Woody vegetation dynamics in the rangelands of lower Omo region, southwestern Ethiopia

Woody encroachment is one of the several factors aggravating rangeland degradation in arid and semiarid areas. The goal of this study is to improve our understanding about the relationship between woody encroachment and its potential drivers by analyzing the temporal and spatial pattern of land-cover changes in the lower Omo region of southern Ethiopia. We used a combination of multi-temporal images, as well as climatic and demographic data for the analysis. Between 1985 and 2010 woody vegetation cover increased by 30.6% in the pastoral landuse type, while declining by 4.4% in the semi-pastoral areas. The increment was negatively associated with altitude and browser livestock density. However, contrary to the traditional presumption, it was not associated with grazer livestock density. Moreover, woody encroachment was higher in remote sites, farther from rivers and towns, where there is relatively lower human activities and livestock disturbance. The finding suggests the ecological significance of landuse type and livestock browsing to regulate the dynamics of woody vegetation in disturbance-adapted rangelands. Thus, a careful introduction of native larger browsers into woody encroached pastoral areas may help to facilitate rapid ecosystem recovery. (C) 2012 Elsevier Ltd. All rights reserved.