Predicting the impacts of climate change on the ecological niche of Uapaca Kirkiana (Müll. Arg.) in Southern Africa

Abstract

Climate change poses a growing threat to the ecological niches of indigenous tree species across southern Africa, with significant implications for biodiversity, ecosystem function, and rural livelihoods. Uapaca kirkiana Müll. Arg. (mahobohobo/wild loquat) is a keystone indigenous fruit tree of the Miombo woodland ecosystem, providing critical food security, income, and medicinal value to millions of rural communities in Zimbabwe and across south-central Africa. Despite its ecological and socio-economic importance, quantitative, spatially explicit assessments of how climate change will affect the distribution of U. kirkiana in southern Africa particularly Zimbabwe remain limited. This study applied the Maximum Entropy (MaxEnt) species distribution modelling algorithm, implemented through the Wallace platform in R, to: (i) determine the key environmental variables driving the current potential distribution of U. kirkiana in southern Africa; (ii) project the impacts of climate change on its habitat suitability at 2070 and 2100 under SSP climate forcing scenarios; and (iii) identify conservation and management implications for Zimbabwe. Georeferenced occurrence records (n = 362) were sourced from the Global Biodiversity Information Facility (GBIF) and subjected to spatial thinning at 75 km. Nineteen bioclimatic variables from WorldClim v2.1 were used as environmental predictors. The optimal MaxEnt model (fc.H_rm.1) achieved excellent predictive performance, with a training Area Under the Curve (AUC) of 0.899 and a Continuous Boyce Index (CBI) of 0.969. Annual precipitation (BIO12), minimum temperature of the coldest month (BIO6), and precipitation seasonality (BIO15) were identified as the principal environmental drivers of the species' current distribution. Current suitable habitat was concentrated across the Miombo woodland belt spanning Zimbabwe, Zambia, Tanzania, Malawi, and Angola. Future projections revealed a progressive and accelerating southward shift in suitable habitat by 2070 and 2100, with substantial new suitable areas emerging in South Africa's interior highlands alongside some habitat loss in northern lowland areas of the current distribution. These findings highlight the urgency of protecting highland refugia in Zimbabwe, integrating U. kirkiana into national climate adaptation strategies, and investing in domestication and agroforestry programmes to safeguard the species' ecological and socio-economic contributions under a changing climate.