Human migration, climate variability, and land degradation: hotspots of socio-ecological pressure in Ethiopia

In Ethiopia, human migration is known to be influenced by environmental change-and vice versa. Thus, degradation of environmental conditions can contribute to out-migration, and in-migration can cause environmental changes at the immigrants' destination. The aim of our study was to systematically identify regions in which socio-ecological pressures can arise from high population densities, migration, land degradation, and/or rainfall variability. We combined population census data at the district level with high-resolution remote sensing data regarding rainfall variability, land degradation, and land cover. We identified districts in which high population density is coupled with both a steep decline in net primary production (NPP) and large precipitation variability. The affected regions are mainly cropping regions located in the northern highlands and in the central part of the Great Rift Valley. We consider these regions to be particularly prone to environmental changes; moreover, high population density places additional stress on local natural resources. Next, we identified districts in which high in-migration is coupled with both a strong decline in NPP and low rainfall variability, proposing that land degradation in these regions is likely to have resulted from human activity rather than climatic factors. The affected regions include parts of the Awash Valley, regions surrounding Lake Tana, and the mountainous regions between Addis Ababa, Bedele, and Jima. We found these hotspots of in-migration and land degradation are dominantly grasslands regions, which have been characterized by significant cropland expansion during the period studied. Whereas exploring causal relationships between migration, environmental change, and land cover change is beyond the scope of our study, we have pinpointed regions where these processes coincide. Our findings suggest that at the regional scale, deteriorating environmental conditions can be both the cause and the effect of migration.