Transformation des mosaïques de forêt-savane par des pratiques agroforestières en Afrique subsaharienne (Guinée et Cameroun)

A comparative analysis of the spatio-temporal evolution of mosaics of forest-savannas subject to local agricultural practices was conducted in two tropical areas (Forest Guinea, Centre of Cameroon). During the last three decades, the spatial influence of the agro-forest systems or « agroforest » associating perennial crops (cocoa, coffee ...) and sub-spontaneous vegetation, strongly increased in these two regions. In Guinea, these systems, mainly based on coffee trees, developed to the detriment of spaces formerly dedicated to annual crops (pluvial rice) in rotation with fallow trees or shrubs. But a dynamic of extension of agroforests with coffee trees in the units of savannah has begun. In the centre of Cameroon, agroforest, mainly with cocoa trees, was implanted first of all in forest relicts and forest galleries. Then, due to lack of forest reserves, the farmers innovated by developing and expanding over large areas of agroforests in the zones of savannah with grasses, traditionally devoted to food-producing annual crops. This dynamic, far from being destructive, contributes to the constitution of a « cultivated forester » ecosystem or agroforest, in regions originally dominated by the savannah and the secondary forest. Faced with these relatively recent processes, the issue of sustainability of agroforests is raised, because of the increase of demand for food therefore needs land for annual crops