Activate Your Learning

Go to the FAO UN website and read their brief description of Conservation Agriculture. Then watch the short video “Conservation Agriculture in Southern Brazil” (4:41).

After Watching the Video, Answer the Following Three Questions:

Pest species can be present in agroecosystems, but not cause significant crop yield loss or livestock productivity reductions. Why? What factors prevent pest populations from reducing yield? One explanation may be that the crop or livestock is resistant to the pest. For instance, a crop plant may produce compounds that fend off pathogen infection or deter insect feeding. And if environmental conditions and resources are ideal, the plant may be able to grow and recover from pest infestation. What other ecological processes and factors might contribute to agricultural resilience to pests or other stresses such as climate change?

Activate Your Learning

In natural ecosystems there tend to be more niches and a higher diversity of species compared to most managed agroecosystems that are simpler, have fewer predatory and parasitic species, and less genetic diversity within a species. As the table below indicates with fewer trophic interactions, there are fewer species to reduce pest populations and prevent them from reducing agricultural yield and quality. Further, with low genetic diversity within agricultural species and across the landscape, the agricultural system is more vulnerable to pest outbreaks than natural ecosystems.

Insects are the most diverse group of animals that are found in most environments. In the Animal kingdom, Insects are in the Phylum Arthropoda; Arthropods have an exoskeleton of chitin that they shed as they grow; they also have segmented bodies and jointed appendages. In addition to the Class Insecta, the Arthropoda also includes the arachnids (spiders and mites), myriapods (ex. centipedes), and crustaceans (crabs, lobsters, etc.). Insects are distinguished from the other Arthropod classes by the following features:

1. As adults and in some species in the juvenile stages, insects have three body parts: the head, thorax, and abdomen. Although in some insect species, some of the three body parts are fused together and may be difficult to distinguish. See this website for images and more discussion of insect anatomy: Purdue University, College of Agriculture, Department of Entomology, 4-H and Youth: Insect Anatomy

2. The adults have antennae on their heads that they use to sense their environment, and they have three pairs of legs or six legs.

   

   Figure 8.1.1: Honeybees are important pollinator insects. Note the three body parts (head, thorax, and abdomen) two antennae, and three pairs of legs. 

   Credit: MaryAnn Frazier, Department of Entomology, Penn State University
3. Most insects undergo a morphological change that occurs between the time they hatch from eggs and develop into adults. The morphological change is called either complete metamorphosis or incomplete metamorphosis referring to how significantly the insect's appearance changes from the early stage of development to the adult stage. Go to these links to see images of the types of metamorphosis and read more about insect metamorphosis: ASU School of Life Sciences: Metamorphosis

Feeding Types

Insects may be herbivores or omnivores. Herbivorous insects may eat plants by directly feeding on plant tissues such as leaves or roots. Herbivorous insects include caterpillars, beetles, grasshoppers, and ants. Some insects pierce plants and suck plant nutrients from the plant vascular system, typically the phloem, (the cells that transport plant carbohydrates and amino acids); although some insects feed on the xylem, the vascular cells that transport water and nutrients. Examples of piercing-sucking insects include aphids and mosquitoes. By contrast, butterflies and moths have siphoning mouthparts for drinking nectar. Omnivore insects consume multiple kinds of food including other insect prey and plant tissues such as leaves and/or nectar and pollen.

Beneficial insects

Although insect pests are major agronomic pests, only about 1% of insect species are agricultural pests. Insects also contribute to important ecosystem processes, including: i. pollination, ii. predation and parasitism (ex. lady beetles, lacewings, praying mantis, parasitic wasps); iii. decomposition of organic materials such as crop residues and manure (Ex. dung beetles) iv. providing food for other organisms, such as fish and birds. Review the photos below for some categories of beneficial insects, and some of their characteristics here: National Pesticide Information Center

Figure 8.1.2: Dung Beetles contribute to decomposing dung or manure. This photo shows a Large Copper Dung Beetle (Kheper nigroaeneus) on top of its dung ball. 

Credit: Bernard DUPONT from FRANCE (CC BY-SA 2.0), via Wikimedia Commons

Figure 8.1.3: A beetle (Chlaneius sp.), predating on insect larvae

Credit: Heidi Myer

Figure 8.1.4: Parasitic wasp laying eggs on an alfalfa weevil

Credit: Arthur Hower, PSU

Figure 8.1.5: Caddisflies: An important food source for fish.

Credit: Jason Neuswanger, Troutnut

Humans have developed methods of insect and pest control for centuries.

Pesticide Resistance

Soon after the development of DDT in 1939 and the dawn of the modern insecticide era in the 1940s, scientists began to understand that pesticides were not the silver bullet of pest control. Particularly when a pesticide or one effective pest control strategy is relied on, the control tactic acts as a strong selective force for the development of resistance to the tactic in the target pest population. With the continuous application of the same pesticide, individuals that are susceptible to the pesticide are killed, leaving the few resistant individuals that survive to reproduce a offspring that are resistant to the pesticide. See the figure below for an illustration of how frequent reliance on one insecticide can select for a resistant insect population. Further, since many early pesticides were broad spectrum pesticides, the natural enemies of agricultural pest populations were also destroyed, contributing to pest population outbreaks.

Figure 8.1.6: How the repeated use of a pesticide results in pest resistance

Source: How pesticide resistance develops. Michigan State University. Excerpt from Fruit Crop Ecology and Management, Chapter 2: Managing the Community of Pests and Beneficials by Larry Gut, Annemiek Schilder, Rufus Isaacs and Patricia McManus

In 1984, the US Board of Agriculture of the National Academy of Sciences organized a committee to explore the science of pest resistance and strategies to address the challenge. A report called "Pesticide Resistance: Strategies and Tactics for Management" was co-authored by the Committee on Strategies for the Management of Pesticide Resistant Pest Populations and published in 1986 by the National Academies Press, Washington D.C. In Chapter 1, G. P. Georghiou (1986) documented the development of pest resistance across multiple pest organisms (see pages 17 and 28 for figure 2 and figure 8), as well as how difficult and costly it was becoming to develop cost-effective pesticides (see figures 12 and 13 on page 36).

In the report, the Committee recommended using Integrated Pest Management or IPM to reduce the evolution of pesticide resistance and provide more long-term, effective pest control. As early as 1959, a team of scientists (Stern et al.) in California had also proposed that pest control that integrated both biological and chemical control approaches, was needed to prevent pest resistance to pesticides and pest control. Stern et al. (1959) defined terms and concepts that are fundamental to IPM today.

Read the following two fact sheets for a description of Integrated Pest Management and the terms that Stern and his colleagues defined in 1959, which are still used today (economic injury level, economic threshold, and general equilibrium position).  Then watch the following short video and answer the questions below:

1. The Integrated Pest Management (IPM) Concept. D. G. Alston. July 2011. IPM 014-11. Utah State University Extension and Utah Plant Pest Diagnostic Laboratory
2. IPM Pest Management Decision-Making: The Economic-Injury Level Concept. D. G. Alston. July 2011. IPM 016-11. Utah State University Extension and Utah Plant Pest Diagnostic Laboratory

Activate Your Learning: IPM Concept and Decision-Making

Describe three things that are integrated into IPM.

Click for the answer.

ANSWER: Pest control strategies are integrated: such as cultural, mechanical, biological, and chemical. The FAO website provides multiple examples of these practices.

On the IPM figure below, which IPM pest population terms from the article could describe the lines labeled A, B, and C?

Figure 8.1.7: Hypothetical pest density over time graph. What IPM pest population term could apply to each line in the above figure?

Credit: Heather Karsten

Click for the answer.

ANSWER:

Figure 8.1.8: Hypothetical pest density over time graph with IPM pest population terms included

Credit: Heather Karsten

How would you describe the damage that the pest had caused to the crop at each of these pest population densities?

Click for the answer.

ANSWER: A: Economic Injury level- the pest damage has caused a significant economic cost or loss in the value and/or quality of the crop; B: Economic threshold: the pest population has reached a density that is cost-effective to control the pest population and prevent economic losses to the crop; it has not yet caused irreversible economic damage; C: The pest population is in equilibrium with natural enemies: pest damage is minor and natural enemies are preventing the pest population from increasing to the density of being an economic threat to the crop.

Watch the first 4.11 minutes of the below video: Integrated Pest Management (IPM) in Apple Orchards, which describes European Red Mite pests and predatory mites in Pennsylvania apple orchards.

Video: Integrated Pest Management (IPM) in Apple Orchards (8.34)

Integrated Pest Management (IPM) in Apple Orchards.

Click here for a transcript of the Integrated Pest Management video

Fruit growers do their best to assure consumers their food is grown in ways that are environmentally, socially, and economically sustainable. Regular field scouting and weather monitoring are key to achieving the production goals of conserving soil and water, reducing pesticide use, and being good responsible employers. In this short video, you will learn some basic orchard scouting principles for common disease, apple scab, and also mite pests and beneficials. Weather stations provide site-specific data on temperature, rainfall, relative humidity, leaf wetness, and degree days, to alert you when conditions are favorable for diseases and insect pests. Routine inspection of trees and the use of pheromone traps to determine thresholds, will help you minimize and better time sprays. Penn State is known for its early work on IPM for biological control of European red mites. European red mite is a major pest of apples, if controlled only with mitacides, With eight to ten generations per year, this pest can build in numbers very quickly and has historically been able to develop resistance to many new mitacides, in only three to five years, if biological control by predators is conserved. European red mite is a sporadic minor pest that is relatively easy to control with only an occasional selective miticide application. And miticide resistance is not an issue. A quick way of determining light levels in your orchards is to use a magnifying hand lens or a headpiece magnifier to determine the percentage of might infested leaves. Select ten trees in the orchard, on the most susceptible variety, and count ten spur leaves from each tree for the presence or absence of mites. Then use this graph to determine the mite threshold level. As a general rule in apples, a spray threshold of only two point five mites per leaf exists early season, before June. The threshold increases to 5 mites per leaf from June through mid-July. Use a threshold level of 7.5 mites per leaf through the rest of the season. If the mites per leaf do not reach these levels, no control action needs to be taken. Orchards with stable populations of T. pyri never reach these thresholds, as long as there's at least one predatory mite for every 10 pest mites per leaf. Our current population of T. pyri probably came to Pennsylvania on Apple bins moved between states, or on nursery stock. A program developed by Penn State, and funded by the USDA conservation programs, move T. pyri from known seed orchards to many new grower orchards, and over eighty percent of Pennsylvania apple orchards have this predator present at some level. Where conserved, T. pyri has reduced the use of miticides by over ninety percent, and some growers have not sprayed mite-susceptible varieties in more than ten years. Establishment of T. pyri into orchards where it is absent is relatively simple and can be accomplished in one to two seasons, once donor orchards with abundant T. pyri populations have been identified as a source. Transfers of T. pyri from these orchards can be successful by physically moving spur leaves in May and June. Transfers after July appear to be less likely to establish populations. If not controlled, apple scab can cause losses of seventy percent or greater where humid, cool weather occurs during the spring months. Losses result directly from fruit infections or indirectly from repeated defoliation, which can reduce tree growth and yield. The pathogen generally overwinters in fallen leaves and fruit on the orchard floor. As a result, orchards are self-infecting. Primary spores develop during the winter and begin to mature early spring. Around bud break, the first mature spores will be released from the infected leaves and or fruit. The length of time required for infection to occur depends on the number of hours of continuous wetness and the temperature during the wetting period. Leaf wetness hours can be calculated by either beginning the count at the time leaves become wet and ending the count when the relative humidity drops below ninety percent, or by adding consecutive wetting periods (hours), if the leaves are again wetted within eight hours from the time relative humidity dropped below ninety percent. For example, if the average temperature is between 61 to 75 degrees Fahrenheit, a minimum of six hours of leaf wetness is required for spores to be dispersed. Once the primary spores have established infection on the plant tissue, and approximately nine to ten days, symptoms can be observed. At that time, secondary spores called conidia, are being produced and will do so the remainder of the season, being dispersed by rain or wind on susceptible tissue. Monitor rainfall and duration of wetness closely, beginning at green tip, since mature spores begin to be released around this time. Peak mature spore release is around bloom time through petal fall. Continue to monitor rainfall and duration of wetness through mid-June, as the final mature spores are released during this time. Start monitoring for lesions (spots) around 10 to 14 days after bud break, which is when the first symptoms can occur, if disease conditions are favorable. For each orchard block, follow a “w” shape pattern within the block when scouting. Evaluate ten trees by examining 20 leaves on each of the five limbs per tree, and record the number of leaves showing any scab lesions. Number one: begin with the flower bud (spur) leaves where early infections are most likely to be noticed. Number two: start with observing the undersurface of leaves, since the undersurface of leaves may become spotted before the top surface. Take notice of early lesions which may be small, light brown, black spots. Number three: as scouting continues during early spring, be sure to observe both the top side and underside of the leaf. Apple scab infection appears as brown velvety lesions, which will become darker as they age. After fruit have set, in addition to leaf observations, examine 20 fruit on each tree and record the number showing any scab lesions. Use this information to better manage scab in the future. It is important to scout and control apple scab early in the season to prevent secondary infections from becoming established. Even if you have a professional consultant who monitors your orchard, it is important to become knowledgeable about basic principles of integrated fruit production. Penn State Extension offers educational programs on current best management practices in nutrition, pruning, tree training, crop load management, farm employee health and welfare regulations, food safety practices, and IPM. For a list of courses, visit the Penn State Extension Tree Fruit Production website. And for timely recommendations, sign up for Penn State Extension, Fruit Times.

Credit: Penn State Pesticide Education Program. "Integrated Pest Management (IPM) in Apple Orchards." YouTube. October 16, 2015.

What are the potential benefits of scouting for the European red mites and predatory mites in Pennsylvania orchards?

Click for the answer.

Answer: If the European red mites have not reached the economic threshold, a farmer can avoid spraying an insecticide and protect beneficial insects that can reduce the pest population and/or provide ecosystem benefits (ex. pollination, nutrient cycling). Avoiding spraying can also save money and time for the farmer and reduce the farmers’ exposure to pesticides.

Part 1: Australian grain crop IPM

Watch the following video that explains IPM adoption in grain crops in Australia; then answer this question:

1. Identify and explain three benefits of utilizing IPM discussed in the Australian video from the GRDC.

Video 1: GCTV2: Integrated Pest Management (5:46)

If the video does not load for you, go to GCTV2: Integrated Pest Management

Part 2: Determining the Economic Threshold of Potato Leafhoppers in Alfalfa

Read the Penn State University Potato Leafhopper on Alfalfa Fact Sheet.

Figure 8.1.9: Economic Threshold for Potato Leafhoppers

Credit: Penn State University Potato Leafhopper Alfalfa Fact Sheet

Scenario

Assume that you followed the procedure described in the Penn State fact sheet to scout for Potato Leafhoppers in an alfalfa field by sweeping 20 times with your sweepnet in each of 5 different locations in the alfalfa field. The number of leafhoppers that you found in the 5 different locations was: 15, 12, 16, 7, 13 when the alfalfa crop was about 11 inches tall. You would like the alfalfa to grow about 25-30 inches height before harvesting it for hay, this could require 2 to 3 more weeks of growth, depending on rainfall. Based on current alfalfa hay prices in your region, you estimate your alfalfa hay is worth about $250/Ton, and the insecticide you would spray to control the leafhoppers would cost about $16/A. If you spray the alfalfa field, it cannot be harvest until 7 days after spraying the insecticide; and due to toxicity to bees, the alfalfa should not be sprayed if it is flowering.

Answer the following questions:

1. Calculate the average number of leafhoppers per sweep. Add the number of potato leafhoppers from the 20 sweeps in each of the 5 locations (20 X 5= 100 sweeps). Divide by 100 to calculate the number of leafhoppers per sweep. Use the Economic Threshold Table from the Fact Sheet for Potato Leafhoppers, shown here. Has the insect population reached an economic threshold for your crop at this height?
2. Based on the average number of leafhoppers per sweep, what should you do? Why?
3. If your crop height was 7 inches tall and you had the same number of leafhoppers per sweep that you calculated here, would your pest management decision change and how?
4. Discuss at least two potential benefits of using the economic threshold decision tool rather than spraying as soon as potato leafhoppers were first visible.

Files to Download

Module 8 Formative Assessment Worksheet

Submitting Your Assignment

Please complete the Module 8 Formative Assessment in Canvas.

A weed is a plant that is not wanted or a plant growing in the wrong place. In agricultural systems, weeds tend to be unwanted because they compete with crops for light, water, and/or nutrients, and can reduce crop yield and/or quality, particularly if weeds are permitted to grow and reproduce. Weeds may reduce crop quality through contamination with seeds or plant parts that may be toxic, or of poor nutritional or culinary quality (produce off-flavor compounds). Some weeds may harbor crop insect pests or pathogens; and when weeds have a significant negative impact, they can reduce the economic value of agricultural land. On the other hand, if weeds are not numerous enough to reduce crop yield and quality, weeds can provide some agroecosystem benefits. For instance, weeds can provide:

1. protection from soil erosion
2. pollen, nectar, and habitat for beneficial organisms and wildlife
3. forage for grazing animals

Competitive Characteristics of Weeds

Weeds tend to be plants that are adaptive and competitive in a range of environmental conditions. They typically have seeds or perennial storage organs that enable them to grow rapidly and produce aboveground canopies that compete with crop plants for light, and root systems that compete for nutrients and water. Annual weed species often grow and mature relatively quickly, producing seeds earlier than crops. To increase survival of their offspring, annual weeds often produce many seeds, and some species produce large seeds. Strategies to control annual weed species target terminating them early, to prevent them from competing with crops and producing seeds.

Figure 8.2.1: Common ragweed (Ambrosia artemisiifolia L.) may produce between 3000-4000 seeds per plant. See Invasive Species Compendium for more information.

Credit: Heather Karsten

Figure 8.2.2: Annual Lambsquarter (Chenopodium album L.) weed in corn. Lambsquarter can produce up to 72,000 seeds per plant. For more information about this weed species see Extension Utah State University.

Credit: Heather Karsten

If perennial weeds are growing from the small seeds they produce, they establish more slowly than annual crop seeds. But seeds are not their primary form of reproduction, recall that perennial plants often spread and reproduce via established storage organs such as taproots, tubers, bulbs, and rhizomes (belowground modified stems that store reserves and enable a plant to spread horizontally), or aboveground stolons or storage stem bases. Perennial weeds growing from storage organs can be very competitive with crop plants. If perennial weed storage organs are cut and distributed over a larger area and reburied or partially covered, they can also establish and spread across a larger area. If weed storage organs are left on the soil surface to freeze and thaw over winter or desiccate in mid-summer, then tillage can terminate perennial storage organs. Repeated mowing of plant regrowth may weaken or deplete plant reserves, particularly if it is prior to the end of the growing season when perennials tend to translocate plant reserves to storage organs. Chemical control of perennials is also often most successful at this time when herbicides can be translocated to storage organs.

Figure 8.2.3: This Phragmites weed spreads by stolons and produces roots and shoots every few inches, that once established could survive as separate plants.

Photo Credit: Rod Stolcpart (Rock County, Nebraska Weed Superintendent)

Figure 8.2.4: Rhizomes on Johnsongrass (Sorghum halepense L.)

Credit: Jack Kelly Clark, courtesy University of California Statewide IPM Program

Figure 8.2.5: Tubers on yellow nutsedge (Cyperus esculentus) 

Credit: Jack Kelly Clark, courtesy University of California Statewide IPM Program

In addition, many weeds have traits that enhance their survival and reproductive success such as: i. hard-seeds or seeds that can remain dormant for long time periods until environmental conditions for germination are good, enhancing weed seed success, ii. plant protective characteristics such as thorns, toxic tissues, protected growing buds, iii. adaptive growth to a wide range of environmental conditions also referred to as plasticity. For example, in a field or lawn that is grazed or mowed to a short height to control weeds, adaptive weeds can produce leaves very close to the soil surface and flowers on short stems below the mowing height.

Figure 8.2.6: Buttercups (Ranunculus L. ) contain protective compounds that are toxic to most grazing livestock. For more information about buttercups see Creeping Buttercup, Pacific Northwest Extension Publications.

