Amazon deforestation could reduce tropical rainfall and affect Brazil’s hydro plans

By Tierney Smith 

Deforestation could significantly reduce tropical rainfall, according to new research.

The study, published in Nature, found that air passing over extensive forests in the Earth’s tropical regions produces at least twice as much rain as air passing over little vegetation. In some cases these forests affected rainfall thousands of kilometres away, according to the study.

The researchers warn this would have dramatic impacts on farmers working within tropical basins – such as the Amazon and Congo – as well as reducing their hydro-electricity capacity from receding river flows.

Since 1970, over 600,000 square kilometers of Amazon rainforest have been lost and current trends predict as much as 40% of the forest could be lost by 2050.

In addition to supplying water to Brazil’s vital hydro-electric fleet, the Amazon rainforest also acts as a carbon sink – but some researchers believe that rising temperatures and drought are limiting its ability to perform this function.

How could deforestation impact rainfall in the Earth's tropical regions?

The researchers modeled their observations against predictions for future deforestation and warn rainfall could be reduced in the Amazon basin by up to a 21% in the dry season by 2050.

The impact vegetation has on rainfall has been debated amongst scientists for some time. Most now agree that plants put moisture back in the air through their leaves, but the quantity and geographical reach is still not fully understood.

The researchers said the latest findings show the importance of initiatives to protect tropical rainforests, warning it would have negative impacts for people living near the Amazon and Congo forests.

“Brazil has recently made progress in slowing the historically high rates of deforestation across the Amazon and our study emphasises that this progress must be maintained if impacts on rainfall are to be avoided,” said Dr Dominick Spracklen from Leeds University.

“The Amazon forest maintains rainfall over important agricultural regions of Southern Brazil, while preserving the forests of the Congo Basin increases rainfall in regions of Southern Africa where rain-fed agriculture is important. Increased drought in these regions would have severe implications for their mostly subsistence farmers.”

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