That’s the conclusion of new research that shows deforestation can significantly reduce tropical rainfall far from the area where trees have been cut down.

That’s because air passing over forests picks up moisture given off by trees and plants, fueling rains. When those trees disappear, so does some of that rain.

“What we found was this really strong impact – air that traveled over a lot of forest brought a lot more rain than air that didn’t travel over very much forest,” said lead author Dominick Spracklen of the University of Leeds.

His research, published yesterday in the journal Nature, helps reconcile a situation that has puzzled scientists.

(Scientists believe that when trees are cut down, the bare surfaces left behind absorb more heat than the forest they replaced. And that heat helps draw air upward, pulling moist air in from nearby forested land that increases rainfall in the immediate area.)

But Spracklen’s study suggests both the climate model projections and the observations may be correct. Deforestation can reduce rainfall over a wide region, even as it spurs increased rainfall in the immediate area where that deforestation took place.

The analysis has “beautifully reconciled the scale of observations with that of models,” Luiz Aragao, an expert in tropical forests at the University of Exeter, said in a commentary published alongside the new study.

Using models and satellites The study authors’ “cutting-edge methodology will allow observations to be used consistently to examine large-scale deforestation impacts on rainfall, and to refine and evaluate current models to support conservation planning in the tropics,” Aragao wrote.

The study authors based their analysis on a combination of satellite observations of rainfall and vegetation and an atmospheric circulation model to track the movement of air masses.

“At any point in the tropics, we’d look at rainfall on a particular day and look at how the air traveled to get to that point over the past four to five days,” Spracklen said. “By making that comparison, we were able to say that if air has traveled over more forest, do you get less or more rainfall – or no change?”

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500