In 2005 and 2010 the Amazon basin experienced two strong droughts, driven by shifts in the tropical hydrological regime possibly associated with global climate change, as predicted by some global models. Tree mortality increased after the 2005 drought, and regional atmospheric inversion modelling showed basin-wide decreases in CO2 uptake in 2010 compared with 2011. But the response of tropical forest carbon cycling to these droughts is not fully understood and there has been no detailed multi-site investigation in situ.

Interannual variations in CO2 exchange across Amazonia, as deduced from atmospheric inversions, correlate with El Nino occurrence. They are thought to result from changes in net ecosystemexchange and fire incidence that are both related to drought intensity. Alterations to net ecosystemproduction (NEP) are caused by changes in gross primary production (GPP) and ecosystemrespiration (Reco ).