Land-use and land-cover dynamics in response to changes in climatic, biological and socio-political forces: the case of southwestern Ethiopia

Few studies of land-use/land-cover change provide an integrated assessment of the driving forces and consequences of that change, particularly in Afri ca. Our objectives were to determine how driving forces at different scales change over time, how these forces affect the dynamics and patterns of lan d use/land cover, and how land-use/land-cover change affects ecological pro perties at the landscape scale. To accomplish these objectives, we first de veloped a way to identify the causes and consequences of change at a landsc ape scale by integrating tools from ecology and the social sciences and the n applied these methods to a case study in Ghibe Valley, southwestern Ethio pia. Maps of land-use/land-cover change were created from aerial photograph y and Landsat TM imagery for the period, 1957-1993. A method called 'ecolog ical time lines' was developed to elicit landscape-scale explanations for c hanges from long-term residents. Cropland expanded at twice the speed recen tly (1987-1993) than two decades ago (1957-1973), but also contracted rapid ly between 1973-1987. Rapid land-use/land cover change was caused by the co mbined effects of drought and migration, changes in settlement and land ten ure policy, and changes in the severity of the livestock disease, trypanoso mosis, which is transmitted by the tsetse fly. The scale of the causes and consequences of land-use/land-cover change varied from local to sub-nationa l (regional) to international and the links between causes and consequences crossed scales. At the landscape scale, each cause affected the location a nd pattern of land use/land cover differently. The contraction of cropland increased grass biomass and cover, woody plant cover, the frequency and ext ent of savanna burning, and the abundance of wildlife. With recent control of the tsetse fly, these ecological changes are being reversed. These compl ex patterns are discussed in the context of scaling issues and current conc eptual models of land-use/land-cover change.