2010 was the warmest year on record and the vast drought in the Amazon rainforest is raising fears that the world's largest forest could be on the verge of a tipping point.
Scientists fear the billions of trees that died during the record drought in 2010 could mean the forest will stop absorbing greenhouse gas emissions and instead increase them.
Amazon's rainforests absorb over 25% of the world's carbon emissions - a crucial buffer against global warming. Massive tree deaths could initiate a feedback loop that causes the Amazon to switch from a vast carbon sink to a carbon source that prompts further droughts and mass tree deaths.
"Put starkly, current emissions pathways risk playing Russian roulette with the world's largest forest," said tropical forest expert Simon Lewis, at the University of Leeds, and who led the research published in Science.
Lewis notes that we can't be 100% sure that natural climatic variation didn't cause the 2005 and 2010 droughts, but "We can't just wait and see because there is no going back," he said. "We won't know we have passed the point where the Amazon turns from a sink to a source until afterwards, when it will be too late."
The droughts are coming at a time when Brazil is making progress at halting deforestation. Satellite imagery by Brazilian law enforcement teams shows that deforestation rates have been lowered dramatically. Deforestation has been cut by a factor of four between 2004-2010.
During the 2010 drought, the Amazon's largest tributary, the Rio Negro, was at its lowest level ever. The drought affected an area 60% wider, and was even a harsher dry season than experienced during 2005.
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