Multi-scale characterization of inland valley agro-ecosystems in West Africa

Abstract

Inland valleys are defined as the upper reaches of river systems. These include valley bottoms and minor floodplains,their hydromorphic fringes and upland slopes and crests. These occupy 22-52 million ha of land in W. Africa and although of good agricultural potential are only marginally used. An agro-ecological characterization developed in the Cte d'Ivoire, is outlined on 4 levels: macro (1:1 000 000-1:5 000 000), reconnaissance (1:100 000-1:250 000), semi-detailed (1:25 000-1:50 000) and detailed (1:5000-10 000). Methods of characterization at each of these levels are discussed and examples of actual application given plus the mechanisms applied in disaggregation (scaling down) and aggregation (scaling up) between levels. This approach allows: (1) a systematic description of different inland valley agro-ecosystems; (2) identification of constraints to agricultural use; (3) targeting and implemention of research; and (4) extrapolation of research results and transfer of new technology to similar areas. Studies carried out show variation in (bio)physical and land use factors is considerable. The set of descriptors now developed allows for: (1) extrapolation of the relation between biophysical driving factors and actual land use; (2) identification of geographical areas where improved management is promising; and (3) indications on the type of improvements required.