Fortunately, we really do have solutions for the great challenges of supplying energy sustainably and economically. This is NOT the course to deal with all the nuances of future energy systems, a hugely important topic but too big for a portion of one Module in a course on the Geology of National Parks. A few key facts follow, though. Note that your course authors don’t really know the exact future of the energy system; if we did, we could turn that knowledge into a lot of money!
The single biggest development in energy has been the immense reduction in the cost of renewable energy. Solar panels that cost more than $100 in 1975 fell to about 25 cents in less than 50 years. The International Energy Agency, founded in 1974, spent decades being unenthusiastic about renewable energy, but by 2020 reported that state-of-the-art solar installations were supplying the lowest-cost electricity in human history, with wind close to solar in price. The energy that must be “invested” to make new solar cells and wind turbines is very small compared to the electricity they then produce, and probably is smaller than the investment needed to find and develop new fossil fuel deposits, helping explain why the costs of renewable electricity have dropped below costs from fossil fuel.
Although the land area (or ocean area) needed to supply all of human energy use from renewable energy sources is large, it is very small compared to the areas we use for some other purposes. For example, we grow food to eat, to feed animals, and to burn as biofuels (corn ethanol, biodiesel, etc.). Biofuels are a small part of our energy mix, much less than fossil fuels, but installing modern solar cells and wind turbines on the area we use for growing biofuels could supply more energy than is used by all humans from all sources because renewables are so much more efficient than plants at capturing the sun’s energy. Some farmers are choosing to combine wind or solar energy (or both) with ranching or farming, increasing farm income. But, renewables do not need to take farmland at all, and instead can be put across irrigation canals to reduce evaporation, above parking lots to shade them, offshore where the foundations can be designed to help provide fish habitat, and in other places.
Renewables have real needs in addition to land or ocean area, including materials, some of them rare. But, geologists remain confident that we can find sufficient materials that, with recycling, can supply a sustainable system involving much less mining and drilling than are required with fossil fuels. And, materials scientists remain confident that they can shift to reliance on more abundant elements, so the geologists don’t need to find more rare things for mining. For example, sodium batteries are already beginning to replace lithium batteries in some uses, and sodium is MUCH more common than lithium and so requires much less mining.
As noted above, anything that we do to supply the huge amount of energy we use will have unintended consequences. Wind turbines do kill some birds, for example, although the number is tiny compared to human-caused deaths from other sources including the current energy system. A full analysis, including the effects of climate change and the disturbances associated with fossil-fuel recovery, shows that switching to a sustainable energy system rather clearly will reduce overall bird deaths. And, we can now forecast and monitor major bird migrations, turning off wind turbines in important places at the right times to further reduce mortality (Sovacool, 2013)
The future energy system might include fusion if we invent that technology, or nuclear fission if costs can be brought way down and other problems can be solved, or geothermal energy, or some others. Biofuels may remain important for some hard-to-replace uses of liquid fuels such as long-haul airlines. So much energy is available at such low cost from renewables, though, that we know a sustainable system can be built, supplying affordable, clean energy for everyone across the world.
Sovacool, Benjamin K., "The avian benefits of wind energy: A 2009 update." Renewable Energy, Volume 49, 2013, doi:10.1016/j.renene.2012.01.074.