The drought in the Amazon last year was worse than the "drought of the century" in 2005, and may have had on global warming a bigger impact than the United States produce in one year, Brazilian and British scientists said on Thursday.
Increased frequency of droughts as the 2005 and 2010 threatens to turn the world's largest tropical forest into a source of greenhouse gases, rather than a sponge that absorbs, accelerating global warming. This is because the trees that normally absorb carbon dioxide as they grow, helping cool the planet, releasing these gases when they die and rot.
"If such events occur more frequently, the Amazon forest would reach a point where, from a valuable store of carbon, reducing the speed of climate change, to a large source of greenhouse gases, which could accelerate the warming," Simon Lewis said the author, an ecologist at the University of Leeds (Britain).
The study, published in the journal Science, shows that last year's drought caused a reduction of rainfall in an area of 3 million square kilometers of forest - far more than 1.9 million square miles affected in 2005.
In addition to broader, the drought of 2010 was also more intense, causing increased tree mortality, and with three major epicenters. The 2005 drought was focused mainly in southwestern Amazonia.
Because of this, the study said, Amazon will no longer absorb at 2010 and 2011 its usual volume of 1.5 billion tons of carbon dioxide from the atmosphere. Moreover, the dead and dying trees will release 5 billion tons of gas over the next year, which causes the cumulative impact will reach 8 billion tons.
In 2009, for comparison, the U.S. emitted 5.4 billion tons of carbon dioxide by using fossil fuels
Emissions caused by two droughts were probably sufficient to cancel all of the carbon absorbed by forests in the last ten years, the study said.