Modelling and Mapping Habitat Suitability for B. aegyptiaca (L.) Del. and B. rotundifolia (Tiegh.) Blatt. under Climate Change in Ethiopia

Abstract

Climate change impacts are posing greater risks to biodiversity, food security, and livelihood in Africa, specifically in arid and semi-arid environments. In Ethiopia, the genus Balanites Del., which belongs to the monogeneric family called Balanitaceae, has the multipurpose B. aegyptiaca and B. rotundifolia. However, these species are overlooked and endangered by climate change, and their species distributions are not well documented and understood in Ethiopia. Therefore, this study aimed to model the habitat suitability of these two species using current occurrence data, climate, and landscape data and predict their distribution under climate change. Occurrence points of B. aegyptiaca (n = 224) and B. rotundifolia (n = 80) were collected from field surveys and herbarium. Bioclimatic (WorldClim.v2), soil, and landscape variables were used in the ensemble species distribution models (SDMs) using six algorithms (GLM, GAM, BRT, RF, MARS, and SVM). The ensemble SDMs under the current climate showed that the Central Ethiopian Rift Valley is highly suitable habitats for B. aegyptiaca accounting for an area of 114,517 km2, and the Southern Ethiopian Rift Valley is highly suitable habitats for B. rotundifolia accounting for an area of 41,373 km2. The performance of ensemble SDM under the current climate for B. aegyptiaca showed 0.95 AUC, 0.80 TSS, 0.79 COR, and 0.87 deviance; and that of B. rotundifolia with 0.90 AUC, 0.80 TSS, 0.80 COR, and 0.50 deviance. Temperature annual range (Bio07) and precipitation seasonality (Bio15) for B. aegyptiaca; and precipitation of driest quarter (Bio17) and annual precipitation (Bio12) for B. rotundifolia are the most key bioclimatic variables that affect their distributions. The ensemble SDMs under SSP2-45 and SSP5-85 (HadGEM3-GC31-LL) climates showed that the highly suitable areas will remain suitable for both species (B. aegyptiaca with 116,934 km2 area cover (ΔA = +2.1%) and 125,757 km2 area cover (ΔA = +7.5%) and B. rotundifolia with 29,547 km2 area cover (ΔA = −28.6%) and 50, 894 km2 area cover (ΔA = +23%), respectively). The findings of this study implicated that the Ethiopian Rift Valley region in general for B. aegyptiaca and the Southern Rift Valley of Ethiopia for B. rotundifolia are suitable areas for conservation and sustainable use of the species.