Impacts of simulated shifting cultivation on deforestation and the carbon stocks of the forests of central Africa

Abstract

Research on shifting cultivation in the tropics has focused primarily on the issues of agricultural productivity and soil degradation. Few have attempted to quantify its impact on forest losses and the carbon cycle in the context of the global change debate. A simulation, which incorporated historic and projected rural population growth, was conducted to investigate the impacts of shifting cultivation on deforestation and the carbon stocks of the humid tropical forests of central Africa. The study demonstrated that in 1950, the central African forest region subjected to shifting cultivation was composed of 92% forest (including primary and secondary forests) and that in 1990 the forest cover had been reduced to 80% of the total simulated land area. The results of the simulation showed that with the current level of technology and consumptive habitats, shifting cultivation under projected rates of rural population growth would increase the annual rate of deforestation to 1.3%, converting 94% of the land area into cropland, fallow and secondary forests by 2050. At that time, only 40% of the potential above-ground biomass carbon (i.e., assuming all the simulated area is occupied by dense forests) will remain, compared to 85 and 74% in 1950 and 1990, respectively. The simulation suggests that there is a need for alternatives to shifting cultivation such as integration of cultivation intensification, fallow management and agroforestry if population pressure on the tropical forests of central Africa is to be alleviated. This preliminary regional study shows that modeling could provide an important tool to explore alternative scenarios of land use and to assist decision makers with forest management.