A globally important carbon sink in the dry tropics, revealed by plots, remote sensing and data-constrained modelling

The terrestrial carbon sink has reduced atmospheric CO₂ concentrations by ~100 ppm, helping to avoid the worst impacts of global heating. The role of tropical savannas and dry forests in this sink is poorly understood, due to myriad global change drivers that increase both sinks and sources of carbon. To date, remote sensing and global models give divergent estimates of the net carbon balance, creating uncertainty in the global carbon budget. To address this, the SECO project has coordinated a global network of in situ observations and combined these with radar remote sensing to estimate the carbon balance of the dry tropics. We find the dry tropics account for ~25% of the global terrestrial carbon sink, similar in magnitude to tropical rainforests. Woody biomass stocks are increasing at ~1%/yr which implies a major shift in the ecology, biodiversity and ecosystem services provided by savannas and dry forests.