Photo: Heather Karsten

Figure 8.2.7: Thistles with protective thorns.

Photo: Heather Karsten

Activate Your Learning: Weed Control Practices

Recall what you have learned about crop plant lifecycle classification and characteristics in Module 6.

Read the Australian Department of the Environment website that describes Integrated Weed Management. Click on and read the links that describe each type of weed management technique. After you have read both of the above readings, answer the questions below.

Although integrated pest management was introduced in the 1980s, the number of weeds that have evolved resistance to new herbicides continues to grow (See Figure 8.2.8 below).

Figure 8.2.8: Global Increases in Unique Resistant Cases

Credit: Dr. Ian Heap, International Survey of Herbicide Resistant Weeds

Similar to other pests, weeds evolve resistance when exposed to the same strong selective force, such as an application of the same herbicide over consecutive years. When the same herbicide is applied numerous times to a field, susceptible weeds are killed, leaving resistant individuals to reproduce and dominate the population, as illustrated in figure 8.2.9 below.

Figure 8.2.9: Selection for herbicide resistance begins when an herbicide resistant biotype survives a particular herbicide application. The resistant biotype survives, matures, and sets seed. If the same herbicide continues to be applied and the resistant weeds reproduce, eventually the majority of the weeks will be resistant to the herbicide.

Credit: J. L. Gunsolus. Weed Science, Department of Agronomy and Plant Genetics. Herbicide-resistant weeds.

Integrated Weed Management

Integrated weed management (IWM) is an IPM approach for weeds that can provide long-term weed control of weeds by integrating multiple control strategies. Some weed scientists have described IWM as utilizing “many little hammers” as opposed to continuously employing one “big hammer” such as an herbicide (Liebman & Gallandt, 1997). Weed control tactics fall into the IPM control categories that you learned about for insect control in Module 8.1. Examples of weed control practices include the following:

1. Cultural control practices are management practices humans can employ to prevent weed establishment and maintain vigorous crop growth. Examples include: crop rotation with crops of different life cycles and seeding densities, planting certified seed that is managed to have minimal weed contamination, planting adapted crop varieties, adjusting row spacing, population density, and timing for a competitive crop and successful crop establishment, maintaining soil health and fertility, and using practices that prevent weed establishment such as cover crops and mulching.

   

   Figure 8.2.10: Straw mulch to suppress weeds in garlic.

   Credit: Heather Karsten
   

   Figure 8.2.11: Buckwheat (Fagopyrum esculentum L. ) cover crop planted mid-season to smother weeds, produce organic matter and provide habitat for beneficial insects.

   Credit: Anna Santini
   

   Figure 8.2.12: Crop rotation of summer annual row crops such as corn (first photo) with densely seeded perennial alfalfa (second photo), and/or densely planted winter annual wheat and spring oats (third photo, wheat is on the right, oats are on the left).

   Credit: Heather Karsten

2. Mechanical or physical weed control includes practices such as plowing, cultivation, hoeing, targeted hand-weeding, and flaming.

   

   Figure 8.2.13: This flex tine cultivator is used to control weeds when they are very small.

   Credit: Heather Karsten
   

   Figure 8.2.14: Rotary harrow for weed cultivation.

   Credit: Heather Karsten
3. Biological control: conserving or introducing herbivorous insects, grazing or browsing animals, or plant pathogens to reduce weed populations. Biological control of weeds is typically used on extensive rangeland where other more labor intensive or expensive methods are not cost effective.
4. Chemical control: the application of herbicides, or the use of herbicide-resistant crops with herbicide applications to control weeds
5. Genetic resistance: selecting crop varieties that are well adapted to an environment and competitive with weeds. Herbicide-resistant crops may also be considered a form of genetic resistance.

Transgenic crops or animals are often referred to as GMO’s or genetically modified organisms. This is misleading because all cultivated crop plants and livestock have been genetically modified through centuries of human selection and traditional breeding. A more accurate name for the genetically engineered organisms that are referred to as GMOs, is transgenic organisms. Transgenic crops or livestock contain genetic material that was transferred from a different species through biotechnology techniques or genetic engineering.

In the 1980s, agricultural input companies began developing and using transgenic techniques to develop new crop varieties. The first traits that were inserted into major crop plants and commercialized on a large scale were genes from two different species of bacteria. The transgenic traits were for insect resistance (Bt) and resistance to the herbicide glyphosate (commercially marketed as Round-up). Since the first commercial release in 1996, these technologies have been widely adopted in the US and other parts of the world (See Figure below).

Figure 8.2.15: Adoption of genetically engineered crops in the United States from 1996 - 2014. Data for each crop category include varieties with both HT (herbicide-resistant) and Bt (stacked) traits. Credit: USDA Economic Research Service, using data from Fernandez-Cornejo and McBride (2002) for the years 1996-99 and USDA, National Agricultural Statistics Service, June Agricultural Survey for the years 2000-14.

Bt is an abbreviation for Bacillus thuringiensis a bacteria that produces an enzyme that is toxic to the digestive system of insects in the Beetle; and Moth and Butterfly families. These two insect families include some major crop pests. Scientists have transferred the genes that code for the production of the toxins into crop plants. Because the Bt trait confers insect pest resistance, the adoption of Bt corn and Bt cotton has contributed to a significant reduction of insecticide use in these crops (See Figures 8.2.16- 8.2.18 below).

Figure 8.2.16: (Figure 12) Insecticide use in corn and cotton production, 1995-2010

Credit: Jorge Fernandez-Cornejo, Seth Wechsler, Mike Livingston, and Lorraine Mitchell. Feb. 2014. Genetically Engineered Crops in the United States. USDA Economic Research Report Number 162.

Figure 8.2.17: (Figure 18) Pounds of insecticide active ingredients (a.i.) per planted acre and percent acres of Bt corn, 1996 - 2008.
Figure 8.2.18: (Figure 19) Pounds of insecticide active ingredient (a.i.) per planted acre and percent acres of Bt cotton, 1996 - 2008.

Click for a text description of Figures 8.2.18 and 8.2.19.

Figure 18 is showing that as the pounds of insecticide/acre is decreasing ( except for an increase from 1998-1999), the percent acres of Bt corn is increasing from 1996 until 2008. Figure 19 is showing that as the pounds of cotton insecticides are generally decreasing, the percent of Bt cotton is increasing from 1996-2008.

Credit: Fernandez-Cornejo, Jorge, Richard Nehring, Craig Osteen, Seth Wechsler, Andrew Martin, and Alex Vialou. Pesticide Use in U.S. Agriculture: 21 Selected Crops, 1960-2008, EIB-124, U.S. Department of Agriculture, Economic Research Service, May 2014.

Prior to the development of Bt crops, spores of the bacteria Bacillus thuringiensis were sometimes used as biological control for insect pests in forestry and agriculture, often on organic farms. Initially, commercial Bt crops were released in the US without any regulations to prevent resistance. But science had shown that pest populations could quickly evolve resistance to Bt, and planting Bt crops on a large scale across the agricultural landscape would create a strong selective force for pests to evolve resistance to Bt. Therefore, in response to public concern about the high risk of pests evolving resistance to Bt, the EPA convened a committee that developed a resistance management plan for Bt crops.

In addition to the crop expressing a high dose of the Bt toxin, to prevent or delay pest resistance to Bt farmers who plant transgenic Bt corn and cotton, are required to plant a refuge, a percentage of the crop field or a field close by that does not express the Bt trait. The refuge area conserves a population of insects that are susceptible to Bt, so that the susceptible insects can reproduce with insects that might have resistance to Bt, sustaining some Bt-susceptible individuals in the population. Depending on the presence of Bt crops in a region, the EPA regulation requires that farmers plant between 5% and 20% of their crop field without the Bt trait. For stacked Bt corn hybrids (with 2 or more Bt traits) farmers must plant the required refuge for each Bt trait that their crop expresses. For more information on refuge requirements, read Insect Resistance Management and Refuge Requirements for Bt Corn, from the University of Wisconsin.

Pest Resistance to Transgenic Bt Crops

Despite the refuge requirement in the US, western corn rootworm resistance to Bt corn was reported in multiple Midwestern states (Jakka et al., 2016). The first reported Bt-resistant corn rootworm populations were found in cornfields in Iowa that had been planted to Bt corn consecutively for at least three years, and the authors suggested that the fields likely did not include refuge corn (Gassman et al., 2011). Additional studies also found that the Bt toxin dose was not sufficiently high to delay the evolution of insect resistance and that corn rootworm could evolve resistance to additional Bt toxins in three to seven generations (Gassman, 2016). Further, in 2013 pest resistance to Bt crops was reported in 5 of 13 major pest species in a survey of 77 studies from eight countries across five continents, where resistance management requirements and enforcement varied. Practices that delayed resistance to Bt included the Bt crop expressing a high dose of the Bt toxin and an abundance of refuge crop planting (Tabashnik, et al., 2013).  In accordance with integrated pest management principles, entomologists also recommend that other control tactics be utilized to control pests targeted by Bt crops.

In a number of countries (ex. most countries in the European Union), Bt crops and transgenic crops were not approved for commercial production.  Concerns about the potential human health and ecological risks of transgenic crops limited acceptance of Bt crops and other transgenic crops. Applying the precautionary principle, some policy-makers and the public require more research and long-term assessment of transgenic traits on human health and ecosystems.  An interest in protecting domestic seed markets and companies may also contribute to policy decisions to prohibit the adoption of transgenic seeds produced by multi-national seed companies.

Herbicide-resistant (or tolerant) crops, such as glyphosate-resistant crops are transgenic crops that are resistant to the herbicide glyphosate. Glyphosate is a broad-spectrum herbicide that controls a wide range of plants and breaks down relatively quickly in the environment; it was first marketed under the trade name: Round-up. Round-up Ready soybeans were released in the US in 1996, and since then, additional glyphosate-resistant crops (corn, cotton, canola, sugarbeet, and alfalfa) have been developed and widely adopted in the US and other countries (Fernandez-Cornejo J. and S. J. Wechsler, 2015; Benbrook, 2014; Duke and Powles, 2009). See Figure 8.2.15 on the Transgenic Crops for Pest Control page: Adoption of genetically engineered crops.

Figure 8.2.19: Roundup Ready Soybeans

Credit: Heather Karsten

Herbicide-resistant (HR) crops such as glyphosate-resistant crops have facilitated the increased adoption of no-till or direct seeding of some HR crops because tillage is not needed for weed control. Once a crop has emerged, the risk of glyphosate herbicide damage to the HR crop is eliminated, making it easier for farmers to plant crops and control weeds without tillage. However, although Bt crops reduced insecticide use, the glyphosate herbicide must be applied to glyphosate-resistant crops to control weeds. Since they were first introduced in 1996, glyphosate use has increased. See the Figure 8.2.20 from the USGS Pesticide National Synthesis project below.

In addition, in contrast to Bt crops, the EPA did not require farmers to employ a glyphosate resistance management plan or refuge, and the number of weeds that are resistant to glyphosate has increased. Weeds have evolved resistance to glyphosate particularly in cases where farmers consistently applied glyphosate to manage weeds in HR crops and terminated cover crops and/or perennials with glyphosate prior to planting an HR crop. See the Figure 8.2.21 from the International Survey of Herbicide Resistant Weeds illustrating the increase in glyphosate-resistant weeds below.

Figure 8.2.20: Glyphosate Use in the United States by Year and Crop

Credit: USGS, Nat’l Water Quality Assessment Program, Pesticide National Synthesis project

Figure 8.2.21: Increase in the Number of Glyphosate-Resistant Weeds Worldwide

Credit: Ian Heap. International Survey of Herbicide Resistant Weeds.

Stacked Herbicide-Resistant Crops

When the number of glyphosate-resistant weeds increased and became difficult to control, the agricultural-input industry developed transgenic herbicide-resistance crops that are resistant to additional herbicides. Dow AgroSciences developed a transgenic trait for resistance to 2,4-D, an herbicide that controls broadleaf weeds (dicot plants) and the company stacked or added the trait to soybean and cotton crops that also have resistance to glyphosate. And Monsanto produced a transgenic trait for resistance to an herbicide called dicamba that they stacked (or added to) soybeans that have glyphosate resistance. Dicamba and 2,4-D herbicides are volatile, and there is a risk that when the herbicides are sprayed, they will drift into neighboring fields and field edges, potentially damaging other crops and other plants. Wild plants in field edges and natural ecosystems often provide habitat for beneficial organisms, such as pollinators, pest predators, and wildlife. In 2017, Monsanto's crops with stacked dicamba and glyphosate resistance were available for use in some midwestern and southern states, where glyphosate-resistant weeds were particularly problematic. In 2017, there were so many reports and complaints from farmers about crop damage due to dicamba drift, that the states of Arkansas and Missouri banned dicamba spraying for some of the growing season. The EPA also investigated the complaints, and in autumn 2017, the EPA announced that the companies had agreed to new steps to reduce the risk dicamba drift with dicamba-resistant crops. For more information, see the EPA Registration of Dicamba for Used on Genetically Engineered Crops.  

We will explore concerns about the stacked, herbicide-resistant technologies and tactics to manage glyphosate-resistant weeds more in the Summative Assessment.

Pathogens include fungi, bacteria, nematodes, and viruses, all biological organisms that can cause disease symptoms and significantly reduce the productivity, quality, and even cause the death of plants. Pathogens can also infect agricultural animals, but for this module, we will focus on plant pathogens. Read the following brief overview of plant pathogens, Plant Disease: Pathogens and Cycles.

Pathogens can be introduced and spread to host plants in many ways. Bacteria and fungal spores can be transferred by wind, in rain, and from the soil via rain splashing onto plant tissues. Insects can vector or infect a plant with a pathogen when they feed on an infected host plant, and then move and feed on an uninfected plant. Pathogens can also spread through infected seeds, transplants, or contaminated equipment, irrigation water, and humans.

Figure 8.2.22: This pumpkin plant is infected with Bacterial wilt (Ralstonia Solanacerarum) that was vectored (introduced) by a cucumber beetle insect.

Photo Credit: Beth Gugino, Penn State University, Associate Professor of Vegetable Pathology

Figure 8.2.23: Center pivot irrigation of crops, such as this canola, could facilitate pathogen infection and disease development via soil-splashing and by creating high humidity in the plant canopy that could favor some pathogens.

Photo Credit: Chad Swank, courtesy of USDA Natural Resources Conservation Services, via Wikimedia Commons.

Plant Disease Triangle: Plant pathologists have identified three factors that are needed for a plant disease to develop:

i. a susceptible host Some pathogens have a narrow host plant range, meaning they can infect just a few host species. For instance, the primary host crops of Late blight (Phytophthora infestans) are tomato and potato. For more information see Tomato-Potato Late Blight in the Home Garden.  By contrast, pathogens with a wide host plant range can infect many different host species. There are almost 200 plant species that can be infected by Bacterial wilt (Ralstonia solanacearum). For more information, see Bacterial Wilt - Ralstonia solanacearum.

ii. a disease-causing organism (pathogen). Plant pathogens include fungi, bacteria, viruses, and nematodes. For examples, again, see the reading: Introduction to Plant Diseases, A. D. Timmerman, K.A. Korus. 2014. University of Nebraska-Lincoln. Extension. EC 1273.

iii. a favorable environment for the pathogen. Pathogens usually require specific humidity and temperature conditions for pathogen infection and disease symptoms to manifest. For instance, Late Blight disease symptoms are most likely to occur when the weather is cool and wet.

Figure 8.2.24: Disease Triangle

Credit Heather Karsten

Disease Diagnosis

The three disease triangle factors are important for diagnosing the cause of disease symptoms. Pathologists consider the weather, environmental conditions and the host species to diagnosis what pathogen is causing disease symptoms. Pathologists also consider other factors that could favor and help diagnose a disease, such as i. the field history, particularly what crops and pathogens were present in the past, ii. current crop management practices, iii. when disease symptoms were visible, and on what other species. To assist farmers and others with disease diagnosis, many land-grant universities in the US have crop and animal diagnostic disease clinics where one can submit diseased tissue samples with detailed information that can aid in the diagnosis, such as the host species, environmental conditions, the site history, and management.

Pathogen Management

Although disease control practices could be categorized into the pest control approaches that were discussed earlier for managing insects and weeds (genetic, cultural, chemical, etc.), plant pathologists typically describe pathogen control tactics with more specific language. For instance, Exclusion tactics involve rejecting infected transplants from being introduced to a farm.

Prevention or Avoidance of pathogen introduction and spread tactics include:

• crop rotation, particularly for pathogens with narrow host ranges
• sanitizing equipment for planting, trellising, pruning, and harvesting
• managing for healthy vigorous crops with optimal soil and water nutrient management
• managing to avoid environmental conditions that promote pathogens, such as avoiding very humid conditions due to over-watering, or promoting drying of plant surfaces with wide row spacing to facilitate air flow, or using drip-tape irrigation that waters plants at or below the soil surface versus over the canopy
• using physical barriers such as row covers, mulch to reduce water splashing; and high tunnel/hoop houses or greenhouses to prevent the introduction of rain and wind-borne pathogens

Figure 8.2.25: Multiple pest control practices on this organic farm help prevent pathogen infection and spread, while also helping to control insect pests and weeds. Wide row spacing allows for inter-row weed cultivation as well as airflow to reduce crop canopy humidity; crop rotation and intercropping plants from different plant families interrupts pathogen and insect spread; and straw mulch that prevents soil-borne pathogens from splashing onto plants also suppresses weeds.

Photo Credit: Heather Karsten

Figure 8.2.26: Drip tape irrigation under plastic mulch avoids splashing soil-borne pathogens onto crops and is also a more efficient use of irrigation water.

Plastic mulch also raises soil temperatures, promoting crop growth and helps to suppress weeds.

Photo Credit: Elsa Sanchez, Penn State, Professor of Horticultural Systems Management, Dept. of Plant Science

Figure 8.2.27: High tunnels, plastic mulch, and sanitized stakes all avoid introducing pathogens to these tomato plants, while also promoting crop growth.

Photo Credit: Elsa Sanchez, Penn State, Professor of Horticultural Systems Management, Dept. of Plant Science

Genetic resistance to pathogens is a very valuable and important pathogen control tool. Many plant breeding programs select for genetic resistance to pathogens. When available, pathogen resistance traits are included in most crop variety descriptions to help growers select appropriate crop varieties for their farm.

Figure 8.2.28: This tomato variety trial included tomato varieties that were resistant or susceptible to late blight.

Photo Credit: Beth Gugino, Penn State, Associate Professor of Vegetable Pathology.

If disease symptoms develop, infected plants may be Eradicated or destroyed. And materials that may have been contaminated with pathogens, such as the soil and planting containers, can be heated to very high temperatures with pasteurization equipment or through solarization. For instance, soil may be solarized by placing black plastic over the crop bed (planting zone) during the warm season to increase the soil temperature and destroy pathogens prior to planting the crop.

Therapy or Fungicides (chemical control) may be applied to infected plants to terminate pathogens. Particularly when plant pathogen symptoms are identified early and favorable weather conditions for the pathogen are projected to continue, fungicides can prevent disease spread and significant economic losses. In some high-value crop systems, the soil may be fumigated prior to planting crops.

Similarly, in agricultural livestock systems, animals with disease symptoms can be treated with antibiotics. And in some livestock production systems, antibiotics and vaccinations are administered to animals to prevent diseases and pathogen infection.

Note

Explore the International Survey of Herbicide Resistant Weeds to examine the trends of herbicide-resistant weeds and answer the questions below. By going to the "US State Map" to click on different states and "map of different countries" to move your cursor over different counties, compare the number of herbicide-resistant weed species across a range of geographical regions.

You will also use the following information in the proposed scenario:

Dow AgroSciences developed a transgenic trait for resistance to 2,4-D, an herbicide that controls broadleaf weeds (dicot plants), that has been transferred to soybean, corn, and cotton crops. The trait is stacked or added to soybeans that also have resistance to glyphosate, and another herbicide called glufosinate.

Monsanto has produced a transgenic trait for resistance to an herbicide called dicamba, that they are stacking (or adding to) soybeans that have glyphosate resistance. Some formulations of the dicamba herbicide are volatile, and there is a risk that when farmers spray dicamba it will drift into neighboring fields and field edges, potentially damaging other crops and wild plants in field edges and natural ecosystems. These field edges and other plants often provide habitat for beneficial organisms, such as pollinators, pest predators, and wildlife.

