|LIAO, CHAUN - University Of Michigan|
|DEGLORIA, STEPHEN - Cornell University|
Submitted to: Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/18/2018
Publication Date: 10/26/2018
Citation: Liao, C., Clark, P.E., DeGloria, S.D. 2018. Bush encroachment dynamics and rangeland management implications in southern Ethiopia. Ecology and Evolution. 8(23):11694-11703. https://doi.org/10.1002/ece3.4621.
Interpretive Summary: Pastoralism, the principal agricultural livelihood in the Horn of Africa, is severely threatened by bush or woody plant encroachment into rangelands which livestock herds depend on as critical sources of forage. A new, innovative approach, based on the State-and-Transition ecological succession model, was developed for mapping current bush encroachment extents and predicting the trajectories of future encroachment in the Borana Zone of southern Ethiopia. Findings indicate nearly 80% of this pastoral landscape is now suffering from bush encroachment; stabilized encroached vegetation states have persisted across 70% of the landscape for more than a decade now; and predicted changes in climate, accelerating human population growth, and consequent increases in rangeland stocking rates all favor continued encroachment and decline in the sustainability of pastoral livelihoods. Well targeted and spatially explicit bush management actions are urgently needed to reverse the trend of bush encroachment in priority areas where this is still ecologically possible and economically practical.
Technical Abstract: Rangelands in the Horn of Africa have been undergoing a rapid shift from herbaceous to woody plant dominance in the past decades, threatening subsistence livestock herding and pastoral food security. Despite of significant rangeland management implications, quantification of the spatial extent of encroachment and the transitional pathways that result in encroachment remain largely unexplored. This paper develops a phenology-based approach to map rangeland vegetation states in the Borana Zone of Ethiopia, and examines potential transition pathways among states using the state-and-transition model. The results indicate that over 70% of landscape remained in the same vegetation classes from 2003 to 2013, and nearly 80% of landscape was dominated by woody plants in 2013. Stable encroached states have been established in both high and low lands by following different transition pathways. Our research findings suggest spatially explicit strategies to reduce the woody plant layer and reverse the trend of bush encroachment.