The classification and mapping of environmental units, and Figures 2 and 6, were undertaken by Dr. Beryl Turner (The Green, Litton, Skipton, Yorks, England). The remaining maps were designed and drawn by Mr. J. F. Antwi (Department of Geography, Bayero University, Kano, Nigeria). The libraries of the Overseas Development Institute, London and of ILCA, Addis Ababa were made available for the author's use. In appendix 2 (Environmental Units) the size of each unit, in square kilometres, was estimated on the basis of the evidence presented in Figure 6 (A-H) by Assefa Eshete of ILCA's Resource Survey Unit.
