More woody plants? The status of bush encroachment in Botswana's grazing areas.
This paper presents a compilation of various information into a single model summarizing the wider issues related to the origin and distribution of bush encroachment in semiarid rangeland in Botswana. Generally, this study determines the nature and distribution of bush encroached browse in a predominately cattle economy such as Botswana. The origin and the present status of bush encroachment in the country are discussed. Evidence from the literature and work within Botswana suggests that bush encroachment takes place as a result of the exclusive use of moisture by encroachers, high soil nutrient concentrations, low fire frequencies and high cattle selectivity. Bush encroachment species, viz., Acacia tortilis, A. erubescens, A. mellifera, Dichrostachys cinerea, Grewia flava, Euclea undulata, Maytenus heteroplylla and Terminalia sericea, tend to increase the cover and density around foci points (e.g. boreholes, wells, kraals, and to some extent settlements) at the expense of the grass cover and composition.