To date, there is no consensus on optimal stocking rates in the semi-arid Sahel. We develop a model for livestock management based on a detailed analysis of ecosystem dynamics, and we apply it to calculate optimal and sustainable livestock stocking rates in a Sahelian rangeland. The general model accounts for stochastic rainfall and the long-term impact of grazing on rangeland productivity. For the case study area, the model shows that the optimal stocking rate is higher than the sustainable stocking rate. Hence, with current prices, it is optimal for the pastoralist society to deplete their resource base. In our case study, we also find that the current stocking rate exceeds the optimal stocking rate, which adds to soil depletion.