A coupled human–environment model for desertification simulation and impact studies

This paper presents the development of a system dynamic model to simulate and analyze desertification. The human–environment coupled model integrates socio-economic drivers with bio-physical drivers of biomass production, land degradation and desertification. It is based on the UN and GEF definitions of desertification. It illustrates the concept of desertification through differential equation and simulation output graphics. It is supplemented with a causal loop diagram demonstrating the existing feed-back mechanisms. The model relates population pressure and dynamics over time to the growth and availability of biomass resources. The human population stock is described as a function of growth rate, death rate and resources dependent in and out migration of people. The relative growth rate of the stock of resources is modeled as a function of climate and exploitation pressure affecting soil erosion and water availability. The model is applied for the Sahelian desertification syndrome using input data to illustrate and simulate a 150 years period (1900–2050) in Kordofan, Sudan. The model indicates that it is difficult to generate irreversible desertification