Drought puts Amazon at risk of ‘large-scale dieback’, researchers warn

Increasingly severe climatic conditions threaten to accelerate a “large-scale dieback” of the Amazon rainforest, according to the authors of a new study concluding that 2.5 billion trees have perished in the biome as a result of ‘a drought several years ago.

Central Brazil is currently reeling from the worst drought in 100 years, which has triggered water shortages and the risk of power outages. Southern parts of the world’s largest rainforest are expected to be hit by the drought wave later this year.

A joint group of British and Brazilian scientists have warned that the loss of trees caused by these periods of extreme drought can push the rainforest beyond its so-called “tipping point”, the threshold at which it can no longer sustain. its water recycling ecosystem. This would result in the death of more trees and trigger strong climatic fluctuations across Latin America.

“As droughts become more frequent and intense, this means more tree mortality and less recycled water. This could lead to large-scale wasting, ”said Erika Berenguer, a Brazilian researcher at the universities of Oxford and Lancaster.

In an eight-year study released on Monday, Berenguer’s team found that the droughts and wildfires that followed El Niño of 2015-16 killed more than 2.5 billion trees and vines. woody in the worst affected area of ​​the rainforest.

By comparison, an estimated 129 million trees have perished in California since 2010 due to droughts and wildfires, according to the US Forest Service.

According to the UK-Brazil study, the destruction of the forest resulted in nearly 500 million tonnes of carbon dioxide emissions. Tree mortality rates were also higher than expected in the three years following the drought.

“After three years, only about a third of the emissions have been reabsorbed by plant growth in the forest. This shows that the Amazon’s vital function as a carbon sink can be hampered for years after these droughts, ”the researchers said.

Scientists generally fear the Amazon may cross its “tipping point” due to man-made deforestation, which has soared under the right-wing administration of Jair Bolsonaro in Brazil. Some environmental activists also believe that the ongoing drought in the country is directly linked to increasing deforestation in the Amazon.

The rainforest has long been seen as a crucial buffer against climate change, with billions of trees acting as a giant sink for carbon emissions.

A slew of new studies, however, including one published last week in Nature, suggest that parts of the biome are now releasing more carbon than they take in as a result of deforestation and farmers using fire to clear land.

Berenguer also highlighted how the drying out of the forest makes it more vulnerable to fires started by farmers, which she says cause six times more carbon emissions than trees that are only affected by drought.

The study was carried out by collecting data on 21 plots of primary forest, regenerating secondary forest and forests that had been logged, with results extrapolated to the region.