From: Allison Winter, ENN
Published September 6, 2012 11:05 AM

Deforestation affects rainfall, another reason to protect the rainforests

From regulating climate systems to offering food and medicines, to being home to many plants, animals, and indigenous people, rainforests are not only a local ecosystem but their benefits extend globally.


Adding to its effects is new research that shows rainforests have a huge impact on rainfall. A team from the University of Leeds and the NERC Centre for Ecology & Hydrology found that air passing over tropical forests produces at least twice as much rain as air passing over little vegetation and can impact rainfall thousands of miles away.

Scientists have long debated whether vegetation increases rainfall. When it comes to the water cycle, plants absorb rainfall, and then put moisture back into the air through evaporation and transpiration, replenishing water molecules that will be used for precipitation. However, the quantity and geographical reach of the rainfall generated by large forests has been unclear until now.

Lead author Dr Dominick Spracklen from the School of Earth and Environment at the University of Leeds said: ''We were surprised to find that this effect occurs strongly across more than half of the tropics. We found that the Amazon and Congo forests maintain rainfall over the periphery of the forest basins - regions where large numbers of people live and rely on rainfall for their livelihoods.''

Researchers used NASA satellite observations of rainfall and vegetation, along with a model that predicts atmospheric wind flow patterns, to explore the impact of the Earth’s tropical forests. The team studied the air masses route over the forest and noted the amount of leaf cover it passed in addition to the amount of vegetation it was over when it rained. They concluded that the more vegetation the air had travelled over, the more moisture it carried and the more rain was produced.

Researchers estimate that deforestation of tropical forests would reduce rain across the Amazon basin by up to 21 percent in the dry season by 2050. This will have significant effects on farmers in outlying regions near the Amazon and Congo forests and others whose livelihood depends on rainfall.

The results of this study put emphasis on the fact that deforestation can have a significant effect on tropical rainfall and therefore needs to be curtailed to lessen the impact. 

Dr Stephen Arnold from the University of Leeds, a co-author on the paper, said: ''This has significant implications for how policy makers should consider the environmental impacts of deforestation, since its effects on rainfall patterns may be felt not only locally, but on a continental scale.''

Read more at the University of Leeds.

Rainforest image via Shutterstock. 

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