Deforestation of tropical rainforests is causing droughts

JUANA SUMMERS, HOST:

As humans change the environment around us, those changes are coming with surprising consequences, some of which are evident in rainforests around the world. Deforestation is destroying their local ecosystems, and it's also affecting the weather. Lauren Sommer from NPR's Climate Desk explains.

LAUREN SOMMER, BYLINE: In a lot of ecosystems around the world, if it doesn't rain, they're out of luck. But not in the big tropical rainforests of the world because they make their own rain.

CALLUM SMITH: I remember learning about this for the first time, and I was just like, wow.

SOMMER: Callum Smith is a Ph.D. researcher at the University of Leeds. He says first, storms blow in from the ocean, and it rains.

SMITH: And those trees receive that rain, and it falls on their leaves and goes into the soils.

SOMMER: And then the trees use that water and release a lot of moisture either through their leaves or evaporation. That humid air rises and helps create clouds.

SMITH: And it's pushed along by the prevailing winds until it is rained out somewhere else on another tree. And then the same thing happens in this big cycle. It's called precipitation recycling.

SOMMER: This recycling process can happen over and over, spanning hundreds of miles across the rainforest, helping it sustain itself. In the Amazon in the Congo, it accounts for almost half of the total rainfall. But millions of acres of rainforest have been cut down over the past several decades, which breaks the cycle.

SMITH: When we're removing trees, we're making the environment drier. And that lack of moisture that's a big cloud above those trees just disappears.

SOMMER: In a new study in the journal Nature, Smith and his colleagues found that deforestation is directly leading to drought. In the Congo, it could reduce local rainfall by 10% by the end of the century. Scientists are also seeing the impact in the Amazon.

BERNARDO FLORES: The forest depends on rainfall. If you don't have enough rain, you don't have this forest. It doesn't exist.

SOMMER: Bernardo Flores is an ecologist at the Federal University of Santa Catarina in Brazil. He says the Amazon is also being stressed by hotter temperatures, and the concern is that the rainforest is heading toward a tipping point.

FLORES: You would trigger this, like, domino effect related to loss of rainfall. Then you would lose a large part of the Amazon. We wouldn't be able to control that anymore.

SOMMER: It would mean a huge hit to the world's biodiversity as well as local Indigenous communities and farmers. Flores says stopping deforestation is key here, but it's not the whole solution. Rainforests also need global temperatures to stop rising.

Lauren Sommer, NPR News.

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