Please also read these short NPR articles on dicamba:

With ok from EPA use of controversial weedkiller is expected to double

A wayward weed killer divides farm communities harms wildlife

If you are interested in more information about the use of dicamba and Arkansas' recent restrictions on the herbicide you may read or listen to the following brief (3-minute) story: Arkansas defies Monsanto moves to ban rogue weed killer

Directions

Read the following scenario and in approximately 450-500 words answer the questions below. I suggest you write your response in a separate document and then copy and paste it into Canvas. Once you have posted your own answers, you need to respond to ONE classmate. Your response should be approximately 150 words.

Assume you manage a 200-acre corn and soybean farm in Southern Pennsylvania. You keep up with the latest technological advances in farming and use seeds from either Dow or Monsanto depending on what your seed salesperson recommends. You are proud of your farm and strive to keep your crops free from both weeds and harmful insects that could damage your crop and cut into your profits. Your immediate neighbors on the East side have a large organic vegetable production farm. Based on what you have observed on the above website, the information mentioned above, and from what you have learned through the readings in this module, answer the following questions:

• What are some potential problems you might encounter if you adopt seeds with the new herbicide traits listed above? How do these problems differ between now and in the future?
• What other weed-control strategies could you use to control glyphosate-resistant weeds?
• How might your pest management system affect your neighbors?
• Are there strategies you can use to mitigate potential harm to your neighbors’ fields?
• If you were farming in Thailand or Egypt instead of in Pennsylvania, what might explain differences in the number of herbicide-resistant species you encounter there compared to your farm in the United States?
• If you farmed in Canada, Australia, or Western Europe what might explain the herbicide-resistant species you encounter there?

Consider the following possible questions when responding to a classmate:

• How do their answers differ from yours?
• Are there suggestions you can make to help them improve their IPM practices-for weeds as well as insects?
• Do they have possible solutions you could use on your farm?
• Is there a question you have about why or how they answered the way they did?

Files to Download

Module 8 Summative Assessment Worksheet

Submitting Your Assignment

Submit your response in Module 8 Summative Assessment Discussion in Canvas.

Understanding the Science of Climate Change: The Basics

Module 9 focuses on how agriculture contributes to global climate and how climate change will affect global agriculture. In addition, we'll explore agricultural strategies for adapting to a changing climate. But, before we explore the connections between global climate change and food production, we want to make sure that everyone understands some of the basic science underpinning global climate change.

Have you ever thought about the difference between weather and climate? If you don't like the weather right now, what do you do? In many places, you just need to "wait five minutes"! If you don't like the climate where you live, what do you do? Move! Weather is the day-to-day fluctuation in meteorological variables including temperature, precipitation, wind, and relative humidity, whereas climate is the long-term average of those variables. If someone asked you what the climate of your hometown is like, your response might be "hot and dry" or "cold and damp". Often we describe climate by the consistent expected temperature and precipitation pattern for the geographic region. So, when we talk about climate change, we're not talking about the day-to-day weather, which can at times be quite extreme. Instead, we're talking about changes in those long-term temperature and precipitation patterns that are quite predictable. A warming climate means that the average temperature over the long term is increasing, but there can still be cold snowy days, and blizzards even!

The two videos below are excellent introductions to the science of climate change. We'll use these videos as your introduction to the basic science behind our understanding of climate change that we'll build on as we explore the connections between climate change and food production in the rest of this module. Follow instructions from your instructor for this introductory section of Module 9.

Optional Video Climate Change: Lines of Evidence

The National Academies of Sciences Engineering and Medicine have prepared an excellent 20-minute sequence of videos, Climate Change: Lines of Evidence, that explains how scientists have arrived at the state of knowledge about current climate change and its causes. Use the worksheet linked below to summarize the story that the video tells about anthropogenic greenhouse gas emissions and the resulting changes in Earth's climate. The narrator speaks pretty quickly, so you'll want to pause the video and rewind when you need to make sure you understand what he's explaining. It's important to take the time to understand and answer the questions in the worksheet because you'll use this information in a future assignment.

If instructed by your instructor, download detailed questions about the Climate Change: Lines of Evidence videos:

• MSWord docx -Climate Change: Lines of Evidence video questions
• pdf -Climate Change: Lines of Evidence video questions

Video: What is Climate? Climate Change, Lines of Evidence: Chapter 1 (25:59)

Another resource you can use to help answer the questions is the booklet that goes with this video: Climate Change: Evidence, Impacts, Choices. It is 40 pages, so you might not want to print it. Use it as an online reference.

Penn State geology professor, Richard Alley's, 45-minute video uses earth science to tell the story of Earth's climate history and our relationship with fossil fuels. There is no worksheet associated with this video.

Optional Video: Earth: The Operators' Manual (53:42)

Optional Follow-up Questions to the Videos

If instructed by your instructor, download the following questions that can be applied to either video:

• MSWord docx - Optional Video Assignment Questions: Understanding the Science of Global Climate Change
• pdf -Optional Video Assignment Questions: Understanding the Science of Global Climate Change

At this point, you should have either watched one or two of the videos from the introduction, or you're already familiar with how human activities have resulted in the warming of the planet in the last century. Now, we'll explore some of the latest data from the National Aeronautics and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA), and the Intergovernmental Panel on Climate Change (IPCC) to review and to help us better understand the connections between increases in atmospheric carbon dioxide and climate change.

Data on current atmospheric concentrations of carbon dioxide are collected and compiled by NOAA and can be found at NOAA Earth System Research Laboratory. The longest record of carbon dioxide concentration in the atmosphere is from Mauna Loa in Hawaii and was initiated in the 1950s. The resulting curve is often referred to as the “Keeling Curve” (Figure 9.1.1) after the atmospheric scientist who first began collecting CO₂ data.

Figure 9.1.1. Monthly mean atmospheric carbon dioxide at Mauna Loa Observatory, Hawaii. The carbon dioxide data (red curve), measured as the mole fraction in dry air, on Mauna Loa constitute the longest record of direct measurements of CO₂ in the atmosphere. They were started by C. David Keeling of the Scripps Institution of Oceanography in March of 1958 at a facility of the National Oceanic and Atmospheric Administration [Keeling, 1976]. NOAA started its own CO₂ measurements in May of 1974, and they have run in parallel with those made by Scripps since then [Thoning, 1989]. The black curve represents the seasonally corrected data. Data are reported as a dry mole fraction defined as the number of molecules of carbon dioxide divided by the number of molecules of dry air multiplied by one million (ppm).

Credit: Earth System Research Laboratory

Carbon dioxide is not the only greenhouse gas. Human activities have also increased concentrations of methane and nitrous oxide. The IPCC has compiled data from many sources to summarize the changes in greenhouse gas concentrations for the last 2000 years (Figure 9.1.2), and concentrations of carbon dioxide, methane, and nitrous oxides have all risen dramatically with industrialization. The increases in carbon dioxide concentrations have the greatest impact on global climate, but the increases in the other greenhouse gases play a supporting role.

Figure 9.1.2. Atmospheric concentrations of important long-lived greenhouse gases over the last 2,000 years. Increases since about 1750 are attributed to human activities in the industrial era. Concentration units are parts per million (ppm) or parts per billion (ppb), indicating the number of molecules of the greenhouse gas per million or billion air molecules, respectively, in an atmospheric sample.

Credit: Forster, P.; Ramawamy, V.; Artaxo, P.; Berntsen, T.; Betts, R.; Fahey, D.W.; Haywood, J.; Lean, J. et al. (2007), "Changes in Atmospheric Constituents and in Radiative Forcing", Climate Change 2007: the Physical Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change

To understand Earth's past climate, scientists use data extracted from air bubbles trapped in ice cores from Greenland and Antarctica to study past carbon dioxide concentrations and temperatures. The longest ice core record is from Vostok, Antarctica and gives us a picture of changes in CO₂ concentrations and temperatures for the last 800,000 years (Figure 9.1.3). In November 2015, CO₂ concentrations in the atmosphere reached 400.16 ppm, a level not seen in the past 800,000 years on Earth. Also, there is a clear correlation between temperature changes and changes in atmospheric CO₂ concentrations.

Figure 9.1.3. Historical carbon dioxide (right axis and blue lines) and reconstructed temperature (as a difference from the mean temperature for the last 100 years in red) records based on Antarctic ice cores, providing data for the last 800,000 years. Atmospheric carbon dioxide levels, as measured in air, are higher today than at any time during the past 800,000 years.

Credit: Used under under the Creative Commons Attribution-Share Alike 3.0 Unported by Leland McInnes at the English language Wikipedia.

NASA has compiled surface air and ocean temperature data from around the globe and summarized temperature changes into an index (Global Climate Change: Vital Signs of the Planet) that compares annual average temperature with the average temperatures from 1951-1980 (Figure 9.1.4). Global temperatures have been rising for the last 100 years. We'll explore more temperature data and consider the impact of rising temperatures as we continue in this module.

Figure 9.1.4. Global Land-Ocean Temperature Index graph. This graph illustrates the change in global surface temperature relative to 1951-1980 average temperatures. The 10 warmest years in the 134-year record all have occurred since 2000, with the exception of 1998. The year 2014 ranks as the warmest on record.

Credit: NASA/GISS

Activate your learning

The impacts of increasing greenhouse gas concentrations are already being felt around the globe, though the degree of change varies with location. The Third National Climate Assessment (NCS), released in 2014 by the US Global Change Research Program (USGCRP), reports that over the last century increasing average temperatures, increasing weather variability, increasing warmer nights and winters, lengthening of the growing season, and an increase in the frequency and intensity of extreme weather events have already been observed. The severity of these impacts varies throughout the US and the world because of regional topography, proximity to the ocean, atmospheric circulation patterns, and many other factors.

Changing Temperature Patterns

The average temperature in the United States has increased in the last century, with each recent decade being warmer than the past, but this warming is not uniform across the United States (Figure 9.1.5). In general, western and northern regions have warmed more than the southeastern US. In the most recent decade, all regions have shown warming. What impact might this warming trend have on our food production and water supply? For example, we know from our study of water for food production that plants evaporate or transpire water and that the rate of evaporation is dependent on temperature. If temperatures go up, we know that plants will transpire more water. The southwestern US is already a water-scarce area, so increasing temperatures will exacerbate that condition.

We'll explore more connections between climate change and food production in the next section of this module. First, let's investigate changes in some other climate variables.

Figure 9.1.5. Observed US Temperature Change. The colors on the map show temperature changes over the past 22 years (1991-2012) compared to the 1901-1960 average for the contiguous U.S., and to the 1951-1980 average for Alaska and Hawai'i. The bar graph shows the average temperature changes by decade for 1901-2012 (relative to the 1901-1960 average). The far-right bar (2000s decade) includes 2011 and 2012. The period from 2001 to 2012 was warmer than any previous decade in every region.

Credit: USGCRP

Changing Precipitation Patterns

In addition to changing temperatures, the recent decades have seen changes in precipitation patterns. Nationwide average precipitation has increased (Figure 9.1.6), but the patterns of change are not as clear as those for temperature. Notice in Figure 9.1.6 that the water-scarce Southwest experienced a decline in precipitation in recent decades. Additionally, some of the precipitation increase in the eastern US came in form of extremely heavy precipitation (Figure 9.1.7) and resulted in flooding (Figure 9.1.8). Both of these effects are anticipated results of increased concentrations of heat-trapping greenhouse gases in the lower atmosphere.

Figure 9.1.6. Observed US Precipitation Change. The colors on the map show annual total precipitation changes for 1991-2012 compared to the 1901-1960 average, and show wetter conditions in most areas. The bars on the graph show average precipitation differences by decade for 1901-2012 (relative to the 1901-1960 average). The far right bar is for 2001-2012.

Credit: USGCRP

Figure 9.1.7. Observed Change in Very Heavy Precipitation. The map shows percent increases in the amount of precipitation falling in very heavy events (defined as the heaviest 1% of all daily events) from 1958 to 2012 for each region of the continental United States. These trends are larger than natural variations for the Northeast, Midwest, Puerto Rico, Southeast, Great Plains, and Alaska. The trends are not larger than natural variations for the Southwest, Hawai‘i, and the Northwest. The changes shown in this figure are calculated from the beginning and endpoints of the trends for 1958 to 2012.

Credit: USGCRP

Figure 9.1.8. Trends in flood magnitude. Trend magnitude (triangle size) and direction (green = increasing trend, brown = decreasing trend) of annual flood magnitude from the 1920s through 2008. Local areas can be affected by land-use change (such as dams). Most significant are the increasing trend for floods in the Midwest and Northeast and the decreasing trend in the Southwest.

Credit: USGCRP

So far in module 9, we've studied the basics of the science of climate change and by now you should have a pretty good understanding of the relationship between greenhouse gases and temperature. We've seen how human activities, including our food systems, are contributing carbon dioxide and other greenhouse gases to the atmosphere. And, as greenhouse gas concentrations increase, more heat energy is trapped, so temperatures at the Earth's surface increase.

We've also seen that temperatures are already increasing around the globe and that precipitation patterns are changing, but what does the future hold? How much will temperatures increase? Will precipitation increase or decrease? Those are very good questions! And, the answers aren't perfectly clear. Atmospheric and climate scientists all over the world are working hard to estimate how Earth's climate will change as greenhouse gas concentrations increase. Future predictions are made by running computer models that simulate natural processes and human activities and estimate future conditions. Model results vary from model to model, but they all predict future warming. Also, as we've already seen, the amount of warming varies from place to place.

What are the predictions for future climate?

The models used to predict future climate are very complicated and incorporate a vast number of variables, natural processes, and human activities. Projecting into the future is always a tricky endeavor and is always fraught with uncertainty. However, all of the models predict continued warming in the future. The magnitude of the warming varies from model to model and depending on which carbon emission scenario is used. For example, warming might slow in the future if we manage to curb our burning of fossil fuels, which would result in lower carbon dioxide emissions.

The model results are presented on two websites (National Climate Change View and Global Climate Change Viewer) that allow us to view the future projections for the US and for the globe on easy-to-read maps. In the summative assessment for this module, you'll explore these websites in greater depth to extract data for your capstone assignment. Right now, we'll just look at a few of the maps to get an idea of how the climate is projected to change in the latter part of this century. Exploring these maps develops our spatial thinking skills, which in turn enhances our math skills! And, who doesn't want to be better at math?

Future climate projections are presented as the projected change compared to the latter part of the last century (1950-2005). So for example, if the projected temperature change for 2050-2074 is 4^oF, then that means the 2050-2074 average temperature is projected to be 4^oF higher than the average temperature from 1950-2005. All of the following maps present projected change in this manner.

First, let's look at temperature. The National Climate Change Viewer (NCCV) (Figures 9.1.9 and 9.1.10) and Global Climate Change Viewer (GCCV) (Figure 9.1.11) both provide maps of projected temperature changes. Notice that the global map gives temperature change in degrees Celsius, and the US map is in Fahrenheit. One notable aspect of all three maps is that temperature is expected to increase everywhere. As you look at these maps, notice where the temperature change is expected to be the greatest. Can you make any generalizations? What is the expected temperature change in the region where you live right now? For example, if we were in New York City, the map in Figure 9.1.9 suggests that the average maximum temperature by 2050-2074 could be 4^oF higher than it was in 1950-2005.

Figure 9.1.9. Projected Change in Annual Mean Maximum Temperature (^oF) 2050-2074 compared to 1950-2005. Model results are based on the RCP 8.5 emissions scenario, which is a scenario projecting continued increases in greenhouse gas emissions.

Credit: National Climate Change Viewer

Figure 9.1.10. Projected Change in Annual Mean Minimum Temperature (^oF) 2050-2074 compared to 1950-2005. Model results are based on the RCP 8.5 emissions scenario, which is a scenario projecting continued increases in greenhouse gas emissions.

Credit: National Climate Change Viewer

Figure 9.1.11. Projected Change in Annual Mean Temperature (^oC) 2050-2074 compared to 1980-2004. Model results are based on the RCP 8.5 emissions scenario, which is a scenario projecting continued increases in greenhouse gas emissions.

Credit: Global Climate Change Viewer

The projected changes in precipitation aren't quite as straightforward or certain as the projected temperature changes. Some regions are expected to receive more precipitation and some regions less. You can see in Figure 9.1.12 the southwestern US, a region that is already water-scarce, is expected to receive less annual precipitation on average. On the global map in Figure 9.1.13, equatorial regions are expected to receive a little more precipitation, and there's a band just north and south of the equator where precipitation is expected to decrease. The certainty in the precipitation predictions is lower than for temperature and the variability within a given year and from year to year in how the precipitation falls is expected to increase.

Figure 9.1.12. Projected Change in Annual Mean Precipitation (in/day, 100ths of an inch)) 2050-2074 compared to 1950-2005. Model results are based on the RCP 8.5 emissions scenario, which is a scenario projecting continued increases in greenhouse gas emissions.

Credit: National Climate Change Viewer

Figure 9.1.13. Projected Change in Annual Mean Precipitation (mm/day) 2050-2074 compared to 1980-2004. Model results are based on the RCP 8.5 emissions scenario, which is a scenario projecting continued increases in greenhouse gas emissions.

Credit: Global Climate Change Viewer

The NCCV also allows you to view projected changes in a few more variables that are not available on the GCCV. Students studying food regions outside of the US will need to work with their instructor to find similar data for their regions.

Precipitation falls on the land surface and flows into streams and rivers, which is called runoff. If precipitation is projected to decrease in the future, it would make sense that runoff would also decrease. Also, as temperatures increase and cause evaporation and transpiration to increase, there is less water available to run off into streams and rivers. The NCCV runoff map (Figure 9.1.14) suggests that runoff will also decrease in many areas of the US. The units for runoff are given in inches of water per month, similar to units for precipitation. In water-scarce regions where the precipitation is low, for example in deserts, often agriculture is irrigation with runoff from upstream regions where the precipitation is higher. Decreases in runoff could have adverse impacts on some regions that rely on runoff for irrigation.

As temperatures increase, there is an expected decrease in annual snowpack. While this is bad news for avid skiers, it's also bad news for regions that rely on water stored in snowpack in the winter that melts and is used for irrigation in the summer months. Figure 9.1.15 illustrates the projected change in annual mean snow in inches. Regions that don't normally get snow are indicated as zero (the deep south and southwest). The Rockies, Sierra Nevadas, Cascades as well as the mountains in the northeast are all expected to see significant decreases in annual snowpack.

The combination of increased temperatures with increased evaporation and transpiration rates will leave soils drier. Soil moisture content is projected to decrease across much of the US (Figure 9.1.16). Soil moisture is measured in units of depth of water (inches) and is the water available to plants. Some of our very important agricultural regions, the Midwest, are expected to see some of the largest declines in soil moisture storage.

The last data set, evaporative deficit, (Figure 9.1.17) gives us an idea of how much water could evaporate compared to how much water is actually available. An increase in evaporative deficit is a symptom of a transition to a hotter and drier climate. Not surprisingly the entire US is projected to see an increase in evaporative deficit, with the highest increases being in the Southwest and Midwest.

In summary, the future projected climate for the US is generally hotter and drier. Precipitation projections are more variable and less certain, but the increase in temperature and resulting increase in evaporation and transpiration will result in less runoff and drier soils in much of the US. The implications for agriculture are significant. We've already seen how water is essential for crop growth and changes in the temperature regime may have some surprising impacts on growing our food. In the next section, we'll explore projected climate changes and the potential impacts on agriculture in more detail. We'll also consider some possible adaptation strategies that can make our food systems more resilient to our changing climate.

Figure 9.1.14. Projected Change in Annual Mean Runoff (in/mo) 2050-2074 compared to 1950-2005. Model results are based on the RCP 8.5 emissions scenario, which is a scenario projecting continued increases in greenhouse gas emissions.

Credit: National Climate Change Viewer

Figure 9.1.15. Projected Change in Annual Mean Snow (in) 2050-2074 compared to 1950-2005. Model results are based on the RCP 8.5 emissions scenario, which is a scenario projecting continued increases in greenhouse gas emissions.

