Paysages forestiers et agro‐forestiers en changement dans la partie septentrionale des Rivières du Sud (Afrique de l'Ouest)

The West African littoral strip between the Delta of Sine-Saloum and the Rio Mansoa corresponds to the transition from sudanese to guinean domains. Three criteria differentiate the wooded landscapes in this area : latitudinal climatic gradient, alternate occurrences of low plateaux and tidal mud flats, numerous practises of local rural societies. This paper aims to put the stress on the effects of rainfall fluctuations on vegetation within its three dimensions: phenology, flora and landscape. West African forests and agriforests have been notably changing for the last decades. These changes have hardly touched the botanical composition of vegetation, although such a statement would need complementary studies. Phenology studied through normalized vegetation index time series and vegetation land-cover studied through multispectral images has shown important changes. The study of a few village territories help us reconstruct landscape trajectories : the sequence of very dry years during the 1968-1994 period often played the part of activating factor, but social ans economical changes have been the decisive factor in deeply modifying the practises. This cannot be a priori interpreted in the negative way of a degradation of the vegetal cover.