The rainforests of the Amazon have long been known as “the lungs of the planet,” yet that may no longer be the case. The region’s forests produce more than a billion tons of CO2 a year, which means that they now emit more carbon than they absorb, according to new research.

The main reasons for the reversal in the Amazon’s role as a major carbon sink include continued deforestation and unrelenting climate change, according to the scientists who conducted nearly 600 vertical profiling measurements by help of small airplanes some 4,500 meters above the forest to monitor concentrations of carbon dioxide and carbon monoxide at four sites between 2010 and 2018.

They found that carbon emissions are greater in the eastern region of the Amazon than in its western part, but it is the southern part of Amazonia that has especially transitioned from being a carbon sink to a carbon source. “Over the past 40 years, eastern Amazonia has been subjected to more deforestation, warming and moisture stress than the western part, especially during the dry season, with the southeast experiencing the strongest trends,” the scientists write.

Most of the carbon emissions from the Amazon derive from uncontrollably burning fires lit by farmers to clear forests to make way for pastures for cattle and land for agriculture. Warming air temperatures and prolonged droughs as a result of a changing climate have also contributed to far more CO2 being released in the Amazon, the experts say.

“The first very bad news is that forest burning produces around three times more CO2 than the forest absorbs,” notes Luciana Gatti, a scientist at the National Institute for Space Research in Brazil who led the research. “The second bad news is that the places where deforestation is 30% or more show carbon emissions 10 times higher than where deforestation is lower than 20%.”

Globally, trees and plants play an important role in mitigating climate change by absorbing around a quarter of CO2 emissions from fossil fuels and the Amazon, and Earth’s largest tropical forest, has been one of the planet’s largest carbon sinks. Losing that benefit of the Amazon spells trouble for our efforts to keep climate change under control.

Other researchers have recently found that tropical forests all around the planet are losing their ability to store carbon effectively with the carbon sink capacity of several African forests alone set to decline by 14% within a decade. At the same time, the carbon sink capacity of the Amazon’s forests will drop to zero by 2035.

The reason is for this is that tropical forests, despite being fairly tolerant of heat, cannot keep up with warming temperatures and prolonged droughts. Trees and other plants perish in greater numbers while many other trees end up with a reduced capacity to photosynthesize normally.

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