Credit: National Climate Change Viewer

Figure 9.1.16. Projected Change in Annual Mean Soil Storage (in) 2050-2074 compared to 1950-2005. Model results are based on the RCP 8.5 emissions scenario, which is a scenario projecting continued increases in greenhouse gas emissions.

Credit: National Climate Change Viewer

Figure 9.1.17. Projected Change in Annual Mean Evaporative Deficit (in/mo) 2050-2074 compared to 1950-2005. Model results are based on the RCP 8.5 emissions scenario, which is a scenario projecting continued increases in greenhouse gas emissions.

Credit: National Climate Change Viewer

Food systems, including agriculture, play a significant role in contributing to global warming, perhaps contributing between 19% to 29% of global anthropogenic greenhouse gas emissions (Vermeulen et al. 2012). Growing food requires energy. While the sun is the source of energy for plant growth, a majority of the energy that fuels our modern food system comes from fossil fuels (petroleum and natural gas). Petroleum is used as a fuel for tractors and other vehicles that transport food. Natural gas is used in fertilizer production and other fossils fuels are burned to generate electricity that is used in the processing and refrigeration of food. The burning of fossil fuels is our largest source of greenhouse gases globally, and food production is a significant contributor to greenhouse gases.

The Food And Agriculture Organization of the United Nations (FAO) estimates that “the food sector (including input manufacturing, production, processing, transportation marketing and consumption) accounts for around 95 exa-Joules (10¹⁸ Joules), ...— approximately 30 percent of global energy consumption — and produces over 20 percent of global greenhouse gas emissions” (from Food and Agriculture Organization of the United Nations).

In addition to carbon dioxide emissions from the fossil fuel consumption associated with agricultural activities discussed above, agriculture also contributes to greenhouse gas emissions in other ways (Figure 9.1.18). The loss of above-ground vegetation when grasslands and forests are converted to agriculture contributes about six percent of the global warming potential from greenhouse gas emissions. In addition, methane released from irrigated agriculture and from digestion and decomposition of manure from ruminants combined with nitrous oxide emissions from mismanagement of fertilizers contributes about 14 percent of the increase in total warming potential (Nelson 2014).

Text description of the Figure 9.1.18.

The image is a pie chart titled “Global warming potential from greenhouse gas emissions by sector (2009)”, sourced from the World Resources Institute (2014). The chart illustrates the percentage contribution of different sectors to global greenhouse gas emissions based on their warming potential. The largest segment, shown in dark blue, represents Energy, which accounts for 70% of emissions, making it the dominant contributor. Other sectors include Agriculture (14%), Land use and forestry (6%), Waste (3%), Industrial processes (5%), and Bunker fuels (2%), which refers to fuel oil used on ships. Each sector is represented by a distinct color, with energy occupying the majority of the circle, emphasizing its overwhelming impact compared to other sources. The chart highlights the critical role of energy production and consumption in driving climate change, while also showing smaller but significant contributions from agriculture and land use.

Credit: Nelson, 2014, p. 16. Data from World Resources Institute 2014

In the first part of this module, we looked at observed and predicted changes in temperature and precipitation. Now, we'll consider some of the impacts that changes in temperature and precipitation may have on crops. For example, the projected increase in temperature will increase the length of the frost-free season (the period between the last frost in the spring and the first frost in the fall), which corresponds to a similar increase in growing season length. Increases in frost-free season length have already been documented in the US (Figure 9.2.1). An increase in growing season length may sound like a great thing for food production, but as we'll see, that can make plants more vulnerable to late frosts and can also allow for more generations of pests per growing season, thus increasing pest pressure. The complexity of the system makes adapting to a changing climate quite challenging, but not insurmountable.

Figure 9.2.1. Observed Changes in the Frost-free Season in1986-2015 compared to 1901-1960. The frost-free season length is the period between the last occurrence of 32°F in the spring and the first occurrence of 32°F in the fall. Increases in frost-free season length correspond to similar increases in growing season length.

Credit: National Climate Assessment, 2014.

Crops, livestock, and pests are all sensitive to temperature and precipitation, so changes in temperature and precipitation patterns can affect agricultural production. As a result, it's important to consider future projections of climate variables so that farmers and ranchers can adapt to become more resilient.

Projected changes in some key climate variables that affect agricultural productivity are shown in Figure 9.2.2. The lengthening of the frost-free or growing season and reductions in the number of frost days (days with minimum temperatures below freezing), shown in the top two maps, can have both positive and negative impacts. With higher temperatures, plants grow and mature faster, but may produce smaller fruits and grains and nutrient value may be reduced. If farmers can adapt warmer season crops and planting times to the changing growing season, they may be able to take advantage of the changing growing season.

The bottom-left map in Figure 9.2.2 shows the expected increase in the number of consecutive days with less than 0.01 inches of precipitation, which has the greatest impact in the western and southern part of the U.S. The bottom-right map shows that an increase in the number of nights with a minimum temperature higher than 98% of the minimum temperatures between 1971 and 2000 is expected throughout the U.S., with the highest increase expected to occur in the south and southeast. The increases in both consecutive dry days and hot nights are expected to have negative effects on both crop and animal production. There are plants that can be particularly vulnerable at certain stages of their development. For example, one critical period is during pollination, which is very important for the development of fruit, grain or fiber. Increasing nighttime temperatures during the fruit, grain or fiber production period can result in lower productivity and reduced quality. Farmers are already seeing these effects, for example in 2010 and 2012 in the US Corn Belt (Hatfield et al., 2014).

Some perennial crops, such as fruit trees and grape vines, require exposure to a certain number of hours at cooler temperatures (32^oF to 50^oF), called chilling hours, in order for flowering and fruit production to occur. As temperatures are expected to increase, the number of chilling hours decreases, which may make fruit and wine production impossible in some areas. A decrease in chilling hours has already occurred in the Central Valley of California and is projected to increase up to 80% by 2100 (Figure 9.2.3). Adaptation to reduced chilling hours could involve planting different varieties and crops that have lower chilling hour requirements. For example, cherries require more than 1,000 hours, while peaches only require 225. Shifts in the temperature regime may result in major shifts in certain crop production to new regions (Hatfield et al., 2014).

To supplement our coverage of the climate variables that affect agriculture, read p. 18, Box 4 in Advancing Global Food Security in the Face of a Changing Climate, and scroll down to the Learning Checkpoint below.

Figure 9.2.2. Projected Changes in Key Climate Variables Affecting Agricultural Productivity. Changes are shown for 2070-2099 compared to 1971-2000 and projected under an emissions scenario that assumes continued increases in greenhouse gases.

Credit: National Climate Assessment, 2014.

Figure 9.2.3. Reduced winter chilling projected for California’s Central Valley, assuming that observed climate trends continue through 2050 and 2090.

Credit: National Climate Assessment, 2014.

Learning Checkpoint

What are some of the challenges that farmers will face in a changing climate?

In the first part of this module, we explored some maps from the National Climate Change Viewer. Discuss how the predicted changes in climate that you saw in those maps (Module 9.1 Projected Climate Changes) will likely affect farmers.

Plants, whether crops or native plant species have adapted to flourish within a range of optimal temperatures for germination, growth, and reproduction. For example, plants at the poles or in alpine regions are adapted to short summers and long, cold winters, and so thrive within a certain range of colder temperatures. Temperature plays an important role in the different biological processes that are critical to plant development. The optimum temperature varies for germination, growth, and reproduction varies and those optimum temperatures needed to occur at certain times in the plant's life cycle, or the plant's growth and development may be impaired.

Let's consider corn as an example. In order for a corn seed to germinate, the soil temperature needs to be a minimum of 50^oF. Corn seed typically will not germinate if the soil is colder than about 50^oF. The minimum air temperature for vegetative growth (i.e., the growth of stem, leaves, and branches) is about 46^oF, but the optimum range of temperatures for vegetative growth of corn is 77-90^oF. At temperatures outside of the optimal range, growth tends to decline rapidly. Many plants can withstand short periods of temperatures outside of the optimal range, but extended periods of high temperatures above the optimal range can reduce the quality and yield of annual crops and tree fruits. The optimal reproduction of corn occurs between 64 and 72^oF, and reproduction begins to fail at temperatures above 95^oF. Reproductive failure for most crops begins around 95^oF.

Water availability is a critical factor in agricultural production. We saw in Module 4 how increased temperature leads to increased transpiration rates. High rates of transpiration can also exhaust soil water supplies resulting in drought stress. Plants respond to drought stress through a variety of mechanisms, such as wilting their leaves, but the net result of prolonged drought stress is usually reduced productivity and yield. Water deficit during certain stages of a plant's growth can result in defects, such as tougher leaves in kales, chards, and mustards. Another example, blossom end rot in tomatoes and watermelon, is caused by water stress and results in fruit that is unmarketable (Figure 9.2.4 and for more photos of blossom end rot on different vegetables, visit Blossom end rot causes and cures in garden vegetables).

In addition to water stress and impacts on plant productivity and yield, increased temperatures can have other effects on crops. High temperatures and direct sunlight can sunburn developing fruits and vegetables. Intense heat can even scald or cook fruits and vegetables while still on the plant.

Figure 9.2.4. Blossom-end-rot in a tomato

Credit: Scot Nelson, Creative Commons

Crop yield

A warming climate is expected to have negative impacts on crop yields. Negative impacts are already being seen in a few crops in different parts of the world. Figure 9.2.5 shows estimated impacts of climate trends on crop yields from 1980-2008, with declines exceeding 5% for corn, wheat, and soy in some parts of the world. Projections under different emissions scenarios for California's Central Valley show that wheat, cotton, and sunflower have the largest declines in yields, while rice and tomatoes are much less affected (Figure 9.2.6). Notice that there are two lines on the graphs in Figure 9.2.6 projecting crop yields into the future. The red line corresponds to temperature increases associated with a higher carbon dioxide emissions scenario. We saw in Module 9.1 that the more CO₂ we emit, the more heat energy is trapped in the lower atmosphere, and therefore the warmer the temperatures. For some crops, those higher temperatures are associated with great impacts on the crop's yield.

Why are some crops affected more by observed and projected temperature increases than others? It depends on the crop, the climate in the region where the crop is being grown, and the amount of temperature increase. Consider the Activate your learning questions below to explore this more deeply.

Why do some crops see a positive yield change with increasing temperatures, such as alfalfa in Figure 9.2.6? Generally, warmer temperatures mean increased crop productivity, as long as those temperatures remain within the optimal range for that crop. If a crop is being grown in a climate that has typical temperatures at the cooler end of the plant's optimal range, than a bit of warming could increase the crop's productivity. If the temperatures increase above the optimal range or exceed the temperature that leads to reproductive failure, then crop yields will decline.

Figure 9.2.5. Climate change effects on crop yields

Credit: Nelson, 2014

Figure 9.2.6. Crop Yield Response to Warming in California’s Central Valley. Changes in climate through this century will affect crops differently because individual species respond differently to warming. This figure is an example of the potential impacts on different crops within the same geographic region. Crop yield responses for eight crops in the Central Valley of California are projected under two emissions scenarios, one in which heat-trapping gas emissions are substantially reduced (B1) and another in which these emissions continue to grow (A2). This analysis assumes adequate water supplies (soil moisture) and nutrients are maintained while temperatures increase. The lines show five-year moving averages for the period from 2010 to 2094, with the yield changes shown as differences from the year 2009. Yield response varies among crops, with cotton, maize, wheat, and sunflower showing yield declines early in the period. Alfalfa and safflower showed no yield declines during the period. Rice and tomato do not show a yield response until the latter half of the period, with the higher emissions scenario resulting in a larger yield response.

Credit: National Climate Assessment, 2014.

Weeds, Insects, and Diseases

Warming temperatures associated with climate change will not only have an effect on crop species; increasing temperature also affects weeds, insect pests, and crop diseases. Weeds already cause about 34% of crop losses with insects causing 18% and disease 16%. Climate change has the potential to increase the large negative impact that weeds, insects, and diseases already have on our agricultural production system. Some anticipated effects include:

• several weed species benefit more than crops from higher temperatures and increased CO₂ levels
• warmer temperatures increase insect pest success by accelerating life cycles, which reduces time spent in vulnerable life stages
• warmer temperatures increase winter survival and promote the northward expansion of a range of insects, weeds, and pathogens
• longer growing seasons allow pest populations to increase because more generations of pests can be produced in a single growing season
• temperature and moisture stress associated with a warming climate leaves crops more vulnerable to disease
• changes in disease prevalence and range will also affect livestock production

Modeling and predicting the rate of change and magnitude of the impact of weeds, insects, and disease on crops is particularly challenging because of the complexity of interactions between the different components of the system. The agricultural production system is complex and the interactions between species are dynamic. Climate change will likely complicate the management of weeds, pests, and diseases as the ranges of these species changes.

Effects on Soil Resources

The natural productive capacity of a farm or ranch system relies on a healthy soil ecosystem. Changing climate conditions, including extremes of temperature and precipitation, can damage soils. Climate change can interfere with healthy soil life processes and diminish the ecosystem services provided by the soil, such as the water holding capacity, soil carbon, and nutrients provided by the soils.

The intensity and frequency of extreme precipitation events are already increasing and is expected to continue to increase, which will increase soil erosion in the absence of conservation practices. Soil erosion occurs when rainfall exceeds the ability of the soil to absorb the water by infiltration. If the water can't infiltrate into the soil, it runs off over the surface and carries topsoil with it (Figure 9.2.7). The water and soil that runoff during extreme rainfall events are no longer available to support crop growth.

Shifts in rainfall patterns associated with climate change are projects to produce more intense rainstorms more often. For example, there has been a large increase in the number of days with heavy rainfall in Iowa (Figure 9.2.8), despite the fact that total annual precipitation in Iowa has not increased. Soil erosion from intense precipitation events also results in increased off-site sediment pollution. Maintaining some cover on the soil surface, such as crop residue, mulch, or cover crops, can help mitigate soil erosion. Better soil management practices will become even more important as the intensity and frequency of extreme precipitation increases.

Figure 9.2.7. Heavy rainfall can result in increased surface runoff and soil erosion.

Credit: Hatfield et al., 2014

Figure 9.2.8. Increasing Heavy Downpours in Iowa. Iowa is the nation’s top corn and soybean producing state. These crops are planted in the spring. Heavy rain can delay planting and create problems in obtaining a good stand of plants, both of which can reduce crop productivity. In Iowa soils with even modest slopes, rainfall of more than 1.25 inches in a single day leads to runoff that causes soil erosion and loss of nutrients and, under some circumstances, can lead to flooding. The figure shows the number of days per year during which more than 1.25 inches of rain fell in Des Moines, Iowa. Recent frequent occurrences of such events are consistent with the significant upward trend of heavy precipitation events documented in the Midwest

Credit: Hatfield et al., 2014

Farmers have had to adapt to the conditions imposed on them by the climate of their region since the inception of agriculture, but recent human-induced climate change is throwing them some unexpected curve balls. Extreme heat, floods, droughts, hail, and windstorms are some of the direct effects. In addition, there are changes in weed species and distribution, and pest and disease pressures, on top of potentially depleted soils and water stress. Fortunately, there are many practices that farmers can adopt and changes that can be made to our agricultural production system to make the system more resilient to our changing climate.

Farmers and ranchers are already adapting to our changing climate by changing their selection of crops and the timing of their field operations. Some farmers are applying increasing amounts of pesticides to control increased pest pressure. Many of the practices typically associated with sustainable agriculture can also help increase the resilience of the agricultural system to impact of climate change, such as:

• diversifying crop rotations
• integrating livestock with crop production systems
• improving soil quality
• minimizing off-farm flows of nutrients and pesticides
• implementing more efficient irrigation practices

The video below introduces and discusses several strategies being adopted by New York farmers to adapt to climate change. In addition, the fact sheet from Cornell University's Cooperative Extension about Farming Success in an Uncertain Climate produced by Cornell University's Cooperative Extension outlines solutions to challenges associated with floods, droughts, heat stress, insect invasions, and superweeds. Also, p. 35, Box 8 in Advancing Global Food Security in the Face of a Changing Climate outlines some existing technologies that can be a starting point for adapting to climate change.

Learning Checkpoint: How can farmers adapt to climate change?

• Watch 15 min video by Cornell University about Agriculture and Adaptation about how New York farmers are adapting to climate change.
• Read the fact sheet from Cornell University's Cooperative Extension about Farming Success in an Uncertain Climate
• Read p. 35, Box 8 in Advancing Global Food Security in the Face of a Changing Climate
• Answer the questions below

Video: Climate Smart Farming Story: Adaptation and Agriculture (15:09)

References:

• Hatfield, J., G. Takle, R. Grotjahn, P. Holden, R. C. Izaurralde, T. Mader, E. Marshall, and D. Liverman, 2014: Ch. 6: Agriculture. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 150-174. doi:10.7930/J02Z13FR. On the Web: http://nca2014.globalchange.gov/report/sectors/agriculture
• Lengnick, L. 2015. Resilient Agriculture: Cultivating Food Systems for a Changing Climate, New Society Publishers.

We've covered quite a bit of ground in this module. We explored how human activities have led to an increase in atmospheric carbon dioxide, which in turn is increasing the surface temperature of the Earth and changing precipitation patterns. The resulting impacts on our agricultural production system are complex and potentially negative. As a result, farmers are adopting new practices and technologies to adapt to our changing climate and create more resiliency in the agricultural system.

Let's put global climate change and its interaction with our agricultural system into the Coupled Human-Natural System (CHNS) diagram that we've been using throughout the course. The development of global climate change is illustrated in the CHNS diagram in Figure 9.2.9, where the increased burning of fossil fuels within the human system results in more CO₂ in the atmosphere. The response in the natural system is that more heat energy is trapped. The resulting feedback that affects the human system is that temperature increases along with all of the other climate change effects that we discuss in this module.

Figure 9.2.9. Coupled Human-Natural System diagram illustrating the development of global climate change

Click for a text description of the Human-Natural system diagram.

This loop shows the human system with an arrow labeled drivers pointing to natural system with an arrow labeled feedbacks pointing back to human system. Those four concepts are defined as follows:

Human system (human system internal interactions): human population growth, industrialization, and increased burning of fossil fuels

Drivers: increased emissions of carbon dioxide and other greenhouse gases

Natural system (natural system processes and interactions): increased greenhouse gas concentrations trap more heat energy in atmosphere

Feedbacks: increased temperatures, extreme weather events, sea level rise and precipitation variability

Credit: Human-Natural system diagram © Penn State is licensed under CC BY-NC-SA 4.0

What would be the next step in the diagram? Consider the feedbacks associated with the arrow at the bottom of the diagram that will affect the human system. What are the possible responses in the human system to these feedbacks? Our response can be categorized into two broad categories: mitigation and adaptation. We've already discussed adaptation strategies that can be implemented by farmers to adapt to a changing climate. Some examples are to change the crops grown to adapt to the higher temperatures or to install more efficient irrigation systems so that crops can be grown more efficiently.

What about mitigation? Mitigation strategies are those that are targeted at reducing the severity of climate change. One important mitigation strategy is to reduce the burning of fossil fuel, and our agricultural system is a significant contributor to greenhouse gas emissions. Shifting to use renewable energy sources and more fuel-efficient equipment are two mitigation strategies. There are other important mitigation strategies that target other greenhouse gas emissions, such as nitrous oxide from fertilizer use and methane from ruminants and some types of irrigated agriculture.

In the next couple of modules, we'll talk more about strategies to make our agricultural systems more resilient and sustainable, and you'll see how our food production can become more resilient to climate change. In addition, you'll get the opportunity to explore the project climate change impacts on your capstone region and to consider how those projected change might affect the food systems of that region.

In the introductory video below you will see a particular local example of a food system, presented by the Food and Agriculture Organization (FAO) of the United Nations. As you watch, look for examples of Human and Natural system components in a local food system particular to the Red River Delta in Vietnam, and the way that the food system has changed over time. Human and Natural system components were introduced in Module 1, and we have been referring to them regularly along the way in the course, as we have considered the natural system elements in agroecosystems and the way these are managed by humans. Now we will begin to take a larger, whole systems view of food systems.

Please watch the below video celebrating world food day 2013, which describes the Vietnamese “Garden, Pond, Livestock Plan” (V.A.C) food system.

