2010 Drought in the Amazon Basin. Rivers of the Amazon Basin face severe drought. © Rodrigo Baléia / Greenpeace

Contact: Hannah Isom, h.isom@leeds.ac.uk, University of Leeds
3 Feb 2011

(University of Leeds) New research shows that the 2010 Amazon drought may have been even more devastating to the region's rainforests than the unusual 2005 drought, which was previously billed as a one-in-100 year event.

Analyses of rainfall across 5.3 million square kilometres of Amazonia during the 2010 dry season, published tomorrow in Science, shows that the drought was more widespread and severe than in 2005. The UK-Brazilian team also calculate 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. For context, the United States emitted 5.4 billion tonnes of CO2 from fossil fuel use in 2009.

The authors suggest 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.

Lead author Dr Simon Lewis, from the University of Leeds, said: "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."

The Amazon rainforest covers an area approximately 25 times the size of the UK. University of Leeds scientists have previously shown that in a normal year intact forests absorb approximately 1.5 billion tonnes of CO2 (1). This counter-balances the emissions from deforestation, logging and fire across the Amazon and has helped slow down climate change in recent decades.

In 2005, the region was struck by a rare drought which 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 unusual drought, affecting south-western Amazonia, was described by scientists at the time as a 'one-in-100-year event' (2), but just five years later the region was struck by a similar extreme drought that caused the Rio Negro tributary of the Amazon river to fall to its lowest level on record. …

Dr Lewis added: "Two unusual and extreme droughts occurring within a decade may largely offset the carbon absorbed by intact Amazon forests during that time. 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. …

2 severe Amazon droughts in 5 years alarms scientists



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