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Droughts may turn Amazon Rainforest into major polluter, scientists warn

By David Hewitt - 11 Feb 2011 14:55:0 GMT
Droughts may turn Amazon Rainforest into major polluter, scientists warn

The days of the Amazon Rainforest acting as a natural buffer against man-made carbon emissions may be drawing to a close. In fact, not only could the South American forest soon lose its status as the planet's most-important 'carbon sink', but an increased frequency of severe droughts could transform it into a major emitter or harmful carbon emissions.

That is according to scientists working in England who have re-assessed the potential consequences of the 2005 drought seen in the Amazon Basin. It is estimated that, with low water levels causing thousands of trees to die, some five billion tonnes of carbon dioxide were released into the atmosphere over the course of the year, making the world-famous forest part of the problem of climate change rather than part of the solution.

More alarmingly, the team working at the University of Leeds has reported that, far from being a once-in-a-century event as it was claimed at the time, the 2005 drought was far from a freak occurrence. Indeed, it is now believed that even less rain fell over the 5.3 million square kilometres of the Amazon in 2010, potentially making last year's drought the worst on record. Writing up their findings in the journal Science, the researchers concede that, though rainfall levels were down in 2010, it doesn't follow that carbon emissions were up. It could be the case, for example, that the 2005 drought killed off those trees more-susceptible to water shortages.

However, if further studies do show that the number of trees that died over the course of 2010 was on a par with the number recorded for 2005, then alarm bells will certainly start to ring. Not only are dead trees incapable of soaking up carbon emissions, but they actually release greenhouse gases into the atmosphere as they rot. Since the five million tonnes of CO2 pumped out by the Amazon in 2005 places the rainforest almost level with the level of man-made emissions produced by the whole of the United States in the same year, the team have warned that should extreme droughts become more frequent, then the days of mankind being able to rely on the rainforest to soak up greenhouse gases will soon be at an end.

"Two unusual and extreme droughts occurring within a decade may largely offset the carbon absorbed by intact Amazon forests during that time," explained University of Leeds researcher and principal author of the study Dr Simon Lewis.

"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."

Notably, the air of uncertainty surrounding this area of research could serve to lessen the perceived immediacy of the problem. As the report authors note, it could be at least a couple of years before the full impact of even the 2005 drought can be known, largely as it takes time for some of the larger dead trees to start breaking down and rotting.

One thing the team, which also included scientists working in Brazil, are certain about, however, is that for this year at least, the Amazon Rainforest will be unable to absorb sufficient carbon so as to offset the ecological damage being wrought by deforestation, logging and fires. If 2011 turns out to be the first of man years in which mankind can no longer rely on Mother Nature to save it from the dangers of climate change, then a Plan B will be needed, and fast.

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