Video: World Food Day 2013 (6:52)

The introductory section below is adapted from "Chapter 3: The food system and household food security” at the document website of the United Nations Food and Agriculture Organization (FAO).

This section attempts to describe the parts of a food system in basic terms, starting from the standpoint of the systems approach. It begins, "the perception underlying the systems approach is that the whole is greater than the sum of its parts. Any situation is viewed in terms of relationships and integration. A food system may thus include all activities related to the production, distribution, and consumption of food that affect human nutrition and health (see Figure 10.1.1, which is reproduced from module 1).

Food production comprises such factors as the use of land for productive purposes (land use), the distribution of land ownership within communities and regions (land tenure), soil management, crop breeding and selection, crop management, livestock breeding and management and harvesting, which have been touched on in previous modules. Food distribution involves a series of post-harvest activities including the processing, transportation, storage, packaging, and marketing of food as well as activities related to household purchasing power, traditions of food use (including child feeding practices), food exchanges and gift-giving and public food distribution. Activities related to food utilization and consumption include those involved in the preparation, processing, and cooking of food at both the home and community levels, as well as household decision-making regarding food, household food distribution practices, cultural and individual food choices, and access to health care, sanitation, and knowledge.

Among the components of the food system, e.g. food processing, communication, and education, there is substantial overlap and interlinkage. For example, household decision-making behavior with regard to food is influenced by nutrition knowledge and by cultural practices with regard to food allocation within the household as well as by purchasing power and market prices."

Figure 10.1.1 Diagram of a food system as a "conveyer belt" of three sequential components delivering Nutrition and Health from Natural Resources and Production Environments. Technical and policy aspects central to food system activities are shown surrounding the three components of production, distribution, and consumption. 

Credit: Steven Vanek, adapted from Combs et al. 1996. Sustainable Food System Approaches to Improving Nutrition and Health.

 

Food systems are further embedded in environments and societies (thus, both natural and social/political contexts) which differ according to a variety of factors such as agroecology (the composition of the local agroecosystem, see previous modules), climate, social aspects, economics, health, and policy. The model presented in Figure 10.1.1 above is useful in conceptualizing the various activities that determine food security and nutritional well-being and the interactions within the food system."

Two important features that we want to emphasize in the passage above from the FAO are first, the fact that food systems involve processes at multiple scales (e.g. local agroecosystems, government policy at a national scale, international research and technology development), which eventually have many impacts at a household scale, either in the livelihoods of food producers (who gain income from the food system and also consume food); and also for consumers around the world. Second, criteria with which we should evaluate food systems are their ability to deliver nutrition and health outcomes (see e.g. module 3), and also the sustainability of natural resources and environments, which we will consider in module 10.2. We note that these criteria of environmental sustainability and health are at opposite ends of this "conveyer belt" model of food systems, where the food system "conveyer belt" can be said to deliver nutrition and health outcomes by transforming the inputs from natural resources and environments. These health and nutrition outcomes are associated with the concept of food security (sufficient access to appropriate and healthy food) which was introduced in module 3 and will be further explored in module 11. Human health and environmental sustainability correspond roughly to the positive objectives that we conceive of for the human system and natural systems, respectively: health and equitable nutrition (or food security) in the human system, and environmental sustainability of natural systems. A final observation from Fig. 10.1.1 is that food systems are ubiquitous and touch on all aspects of human societies. We are all participants in food systems, either as producers, consumers, in the distribution or in other myriad ways.

Activate Your Learning: Food's Journey in the Food System

Figure 10.1.2. Supermarkets like this one are one of the most commonly accessed nodes for consumers in the modern globalized food system.

Image Credit: Steven Vanek

Food systems comprise the interacting parts of human society and nature that deliver food to households and communities (see the previous page), and can be used to understand food in its relation to the earth system. To better understand food systems, in the exercise below you'll be asked to consider a familiar food of your choice, and the journey this food takes from where it is produced to the meals that we consume every day. Within the food supply chain for this food, you'll be asked to distinguish between social (human system) aspects and environmental (natural system) aspects of that product's food production and supply chain.

Activate Your Learning Activity:

In the blanks below, fill in the blanks regarding the supply chain for food products. You can also download the worksheet for filling in offline, or as part of a classroom activity.  As depicted in Fig. 10.1.3, you’ll need to give the origin, some intermediate destinations, and then the final consumption point for the food product.  Then you should think of some social or human system dimensions of the production, supply chain, or consumption of this product, as well as some ecological or natural system dimensions and fill in the corresponding blanks. Do this first for a product familiar to you, whose supply chain you either know about or can research quickly  (part 1).  Then repeat the activity for a food product in the online introductory video from the first page of this module, about food systems in Vietnam (part 2).  When you are done with each part you can click on the ‘answers’ link in the below each part, and see how your answers match up.

Text description of the Figure 10.1.3 diagram.

The image depicts a simple linear flowchart representing the stages of a supply chain or process. It consists of four rectangular boxes connected by right-facing arrows, indicating a sequential progression. The first box on the left is labeled “Source:” with a blank line underneath for input. The second box is labeled “Intermediate destination 1:” followed by a blank line, and the third box is labeled “Intermediate destination 2:” with another blank line. The final box on the right is labeled “Consumption point:” with a blank line beneath it. The design uses thin blue outlines for the boxes and arrows, set against a white background, giving it a clean and minimalistic appearance. This diagram is intended to illustrate the movement of goods, resources, or information from the original source through intermediate stages to the final point of consumption, allowing customization by filling in specific details for each stage.

Credit: © Penn State is licensed under CC BY-NC-SA 4.0.

Fill in the blanks below.  If you are doing this online, just note your answers on a piece of paper regarding the food product you have chosen, or download the worksheet. When you are done you can click on the ‘answers’ link below to see some possible examples and see if your answers match up with these answers.

1. Food product: x
2. Food supply Chain:
   1. Source: Where main raw material is produced, fished, hunted: x
   2. Intermediate destination 1: x (e.g processing plant, washing, trucking, warehouse, etc.)
   3. Intermediate destination 2: x (e.g processing plant, washing, trucking, warehouse, etc.)
   4. Intermediate destination 2: x (if needed)
   5. Consumption point: x
3. Up to three social or human system dimensions of this food chain (e.g. policy, economic, or cultural factors associated with the production and consumption of this food, recall the Human System factors in a Coupled Human Natural Framework, module 1.2)
   1. x
   2. x
   3. x
4. Up to three ecological or natural system dimensions of this food chain: (ecological factors would include crop and animal species, agroecosystems, climate, water, and soil influences on food production):
   1. x
   2. x
   3. x

Example answers

(These may be a good deal more complete than your examples but give a sense of the range of possible answers)

Exercise 2:

Recall the video celebrating world food day 2013, World Food Day 2013 Video: the Vietnamese “Garden, Pond, Livestock Plan” (V.A.C) food system". You may want to quickly skim the video again and note the food pathways that foods are following in these systems. Then choose either a product that is consumed within the household that appears in the video or one that is sold outside the household (some products fit into both categories). Fill in the same set of production and transport steps for this product as you did in part 1, as well as some social and ecological aspects.  You can use a piece of scrap paper or the downloaded worksheet.  Note that a product consumed in this farming household may have a very short food supply chain!

Look at the following worksheet and fill in the blanks corresponding to the blanks below. When you are done you can click on the ‘answers’ link to see some possible examples and see if your answers match up with these answers.

1. Food product x
2. Food supply Chain:
   1. Source: Where main raw material is produced, fished, hunted: x
   2. Intermediate destination 1: x (e.g processing plant, washing, trucking, warehouse, etc.)
   3. Intermediate destination 2: x (e.g processing plant, washing, trucking, warehouse, etc.)
   4. Intermediate destination 2: x (if needed)
   5. Consumption point: x
3. Up to three social or human system dimensions of this food chain (e.g. policy, economic, or cultural factors associated with the production and consumption of this food, recall the Human System factors in a Coupled Human Natural Framework, module 1.2)
   1. x
   2. x
   3. x
4. Up to three ecological or natural system dimensions of this food chain: (ecological factors would include crop and animal species, agroecosystems, climate, water, and soil influences on food production):
   1. x
   2. x
   3. x

Example Answers

A good way to understand the complexity of different types of food systems is to look for organizing principles to classify them. In the introductory food supply chain exercise at the beginning of this module, if you chose a product that was produced a long distance from where you consumed it, you are aware that the global food system today handles food at an enormous spatial scale. This example leads to one way to organize our understanding of food systems, which is the hierarchy global, regional, and local scales of food systems (Fig. 10.1.4).

Figure 10.1.4. Spatial scale of organization in food systems

Click for a text description of the spatial scale diagram.

Scale	Examples
Global	Global grain and meat production (commodities), Global fisheries
Regional	Most supermarket and restaurant foods
Local	Farmer's market, local hunting and fishing
Household	Home gardens and subsistence agriculture

Credit: Steven Vanek

Another helpful way to classify food systems is to look for typologies of food systems. Building typologies is a somewhat subjective but often helpful process where we look for groups of systems or components that hang together in order to better understand their function, importance, or other attributes. For the typology of food systems we present here, we are thinking about classifying food systems based on how production occurs and at what scale, which portions of society are involved in production and distribution, and the rationale underlying production, distribution, and consumption. In this course, we use the scheme of three overlapping food systems that exist at global, regional, and local scales shown below in Fig. 10.1.5.

Figure 10.1.5. Typology of Food Systems

Click for a text description of the Food Systems Typology diagram.

Typology of Food Systems into Smallholder, Globalized Corporate, and Alternative types. Two major types at left are the globalized corporate system which is dominant in the industrialized world and in terms of trade of major commodities, and smallholder systems which are in fact extremely important at local and regional levels in the developing world, with more than two billion smallholder farmers globally growing, trading, and selling food in these contexts. The vertical and horizontal axes in the diagram attempt to capture the variation in these systems regarding their integration into global markets and specialized industrial production (vertical axis), and the way in which the systems at right are responses to sustainability challenges of the modern food system (horizontal axis). The alternative types at right, which reflect current trends and movements in the modern food system towards sustainability, are divided into an alternative global or "ecologically modernized" type (see module 2 on the history of food systems) along with a more local or community-based food system type, with both alternative food system types responding to sustainability critiques of the globalized food system in recent history. It is also important to realize that different food systems overlap and are certainly not spatially isolated: for example, smallholders in the developing world simultaneously participate in both smallholder and global ways of producing and consuming food, and urban consumers the world over may simultaneously purchase food from all four systems.

Global Corporate Food System

• High volume, minimized production costs
• Simplified farms that specialize in particular crops
• Global and regional shipping
• Unprocessed and processed foods
• Coordinated through major agribusinesses and food companies
• Goals: markets and return on investment
• Local producers participate via commodity production

Smallholder Food Systems

• Smaller-volume production on many more farms
• Complex, diverse farming systems with e.g. livestock and many crops
• Local/regional shipping and marketing
• Unprocessed foods
• Goals: generating farmer livelihoods and food for direct consumption and local markets
• Mixed production and consumption roles
• Produces a large proportion of food in developing countries

Alternative Food Systems: Globalized and Community-based

• Globalized
  • "Ecological modernization" of globalized food system
  • Global/national trade networks
  • Goals: reform of industrialized farming practices
  • Certification schemes: fair-trade, sustainable forestry, etc
  • Unprocessed and processed foods
  • Mainstreaming of organic products in national/global distribution
• Community-based
  • Emphasis on reintegration of local rural-urban economies
  • Goals: reform of industrialized farming, local economies
  • Local/regional shipping and farmers' markets
  • Mainly unprocessed foods
  • Organic and local criteria/certification

Credit: Steven Vanek and Karl Zimmerer

Consumers worldwide who enter a supermarket are largely interacting with this type of food system. Some local and regional products are provided, but food is largely sourced from major national and global production regions and can be transported long distances (100 to thousands of miles or km) with enormous quantities of food moving through the system as a whole. There is an emphasis on modern production and processing techniques, efficiency, and lowering the immediate costs of production. Also, many of the products moving through this system are thought of as commodities: products that are generic and replaceable regardless of their origin and that carry standard global and national pricing frameworks. Examples would be corn grain for food, different grades of rice, soy and corn oils, supermarket potatoes and tomatoes, and cuts of pork for supermarket consumption.

Figure 10.1.6. Summary of characteristics for the globalized corporate food system, taken from the previous page.

Click for a text description of the globalized corporate food system.

Globalized Corporate Food System

• High volume, minimized production costs
• simplified farms that specialize in particular crops
• global and regional shipping
• unprocessed and processed foods
• coordinated through major agribusiness and food companies
• goals: markets and return on investment
• local producers participate via commodity production

Credit: Steven Vanek and Karl Zimmerer.

Calling this a ‘corporate’ system may obscure the fact that production for this national/global scale system occurs most commonly not on corporate property or company farms, but in family farm enterprises like the thousands of dairy and grain farms that populate many regions of the United States. For example, family farms still constitute about 97% of farms in the United States by number, although the acreage in company-owned farms and the value earned by these company-owned farms is larger than this numerical count suggests (top pie-charts within Figure 10.1.8a below). Also, in some areas of the country, ‘large’ and ‘very large’ family farms have mean farm sizes of many thousands of acres, which contradicts the traditional image of a small family enterprise, and illustrating the pressures for farms to become large in modern industrialized food systems, in order to take advantage of economies of scale in farming (economies of scale refers to the idea that as the size of an enterprise goes up, the efficiency of producing a given item goes up and the cost per item goes down, e.g. baking one tray of muffins every Saturday versus opening a muffin shop making hundreds of muffins every day).

Figure 10.1.7. This landscape in central Europe appears quite traditional but is, in fact, a production zone for commodity crops in the globalized corporate food system

Credit: Steven Vanek

Nevertheless, this portion of the food system is called both ‘global’ and ‘corporate’ because most organizations that coordinate demand and organize processing and distribution of foodstuffs in this layer of the global food system are corporations seeking benefit for their shareholders. In module 3 on nutrition we discussed the way that food has become fiscalized, i.e. it is not only a product working its way through a marketplace to consumers but an active object of investment in the future growth potential of the business of food. These investments are managed through large-scale exchanges like the stock exchange here in the United States. These exchanges allow large swaths of relatively wealthy world citizens (including many in the middle class) to invest in the large-scale production of food and reductions in prices, but can create sustainability issues within the food system because the return on investment rather than food security or environmental sustainability becomes the predominant objective of investors and corporations. Nevertheless, not just corporate entities but also government and civil society (e.g. farmer and community organizations, universities) are also heavily involved in these global systems and can act to reform problems or regulate damaging or unjust practices. They act by way of advocacy and regulation, national/international food policies and support structures such as research on food production and food processing methods.

Within this global system, then, local farmers and fishing communities often act as producers selling into commodity markets, alongside industry-owned farms, feedlots, and other production facilities. In addition to unprocessed food ingredients, the globalized corporate food system has also been largely responsible for the expansion in processed and prepared foods, that seeks to provide convenience for consumers as well as capture the added market value of more prepared foods. Processed foods have been criticized, especially by those advocating community food systems (see description further on), because they displace fresh and whole food components of diets that are important to good nutrition outcomes (see module 3). Processed foods often contain processed industrial ingredients such as corn syrup and processed, low-quality fats along with a lower fiber and vitamin content, which is usually not true of whole unprocessed foods.

Farms and acreage of different crops in United States agriculture:

The pie charts below demonstrate aspects of the description of the globalized food system above. For example, at least in terms of numbers, smaller, family-owned farms with an average size of approximately 240 acres (around 100 hectares with one hectare = 100 x 100 m) dominate the numbers of farms in the United States (Fig. 10.1.8a). Nevertheless, large farms dominate to a greater extent than these smaller farms when considering the total area taken up by farms of different sizes, and a large proportion of income is going to larger operations in a number of classes of farm products (Fig. 10.1.8b). These patterns vary somewhat by what sector of the farming economy is being described, and we include some separate graphs for maize, vegetables, and dairy farms. You will use these graphs in the knowledge check activity below.

Figure 10.1.8a. Charts summarizing USDA Census data from the 2012 agricultural census on numbers, size, and earnings of U.S. farms. It is notable that by numbers of farms, smaller farms dominate, but the total area taken up by larger farms is substantially greater than their small numbers would suggest.

Image credit: Steven Vanek, based on the United States Department of Agriculture (USDA) 2012 agricultural census

Figure 10.1.8b. Charts summarizing how the total revenue of farm products breaks down among farms of different size classes. Note that when all farm products are included in the estimates of revenue, there is a relatively even division of revenue among the farms of different size classes. However, the much larger numbers of farms in the small size category (88% of all farms, see figure 10.1.8a above) mean that the revenue per farm for these products is likely less. The graphs allow comparison of different products in terms of how different size classes of farms are participating in the markets for different types of products, e.g. "how do mid-size farms compare in the share of total revenue between maize and vegetables?"

Credit: Steven Vanek, based on the United States Department of Agriculture (USDA) 2012 agricultural census.

Knowledge Check: Food products and farm sizes in U.S. agriculture

Choose the correct answers based on the graphs in Figure 10.1.8 above and then click on the space for the correct answers.

Figure 10.1.9. This patchwork landscape of sloped fields and hedgerows with dozens of family farms in western Kenya is typical of smallholder food systems.

Credit: Steven Vanek

Approximately 500 million smallholder farms with areas less than 2 hectares (5 acres) support the nutrition and livelihood of approximately two billion people in smallholder farms globally (IFAD, 2013). As such smallholders form an important sector of the global food system, producing up to 80% of local and regional food supplies in Sub-Saharan Africa, South/Southeast Asia, and China. You saw an example of a smallholder system in the summative assessment for module 1. Livelihood strategies of households in this system attempt to overcome risk and guarantee subsistence as well as cash income. For this reason, these "semi-subsistence" farming systems are often complex, for example integrating agriculture, livestock, and agroforestry food production with off-farm livelihood activities that overlap with consumption from the globalized food system (previous page). Most food is consumed either on the farm where it is produced or locally and regionally, with transport and distribution handled by relatively short-distance networks.

Figure 10.1.10. Smallholder systems often include livestock for purposes of economic value (meat, wool) and better use of landscapes that are not optimal for cropping, such as this rugged patchwork of rangeland and cropped fields in Bolivia where goats are being grazed.

Credit: Steven Vanek

Figure 10.1.11. Hardy, early yielding crops such as barley, pictured here in the Andes, are a good way for smallholders to produce staple grains in difficult environments. Depending on the elevation of a smallholder community in this Andean context, maize and potatoes round out a full range of options for producing carbohydrate staples in this risky mountain environment.

Credit: Steven Vanek

"Quasi-Parallel" Alternatives to Modern Food Systems

You may recall that the concluding section of module 2 on the history of crop domestication and food systems we presented the recent development of alternatives to the modern globalized food system as "quasi-parallel" new movements as well as food production and distribution strategies intended to address sustainability issues. We use the word "quasi-parallel" because the global and local variants of these responses focus on different strategies and scales within the food system, and target different outcomes, even though both consider themselves to be responding to the sustainability challenges in the modern food system, sometimes using similar practices at the farm scale for managing crops and soils. Also, we acknowledge at the outset that dividing these strictly into two variants may not cover every case. The intention is to give you a sense of the range of alternatives being proposed so that you can potentially look for these types of alternative food systems in your capstone regions and integrate them into proposed sustainability strategies for the future of food in these regions. Also, it is likely that both variants will have advantages and disadvantages that are pointed out and debated by proponents and critics. From this debate we can see that sustainability is a contested concept, depending on the assumptions, goals, and arguments used by different advocates: it does not have a single definition to different camps in the debate over sustainability.

