Role of natural vegetation dynamics in the Sahel drought

The Sahel region in West Africa has experienced an extended drought since the late 1960s, whose root causes and persistence mechanism are still not well understood. In this study, we investigate the role of natural ecosystem dynamics in the Sahel drought using a synchronously coupled biosphere-atmospehre model. The ecosystem in our model is represented using a mosaic combination of managed landscape and natural landscape. Driven by the sea surface temperature variations from 1950 to 1997, the model is run with various senarios of human land use to investigate how the natural ecosystem dynamics have influenced the drought dynamics. Our results suggest that the natural ecosystem dynamics significantly enhance the climatic impact of anthropogenic desertification thus contributing to the drought in its early stage. However, after the late 1980s, the role of natural ecosystem dynamics is less important compared with the role of tropical Atlantic SST forcings.