Amazon out of breath

The rivers of the Amazon basin are recycling carbon dioxide far more quickly than environmental scientists realized, according to the latest radiocarbon dating study, using both carbon-13 and -14, reported in Nature. The reports shows that most of the carbon being "exhaled" - or outgassed - as carbon dioxide from Amazonian rivers and wetlands has spent just five years sequestered in the trees, other plants and soils of the region. Emilio Mayorga of the University of Washington and colleagues suggest that their finding is rather surprising because earlier measurements showed carbon in the rivers that has come from surrounding forest to be anywhere from 40 to more than a thousand years old. The new lower limit on this range suggests that the Amazon basin is not the long-term carbon sink scientists had hoped, which could be bad news for global chemistry and the environment.