The impact of changes in land-use patterns and rainfall variability on range condition and pastoral livelihoods in the Borana rangelands of southern Oromia, Ethiopia

Abstract

This study was conducted in the Borana rangelands, southern Oromia, Ethiopia with the aim of investigating land-use/cover changes, rangeland condition and indentifying major change drivers in the rangelands. Satellite image scenes, ground survey and people’s perceptions were assessed to identify changes on herbaceous and woody species composition. Ordination techniques were used for correlation of grass and woody species into environmental variables. Piospheric effects on vegetation composition around patch resources were also examined. These assessments were designed to bring out both spatial and seasonal variation in vegetation parameters. Rangeland condition was determined using the ecological index (EIM) and the weighted palatability composition (WPC) methods. Grazing capacity assessment was largely based on rain-use efficiency, range condition, density of woody plants. Woody cover in the Borana increased from 11.3% in the 1970s to 49.26% in 2000s, while, grassland cover declined from 58% to 32% during the same period. The cultivated/built up area also increased gradually over the years though the extent of increment was less compared to the woody cover changes. The calculated NDVI values for the 2000s were low relative to the 1970s. Ground survey results demonstrated that herbaceous biomass production and woody plant density varied significantly (P < 0.01) for the different sites in Borana. Nevertheless, herbaceous plant diversity and evenness did not differ significantly (P>0.05) across the different sites and around patch resource areas. This confirms the resilience of the Borana rangeland to the effects of grazing pressure and climatic variability. Overall, the density of woody plants varied from moderate to sever encroachment, which corresponds to the rangeland condition classes from very poor to fair. The results of the present study showed that the nutrient contents of herbaceous plants (CP, NDF, ADF, ADL and ash) were greatly influenced by species, stage of maturity, site and season. Herbaceous species with high crude protein content based on laboratory results were also ranked as the top important species by the pastoralists. Similarly, herbaceous forage species with a high structural fiber were considered inferior. Pastoralists’ knowledge and laboratory results on the nutritive value of key herbaceous species complemented each other. The stocking density of livestock units was higher than the grazing capacity for the Borana rangelands. Stocking density for the Borana rangeland using rain-use efficiency was 1.43 ha/TLU. There was no significant difference in the grazing capacity across the different sites in the study area under the existing management. The majority of pastoralists believed that the rangelands in Borana have been degraded, as consequence of recurrent drought (83%), population pressure (65%), poor management and inappropriate government policy (38%). The majority of the respondents (94%) also asserted that the traditional coping mechanisms of Borana pastoralists have declined. There is therefore a need for designing appropriate pastoral land-use policies that fit the ecological potential of the region to ensure sustainable ecosystem functioning. We suggest a comprehensive and adaptive range management for the implementation of appropriate land-use systems for the different livestock species. There is need to adjust stocking rates based on seasonal availability of forage. This would foster economic feasibility and ecological sustainability of the Borana pastoral production system.