This comprehensive survey comprises a documentation of the climatic and geological factors and an analysis of the natural plant communities of the sahelian ecosystems. Moreover, studies of the land-use and livestock production systems, and the primary and secondary productivity of the Sahel are presented, taking into account the various physical, biological, societal, political and economic factors influencing or constricting their development. The principles, methods and possible data interpretation for the monitoring of ecosystems are discussed, supplemented by a case study in Senegal. The...