Modelling land-use dynamics in Western Sahel since 1960

Climate change and demographic growth are particularly acute in the Sahel, jeopardizing the sustainability of human land-uses. This call for research to provide relevant outputs to support policy-making in this area, especially in terms of land management and land degradation. In the Sahel, detailed observations of land use dynamics and drivers are scarce and existing global land-use models have difficulty representing it. One regional model has been developed by Stephenne and Lambin (2001) to fit the regional characteristics of Sahelian land use (SALU).

This communication explains how we adapted this model to the current state of the art to reconstruct past land-use dynamics in Senegal from 1961 to 2020. For that purpose, we warried out an extensive bibliographic search to obtain the most updated ranges for parameter values. We performed an in-depth analysis of the model's sensitivity to parameter uncertainties through delta-indices calculation. When applying the new model at national scale to Senegal, the so-obtained trends were consistent with available literature, exhibiting first agricultural expansion leading to deforestation, and then a switch to intensification in the mid-1990s, which affected both livestock forage consumption and fallow duration.

Finally, we apply the new model to a sub-region of Senegal: the Groundnut basin, that concentrates a large proportion of the national land-demand. This case-study showed the limits of the model when downscaling, as these demands were too high to be satisfied by the local production. This study thus opens perspectives for the refinement of landuse modelling in the Sahel, including for prospective scenarios addressing the future decades.