Dynamics in bush cover, local uses of encroaching woody plants and their preferences by foraging livestock in semi-arid rangeland in northern Tanzania

Abstract

Bush cover is high in some semi-arid African grasslands, and these woody plants have various socio-cultural uses and potential as livestock feed resources. The current study was conducted in northern Tanzania to investigate the changes in bushland cover, identify general uses of woody plants by agro-pastoral farmers, determine livestock preferences, and the nutritional values of selected plants. We determined bush cover changes from 2000 to 2022 by Google Earth Engine using the Random Forest algorithm during land cover classification. Livestock observation and participatory rural appraisal were used to sample woody plants foraged by livestock. Farmers named woody plants in a local language, listed their uses and ranked them as livestock feed. Farmer-preferred plants were analysed for nutritional values and screened for preference using goats. Bush cover had increased by 6.9–90.2% at 0.6–4.5% per year in the studied area, where 32 woody plant species were ranked and had other socio-cultural uses. These uses were medicine (78%), firewood (59%), a food source (31%) and construction (28%), with Grewia bicolor and Cordia sinensis possessing many of the uses. Farmers ranked woody plants highly as the feed if they were available all year round, readily eaten by livestock (palatable) and led to high performance. The coefficient of preference (COP) varied (p < 0.001) among goats fed the selected plants. Grewia similis (COP = 1.8) and Haplocoelum foliolosum (COP = 1.7) were highly preferred, while Combretum campestris and C. sinensis were the least preferred. There were differences in nutritional values among key woody plants, and G. similis had the highest digestibility (59%), making it a suitable species for agroforestry. Encroaching non-invasive woody plants can be used as livestock feed or serve other socio-cultural uses; their control should be informed by participatory appraisal involving locals in semi-arid areas.