The semi-arid regions of the Earth are particularly vulnerable to wind erosion. Low annual precipitation, often combined with long periods of drought during the year, lead to a sparse herbaceous vegetation, which annual density varies from one year to another, and a sparse woody plant cover, which density can largely vary over several years. These vegetated surfaces in the Sahel have usually been dedicated to pastoral livestock, but are increasingly used for agricultural purposes. As a result, a significant proportion of the land is bare or sparsely vegetated, and thus is not efficiently protected from the erosive action of wind. In this region, wind erosion tends to decrease the productive capacity of the soils whose fertility is already very low. In addition, the impact of wind erosion is expected to increase significantly in the near future (1) in relation with the expected changes in climate (in particular the modifications of precipitation and surface wind) and (2) in response to the increasing land use due to population increase and the related food needs. The project aims to develop an integrated modeling tool to describe the evolution of wind erosion in the Sahel in connection with climatic changes and land use change, to validate this tool in the current period by making the best possible use of the numerous data sets acquired in recent years over West Africa and to test its ability to reproduce specific events (such as the drought in the Sahel) of the recent past (about the last 50 years). This project is based on a simulation approach of this recent past (hindcasts) that is justified by the need to ensure the robustness of the simulations with different forcings prior to any simulation of future scenarios.
The proposed strategy is (1) to develop / optimize / couple reliable modeling tools for quantifying the various terms (land use, changes in aridity …) responsible for changes in the intensity of wind erosion (2) to synthesize quality-checked observations for the studied period, that can be used as direct or indirect indicators of wind erosion (precipitation time series, changes in vegetation cover, atmospheric dust load …) (3) to implement a validation strategy based on the quantification of wind erosion both locally, measured on grazed and cultivated plots, and at the regional and continental scales (using proxies like the dust content of the atmosphere).