Nature 509, 86–90 (2014)

Tropical forests are globally important for biodiversity and have the potential to modulate climatic changes through feedbacks to the climate system. Central African tropical forests — the second largest forests globally after those of South America — are experiencing a long-term drying trend but the large-scale ecological response remains poorly studied.

To overcome the paucity of on-the-ground observations, Liming Zhou from the State University of New York, and co-workers, use satellite-based measurements (optical, thermal, microwave and gravity) to detect vegetative changes over the Congo Basin. They find a widespread trend — over the past decade — towards declining forest greenness along with decreases in rainfall and terrestrial water storage. Together, these results are consistent with reductions in water content in aboveground wood and leaves, and changes in the structure and moisture of the upper forest layers — findings that indicate Central African forests may be sensitive to chronic drought.