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Deforestation in the tropics linked to reduced rainfall

New research conducted by the University of Leeds has found that deforestation leads to reduced rainfall across large areas of the tropics. Although people inhabiting these regions have often complained that the climate gets hotter and drier once trees from these areas are cleared, this is the first study to identify a clear link between the loss of tree cover and significant declines in rainfall.

The experts examined the impact of forest loss on rainfall patterns in three areas of the tropics – the Amazon, Congo, and Southeast Asia – that have recently experienced rapid land-use changes. By using satellite observations from 2003 to 2017, they identified the areas where forests have been cleared, and compared rainfall data from these regions to data from nearby locations where forests have not been lost.

The analysis revealed that tropical forest loss led to reductions in rainfall throughout the entire year, including in the dry season, when any further drying severely impacts plant and animal ecosystems. However, the largest decline in precipitation was observed in the wet season, with nearly 0.6 mm a month reduction in rainfall for each percent of forest cover loss.

“Tropical forests play a critical role in the hydrological cycle through helping to maintain local and regional rainfall patterns,” said study lead author Callum Smith, a doctoral student in Environmental Sciences at Leeds. 

“The reduction in rainfall caused by tropical deforestation will impact people living nearby through increased water scarcity and depressed crop yields. Tropical forests themselves rely on moisture to survive and remaining areas of forest will be impacted by a drier climate.” 

According to the scientists, the loss of tree cover disrupts the process in which moisture from leaves is returned to the atmosphere through a mechanism called evapotranspiration, where it eventually forms rain clouds. 

Besides impacting natural ecosystems, reductions in rainfall are also detrimental to agriculture and hydropower plants and are thus likely to affect not only the healthy functioning of forests, but also local communities. In addition, these declines have a negative impact on biodiversity, increase the risks of forest fires, and reduce carbon sequestration.

These problems will likely get worse by the end of the century, with researchers estimating that, if the rate of deforestation in the Congo was to continue as before, rainfall in the region could be reduced by eight to 12 percent, severely affecting both biodiversity and farming, while threatening the viability of the Congo forests, which are among the world’s largest carbon stores.

“The study shows the critical importance of tropical forests in sustaining rainfall. Although there have been efforts to halt deforestation, the loss of forest cover in the tropics has continued. There needs to be renewed efforts to stop forests being lost and to regenerate lost and degraded areas,” concluded senior author Dominick Spracklen, a professor of Biosphere-Atmosphere Interactions at Leeds.

The study is published in the journal Nature.    

By Andrei Ionescu, Staff Writer

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