Prioritize...
After completing this section, you should be able to:
- Define "redlining" and how redlining sets the stage for inequities within cities based on class and ethnicity.
- Explain how the urban heat island effect actually varies within a city and why this is the case.
Read...
When we talk about climate justice, it’s not just "far away global issues" -- it hits close to home, too. Even here in the U.S. – a country we’ve already noted as a high GDP one -- climate change impacts don’t play out equally across communities. Some groups, particularly low-income families, communities of color, and indigenous peoples, are hit harder. How does this happen?
First, you need to know that not all neighborhoods are created equal when it comes to dealing with climate change. Vulnerable communities are often located in areas more prone to flooding, extreme heat, and pollution. They’re also less likely to have the resources to adapt. For example, during a heatwave, wealthier neighborhoods might crank up the air conditioning or visit nearby cooling centers. However, lower-income areas may not have access to reliable AC or safe public spaces to cool off. Similarly, coastal communities composed of more marginalized populations face rising sea levels and stronger storms, but they often lack the financial means to rebuild after disasters, trapping them in a cycle of risk and recovery. This stands in stark contrast to coastal communities of more affluent denizens.
Redlining
These inequalities didn’t just happen by chance. They are deeply tied to systemic practices like redlining. Starting in the 1930s, redlining was a discriminatory policy in which banks and financial institutions refused to offer mortgages or loans to people in certain neighborhoods—usually communities of color. These areas were literally outlined in red on maps, signaling them as too risky for investment. This practice is where the term redline comes from. The result? Widespread disinvestment in these neighborhoods, leaving them with poor infrastructure, underfunded public services, and limited opportunities for growth.
Take Bedford-Stuyvesant in Brooklyn, for example. In the 1930s, a government appraiser assessed the neighborhood, noting its aging brownstones and residents who were mainly clerks, laborers, and merchants, with about 30% being foreign-born Jewiss and Irish. They also flagged "colored infiltration" as a negative factor. This led the Home Owners’ Loan Corporation to redline the area, labeling it “hazardous” for mortgages and cutting it off from critical investments. Check out the map below; these neighborhoods were literally marked in red.
Over time, redlined neighborhoods became more vulnerable to environmental hazards, offering a stark example of environmental racism. They were undesirable, not areas where new homeowners with wealth were flocking to. These are the same communities—often communities of color—that are disproportionately exposed to pollution and other environmental risks. Thanks to redlining and similar discriminatory practices, many minority neighborhoods ended up near factories, highways, and other sources of pollution. They often lack parks, green spaces, and clean air or water, and rarely receive the resources needed to deal with environmental challenges.
Unfortunately, the consequences are severe. Living close to industrial zones means increased exposure to air pollution, which leads to higher rates of asthma and other respiratory problems. When natural disasters like floods or hurricanes strike, these neighborhoods typically suffer the most because they already have underfunded infrastructure and poorly equipped emergency services.
Urban Heat Islands
But what does redlining have to do with climate change? On the surface, this feels like a social policy issue, not one that is concerned with climate science. Yet, the legacy of redlining is deeply intertwined with how communities experience the effects of climate change today. Let’s take a closer look at one example: urban heat islands.
We've already talked about these effects a bit. You may remember our earlier discussion about how cities can influence local climate, creating areas that are significantly warmer than their surroundings. What we didn't talk about was that urban heat islands are most intense in poorer neighborhoods, which often have disproportionately high Black and Hispanic populations. That is, the added "juice" to the air temperature from urbanization is highest in these redlined areas.
The figure below highlights this connection in Baltimore, Maryland. The map on the left shows surface air temperatures by zip code, while the map on the right shows income levels. Notice the pattern: the warmer areas (darker red) tend to overlap with the poorer neighborhoods (lighter green). Why is this happening? Redlined neighborhoods often lack trees and green spaces to provide shade and cooling. Instead, they’re dominated by concrete, asphalt, and other heat-trapping surfaces. These neighborhoods are also more likely to be near highways and factories, which adds to the problem.
And there’s another layer of inequity: the “double whammy” effect of heat generated elsewhere. In downtown business districts, for example, office buildings rely on air conditioning that pumps heat into the surrounding air. Really, that's all an air conditioner is doing -- moving heat from inside a building to outside. If you've ever walked by a central or window AC unit on a hot day, you've gotten a blast of hot air and you know what I am talking about! Breezes then carry this hot air into nearby residential areas—often poorer neighborhoods—making an already hot environment even hotter. It’s essentially a "heat island within a heat island," compounding the risks for the most vulnerable communities.
Take some time to go to this website to check out some other major cities and see if you see the same trends. You can even download their source code and play with it yourself if you are so inclined (not required!).
(left) Zip code level map of the magnitude of the urban heat island effect in Baltimore, Maryland and (right) the median income for those zip codes.