Evolution of vegetal production in Sahelian natural range lands: the case of North West Senegal in the 1990s

In the Sahel, spontaneous and post‐cultural vegetation areas are used as pasture lands for cattle. Can it be inferred from this that natural fodder and cattle undergo the same constraints and run the same risks as the vegetation cover, in particular that of being dependent of rainfall? With a view to answer this question, the distribution of vegetal production in 59 rural communities of North‐West Senegal over 8 years (1987‐1996) is analysed using a series of detailed maps established by the Dakar‐based Centre de suivi ecologique (Ecological Monitoring Centre) from remote sensing data and in situ biomass surveys. The simplified contents of these maps and the diachronic analysis of the statistic data which can be derived from them are sufficient to highlight the kinematics of these natural range lands through the time span referred to. The conclusion is that the vegetal yield of natural range lands is distributed in a very variable fashion and mainly depends on three simultaneous factors: the yearly rainfall; the North‐South rainfall gradient; and the East‐West differenciation of land use.