Globalized Alternatives: "Ecological Modernization" as a Reformation of Globalized Food Systems

Globalized variants of alternative food systems seek to correct issues of sustainability from within the framework of global food production and food trade networks. This has been called a case of "ecological modernization" because it seeks to reform certain aspects of globalized corporate food systems (previous pages) such as environmental impact and labor standards, while not altering the main features of the modern global system, for example, large scale of production, long-distance distribution, and leveraging the economic power of global investment to expand production and increase efficiency. Advocates of this approach promote strategies such as the "triple bottom line" for companies, which refers to positive environmental and social benefits from company activities being measures of company success in addition to economic profitability (thus a triple measure mirroring the "three-legged stool" of sustainability, see Module 1 and following pages in this module). Advocates also generally point to the fact that given the globalized corporate food system embodies by far the largest impact on levels of social equality and natural systems currently, reforming its activities and standards for performance is a way to have a tremendous impact on global sustainability. Detractors of "ecological modernization", including advocates of community-based food systems below, complain that these reform efforts leave in place unsustainable features of the system, such as large-scale production that is corrosive to local communities, or marginalization of smallholder farmers within markets or in land distribution in some cases (see the "agriculture of the middle" critique and the concept of a poverty trap in the following pages).

Notwithstanding this debate, it is useful to note some main features and trends in this globalized approach. Like the community-based variant, the globalized variant has prescriptive goals for the food system in response to sustainability problems of the modern food system. It supports substitution of more sustainable methods of food production, such as integrated pest management, organic methods, reduced tillage, and protection of watersheds from pollution with improved farming techniques, some of which have been seen in previous modules. Certification schemes are promoted that hold producers and distribution networks to a higher standard, such as organic certification (which generally must conform to standards in the country where the food product is sold). As another example, fair trade certification seeks to improve the price paid to local producers in source regions, who have generally received very low prices for their products, and thus shares the approach of strengthening local economies with the community-based approaches below, even if it uses global trading networks.

Figure 10.1.12 Characteristics of two types of alternative food systems that are responses to sustainability concerns in food systems. A more global or "ecologically modernized" variant seeks to bring sustainable and fair trade principles into the global food system, while a local and community-based variant seeks to reconnect consumers and communities to food producers at a local scale.

Click for a text description of the Alternative Food Systems diagram.

Alternative Food Systems: globalized and community-based

• Globalized
  • "ecological modernization" of the globalized food system
  • global/national trade networks
  • goals: reform of industrialized farming practices, capturing market niches
  • certification schemes: fair-trade, sustainable forestry, etc.
  • unprocessed and processed foods
  • mainstreaming of organic products in national/global distribution
• Community-based
  • emphasis on reintegration of local rural-urban economies
  • goals: reform of industrialized farming, local market reintegration, market niches, local/regional shipping and farmers' markets
  • mainly unprocessed foods
  • organic and local criteria/certification

Credit: Steven Vanek and Karl Zimmerer.

Community-based Alternatives

Like the globalized variant, community-based alternative food systems define prescriptive goals but oppose many elements of the globalized corporate food system. The community food system primer (Wilkins and Eames-Sheavly 2010, see link below if further interested) states that "a community food system is a food system in which food production, processing, distribution, and consumption are integrated to enhance the environmental, economic, social and nutritional health of a particular place". Three examples of these prescriptive goals within common components of community food systems are:

1. Organic agriculture as a way to reduce contamination of food with pesticides and improve the ecosystem health of farms
2. Farmers markets and community-supported agriculture schemes that allow consumers to more directly support the activities of farmers
3. An emphasis on supporting the activities of small and medium producers and resisting pressures for production and distribution enterprises to grow larger and larger

Many other examples of community food systems can be found, which also include efforts to link smallholder farmers and their food production systems (see previous page) as producers for burgeoning urban markets in developing countries, thus substituting some of the supply from the globalized corporate food system beyond the food products that are already supplied by smallholders to cities in these countries. The overall volume of food handled by these community-based food systems is generally much smaller than the globalized or smallholder types of food systems. Nevertheless, advocates point out that the potential market of urban consumers in relatively close proximity to small-scale producers around the world is potentially enormous. In fact, channels of alternative food production and distribution (e.g. organic agriculture) are among the fastest growing sectors in volume and economic value on a percentage basis, year after year [USDA-Economic Research Service].

Figure 10.1.13. This small-scale pork and poultry farm, with direct self-service marketing to consumers, is a highly functional part of a community-based alternative food system.

Credit: Karl Zimmerer

Figure 10.1.14. These organic soybeans are being harvested at a relatively large scale (hundreds of hectares in aggregate, within a production region of the Northeastern United States) to manufacture and sell tofu within a regional alternative food system. Soybeans are also a commodity crop largely handled by the globalized food system.

Credit: Steven Vanek

Knowledge Check: Food System Typologies

For each of the following concepts, give which of the three types of food systems it pertains to (global corporate, smallholder, local/alternative).

1. Shareholders invest in food companies
2. Fairtrade organizations link smallholders in Kenya to consumers in the U.K.
3. A dairy farmer sells small lots of milk using weekly deliveries to a mid-size city in New Hampshire.
4. Most supermarket items
5. Very important in densely populated rural areas of the developing world e.g. Ethiopia, Peru.
6. Buying butternut squash at the local farmers market.
7. Large wheat fields near Ciudad Obregón, Mexico for export to processors in Mexico, United States, and Colombia.

Fig 10.1.15. Three-legged Stool of Sustainability

Click for a text description of 3-Legged Stool of Sustainability.

The image illustrates the concept of a Sustainable Food System using a three-legged stool as a metaphor for stability and balance. The seat of the stool is labeled “Sustainable Food System,” supported by three legs representing the essential pillars: environment, community, and economy. Each pillar is associated with key principles. For the environment, the focus is on reducing pollution and waste, using renewable energy, conservation, and restoration. The economy pillar emphasizes employment, profitable enterprises, infrastructure, fair trade, and security. The community and social sustainability pillar highlights good working conditions, health care, education, and fostering community and culture. The design uses green tones to symbolize sustainability and growth, with the text clearly organized around the stool to show how these interconnected elements collectively uphold a resilient food system. If any pillar is weakened or missing, the system becomes unstable, underscoring the importance of integrating environmental, economic, and social considerations for long-term sustainability.

Credit: Steven Vanek, based on multiple sources and common sustainability concepts

 

Challenges to Food Producers: The issue of scale and the “three-legged stool” of sustainability

The previous page on different variants of alternative food systems stressed different ways of analyzing and critiquing the modern global food system based on issues of sustainability. In your capstone projects, you are asked to propose ideas for sustainable food systems in your capstone regions. Therefore, in this page, we repeat from module one the concept of sustainability as a "three-legged stool" combining aspects of environmental, social, and economic sustainability (Fig. 10.1.15, also seen in module 1). We may be most used to thinking about Environmental Sustainability, for example in the need to conserve energy or recycle food containers to reduce pollution and energy generation by fossil fuels, as well as avoiding litter and saving on landfill space. As we presented in module 1, however, sustainability also contains economic or financial aspects devoted to employment, livelihood, and profitability, as well as the concept of social sustainability that embodies goals of social equity and more harmonious societies. Therefore, we are also interested in the nodes of food production such as farms because of the challenges to the economic sustainability of farm (and fishery) enterprises. It is important to think about economic sustainability because of the economic risks that food producers are exposed to. Economic risk is inherent in producing for local, regional and global food systems because producers may not be producing high-value products and must absorb environmental risk, for example from droughts, floods, or pests (see the previous modules, and module 11, next, regarding adaptive capacity). In a drought year, for example, selling vastly reduced yields of soybean or maize crops usually mean an economic loss for a farm because the price of these crops is not very high on the global or local market.

In addition, social sustainability concerns regarding food production are an important part of debates about modern society: for example, smallholder farmers, and laborers on larger farms and within fisheries in the United States and globally, are some of the most economically and politically marginalized populations in the world. Many researchers and advocates point out that food systems cannot be truly sustainable until they embody a more just distribution of resources and power. In this short section, we want to highlight two important concepts that link to these ideas of social sustainability and justice: first, the idea of “poverty traps” within smallholder farming around the world (see Carter and Barrett 2006, reference below), and on the next the threat posed to so-called “agriculture of the middle” in industrialized countries where pressures on producers lead either to a small-scale, niche markets orientation (e.g.. farmers markets) or an inexorable growth toward larger and larger farms that capture economies of scale in agriculture. By introducing these concepts now, you should see both how they fit into the analysis of vulnerability and resilience in the next module. You may be able to incorporate these challenges and potential solutions into your capstone region scenarios.

What is a poverty trap in smallholder agricultural systems?

As you’ve seen in the “pond-garden-livestock” (VAC) system of Vietnam in the video at the beginning of this module, agriculture practiced in smallholder food systems on small plots of land (less than 10 acres or 4 hectares, say) around the world is a hugely important and often quite sustainable enterprise. Smallholder agriculture can embody some of the most efficient use of resources in use today, whether these are traditional methods, well-adapted domesticated plants, new innovations taken up by smallholder families, or labor that is efficiently allocated by a family that is in constant contact with their enterprise and ecosystem. However, a concern about the most impoverished smallholders is that they can fall into what is called a poverty trap, where smallholders produce food from a degraded resource base, either because they have degraded it or because they have been forced to the margins of local society, and many times, both. The diversity of diets can also suffer when the least expensive food sources are local cereal and starch crops or calories coming from the globalized food system. The combination of poverty and degradation of soils and other resources does not permit these farmers sufficient income or well-being to invest in and therefore improve their soils or other aspects of local agroecosystems, and so it is likely that they, and their farm ecosystems, will remain in a low level of productivity and earnings. This is therefore called a poverty trap, and it essentially combines a lack of economic, social, and environmental sustainability for these smallholder households. It has also been linked to the concept of a downward spiral of poverty and soil degradation (Fig. 10.1.16).

Fig 10.1.16 -- Spirals of soil regeneration and improved livelihoods (top) versus poverty and soil degradation (bottom). The reinforcing feedbacks between soil quality and productivity with social and economic marginalization illustrate the connections between social and environmental sustainability.

Credit: Steven Vanek

An example of this poverty trap "downward spiral" is furnished by the dust bowl of the 1930s in the United States, in the case of many families who farmed small plots of land during the depression. The combination of overexploited soils from decades of agricultural expansion after the U.S. civil war, a depressed economy contributing to overall hardship, and a multi-year drought led to a downward spiral in which many poor farmers were finally forced to leave their land and migrate to other areas of the country seeking employment and public assistance. In module 11, we'll examine further how combined human and natural system factors (like poverty and drought, for example) interact to create vulnerability for parts of human society, and ways that human systems have adapted to surviving such shocks and perturbations as drought. We'll include an example of a native American population that was relatively successful in weathering the Dust Bowl and was not subjected to this sort of poverty trap or downward spiral. Also, in the years after the dust bowl, the Soil Conservation Service of the United States Department of Agriculture (USDA) was highly active in helping farmers to transition to practices that helped to avoid soil erosion and aid in regeneration of degraded soils (see the additional reading resources below for this history of the Soil Conservation Service).

In current-day contexts where poverty traps represent a risk or chronic problem for small producers, then, both government agencies and development organizations focus on reducing barriers to practicing more sustainable agriculture. Development organizations include those called non-governmental organizations or NGOs, nonprofits, international aid organizations, as well as organizations founded by and managed by farmers themselves. For example, see the blog article below in "additional reading", regarding efforts to promote agroforestry in Haiti, where poverty and land degradation have long been intertwined. These organizations try to reduce barriers to investment in sustainable food production through the promotion of simple, low-cost strategies to conserve soils and raise crop diversity and productivity (see the previous modules for examples) that are within financial reach of smallholder producers. These technology options are optimally combined with credit and direct aid that helps farmers to overcome the resource barriers for investing in the protection of the natural systems that sustain their production. This sort of knowledge and technology, and the ability of farmers to invest in the productivity of their soils are an example of adaptive capacity, a concept that will a major topic of module 11. In addition, government, NGOs, and farmer organizations may also engage in political advocacy that seeks a more just distribution of land, credit, or access to markets that can help producers to avoid or move out of poverty traps.

One of the characteristics of a globalized food system is that a smaller proportion of the population is needed to produce the large amounts of food for the global system. As a result, many analysts have noted shrinkage of the rural population in the rural United States over the last 100 years. Similar out-migrations from rural areas to cities have happened in Europe. Among other factors, this process has been hastened by the use of mechanization for agriculture (tractors, combine harvesters, mechanized crop processing, and transportation; we analyze the environmental impact of this in module 10.2). Mechanization and other factors mean that the cost of producing a bushel of corn, for example, and moving it into the global food system is cheaper when the scale of the farm and transportation infrastructure is larger. This phenomenon is referred to as economies of scale (recall also the example of dramatically scaled-up beef production in Greely, Colorado featured in the video of Module 1.2.) Farm producers in the United States and other industrialized economies thus often face pressures to grow their operations larger so that they can become more profitable, accentuated by competition against larger producers with lower prices, sometimes in other countries with lower labor prices.

These twin trends towards “get big or get out” and “get small for local markets” have left out a huge sector of farms that are mid-sized and that still generate a substantial amount of farm income in the U.S. economy and utilizing the lion’s share of cultivated soils (see figure 10.1.8 with pie-charts of earnings distributions different size farms in the United States). The analysis regarding this “Agriculture of the Middle” (Kirschenmann 2012) points out the threat posed to millions of farming households, most of whom produce for national and global commodity markets (e.g. soybeans, dairy). This analysis also points out that this sector of farms is vital as productive rural citizens that drive social organization, effective policy-making, and community values in most regions of the country. These mid-size farms are often leaders in the adoption of sustainable practices – especially when they are financially successful, illustrating potential linkages between financial and ecological sustainability. In any case, small and medium-sized farms have always played an important role in the maintenance of a rural landscape that most governments and citizens see as valuable. Agricultural landscapes and enterprises often contribute to the tourism value of a particular region, for example, the Pennsylvania Dutch region or wider presence of dairy farms in diverse, forested landscapes of Pennsylvania, or wine-producing regions of California and New York State.

The role of “Agriculture of the Middle” in sustaining rural life according to this analysis is worth protecting, and advocates of this analysis and action to support mid-size farm enterprises point out a few advantages these farms have in interacting with regional farm systems. When effective linkages can be built to regional markets, these farms usually combine production at a medium to large scale (compared to small diversified farms supplying farmers’ markets, say) with a flexible outlook that can allow them to change products and markets quickly, and best adopt sustainable production methods in a way that is visible to consumers and local communities (Kirschenmann 2012). As in the case of poverty traps for small farms discussed above, organizations that promote agriculture of the middle seek to clear barriers to these mid-sized producers. Note also that these “mid-sized” producers are enormous compared to farms in smallholder contexts throughout the developing world, though they are community members in an equivalent way to the role of smallholders in a rural third-world context). Mid-size producers and the food distribution organization that work with them may seek to promote “values-based food supply chains” where not just the commodity value of a food product is taken into account but also the value of a farm that demonstrates environmental sustainability and positive participation in rural communities. For example, many agricultural states now have state-level marketing efforts that promote state and regional agriculture, and these programs increasingly integrate ideas that help to promote mid-sized producers. Farmers, distribution network companies, and food markets have also banded together in different configurations to form networks that seek to support not only food availability for consumers but environmental, social, and economic sustainability along the entire food chain. Some examples of these are the Organic Valley dairy cooperative which now operates across the entire United States, the Red Tomato regional fruit and vegetable marketing effort in New England, U.S.A. (see Fig. 10.1.17 and 10.1.18), or the Country Natural Beef producers in the Northwest United States.

Figure 10.1.17. Photos showing on-farm production, harvest, packing, distribution, and marketing from a "values-based food chain". This example is from Red Tomato, a local/regional network linking farms to consumers in the states of Massachusetts, Connecticut, and Rhode Island in the United States.

Credit: Red Tomato Non-Profit and used with permission.

Figure 10.1.18. The Red Tomato Logo used in marketing the produce above.

Credit: Images courtesy of Red Tomato Non-Profit and used with permission.

More Information on Values-Based Food Supply Chains

You can view a PowerPoint slide set introducing nine case studies on values-based food supply chains like the ones described above: Agriculture of the Middle, a research and education effort of the University of Wisconsin.

Integration into the Capstone Project

As you consider the food system of your capstone region, you may want to incorporate references to efforts that support either smallholder farmers in avoiding poverty traps or encourage continued participation of “Agriculture of the Middle” in the regional food system. The formative assessment for this module asks you to address whether you think there are concerns about poverty traps or agriculture of the middle in your capstone region. As you develop your capstone project final scenarios for sustainability, you may want to search on the internet for resources on regional food chains and food systems, as well as local farmers' markets and other initiatives, within your region of interest.

As you saw in the introductory video about a food system in Vietnam, food systems incorporate both natural and human components. In fact, because of the ubiquitous need for food, food systems are among the most important ways that human societies interact with the physical and biological elements and processes on earth's surface. Land used in some way for food production already occupies over two-thirds of the ice-free land surface (Ellis, 2011 or similar on anthromes) and the trend is for this proportion as well as for the intensity (roughly, the production from each unit of land area) to increase. Human fisheries and other forms of food production from oceans (for example, kelp farming) are also tending to exploit wider and wider areas. In addition, as seen in the multiple types of food systems presented above in section II of this unit, the interactions of human societies with earth's ecosystems in food production is not governed by a single human process but depends greatly on human priorities, land management and food production knowledge, rationales and prescriptive goals for food systems, and government policies that regulate and reward food system outcomes. Understanding these societal factors is key to improving the sustainability of food systems in their impact on the earth's ecosystems.

To understand the interaction of human societies with the earth's surface, a common and productive framework is that of coupled natural-human systems [Liu et al., 2007]. These start from a relatively simple diagram (Fig. 8.9), in which a generic human system (e.g. a community within a human society) interacts with a generic natural system (e.g. a farming-dominated landscape within a production region). The framework also recognizes that natural and human systems have many internal interactions and processes such as biogeochemical nutrient cycling (e.g. the nitrogen cycle, see unit N.N in this course) or the policies, corporate actors, and markets determining food supply chains (a human factor).

Fig. 8.9. A generic natural-human system that can be applied to the food system in its interactions with earth system processes

Click for a text description of Natural-Human sytem diagram.

Generic Natural-Human system that can be applied to the food system in its interactions with earth system processes

Arrows labeled human to natural coupling and natural to human coupling form a circle between human system and natural system. Those are defined as follows:

Human system: human system internal interactions

Human to natural coupling: Human system impacts and reorganizes natural system

Natural System: natural system internal interactions

Natural to human coupling: Natural system a)presents food production conditions to the Human System b) responds to human management and other drivers in ways that affect the human system (feedbacks)

Credit: National Science Foundation Coupled Natural Human Systems research grant program

So, for example, in the video that you watched on the food system from the Red River delta in Vietnam, the river delta is the initial, broad natural system context that presents opportunities for farming, livestock production, and aquaculture to farming households and national/local government policies. Human farming/aquaculture knowledge and practices, markets and government policies are part of a human system that impacts and reorganizes the natural system over time into its current state. Over time the natural system internal interactions and processes may also change, for example, increases or decreases in soil fertility, crop pests, or animal diseases. Because of the evolution over time of the system, it is useful to reorganize the coupled natural-human system as evolving over time (Fig. 8.10).

Fig. 8.10. A coupled natural-human food system developing over time. The initial coupling at time 0 is the natural system presenting itself to human society with its properties for potential food production. The Human system "responds" by reorganizing the natural system for food production (time 2), and feedbacks from the natural system ensue, with impacts on the human system. These feedbacks are either intended consequences (e.g food production and income generation) or unintended consequences (e.g. river and estuary pollution, greenhouse gas emissions)

Credit: Karl Zimmerer/Steven Vanek

Overlap and Transition in Food Systems

As a final observation about ourselves as consumers within different food system types, it is important to stress that most consumers and households participate in multiple types of food systems at once. For example, someone in a modern society might consume a breakfast energy bar with globally sourced processed ingredients, along with a fair-trade certified cup of coffee and regionally sourced milk, on the way to picking up sweet corn at a direct-marketing farm stand of a local farmer. In addition, and of special importance for thinking about sustainable scenarios for your capstone project, it is important to find explanations of how transitions occur in food systems from one type of predominant system, to the inclusion of alternatives, or in some cases a wholesale change from one food system type another.

