Published today online in Nature is a study authored by nearly 100 people who have been studying the Amazon (approximate size = 3 000 000 000 trees) across the last 30 years. In the last 10 years the amount of carbon dioxide [ CO2 ] being sequestered has decreased about 30% according to their work "Long-term decline of the Amazon carbon sink".
500 people at 300 sites across 8 countries monitored trees from 1983 through 2011 to get these results. Now ask if the same processes are at work in other tropical rain-forests of the world. Some people think [CO2]-induced stimulation of tree growth increases the dynamism of the forests. Others conclude that the widespread assumption of a CO2-induced stimulation of tropical tree growth may not be valid.
Is there underway a profound reorganization of tropical forest ecosystems? If so, what is driving it? Besides increasing atmospheric CO2 concentrations, other potential widespread drivers of environmental change have been identified: temperature, precipitation, solar radiation, climatic extremes (including El Niño Southern Oscillation events), nutrient deposition, O3/acid depositions, hunting, land–use change and increasing liana numbers (by which I mean more woody long-stemmed vines that displace trees thus reducing forests’ overall ability to store carbon). Which of these may contribute to increased tree mortality as one of the environmental changes that can account for a recent decrease in CO2 sequestration?