There is much debate over the effects of pastoralists and their livestock on the sustainable productivity of drier environments. Negative trends such as desertification and bush encroachment have been commonly attributed to overgrazing and/or cultivation inappropriate to pastoral systems (Charney et al, 1975; Lamprey and Yussef, 1981; Lamprey, 1983; Billé 1985; Sinclair and Fryxell, 1985; Cloudsley-Thompson, 1988). In contrast, others contend that vegetation dynamics are more attributable to rainfall fluctuations independent of human activity (Rasmusson, 1987; Ellis and Swift, 1988). One central aspect of the debate is thus defining the degree to which climate or people influence environmental trends.
The primary objective of this chapter is to review and synthesise results that pertain to the effects of the Borana pastoralists and their livestock on vegetation composition and trend, as well as those which deal with the competitive interactions among woody and herbaceous plants and aspects of seed production and germination of important woody species. A secondary objective is to review pastoral use of vegetation, including livestock feeding habits, uses of plants by households and perceptions of the Boran regarding environmental change. The third objective is to present current patterns of land use based on an ecological mapping exercise.
