When Forests Are Cut, Rainfall is Affected and Temperatures Increase


Deforestation of tropical forests in the world's southern hemisphere is threatening world food production by distorting rainfall patterns across the rest of the globe, a study has indicated.

The deforestation is accelerating global warming and could result in changing rainfall patterns across Europe, the U.S. Midwest and China, researchers said.

In addition, tropical regions in Southeast Asia, Central Africa and the Amazon region of South America could see a 15 percent drop in rainfall by 2050, the study authors reported in the journal Nature Climate Change.

"When you deforest the tropics, those regions will experience significant warming and the biggest drying," study leader Deborah Lawrence of the University of Virginia said.

Most deforestation is done to provide cleared land for agriculture, but the cutting down of trees and the planting of crops releases large amounts of carbon dioxide into the atmosphere, which adds to global warming, the researchers said.

Crops are also less efficient in retaining moisture than forests, with immediate effects on local weather.

"Tropical forests are often talked about as the 'lungs of the earth,' but they're more like the sweat glands," said Lawrence.

"They give off a lot of moisture, which helps keep the planet cool. That crucial function is lost -- and even reversed -- when forests are destroyed," she explained.

Even deforestation at small local scales can alter the climate, with implications for agricultural efficiency and food security in some parts of the world, the researchers said.

A possible "tipping point" in Central Africa and the Amazon could be between 30 percent and 50 percent deforestation, Lawrence said, beyond which disaster could lurk.

"Significant large scale deforestation in any of these regions could have impacts on agriculture -- across the world there will be regions that suffer," she said.

The Amazon region has already seen about 20 percent of its area deforested, with climate scientists already noting changes in regional climate, including a lengthening dry season.

Global efforts to slow deforestation have had mixed results, Lawrence noted, with Brazil's work to bring its rates down representing a "wonderful success story" while in Indonesia's tropical forests the situation has become worse.

No region on Earth can consider itself immune to the problem, she said.

"Farmers in one place are connected to farmers in another. Countries are connected to each other," Lawrence said. "We don't want to wait until the climate system has shifted so we can measure it on the ground."

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