Mapping cropland evolution based on biophysical data and cropping history in the Borana rangelands, Southern Ethiopia

Many smallholder farmers grow crops using low-intensity management in the different rangelands of Eastern Africa. This crop cultivation also substantially contributes to the income of farmers. However, the extent of cropland expansion, the driving factors and the impacts have not been mapped on smaller scales. We obtained this information by interviewing farmers in the Borana rangeland who started cultivating in 1984-2014, and we demarcated samples of crop fields acquired using a handheld global positioning system (GPS) data collector device. We integrated layers of soil type, drainage, slope and elevation data into a Geographical Information System (GIS) to determine how and why cropland expansion changed over time. An overlay and surface analyses showed that farmers converted low-lying wet areas in the Borana rangeland into cropland fields. We detected that cropland expansion has since been possible because of the flat elevation, gentle slopes and moist soils along the seasonal river valley. Cropland expansion in low-lying wet areas of the rangelands contributes to the reduction of dry-season grazing reserves and forage availability for livestock. If the impacts of cropland expansion are to be minimized, rangeland managers must identify the land cover prone to degradation and revise pastoral land use plan. While this study focused on the Borana rangeland, the methodology is vigorous and generic enough to allow analysing retrospective changes in cropland expansion in other regions. In future studies, integrating information about wood density would increase the diagnostic power of this method.