• ex-situ biodiversity;
  • on-farm trees;
  • species diversity


Species richness and diversity in agricultural landscapes are important characteristics of agro-ecosystems that determine their potential for biodiversity conservation. This study assessed species composition, richness, diversity and local use of on-farm trees in predominantly agricultural landscape in the Usambaras, north-eastern Tanzania. Assessments were carried out in 90 randomly selected individual farmlands. We identified 47 tree species belonging to 23 families and used by local people for various purposes. The most dominant species were Albizia gummifera (Gmel) C. A. Sm. (mkenge), Parinari excelsa Sabine ssp holstii (Engl.) R. Grah. (muula), Newtonia buchananii (Bak.) Gilb. and Bout (mkufi), Syzygium guineense (Willd) D.C. (mshihwi), Ficus capensis L. (mvumo) and Casearia engleri (Gilg) (mkokoko). These species are indigenous and were retained from existing ones during farm clearing. The species diversity (by the Simpson’s and Shannon–Wiener diversity indices of 0.07 and 2.8 respectively) is comparable with that of adjacent natural forests. There are apparently high on-farm tree species richness and diversity, the conservation of which can contribute to ex-situ biodiversity conservation. On-farm tree management should be encouraged, especially where there is population pressure on the existing natural forests. Research to enhance sustainability of the farming system is important for biodiversity management on farmlands.