Usable wild plant species in relation to elevation and land use at Mount Kilimanjaro, Tanzania

We used the broad elevational gradient of Kilimanjaro ranging from warm tropical lowland to cold Afro-alpine temperature regimes and the occurrence of natural, nearly untouched as well as of anthropogenic and heavily disturbed habitats to study how elevation and disturbance by humans affect the proportion of useful plant species in different habitat types. Of the 962 vascular plant species recorded in our 60 study plots, 563 species turned out to be listed as useful in the literature. We classified these species into six usage categories. With linear models we tested for relationships between the proportion of useful species per plot and elevation for natural habitats, and with analysis of variance we compared the proportion of useful species between plots in disturbed and natural habitats at similar elevation. The proportion of useful species for all usage categories increased from 860 to 2500 m asl and decreased with higher elevation. We also found an overall positive correlation between the number of useful plants and the species richness of our plots. Human-influenced habitats had higher proportions of useful species for all usage categories, except for construction and fuel wood usage which were higher in natural savanna and lower montane forest than in used habitats at these elevations. Given the high proportions of useful species, we conclude that preserving the biodiversity of Kilimanjaro ecosystems is indispensable for maintaining the diversity of useful plants species for the local people who rely on it for food, sustainable access to medicinal, fuel, construction and forage material.