Amazon may become greenhouse gas emitter
Rain forest could go from sink to source
By Devin Powell
Web edition : Monday, January 23rd, 2012
In the struggle against global warming, the Amazon rain forest may be about to switch sides.
Its dense vegetation has long helped cool the planet by removing carbon dioxide from the atmosphere. But mass tree deaths brought about by recent droughts and deforestation may be pushing the region to a point at which it will give off more of the greenhouse gas than it absorbs.
“The Amazon might still be a sink for carbon, but if it is it’s definitely moving towards being a source,” says Eric Davidson, director of the Woods Hole Research Center in Falmouth, Mass. Reporting in the Jan. 19 Nature, Davidson and 14 other researchers from the United States and Brazil weigh evidence that the world’s largest rain forest has become increasingly vulnerable to change.
Thanks to regular measurements of 100,000 trees, scientists estimate that the Amazon was sucking up about 1.5 billion tons of carbon dioxide annually at the turn of the century. Plants absorb the gas during photosynthesis, storing the carbon component as leaves, wood and roots and injecting it into the soil. The entire rain forest is thought to contain about 100 billion tons of carbon, equivalent to 10 years of global CO2 emissions from burning fossil fuels.