Human-Natural Interactions as Drivers of Food System Variation and Transitions

Recall that in Module two we presented the broad strokes of the history of food systems, from prehistoric times to the modern-day, including the globalized and local-regional variants of alternative food systems that were featured on the previous page of this module. In module two, we presented the idea of drivers and feedbacks that have caused large changes in the environment-food relations over human history (for example, from hunting and gathering to agriculture). In this final page of module 10.1 we want to develop concepts that constitute Coupled Human-Natural Systems explanations or "ways of seeing" that can help to understand two different processes:

1. The way that two different and parallel food systems can exist in the same place, based on divergence from a common origin
2. The transition from one food system type to another, considering the three major types of food systems and the different variants of alternative food systems.

Both of these ways of seeing may be useful in understanding proposals for sustainable food systems, as well as the issues of resilience and vulnerability of food systems presented in the next module.

Regarding process (1) above, The fact that food systems develop over time due to the interactions of human and natural systems means that different food systems can develop in the same natural system environment. For example, the same environment or natural system can support either a smallholder type of food system (small plots, less mechanization, local consumption) or a global corporate food system (larger land sizes, more mechanization and industrially-produced soil inputs, global distribution and consumption). It can also support a mosaic of the two types. This overlay of two types is in fact fairly common: for example, smallholder agriculture on smaller plots for mixed home and regional consumption coexists in Central America with the export agriculture of major food commodities such as bananas or vegetables, and often involves marginalization of smallholders to smaller landholdings in less productive and more difficult to manage soils. This mosaic of food system types is also increasingly true in Southeast Asia as globalized agriculture for cassava and maize production for export to China as well as domestic consumption coexists with more traditional smallholder agriculture as portrayed in the Vietnamese "VAC" system in the introductory video for this module. Figure 10.1.19 shows how two parallel food systems can develop in the same environment according to the Coupled Human-Natural System diagram we have seen at other points in the course. Starting at "time 0" in the middle we can see how an initial food system type might develop via human system management (e.g., the smallholder system in the Central American or Southeast Asian case). At "time 1", meanwhile, differences in the human system (say marginalization of smallholders to certain environments, investment in industrial farming in other environments) have created two divergent food system types. These divergent types then develop on their own through times two and three, and into the future, incorporating interactions between human and natural systems that embody the issues of social, financial, and environmental sustainability. As we can see by the Central American and Southeast Asian examples, this parallel trajectory of two different food system types is highly relevant, since it represents exactly what has happened in developing countries that seek to industrialize their agricultural sectors but retain a large rural population practicing smallholder agriculture, often in more marginal regions with greater heterogeneity of environments (e.g. mountainous areas of Central and South America, mosaics of large export-oriented farms alongside smallholder agriculture in South and Southeast Asia as well as Eastern and Southern Africa)

Fig. 10.1.19. Divergence of the process of coupled human-natural system development to produce two different types of food systems.

Click for a text description of Figure 10.1.9

The image is a conceptual diagram illustrating the divergence of two food systems over time, focusing on the interaction between human systems and natural systems. At the center, the diagram begins with Time 0, labeled “Initial coupling,” where a Human system (in red) and a Natural system (in green) are shown side by side, indicating an initial integrated relationship. From this point, two curved arrows branch out, representing the progression of time and the divergence of these systems.

On the right side, the blue arrow labeled divergence leads to Time 1, where the natural system splits into Natural System 1 and Natural System 2, both in green boxes. This suggests that natural systems evolve differently under separate food systems. On the left side, a black arrow shows the human system evolving into Human System 2 at Time 2, and then continuing toward Time 3, etc., where two boxes appear at the top: one labeled Food system 1, e.g., global corporate and another labeled Food system 2, e.g., smallholder. Each of these boxes contains a stylized representation of human and natural components, but the alignment differs—indicating that the coupling between human and natural systems changes over time and across food systems.

The color scheme uses red for human systems and green for natural systems, with arrows in black and blue to indicate different trajectories. The black arrows primarily represent human system evolution, while the blue arrows represent natural system divergence. The overall layout conveys that initially coupled human and natural systems become increasingly distinct as food systems specialize and scale differently, such as global corporate versus smallholder models.

Credit: Karl Zimmerer, based on the National Science Foundation Coupled Human-Natural Systems program.

Regarding the transition from one food system type to another (process 2 as listed above), the CNHS diagram (figure 10.1.20 below) can help to understand these transitions. As an example, we'll use the transition to alternative food systems from the globalized industrial food system we described in module two and again in this module. In figure 10.1.19, between the "initial coupling" point at center and "Time 1", expansion of a dominant food system begins to create strains on both the natural and the human components of the system. In the case of the globalized industrial food system that emerged in developed countries (sometimes called the global north) after World War II, this system eventually created strains in the natural and human systems and a critique responding to the unintended consequences of the expansion of this industrial and globalized model. You'll recognize these strains and critique as the same issues of sustainability discussed in the previous modules:, "diseases of affluence" from poor nutrition, food insecurity, concerns about water use and the water footprint of food, soil degradation, pest and weed resistance to pesticide and herbicide management, and others. Between Time 1 and Time 2, the human society thus receives signals from the interactions and drivers within the coupled system, and then responds, in the form of a wide range of new policies and "models" of the new system that emerge during Time 3. In some cases, these responses are modest, for example, a new regulation on fertilizer or pesticide application to moderate the unintended negative consequences. In other cases, the responses are more dramatic and become the alternative food system types described in this module, both global and community-based. These different variants of the transition may increasingly create aspects of a "complete" food system, e.g. production, distribution, and consumption pathways in an integrated whole, as compared to their initial state as outliers, regulations, or policy proposals. Through different drivers and feedbacks from the natural and human sub-systems, a transition to new food system types occurs. These new types often coexist with a more dominant food system, which is certainly the case with the coexistence of alternative food systems in the present day with the still-dominant global corporate food system.

Fig. 10.1.20. A model of the way that a crisis in the social and environmental sustainability of a food system can drive a transition to a new type of food system, considered as Coupled Human-Natural Systems (CNHS). See text for more detailed description and example of this process.

Click for a text description of Figure 10.1.10

The image is a conceptual diagram illustrating the transition of food systems over time, focusing on the dynamic interaction between human systems and natural systems. At the center, the diagram begins with “Before Transition – Initial coupling”, where a Human system (in red) and a Natural system (in green) are shown side by side, indicating an integrated starting point. Below this, a note explains that feedback from the coupled Human-Natural system informs food production managers, communities, and societal decision-makers, signaling the need for change toward a new system.

From this initial point, two curved arrows branch outward, representing the progression of time and system evolution. On the right, a blue arrow leads to Time 1, where the diagram shows a combined box labeled Human-Natural, indicating that the natural system is exceeding sustainability limits and human system consequences (such as poor nutrition and inequality) are becoming increasingly apparent. A text box nearby explains that the expansion of the food system model creates strain on natural systems, pollution, and human system consequences.

On the left, a black arrow leads to Time 2, where two separate boxes appear: Human system and Human system (both in red), suggesting diversification or intensification of human-driven changes. A text box lists examples of changes at Time 2, such as:

• Emergence of organic and other sustainable agricultural management.
• New thinking on human nutrition and food policy.
• Mitigation of climate change impacts.

At the top, the diagram shows Time 3, where a box labeled Human-Natural appears again, but with a different alignment, representing the emergence of alternative food system types. The accompanying text explains that these new systems are embodied in alternative production, distribution, and consumption models, and may exist in parallel with pre-transition types.

The color scheme uses red for human systems, green for natural systems, and combined boxes for integrated states. Arrows in black and blue indicate different trajectories and transitions. Overall, the diagram conveys that initial coupling between human and natural systems becomes strained under conventional food system expansion, leading to sustainability challenges and social consequences, which eventually drive the emergence of alternative, more sustainable food systems.

Credit: Steven Vanek and Karl Zimmerer, based on the National Science Foundation Coupled Human-Natural Systems program.

Human System Impacts on the Environment Within Food Systems

Figure 10.2.1. The collection, transport, and application to the soil of plant nutrients using animal manure (left), and the destructive effects of erosion from tillage on sloped land (right) are two human system impacts on the earth system.

Credit: Steven Vanek

Figure 10.2.2. Fertilizer production, like in this old print of a factory in Philadelphia, Pennsylvania, and a large new plant in India, represents a substantial contribution to the energy expenditure and greenhouse gas footprint of food production via modern agroecosystems.

Credits: top, Boston Public Library, used with permission via a creative commons license; bottom: used by permission through the Wikimedia Commons.

In modules one and two of this course, and most recently in this module, we represent food systems as coupled human-natural systems. Throughout the course, we have tried to emphasize the dramatic impacts that human food production has had and continues to have on earth's natural systems. Here are some examples from previous modules:

• Changing river basins to create irrigation systems
• Exposing soils to greater rates of erosion, and stabilizing some soils against erosion
• Domestication and development of new crop types, including transgenic engineering of new crop traits in the recent past
• Contributions of agriculture to greenhouse gas emissions that are warming planet earth and leading to climate change

Different types of food systems – global, smallholder, and alternative, as we summarized in module 10.1 -- may all impact the earth's natural systems in a different way and to different degrees. You may recognize on the short list of examples above that the impacts from these changes and the creation of agroecosystems by humans may have both positive and negative aspects. For example, irrigation and crop breeding both have as objectives increasing the productive potential of crops. They may carry other unforeseen consequences, such as depletion and collapse of water resources, changes in the dietary quality of food with domestication and breeding, and greater use of herbicides in the case of Roundup-ready crops. These human system actions within the food system improve production can be seen as the initial driving arrow as part of a human-natural system coupling (Fig. 10.2.3) and generally involve management, reorganization of the ecosystem, and energy and nutrient inputs (e.g. the use of fossil fuels to create fertilizers). The natural system then responds with positive and negative impacts on productivity and other natural system processes, which can include positive and negative consequences. These consequences eventually determine the level of sustainability of the food system. The massive extent of food systems and food production globally, within different types of food systems, translates into a large effect, or leverage, on the sustainability of human societies. To promote the sustainability of food systems, we must understand how food systems as a whole affect measures of sustainability. In this unit, we will first refer to the different human system impacts on natural systems, and then allow you to practice life-cycle assessment (LCA) to compare the energy use of two food production systems in the Andes and North America.

Figure 10.2.3. Human system impacts of food production activities. The human system reorganizes and provides energy and nutrient inputs to the natural system (1), which induces changes in natural system processes such as nutrient cycling, greenhouse gas emissions, and agrobiodiversity (2a). The changes in the natural system allow the human system to produce food but may also alter ecosystem services in harmful or unintended ways (2b: e.g. water pollution, global warming, and biodiversity changes in land and ocean systems).

Credit: Karl Zimmerer / Steven Vanek

Life Cycle Assessments

Life cycle assessments or life cycle analyses (LCAs) are defined as “a tool to analyze the potential environmental impacts of products at all stages in their life cycle” (International Standards Organization). Analogous to the food supply chain activity you completed in module 10.1, LCAs follow products (foods and otherwise) from production, through transport and assembly steps, to the consumption or operation of the product, and in some cases even its disposal. In contrast to the supply chain descriptions in module 10.1, at each of these stages of production, transport, consumption, and disposal, LCAs keep a running total of environmental costs or impacts of the product. Common impacts that are tracked by LCAs across product life cycles are greenhouse gas emissions, water pollution impacts, and energy use. As such LCAs are a key tool in analyzing the impacts of human on natural earth surface systems within the coupled natural-human food system (Fig. 10.2.3). LCAs require some careful thinking about where to draw the boundaries of the system for considering the life cycle of a product. For example, an LCA devoted to carrots would probably include the energy required to operate the refrigerated truck used to transport the carrots but not the energy needed to make the truck. Also, many LCAs are “cradle to grave” and include both impacts of all raw materials used in production as well as disposal impacts for the product, but some do not focus on the entire life cycle and assess other segments of the lifecycle such as “cradle to farm-gate” or “cradle to plate” in the case of food products.

Life cycle analyses are an excellent way of putting into practice a geosciences "habit of mind" of using systems thinking. Because food systems are complex, we think about a way to measure its performance and then explore all the linkages in the system within that single metric or measurement parameter (see module 1.2 for a discussion of complex systems behavior). That is, we don't content ourselves with just thinking about a crop plant in a field, the entire farm field, or the highway where foods are transported; we go several levels up to measure impacts along the entire pathway or web of interacting system parts. Along the way, it is likely that we will start to think in new ways about the linkages between parts of the system, about the most important contributions to impact, or about previously hidden factors or unexpected outcomes that explain the performance of the system.

Life cycle assessments are often used in two important ways. The first is to compare the costs or impacts of different products or production systems in a rigorous way, seen in Fig. 10.2.4 which compares the phosphorus water pollution resulting from three ways of producing pork meat in France (Basset-Mens and Van Der Werf, 2005). This “cradle to farm-gate” pork LCA includes the cropping used to produced pig feed as well as the animal raising methods at pig farms that use three different standard methods. In this example, two different ways of expressing LCA results show how different messages can emerge depending on how results are presented. The graph at left shows the impacts at a per-area of land used basis (per hectare), while the graph at right expresses the impact as a per-kg of food produced, which means that if a production method yields more on a per-area basis, its impact can be reduced compared to one with less productivity per hectare. Organic and red-label humane methods with straw-bedded barns pollute less on a per-hectare basis, but the organic methods are not less polluting than the conventional treatments on a per-kg of pig basis because more area is needed to both raise the pigs and grow the crops for feed in the organic system. Therefore if demand (in kg pork) remains the same for pigs while consumers switch from conventional to organic pork, total water pollution from phosphorus in pig production is unlikely to decline, at least according to this study. Rather, the red-label option seems to be able to shrink pollution per kg of pork consumed in the food system. Meanwhile, if you limited your viewpoint to a single watershed with a delimited area, you would say that both the red-label and organic methods reduce pollution. Despite some of the benefits of organic management generally, in reducing toxins in the environment and building soil quality (for example), this study can give us some pause in thinking about the particular system we are talking about (e.g. organic hog production versus organic apple production, for example) and the need to respect specific case analyses and the measures used in LCA analysis. When we talk about a whole food system, it may be best to employ a per-kg of food produced approach.

Figure 10.2.4. Results of a life cycle assessment for eutrophication impacts (water pollution, see modules 3 and 4; in this case, via phosphorus or P runoff into surface waterways of pork production under different standard methods in France: European Union (EU) standard best conventional methods using confinement of hogs; a "red label" which denotes a defined-origin producers' standard using more humane methods and sustainable but non-organic crop practices, and organic standard methods including more humane treatment and organically produced crops. (data adapted from Basset-Mens and Van Der Werf, 2005).

Credit: Steven Vanek

The second main way of using LCA is to assess which steps or process inputs in the production, consumption, and disposal of a product are most responsible for human negative impacts of practices. These “hot spots” in the analysis can then be the focus for better measurement to confirm the findings of the LCA and/or innovations in practices that eliminate these practices or limit their impact. One type of LCA uses the common measure of external energy inputs for food production (i.e., those not related to solar energy that is used by plants "for free") to analyze one aspect of the sustainability of food production. These energy inputs are visualized in Figure 10.2.5.

Figure 10.2.5. Principal human-managed energy inputs involved in food production, in addition to resources of soil and water as well as the solar energy captured by plants. Energy expended in irrigating crops, and in the growing of seed, would be additional flows that might be especially important in other systems. These energy flows are summed up using an LCA approach, noting which ones account for most of the impact, creating "hot spots" that should be researched further and targeted to increase efficiency and reduce the impacts of food production.

Credit: Steven Vanek

Dissecting an LCA

An LCA for energy use is illustrated below in Fig. 10.2.6 which shows the comparison of total energy used in different crop production practices in a long-term trial of farming practices in Switzerland. This graph shows the energy used in food production in two formats: stacked colored bars as kilowatt-hours (kWh) energy equivalent per land area under production (i.e. per Ha or 100 x 100 m area) of food production, and also as a total watt-hours (Wh) per kg of food produced (dark green lines and points above the stacked bars).

It's worth considering these results and the units used in more detail. First, for comparison, a typical U.S. home uses about 72 kWh per day for heating, cooling, and electricity, if we boil all these energy uses down to one energy equivalent^* (calculations based on the U.S. Energy Information Administration, 2009 data). Some further "ballpark" or rough calculations allow us to see that the fertilizer-based system (bar at right) uses a total of about 100 days of mean household energy^**to produce food on one hectare in a year (per year), while the organic system (bar at left) uses a little over half this amount of energy. Meanwhile, if we express this daily household energy use as the energy used for food per kg of food, the 72 kWh become 94 kg of food in the fertilizer-based case at right, and 144 kg of food in the organic management case at left ^***. Expressing LCA results as energy per land area and energy per kg food produced are common approaches, analogous to the pollution impact analysis on the previous page. In the summative assessment on the next page, you will use an LCA to calculate energy inputs per kg of potato production in two systems.

• That is the amount of heat and light given off by 30 100-watt light bulbs burning for 24 hours.
  • That is, about 7200 kWh (height of rightmost split bar on the left axis showing energy use per hectare), divided by about 72 kWh household use per day, which is equal to 100 days.
    • Dividing 72 kWh by the energy amounts per kg from the green point+line data above the stacked bars, e.g. 72 kWh / 0.77 kWh per kg or 93 kg food for the fertilizer based-case, and 72 kWh / 0.50 kWh per kg, or 144 kg of food, for the organic case.

Figure 10.2.6. Results from a life-cycle analysis on energy use equivalents to compare three farming methods growing a variety of food crops in a long-term research trial (DOK Trial, Therwil, Switzerland). The left Y-axis and stacked colored bars give the energy use per land area (i.e. per Ha or 100 x 100 m land area) and might be helpful to know if we have the total production land area of a farm or region. Meanwhile, the plotted points above each stack and right y-axis give the energy use per kg of dry matter of crops produced, which may be a more useful measure for a food system where we want to adjust for the productivity of different food systems. It is notable that the largest differences between the three systems derive from in the energy used to manufacture chemical fertilizer (yellow bars). Figure adapted from data cited in Nemecek, T. 2005. Life Cycle Assessment of Agricultural Systems: Introduction.

Credit: Adapted from data in the study cited in caption (Steven Vanek)

Fertilizer Use as a "Hot Spot" in the Analysis

Two additional observations: first, in this LCA there emerged large differences in energy use that have to do almost completely with the energy used to produce chemical fertilizer, especially of nitrogen fertilizers like those produced in the large fertilizer plant in India shown in Fig. 10.2.2. Energy inputs to fertilizer production are especially high for nitrogen fertilizer because it takes a great deal of energy to fix inert nitrogen in the atmosphere (N₂) into reactive forms like ammonium and nitrate that can be easily taken up by crops (see module 5 and other previous modules). Fertilizer use emerges as a "hot spot" in this analysis and might prompt managers or policymakers to work towards reducing fertilizer use by incorporating aspects of the organic and manure-based system into the more conventional, fertilizer-based system. Many energy inputs in agriculture, such as these fertilizer inputs or tractor fuel that are tallied in the LCA above, are important to consider because they represent non-renewable fossil fuel energy sources that contribute to greenhouse gas emissions and anthropogenic climate change through the release of carbon dioxide. The LCA thus helps to measure natural system impacts and sustainability of food systems. Second, this LCA used energy as a yardstick to measure the impact of food production. As we will note for your summative assessment, such an LCA using energy inputs is only ONE measure of sustainability, and may not capture other measures of sustainability, like forest clearing needed to establish agroecosystems, runoff of nutrients that contribute to dead zones, pesticide effects on beneficial insects like pollinators, or whether farming practices provide sustained income and other livelihoods to farmers. As an example of using a different yardstick for LCAs, consider the emissions of greenhouse gases (GHG) by different pork production systems on the previous page, in which the organic management system, in fact, had higher potential to pollute waterways with phosphorus runoff per kg of pork produced, than either conventional or "best practices" red label standard in the European Union. This result contrasts with the favorable result shown on this page for organic management when energy inputs were used as a yardstick.

Knowledge Check: Earth System Impacts and Life Cycle Analysis

Instructions

This assignment has been broken down into three steps. First, you need to understand the LCA Spreadsheet, next you will need to complete the spreadsheet and finally you will complete the Summative Assessment Worksheet using the results of the completed spreadsheet. Please read all of the instructions very carefully. They are presented in the next three pages.

