How Trees Make Rain
Our forests are revered around the world and yet are underrated in terms of how they transform their local climates and COULD transform our global climate.
We need our forests, for many reasons. They provide habitat for wildlife, they absorb carbon from the atmosphere, they prevent erosion and they make our streams flow more steadily, instead of gushing with flood waters.
But not least of all, forests make rain.
Let’s follow the course of a raindrop as it falls from the sky.
If the raindrop falls on a tree, that’s much better than falling on bare ground or pavement. A raindrop that hits a leaf or a branch will cling to it, at least for a while, until it flows or falls downward or evaporates back into the air.
By contrast, a raindrop that hits bare ground or pavement will rush into the streams or storm drains, potentially causing a flood.
If the raindrop instead falls on the ground beneath the tree, then it is more likely to hit leaf litter or fertile soil. There again, the tree is responsible for slowing the progress of the raindrop, so that it slowly percolates through the ground instead of rushing into the streams.
But how does the raindrop form in the first place? And what role do trees play?
We were taught in school that moist air blows in from the ocean or other body of water. There’s some truth in that, but much more to the story. Forests create their own rain.
What we did not learn in school is that trees have a way of creating the very rain that they need to thrive.
As air rises from the forest, it cools. As it cools the water vapor tends to condense. As water vapor condenses, it takes up less space and creates a vacuum that pulls air up from below, continuing the cycle of cooling and condensation.
This could happen anywhere, but it’s more likely to occur over a forest.
But the cooling is not the only thing that causes condensation. Condensation also occurs due to organic chemicals and bacteria from the trees. These bacteria (called aerobacter) and organic chemicals (called terpenoids) are “condensation nuclei.” This means they cause water droplets to coalesce into raindrops.
So what happens is that when water condenses into raindrops and falls? A vacuum is created which pulls forest air upward. This forest air is strongly eligible for further condensation, because
It is cool.
It is moist. It is rich with water vapor.
It is often nearly 100% relative humidity.
It contains condensation nuclei.
Such are the characteristics of air that is ready to make rain. You can’t say that about air that rises from:
A desert floor
A deforested area
A bare agricultural field
Pavement or concrete.
In fact, according to my sources in the scientific community, a mature or old growth forest is much more useful in creating rain than a young forest or a tree plantation in the same location.
This is yet another reason we need our forests. They make rain. Without them, we will have much less rain. Without our forests, we will have much more drought.
As if we needed another reason to preserve our forests.
But as we speak, our forests in the Southeastern U.S., in British Columbia, in Indonesia and in Europe are being clearcut, turned into wood chips and burned as fuel. This is called “renewable energy.” But it is not renewable. It is destructive and stupid.
For more on clearcutting, please see my interview with Scot Quaranda of Dogwood Alliance.
Here is a video I made on how Forests Bring Rain
And another one on How Trees Bring Rain
Here is a great five minute video on How Plants Could Save Us. It is from Jimi Eisenstein. I have studied it closely, and it is very good.
Bottom line, trees are revered around the world, and yet grossly underrated and undervalued in terms of what they can do for our climate, by preventing drought and bringing steady rainfall.