Plants are Solar Powered Air Conditioners
Here lies a neglected opportunity to let plants do much of the work of cooling the climate and creating pleasant, positive microclimates
Climate change and the greenhouse effect are not just about greenhouse gases.
The opportunity and the call to action are to increase plant matter at every opportunity.
Opportunities
What does it mean to “increase plant matter” and what difference would it make?
In our yards and landscapes, we can increase plant matter by letting our grass grow and letting trees grow up within the grass.
Taller grass casts more shade and absorbs more water. When we allow trees to grow, they cast more shade and absorb more water, which they then “transpire.”
People perspire. Plants transpire. When plants transpire, they release water, which then evaporates. When you walk into a forest, the air is cool largely because of evaporation.
For every gram of water that plants transpire, 540 calories gets converted from sensible heat--heat you can feel--to latent heat. This 540 calories is called the “latent heat of vaporization.”
Solar Powered Devices
You cannot feel “latent heat” because it’s a form of motion energy … the energy required to keep water molecules moving so fast that they form a vapor, not a liquid.
So plants literally cool the air. They are solar powered air conditioners. They get energy from the sun and they use it to grow, to make food for themselves and others, and to transpire water into their environment.
One function of this transpiration is to keep the ground moist and cool, so that the ground does not dry out. Another function (I’m sure) is to provide a wet environment that surrounds the plant with an ecosystem that includes animals, fungi, bacteria and other plants.
So plants do a lot of work, for the benefit of their environment.
Maybe I’m lazy. But I want plants to do some of my work for me. We should want plants to do some of our work for us, including cooling the air in a way that is clean, safe and natural.
Temperature Differences
I have a laser thermometer that looks like a gun with a trigger. I can point the laser at the ground and pull the trigger. It tells me the temperature. The temperature varies greatly depending on whether I am pointing it at pavement, grass or the shade under a tree.
More plant cover means more cooling effect and more moisture. Or we can remove all the plant cover, and lose those cooling effects.
This is a choice. And this is why climate change is not just about what comes out of our tail pipes. It’s about what covers the land. Is the land covered or uncovered? Protected or not?
Choices
Do we employ solar powered air conditioners (plants) or solar powered frying pans (pavement, roofs, etc.)?
We need some pavement and some roofs, at least in the foreseeable future. But we could easily fit more plant matter into our existing spaces.
And then we can ask whether we are building roads, parking lots and buildings for purposes that are not overwhelmingly positive or helpful for average people. For example, we charge people to build infrastructure for defense, surveillance and for agrochemicals. People would not approve of these “developments” if they had the relevant knowledge and the power to change things.
But that’s another conversation.