Amazon deforestation causing measurable drop in rainfall: study
Significant deforestation led to a measurable drop in precipitation across portions of South America
The rich plant life that makes up the Amazon rainforest contributes a significant amount of water vapour to Earth’s atmosphere. A recent study found that extensive deforestation here has caused a measurable drop in precipitation across the region.
Published in April, the new research highlights how human activities can directly alter the climate beyond the effects of greenhouse gases.
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The Amazon rainforest covers nearly 6 million square kilometres of South America, with a majority of the rainforest falling within Brazil’s borders. Significant deforestation reportedly led to the loss of about 27,000 square kilometres of forest each year between 2001 and 2016.
Dense rainforests play a critical role in the water vapour cycle. Trees and other plant life absorb water from the ground and release water vapour back into the atmosphere, a process called evapotranspiration.
Research recently published in AGU Advances used satellite data and weather models to simulate the effects of severe deforestation in southern Brazil, tracing water vapour paths to measure how the dramatic change in land coverage has affected precipitation trends in the region.
The team found that every 1 per cent loss of forest coverage resulted in an estimated 1.69 per cent reduction in precipitation during the dry season, which runs from June through August.
“Our results suggest that changes in local moisture recycling lead to atmospheric responses that amplify the precipitation reduction due to forest loss,” they said in the study.
Deforestation reduces the amount of evapotranspiration in the region, which causes the surface to warm up and dry out. Lower humidity in the lower levels of the atmosphere reduces instability, leading to fewer showers and thunderstorms bubbling over and around the deforested areas during the drier months of the year.
Header satellite image courtesy of NOAA.