Which came first the forest or the rain?

October 20th, 2010

By: Douglas Sheil
Repost from Bwindi Researchers on Wildlife Direct

During the rainy season in the Bwindi Impenetrable National Park, Uganda, there’s an impressive storm and our water tanks overflow nearly every day. We’re in the equatorial rain forest after all: we have the location, trees and weather to prove it. But is the forest here because of the rain or is it the other way around? Being in a highland area we probably get much of our rain simply due to the terrain (mountains tend to be wet even in dry regions) and the forest vegetation takes advantage of that.

Clouds over Bwindi Impenetrable National Park, Uganda. Clouds are often found over forests. What causes what?

But what about in the wet lowland forests of the Congo and Amazon basins? How does so much rain get so far inland from the oceans? You might think that climate scientists know the answer. Actually they don’t. That troubles me.

I have spent some time trying to understand how so much rain gets into the interior of wet continental regions. Why do winds blow the way they do and why do they carry so much rain?

One new theory really deserves recognition. The theory suggests that forests are the reason: they attract rain. The physical principles behind this idea have been explained by two Russian physicists. Their publications are not easy to read and follow, but I have spent some time trying to share their ideas because I think they are important.

Clouds forming over the forest — Bwindi Impenetrable National Park, Uganda.

The basic concept relates to how water vapor, via condensation and evaporation, gives rise to differences in atmospheric pressure between areas and thus cause winds — these winds in turn control where water (i.e. rain) comes from and goes to. If the theory is true we have a whole new way to understand how climate works and a whole new reason to value forests.

Last year, Daniel Murdiyarso and I published an overview of the basic ideas that got some media coverage. You may have seen some of it: e.g. Mongabay, New Scientist and Scientific American. We even got a recent mention in to the Economist. . If you like, you can see our original article in Bioscience. So why is this news? Well, I’ll get there in a moment.

Morning time clouds — Bwindi Impenetrable National Park, Uganda. Would the clouds be there without the forest?

The theory received its fair share of criticism. We should not be surprised—science works through critical scrutiny and radical ideas should certainly be well scrutinized. I welcome that. But it also seems to me that some, perhaps most, of the comments are misdirected—when we look in detail the theory is not being understood in the manner intended. Misreadings and assumptions get in the way.

So to get a fair hearing we need to communicate the ideas as clearly as we can. To do so I have teamed up with the physicists themselves: Drs. Anastassia Makarieva and Victor Gorshkov (you can learn more if you visit their site). We now have a new manuscript up for anyone, including you, to see. Feel free to take a look at the text here. It’s technical because climate science needs to be, but we also hope it makes good clear sense.

Will it change the world? I don’t know. But it might.

So now we wait and see what the rest of the scientific community thinks. Some may like it, others may not. If their comments are insightful I wont mind either way (well not too much). After all, that’s how science moves forward.