Effects of livestock grazing on rangeland condition, plant species richness and wild ungulate population in a semi-arid savannah

Abstract

This field study in a semi-arid savannah at Senkelle Swayne's Hartebeest Sanctuary, Ethiopia, examined livestock grazing effects on rangeland condition, plant species composition and richness, and population of the endangered Swayne's hartebeest (Alcelaphus buselaphus swaynei). Rangeland condition was analysed using a common protocol for the assessment of semi-arid rangelands. A total count method was used to estimate ungulate numbers. Grazing reduced all measures of range condition and productivity and affected the composition and richness of the herbaceous species. Grazing also induced an increase in the density and number of encroaching woody species Vachellia seyal and Senegalia senegal. The population of the Swayne's hartebeest significantly affected by livestock grazing (mean number of hartebeests observed under moderately and lightly grazed sites were 10.00 ± 2.49 and 6.75 ± 2.06, respectively). No individual hartebeest was observed roaming in the heavily grazed zone, which implies an effective reduction in the extent of habitat available for the hartebeest. The overall condition of the rangeland was poor. Measures to reduce livestock presence in areas from which the hartebeest has been displaced and controlled seasonal livestock grazing within non-sensitive parts of the Sanctuary may benefit the hartebeest. Coupled with these, livestock exclusions for up to a year and interseeding may help improve rangeland condition and hartebeest's habitat.