AmazonFACE: Current status and scientific objectives of the large-scale Free Air CO2 Enrichment Experiment in the Amazon rainforest

The AmazonFACE experiment is a large-scale Free-Air CO₂ Enrichment (FACE) experiment designed to assess the responses of Amazonian tropical rainforests to elevated atmospheric carbon dioxide concentrations. As the world’s first FACE experiment in a mature tropical forest, AmazonFACE addresses a critical gap in our understanding of how these ecosystems will function under future climate conditions. The primary objective is to quantify the impacts of elevated atmospheric CO₂ concentration on forest carbon cycling, productivity, nutrient dynamics, biodiversity, and ecosystem resilience. The experiment is currently in the construction phase, with infrastructure installation, site preparation, and system testing actively underway. In parallel, extensive baseline measurements of atmospheric, ecological, and biogeochemical variables are being conducted to characterize pre-treatment conditions. Recent years have seen a growing body of scientific publications, technical reports, and outreach materials that document the experimental design, methodological challenges, and expected research outcomes, and the importance of AmazonFACE for policy making. These contributions highlight the complexity of operating FACE technology in remote tropical environments and the innovative solutions being developed. Once operational, AmazonFACE will enable the assessment of ecosystem responses to elevated CO₂ under realistic field conditions. The data generated are expected to substantially improve Earth system models and projections of the global carbon cycle. Overall, AmazonFACE represents a major international research effort with far-reaching implications for climate change science and tropical forest management.