1. Yabello Pastoral and Dryland Agriculture Research Centre, P.O. Box 85, Yabello, Ethiopia
2. Department of Agroecology in the Tropics and Subtropics, University of Hohenheim, Garbenstr. 13, University of Hohenheim, 70599 Stuttgart, Germany
3. Department of Agricultural and Resource Economics in the College of Agricultural Sciences, Colorado State University, USA
4. Nelson Mandela African Institution of Science and Technology, Arusha, Tanzania