Biogeochemistry: signs of saturation in the tropical carbon sink.

Abstract

The carbon sink in the land biosphere has grown during the past 30 years, taking up much of the carbon dioxide produced by human activities. The first signs of this growth levelling off have been spotted in Amazon forests. See Letter p.344 The Amazon is a globally important carbon sink, with tree growth incorporating carbon dioxide from the atmosphere. This paper suggests that the capacity of Amazonian forests to sequester carbon has weakened, with potentially important implications for climate change. Using on-the-ground measurements from a network of more than 300 long-term monitoring plots across the region, Roel Brienen and colleagues show that the rates of net increase in above-ground biomass have declined by a third during the past decade compared to the 1990s as a consequence of growth rate increases levelling off. At the same time biomass mortality persistently increased.