Washington, Feb 4 (ANI): A new study has revealed that two severe and unexpected droughts in the Amazon basin in just five years have devastated the region's rainforests, and could make global warming worse.
Scientists from the UK and Brazil have calculated that the last year's drought was more widespread and severe than the 'one-in-100-year' drought of 2005.
The team, who analysed rainfall across 5.3 million sq km of Amazonia during the 2010 dry season, also found that the carbon impact of the 2010 drought may eventually exceed the 5 billion tonnes of CO2 released following the 2005 event, as severe droughts kill rainforest trees.
They suggested that if extreme droughts like these become more frequent, the days of the Amazon rainforest acting as a natural buffer to man-made carbon emissions may be numbered.
"Having two events of this magnitude in such close succession is extremely unusual, but is unfortunately consistent with those climate models that project a grim future for Amazonia," said lead author Simon Lewis from the University of Leeds.
In 2005, the region was struck by a rare drought that killed trees within the rainforest. On the ground monitoring showed that these forests stopped absorbing CO2 from the atmosphere, and as the dead trees rotted they released CO2 to the atmosphere.
The new research, co-led by Lewis and Brazilian scientist Paulo Brando, used the known relationship between drought intensity in 2005 and tree deaths to estimate the impact of the 2010 drought.
They predict that Amazon forests will not absorb their usual 1.5 billion tonnes of CO2 from the atmosphere in both 2010 and 2011, and that a further 5 billion tonnes of CO2 will be released to the atmosphere over the coming years once the trees that are killed by the new drought rot.
"Our results should be seen as an initial estimate. The emissions estimates do not include those from forest fires, which spread over extensive areas of the Amazon during hot and dry years. These fires release large amounts of carbon to the atmosphere," said Brando.
Some global climate models suggest that Amazon droughts like these will become more frequent in future as a result of greenhouse gas emissions.
"If events like this happen more often, the Amazon rainforest would reach a point where it shifts from being a valuable carbon sink slowing climate change, to a major source of greenhouse gasses that could speed it up," said Lewis.
The study will be published in Science. (ANI)