1. Department of Agriculture and Animal Health, College of Agriculture and Environmental Sciences, University of South Africa, Private Bag X6, Florida 1710, South Africa
2. Agricultural Research Council-Natural Resources and Engineering, Private Bag X79, Pretoria 0001, South Africa
3. Risks and Vulnerability Assessment Centre, University of Limpopo, Private Bag X1106, Sovenga 0727, South Africa
4. Arid Land Research Center, Tottori University, 1390 Hamasaka, Tottori 680-0001, Japan