Files to Download

Energy Input LCA Activity Spreadsheet
Summative Assessment Worksheet

Submitting Your Assignment

Please complete the Module 10 Summative Assessment in Canvas.

Perturbations and shocks are common in food systems and involve both the “natural system” components and the “human system” components in these systems. Throughout modules 11.1 and 11.2, we will use the word shocks and perturbations fairly interchangeably to refer to these negative events that challenge food systems and their proper function, although the word "shock" denotes a perturbation that is more sudden and potentially disastrous. Perturbations and shocks in “natural” components include dramatic changes in climate factors such as rainfall, as well as changes brought on by biological components such as disease and pest outbreaks that affect plants and livestock. Similarly, perturbations can occur within the “human system” components of a system. For instance, food prices are rarely entirely constant and farmers and consumers are said to face "price shocks" in the purchasing of food.

Figure 11.1.1. A photo of an Andean agroecosystem during the long dry season shows how water limits food production in some parts of the Andes. This system is thus very vulnerable to drought shocks, and its vulnerability is compounded by shallow, eroded soils that result from cultivating sloped land. These soils store less water than under their original vegetation cover and are thus more vulnerable.

Credit: Steven Vanek

Figure 11.1.2. This photo of dramatic flooding in Wisconsin, United States shows conditions of near certain crop failure or damage to pastures for these fields, which is a strong negative shock to local food production and farmer livelihoods. Farmers may, however, be somewhat buffered from economic hardship if they have crop insurance, and food security for local inhabitants may be buffered by movement and sales of food from elsewhere in the regional and global food system.

Credit: United States Federal Emergency Management Agency, used with permission through a Wikimedia Commons creative commons license.

Extreme conditions can result in major perturbations and shocks in agri-food systems. Major climate variation, such as severe or prolonged drought, is a common example with regard to major changes emanating from the natural system (see figure 11.1.1). Gary Paul Nabhan, the author of the required reading in this module, uses the example of the extreme "Dust Bowl" drought in the United States in the 1930s. Since it is already a region that receives little rainfall, the agri-food systems in the U.S. Southwest were considerably threatened by this drought. Extreme conditions endangering food-growing and availability can also arise in human systems. Examples include political and military instability as well as market failures and volatility (such as the sharp increase in prices).

The human-environment dynamics of major perturbations and shocks in agri-food systems are shown in figure 11.1.3. This figure uses the already familiar approach of Coupled Natural-Human Systems (CNHS) introduced in Module 1 and applied in module 10 and throughout the course. Here we apply it to interactions of the natural and human systems that result in reduced production and accessibility of food. The human response to perturbations and shocks can be understood by applying the CNHS framework to agri-food systems. Within this diagram, we also want to emphasize that because of the coupling and interactions within and among these systems, the human and natural systems are never just passive recipients of a shock. Both subsystems have mechanisms for responding that can either ameliorate or worsen the "crisis" effects of perturbation. These system properties and responses to shocks are considered through the concepts of resilience, adaptive capacity, and vulnerability (RACV), defined on the next page. In the next module (11.2) we will use the RACV and human-natural systems framework to understand shocks and system responses that result in famine and severe malnutrition.

Figure 11.1.3. The framework of Coupled Natural-Human Systems (CNHS) applied to Perturbations and Shocks in Agri-Food Systems. For both the human and natural systems, the characteristics and internal interactions of each will determine properties of resilience versus vulnerability, which influences what the final effect of a shock or perturbation will be. The internal interaction arrow of the human System is given a larger size, at center left of the image, to describe human-generated shocks such as conflict or economic crises (as well as their human mitigating factors in the form of preparedness or food aid, e.g.) can have in improving or worsening the impacts of shocks. Natural to human coupling is conceived of both as drivers and feedbacks because shocks that may seem to originate purely in the natural system, such as droughts and flooding, are increasingly understood to be feedbacks or responses to the damaging effects of human systems on natural systems such as soil erosion or climate change.

Credit: Karl Zimmerer, adapted from the National Science Foundation.

Introductory Video and Knowledge Check

Please watch the brief video about resilience and adaptive capacity. The presenter, Terry Chapin of the University of Alaska- Fairbanks, is an ecosystem ecologist who is used to thinking about the stresses that whole systems like ecosystems and food systems confront. Note that he uses the term 'resources' as roughly equivalent to the components of natural systems that support coupled human-natural food systems presented on the previous page. After the video in the knowledge check activity below, we'll ask you to identify the types of resources (i.e. components of natural systems) we've presented as vital to food systems in this course. You should, therefore, think about how the example he presents of Alaskan Native American communities and peoples can extend to many other elements of the food system.

Video: Resilience: The importance of adaptive capacity (2:10)

Knowledge Check Activity

Based on your learning in the course so far:

Definitions of Resilience, Adaptive Capacity, and Vulnerability

Resilience, adaptive capacity, and vulnerability (RACV) are three concepts used to explain how human and natural systems respond to perturbations and shocks. We can use these concepts to understand the responses of agri-food systems to such factors as drought or the occurrence of market shocks or political crises. Here are some definitions of the RACV concepts, understood within a Coupled Natural-Human System Framework.

Resilience

Resilience is a system property which denotes the degree of shock or change that can be tolerated while the system maintains its structure, basic functioning, and organization. Talking about resilience usually implies thinking about the resilience “OF what TO what”. That is, we need to understand the resilience of a system (what system or process?; e.g. crop production; food distribution; farming or culinary knowledge) TO a threat or shock (what kind?; e.g. drought, war, plant disease). A recent report from a United Kingdom scientific commission states that resilience is “the capacity to absorb, utilize or even benefit from perturbations, shocks and stresses” which includes the idea that resilient systems, provided they are sufficiently robust, can even benefit from perturbations.

Figure 11.1.4. A farmer-educator with a Peruvian NGO at a “knowledge fair” describes strategies to adapt to climate change and resulting weather shocks that are being evaluated and promoted by a local non-governmental organization in conjunction with indigenous communities. The poster behind the promoter describes how organic matter in the soil helps to retain moisture to adapt to drought shocks.

Credit: Steven Vanek

Adaptive Capacity

Adaptive capacities are the social and technical skills and strategies of individuals and groups that are directed towards responding to environmental and socioeconomic changes. In the context of food systems, adaptive capacity is usually exhibited or deployed to maintain livelihoods, food production, or food access. In the context of climate change, it is important to distinguish between adaptive capacity vs. mitigation: Adaptive capacity is deployed to adapt to perturbations in growing or living conditions or shocks brought on by climate change. Mitigation involves actively reducing the threat of climate change, rather than adapting to its effects: for example reducing emissions, reducing meat consumption among high-meat consuming populations, or geoengineering of the atmosphere to reduce CO₂ concentrations.

Adaptive capacity is the second important property that refers to the responsiveness of agri-food systems when faced with extreme conditions. Human systems might, for example, have the capacity to switch to alternative land use within the agri-food systems. In these cases, people would be able to adapt to change since they have the capacity to shift their use of land and other resources. Adaptive capacity in the case of natural systems is exemplified by drought-tolerant crops (figure 11.1.5). Such crops may have more developed root systems or biological adaptations for conserving moisture.

Figure 11.1.5. The Andean lupine, Lupinus mutabilis, pictured here in Bolivia, has a deep root system, superior ability to acquire its own nitrogen for protein from the air, and drought-adapted physiology that allows it to survive and produce lupine beans well into the dry season. It is also a highly nutritious and versatile food crop for consumption and income generation, once bitter alkaloids have been removed from the beans. It thus forms part of a human adaptive capacity in the local agri-food system to a dry climate and drought.

Credit: Paul VanDerWerf, Flickr

Vulnerability

Vulnerability is the exposure and difficulty of individuals, families, communities, and countries in coping with shocks, risk, and other contingencies. This can be thought of as the opposite of adaptive capacity, with a continuum of mixed adaptation/vulnerability in between the two extremes of adaptive capacity and vulnerability. Farmers and consumers in extremely poor and isolated circumstances (whether in urban or remote areas) can be considered highly vulnerable because they lack their own ability to adapt to threats, and may be cut off or marginalized from external resources (family, government assistance etc.) that allows them to adapt to changes.

Now we can apply the concepts of resilience, adaptive capacity, and vulnerability to agriculture and food, using a Coupled Natural-Human System (CNHS) framework (Figure 11.1.6)

Figure 11.1.6. Examples of Resilience (R), Adaptive Capacity (AC), and Vulnerability (V) in coupled agri-food systems. These examples are shown interior to each of the human and natural systems. Many of the positive practices regarding soils, water, and pests in the previous modules of the course can be considered additional examples of adaptive capacity because they contribute to greater levels of resilience to shocks, in addition to increasing or maintaining production under average conditions.

Click for a text description of the Resilience, Adaptive Capacity, and Vulnerability examples image.

Examples of Resilience (R), Adaptive Capacity (AC), and Vulnerability (V) in Human systems and natural systems

Human Systems:

R: Social infrastructure and social learning

AC: Alternative land use and crops, social assistance

V: Extreme poverty

Natural Systems:

R: Biotic diversity and healthy soils

AC: Tolerance to extremes of diverse crops, insect, and soil biota and well structured soils

V: homogeneity of seeds, eroded and low organic-matter soils

Credit: Karl Zimmerer and Steven Vanek

As shown in Figure 11.1.6, resilience can be found in both the natural and human subsystems of food systems. You may recognize that many of the examples of natural system adaptive capacity refer to the "best practices" that we have advocated for water, soils, crops, and pest management in sections II and III of this course. These would include examples such as reducing the water footprint of food production, managing soils in a system framework for greater "soil health", and managing pests with ecological practices that seek to avoid pest and weed resistance to our management approaches (Modules 4, 5, 7, and 8 respectively). These approaches are not only important in increasing productivity under average conditions, but also help a food production system to adapt to shocks and perturbations.

Meanwhile, the human component of coupled human-natural food systems also is a vital part of resilience and adaptive capacity. Resilience is higher where there are higher levels of social infrastructure that enable people to share learning and resources in response to shocks and perturbations, such as extreme drought. Social infrastructure, shown in Fig. 11.1.6, includes mutual assistance within families and communities or among regions in a country, coordinated by governments to assist in the case of shocks that affect food production. Social learning is vitally important since it’s one of the main ways that people would learning new techniques based on the conditions prevailing in their area. For example, farmers could use social learning to acquire the skills and knowledge to lessen water use, and thereby lessen the degree of agricultural production decline and reduced food access. Biological diversity is a major example of higher resilience functioning in the natural components of coupled agri-food systems. Food production systems with more biological diversity---a property referred to as agrobiodiversity and covered on the next pages---typically have the capacity for greater levels of resilience. This greater level of resilience may result from a mixture of crops and varieties combining vulnerable and resistant type of crop, for any given stress, so that even if some crops fail, others will do well. Different crops and land uses may also produce positive or facilitating interactions in which one crop type or wild plant species, for example, provides benefits to another (e.g. nitrogen fixation and better soils or screening from an important pest; see module 6 on crops and the previous section on systems approaches for management for additional examples).

Resilience vs. Adaptive Capacity: What's the Difference?

On the surface, resilience and adaptive capacity in systems may seem very similar, and it is true that as defined here they are very aligned. One way to remember the difference is that resilience is a broader system property that may have to do with the interplay of human and natural systems, or one or the other of these subsystems. We can say that a region's food system is quite resilient to drought (a more general statement) if we think for a number of reasons that its food supply would be able to continue mostly without issues during a drought. Adaptive capacity meanwhile is more narrowly focused on the specific skills and mechanisms that are deployed by human systems to contribute to resilience. In other words, we might identify that the system or component thereof is resilient (like the region mentioned above), and then identify sources or mechanisms of resilience in terms of particular knowledge, practices, land uses, or biological properties that are functioning in a food production system, referring to these as adaptive capacity. We turn next to agrobiodiversity as an example of adaptive capacity that can contribute to food system resilience (can you see the difference between the two words in this last sentence?).

One major way of increasing the resilience and adaptive capacity of agri-food systems in response to perturbations and shocks is to be certain they contain components with high levels of agrobiodiversity.

Here is a standard definition of agrobiodiversity:

Agricultural biodiversity…includes the cornucopia of crop seeds and livestock breeds that have been largely domesticated by indigenous stewards to meet their nutritional and cultural needs, as well as the many wild species that interact with them in food-producing habitats. Such domesticated resources cannot be divorced from their caretakers. These caretakers have also cultivated traditional knowledge about how to grow and process foods.. (which) is the legacy of countless generations of farming, herding and gardening cultures.

This definition is taken from Gary Nabhan’s book Where Our Food Comes From and is based on work of the United Nation’s Food and Agriculture Organization (FAO)

Figure 11.1.7. A farmer-educator working with a Peruvian Non-Governmental Organization (NGO) presents several dozen native potato varieties from the department of Cuzco, Peru. In addition to showing the ingenuity of local potato selection and breeding by farmers, these varieties are part of a rich cultural heritage and social infrastructure, and a facet of adaptive capacity via agrobiodiversity.

Credit: Steven Vanek

There are two important points to note about this definition:

• First, and most importantly, the biological diversity of agri-food systems includes vital coupling to the human system, most directly the people who are growers and their skills, knowledge, and other factors. These growers are “caretakers” in Nabhan’s definition; see Fig. 11.1.7 for potato varieties and a representative "caretaker" - a local farmer with working knowledge of these varieties. Agrobiodiversity exists squarely at the intersection of human and natural systems conceptualized in this course.
• Second, it encompasses both our cultivated species of plants and animals, which are crops and livestock chosen and evolved for production, as well as their still living wild relatives and the biodiversity of the ecosystems associated with this production (both the agroecosystem itself and the surrounding uncultivated ecosystem). Agrobiodiversity production in the natural system must be sufficient to offer positive feedbacks into the human system in order to offer the incentive for continued production.

The above-mentioned points in the definition of agrobiodiversity are illustrated in figure 9.6, which depicts agrobiodiversity as a Coupled Human-Natural System (CNHS).

Figure 11.1.8. Factors in human systems and natural systems commonly associated with active use of agrobiodiversity

Credit: Karl Zimmerer

The growers of agrobiodiversity range widely around the world. They include the people of traditional and indigenous cultures who often live in more remote locations. Many of these people live in mountainous regions and hill lands of the tropics and sub-tropics. Their use of agrobiodiversity in agri-food systems is reflected in certain global centers of diversity, as shown in the map that we presented in Module 2 regarding the sites of crop domestication in the early history of food systems. Such centers are sometimes called “Vavilov Centers” in recognition of the pioneering contribution of the scientist Nikolay Vavilov in the 1920s.

Figure 11.1.9. Global areas of concentrated agrobiodiversity corresponding to the Vavilov "centers of diversity" introduced in Module 2.

Credit: used with permission from the Wikimedia Commons project

Increasingly it’s recognized that significant agrobiodiversity also occurs outside the Vavilov Centers. For example, many urban and peri-urban dwellers grow small fields and gardens as part of local, small-scale agri-food systems. Producers of diversified production for local markets in North America and Europe are still another important group of agrobiodiversity-growers.

The extent of agrobiodiversity, in terms of crops and livestock, may vary from only a few types in a field or farm to many dozens. Agri-food systems with only a few types are quite important since they can confer significant resilience to perturbations and stressors. For example, cultivation of only a few types of barley, wheat, or maize (“corn” in the U.S.) among neighboring farms and communities can offer a much higher degree of resilience than the monoculture of a single type.

Figure 11.1.10. A sampling of the many present-day native varieties or landraces of barley from that crop's center of domestication in Ethiopia.

Credit: Used with permission under a creative commons license from the Global Crop Diversity Trust

Equally important is the case of the megadiverse agri-food systems. In the potato fields of the Andes Mountains of western South America, for example, a farmer may grow as many as 20-30 major types of potatoes in a single field. (Figure 11.1.11). Here, in tha global “Vavilov Center” of the Andes mountains, high levels of agrobiodiversity are integral to the agri-food system as a result of factors in the human system (skills, knowledge, labor-time, cultural and culinary preferences) and the natural system (highly varied climate and soil conditions characteristic of tropical mountains).

Figure 11.1.11. Nearly 70 varieties of Andean potatoes in a local agri-food System in the Peruvian Andes

Credit: Karl Zimmerer

Activate Your Learning: Agrobiodiversity and Resilience

Assigned Reading:

Please read the brief "introduction to the reading" below and then the following pages from Gary Nabhan's book "Where Our Food Comes From":

Nabhan, G.P. "Rediscovering America and Surviving the Dust Bowl: The U. S. Southwest ", p. 129-138, part of Chapter 9, Where Our Food Comes From: Retracing Nikolay Vavilov's Quest to End Famine. Washington: Island Press.

Introduction to the reading: The reading describes part of a much longer account of travels by Vavilov (for whom the Vavilov centers of agrobiodiversity are named, see the previous page in the book, and module 2.1 in this course) from 1929 to 1934 in North America. During this trip, the Russian crop researcher met with U.S. researchers as well as "keepers" of U.S. native agrobiodiversity. This chapter describes Vavilov's trip to the Hopi Indians in 1930, in which he and the U.S. scientists were able to observe firsthand the seed systems and their resilience to the drought that was currently going on in the United States. The author of the book, Gary Nabhan, relates this account of the visit and then compares it to similar visits he made to the Hopi in the more recent past. This compiled history of seed systems and their relation to both human and natural system changes in the U.S. Southwest is a sort of case study, from which the assessment worksheet will ask you to draw conclusions.

Download Worksheet

Food access is a variable condition of human consumers, and it affects all of us each and every day. If you have ever traveled through an isolated area of the country or the world and encountered difficulty in encountering food that is customary or nutritious to eat, or within reach of your travel budget, you have an inkling of what it means to have issues with food access. For those with little capacity for food self-provisioning from farms or gardens, food access is determined by factors influencing the spatial accessibility, affordability, and quality of food sellers. The consistent dependability of adequate food access helps to enable food security whereby a person’s dietary needs and food preferences are met at levels needed to main a healthy and active life. Famines are conditions of extreme food shortage defined by specific characteristics (see below). Food-insecure conditions, such as acute and chronic hunger, are important conditions that affect many people both in the United States and in other countries.

A global overview of food insecurity can be obtained by mapping the average daily calorie supply per person for each country (see Figure 11.2.1). Mapped values are shown as ranging from less than 2,000 calories per person (e.g., in Ethiopia and Tanzania) to the range of 2,000-2,500 calories per person, which covers several countries in Africa as well as India and other countries in Asia in addition to Latin America and the Caribbean. Calories are a reasonable way to begin to understand large-scale patterns related to the lack of food access around the world. Nevertheless just looking at calories hides other aspects of human nutrition, such as the need for a diverse diet that satisfies human requirements for vitamins, minerals, and dietary fiber, which were described in module 3.

Figure 11.2.1. Global Food Insecurity: calorie measures. This map is a good first approximation though it does not address vitamin or micronutrient-based malnutrition, which was described in module 3 of this course.

Credit: Atlas of Population and Environment

Required Readings

The following brief readings are good ways to appreciate the analyses and debates surrounding food insecurity and the challenges of "feeding the world", especially in the emerging scenario of climate change impacts on food production. They form part of the required reading for this module and will help you to better understand the materials and the summative assessment.

1. Bittman, Mark. "Don't Ask How to Feed the 9 Billion" NYT, Nov 12, 2014. (Note: The link is available only for users with Penn State accounts.)
2. Deering, K. 2014. Stepping up to the challenge – Six issues facing global climate change and food security, CCAFS (Climate Change and Food Security Program)-UN (United Nations), 2014. Read the page headings on each challenge and the brief description of the response below.

Food Crises and Interacting Elements of the Natural and Human Systems

This section employs the framework of Coupled Natural-Human Systems (CHNS) in order to illustrate the interacting elements of natural and human systems that can combine to produce severe food shortages, chronic malnutrition, and famine food systems around the world. These CHNS concepts build on the diagrams and concepts in modules 10 and 11.1. You will also apply these concepts in the summative assessment on the next page.

As you read this brief description consult figure 11.2.2 below. It depicts that interacting conditions within the human and natural systems, combined with driving forces and feedbacks, are at the core of many cases of severe food shortages, chronic malnutrition, and famine in agri-food systems.