A dynamic simulation model of land-use changes in Sudano-sahelian countries of Africa (SALU)

This paper presents a simulation model to project land-cover changes at a n ational scale for Sudano-sahelian countries. The aim of this study is to be tter understand the driving forces of land-use change and to reconstruct pa st changes. The structure of our model is heavily determined by its spatial ly aggregated level. This model represents, in a dynamic way, a simplified version of our current understanding of the processes of land-use change in the Sudano-sahelian region of Africa. For any given year, the land demand is calculated under the assumption that there should be an equilibrium betw een the production and consumption of basic resources derived from differen t land-uses. The exogenous variables of the model are human population (rur al and urban), livestock, rainfall and cereals imports. The output are the areas allocated to fuelwood extraction, crops, fallow and pasture for every year. Pressure indicators are also generated endogenously by the model (ra te of overgrazing and land degradation, labour productivity, average househ old "budget"). The parameters of the model were derived on the basis of a c omprehensive review of the literature, mostly of local scale case studies o f land-use changes in the Sahel. In agreement with farming system research, the model simulates two processes of land-use change: agricultural expansi on at the most extensive technological level, followed by agricultural inte nsification once some land threshold is reached. The model was first tested at a national scale using data from Burkina Faso. Results simulate land-us e changes at two time frequencies: high frequency, as driven by climatic va riability, and low frequency, as driven by demographic trends. The rates of cropland expansion predicted by the model are consistent with rates measur ed for several case studies, based on fine spatial resolution remote sensin g data. (C) 2001 Elsevier Science B.V. All rights reserved.