Don’t get me wrong. I’m not against renewable energy, but it pains me to see prime farmland being taken out of production permanently. Food shortage could be a real problem if this trend continues.
With rising worldwide population, we need to take advantage of our most productive land. Converting agricultural land into roads, shopping centers, housing developments and even solar farms is irreversible.
There are plenty of places we can generate power. There are many fewer ones where we can produce high-value agricultural products. I’d love to see more solar powered roofs, for one thing. I’d also like to see more in places where large amounts of vegetation aren’t removed from the environment.
Another problem nobody talks about is the reduction in photosynthesis and therefore the greater potential increase in temperature caused by removing plants from the landscape. Photosynthesis is an endothermic reaction. That means energy must be added for the process to proceed.
Plants capture energy from the sun and sequester carbon dioxide in the form of sugars. In the process, plants take in liquid water from their roots and give off water vapor through transpiration. This happens both by photosynthesis and plant respiration.
When water changes from a liquid to a gas, about 540 calories of energy are required to convert one gram of liquid water to water vapor. This is called the latent heat of vaporization and the process cools the environment.
Therefore, when we have less photosynthesis, we have less potential cooling. We also have less uptake of carbon dioxide. These thermodynamic facts are quantitative and undeniable.
When I was in college in the late 70s, we deliberately burned unvented heaters in our greenhouses to increase carbon dioxide levels and promote plant growth. The theory works, but it assumes that we maintain proper nutrient levels. Lack of nitrogen could mean less chlorophyll production, and that would lower photosynthesis.
It’s no accident that tropical rainforests are much cooler than their desert counterparts in similar latitudes. High levels of photosynthesis have a dramatic effect on climate.
Any time we remove plants and create roads, buildings, solar farms or whatever, we create heat islands. We also lessen our ability to produce food and fiber.
We obviously need roads, homes and businesses, but anything we can do to increase plant growth is beneficial. Renewable energy is also a good thing, for many reasons. Even if they had no ill effects, fossil fuels won’t last forever anyway.
So, what does it all mean? It’s complicated since there is a loss of energy created by longer distances between solar energy production and subsequent use. If we used only barren areas to produce solar electricity, efficiency would suffer. So would profit.
In Europe, many solar farms are elevated so that crops can still grow underneath them. From what I’ve read, the system works. Most pictures I’ve viewed show panels much further apart, which would be necessary for crops to receive enough light.
I’m not sure how practical that is in hurricane-prone places like eastern North Carolina. I also don’t know how much it would cost, but we can’t lose sight of the fact that land, especially prime farmland is a precious irreplaceable resource.
Ted Manzer teaches agriculture at Northeastern High School (firstname.lastname@example.org).