CRISISBOOM

Two severe Amazon droughts have sparked fears that the rainforest’s ability to absorb carbon emissions is being diminished – and, worse still, it may soon release almost as much CO2 as the US.

A rare drought in 2005 – billed as a once-in-a-hundred-years event – was then followed by another drought in 2010 that may have been even worse, according to a study by a team of British and Brazilians scientists in the journal Science.

With a huge number of trees dying as a result of the droughts, the scientists predict that the Amazon will not be able to absorb as much carbon dioxide from the atmosphere as usual in future.

This would remove an important global buffer against pollution.

Even worse, rotting trees may release into the atmosphere as much as five billion tons of C02 in the coming years.

That would be almost as much as the 5.4 billion tons emitted from fossil fuel use by the US in 2009.

Based on the impact of the dry spell on tree deaths in 2005, the team projected that “Amazon forests will not absorb their usual 1.5 billion tons of CO2 from the atmosphere in both 2010 and 2011”, the study said.

A months-long drought has drained the mighty Negro river

In addition, “a further five billion tons of CO2 will be released to the atmosphere over the coming years once the trees that are killed by the new drought rot”.

“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 of the University of Leeds.

“We don’t know yet if the change is natural,” Dr Lewis told Sky News Online, “or if it is consistent with climate change in which case we might expect more of this in the future.

“The Amazon would then move from being a net absorber of CO2 to a net emitter of CO2.”

If the droughts are a symptom of climate change, Dr Lewis says, then “we really do need to urgently reduce our use of fossil fuels and to curb deforestation”.

Co-author Paulo Brando, a Brazilian scientist, said more research needed to be done to see how many trees died, and what their impact will be.

“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,” he said.

“These fires release large amounts of carbon to the atmosphere.

“It could be that many of the drought-susceptible trees were killed off in 2005, which would reduce the number killed last year.”