Résumé
This paper will discuss the concepts of resilience and social-ecological system, applied to Sahelian pastoralist's societies, proceeding with an analysis of pastoral mobility as a "total social fact". Sahelian pastoralists live and keep their herds at multiple time scales : seasonal and intra-seasonal pasture prospection, weekly rotation of markets, religious slaughter based on lunar calendar, heavy annual rainfall variability (30% on average), historical transformation of the territories they use, multi-year drought, and the decennial history of development interventions, from state enterprises to local and international projects, through decentralized cooperation. The flexibility of their mobility patterns and systems of activities allowed pastoralists to resist and cope with evolving changes, constraints and uncertainties. Access to different and complementary ecosystems guarantees "functional integrity" to pastoral systems as well as the plasticity of the activities enables pastoral societies to withstand crisis relatively better than other rural professional groups. Mobility is not just technical, it's multidimensional (zoo-technical, economic, social, political, cultural), it's a "total social fact". Science sometimes tends to simplify this complexity : thus, the concept of socio-ecological system, assuming a social group confined in "his" ecosystem, is challenged by the pastoral mobility, which is based on the complementarities and rhythms of areas. In the same way, the notion of resilience, supposed to describe the capacity of systems to adapt and persist on the long term, paradoxically fail to analyze processes of change. In northern Senegal, pastoral systems have experienced deep social, territorial and environmental changes. Behind the "resilience of pastoral systems," the pastoralists themselves, their social relations related to land and livestock, their technical and economic issues and even their cattle have changed. What then could be the scope of this concept in the social sphere? From a strictly functional point of view, systems resist and adapt : most likely pastoralists and herds will continue to dwell in the Sahel for long time. But how many ? What would their livelihood be based on? Under what conditions ? Producing what, in which ecosystem(s) ? How insuring the transmission of knowledge and properties ? It is a development issue to admit that the concept of resilience does not allow to take into account dynamics of change, transformation and failure of societies, nor their universal issues (living in dignity, producing, reproducing, maintaining, transmitting...). Without defining the scope and the limits of these concepts, the risk is to compromise the living balances, complex and evolving, with dogmatic interventions (specialization of activities, functions of the herds, segmentation of spaces and ecosystems ...). The first part of the paper will present the main changes around and within the pastoral society in Ferlo and how the pastoralists manage natural resources and social relations. The second part will focus on the creation of a local dairy market as an indicator of current dynamics of change in the pastoral system. In the last part the authors will attempt to clarify to what extent the concepts of socio ecological system and resilience are useful for understanding sustainability and change. (Texte intégral)