Broad-scale increase in NPP quantified for the African Sahel, 1982-1999

In association with a recently discovered greening trend in the Sahel, several interesting new perspectives have appeared in the literature regarding its climate and ecology. In this Letter, satellite data from 1982 to 1999 and a light use efficiency model are used to map net primary production (NPP) increases throughout the Sahel (total area of 1.13 x 10(13) m(2)). A patchy, east-west band of increasing NPP is identified, with several hotspots showing large increases. The total rate of NPP change for the Sahel is estimated to be 51.0 Mt C year(-1) over the 18-year period, yielding an absolute net gain of 918.0 Mt C. This increase is associated with a decrease in the inter-annual variability of NPP for the 1990s compared to the 1980s. These results lay the groundwork for untangling the effects of direct, localised human impact and climate forcing on land cover by conducting model intercomparison experiments, contextualizing the role the Sahel may play in the tropical carbon cycle, and for reducing the uncertainty regarding Sahelian carbon sequestration.