Part of the Amazon now releases more carbon than it stores

Part of the Amazon rainforest has been transformed into a significant source of carbon dioxide emissions, according to a long-term study. Experts at NOAA report that deforestation in eastern Brazil has led to less rainfall and hotter temperatures, which has flipped the forest from a carbon sink to a source of carbon dioxide. 

Based on nearly 10 years of CO2 measurements, the researchers found that the most deforested parts of the eastern Amazon – mainly in the southeast – are releasing more carbon than they store. 

“On the other hand, the wetter, more intact western and central Amazon, was neither a carbon sink nor source of atmospheric CO2 , with the absorption by healthy forests balancing the emissions from fires,” explained study co-author and NOAA scientist John Miller. 

The Amazon is made up of 2.8 million square miles of jungle and represents more than half of the remaining tropical forest on the planet. Scientists estimate that the Amazon locks up about 123 billion tons of carbon, both above and below ground.

In 2010, study lead author Luciana Gatti and an international team of experts set out to investigate whether the combined effects of climate change and land conversion is compromising the Amazon’s ability to store carbon.

“The regions of southern Pará and northern Mato Grosso states represent a worst-case scenario,” said Gatti. 

The southeast region of the Amazon has experienced 30 percent deforestation over the last four decades. Nine years of airborne measurements showed that this region is a net emitter of carbon. On the other hand,   the western portion of the rainforest has experienced less clearing still serves as a carbon sink. 

According to the researchers, the increased emissions were likely due to the fires that are used to convert jungle to cropland, and by reduced uptake of CO2 by the trees that remained. 

“The big question this research raises is if the connection between climate, deforestation, and carbon that we see in the eastern Amazon could one day be the fate of the central and western Amazon, if they become subject to stronger human impact,” said Miller.  

The study is published in the journal Nature.

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By Chrissy Sexton, Earth.com Staff Writer