A free-air CO2 enrichment (FACE) experiment assessing the effects of increased atmospheric CO2 on the ecology and resilience of the Amazon forest is proposed for a primary, old-growth forest in the Amazon basin. The experiment will simulate the atmospheric CO2 composition of the future in order to help answer the question: “How will rising atmospheric CO2 affect the resilience of the Amazon forest, the biodiversity it harbors, and the ecosystem services it provides?”

One of the top-priority questions in global change research currently is whether the results found in the temperate forest FACE experiments are valid (or representative) also in tropical forests or not. Such a kind of experiment has never been implemented in a tropical forest (Fig. 1).


Results from dynamic vegetation modeling indicate that the effects of elevated CO2 on net primary productivity would be more pronounced in tropical forests compared to temperate forests. This finding is corroborated, at least partially, by long-term biomass inventories: the global rise in atmospheric CO2 is currently suggested as the explanation for the increase in recruitment and growth rates of vegetation in the forests of the Amazon and central Africa in the last 3 decades. The Amazon-FACE experiment may help elucidate these and other hypotheses (Fig. 2).

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Some specific points make a FACE experiment in Amazonia even more relevant. Climate change projections in the Amazon vary considerably, with an extreme scenario projecting an increase of more than 6° C and pronounced rainfall decline in much of the region. These climatic changes will certainly represent an additional pressure on the Amazon system, upon which the effect of CO2 fertilization can have a buffering effect (Fig. 3).

The project is a multi-institutional effort to implement the experiment and improve our knowledge on the future of the Amazon forests in light of the climatic change in course on our planet. The Amazon-FACE experiment will be a flagship scientific endeavor that will stimulate the scientific empowerment of research institutions in Brazil as well as strengthen cooperation with US and European research groups in the science of carbon cycle, ecosystem function and ecosystem-climate interactions in the Amazon.