(CN) — A major drought, forest fires and deforestation have turned the Amazon rainforest from one of the world's largest carbon sinks into one of its biggest polluters, according to a new study published Monday.
Scientists who’ve been studying the area for more than eight years say around 2.5 billion trees and plants died as a result of extreme drought and “mega-wildfires” triggered by the 2015-16 El Niño, during which 495 million tons of carbon dioxide were emitted from an area that makes up just 1.2% of the entire Brazilian Amazon rainforest.
El Niño is an abnormal climate pattern that weakens Pacific ocean trade winds and brings warm water back toward the west coast of the Americas, causing significant weather alterations with some areas seeing drought and other areas experiencing major flooding.
“Our results highlight the enormously damaging and long-lasting effects fires can cause in Amazonian forests, an ecosystem that did not co-evolve with fires as a regular pressure,” Erika Berenguer, the study’s lead author, said in a statement.
Under normal circumstances, because of high moisture levels, the Amazon rainforest does not burn. But extreme drought makes the forest temporarily flammable, and fires started by farmers can escape quickly.
The loss of vegetation was much worse in areas that have suffered from centuries of deforestation, much of which has been driven by the demand for timber.
Smaller trees with lower wood density and thinner barks and trunks, which are more common in areas where deforestation has occurred, were more prone to dying from drought and fires, according to the study published in the journal PNAS, short for Proceedings of the National Academy of Sciences of the United States of America.
Researchers estimate that, while around 447 million large trees died, around 2.5 billion smaller trees died across Brazil’s Lower Tapajós region, which they say highlights how interference by people can make the Amazon forests more vulnerable and underlines the need to reduce illegal logging and other large-scale human disturbances of forests in the Amazon.
Additionally, the study found that carbon emissions from forests burned by wildfires were almost six times higher than forests affected by drought alone.
Those regions released as much carbon emissions over a three-year period as some of the world's worst polluting countries do each year — exceeding the yearly emissions of developed countries such as the United Kingdom and Australia.
After three years, only around 37% of those emissions were reabsorbed as plants grew in the forest.
If not addressed, the cycle of releasing more carbon dioxide into the atmosphere could further advance climate change and lead to more droughts and fires, which would lead to even more carbon dioxide in the atmosphere, Berenguer noted.
“The results highlight the need for action across different scales,” Jos Barlow, principal investigator in the research, said in a statement. “Internationally, we need action to tackle climate change, which is making extreme droughts and fires more likely. At the local level, forests will suffer fewer negative consequences from fires if they are protected from degradation.”
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