Spatio-temporal extension of agroforestry systems in "Guinée Forestière" (Guinea, West Africa)

"Guinée Forestière" is an administrative region located in the southern part of Guinea (West Africa). It is characterized by agro-ecological conditions suitable for most types of agricultural production typical of the low elevation humid tropics. The population is mainly rural and their livelihood depends on food crops and cash crops, cultivated in various combinations. A combination of high demographic growth rate, economic and political changes, return of displaced people, and a massive but temporary flood of refugees, has led to important land-use changes in the last decades. In terms of sustainable development of the region, one of the most exciting features is the recent dynamic extension of agroforests around most villages. We report here on this extension, that we studied in detail in Nienh (8°59'N;7°54'W, Kobela CRD) which is representative of the agro-ecological and socioeconomic conditions of most villages of "Guinée Forestière". Two main cropping systems were characterized, that both have an important tree components: (1) Coffee-based agroforests, which are the main cash income system, and (2) Elaeis parklands dedicated to rainfed rice and food crops cultivation after slash and burn, combined with 2 to 10 year fallows. The village territory was organized into concentric belts. The coffee-based agroforest makes up the first belt, directly surrounding the village. It may be subdivided into a first ring, with old coffee trees in association with Cola nitida and an upper stratum mixing various primary forest tree species, surrounded by a second ring that corresponds to a recent extension of coffee-based agroforests. This second ring differs by its younger coffee trees and its upper stratum mixing Elaeis guineensis and various heliophilous tree species. Land-use changes were quantified using a GIS analysis to compare aerial pictures from 1979 and a SPOT image from 2003. The agroforest area increased by nearly 70 % in 25 years (868 ha in 2003 versus 513 ha in 1979). This remarkable extension of the agroforest area occurred through the conversion of land under food crops and fallows into agroforests. These dynamics reveal that an increasing integration into the market economy may be achieved while increasing the ecological sustainability of the mixture of cropping systems at the village scale. (Résumé d'auteur