Desertification in northwestern Namibia is widespread but spatially constrained by climate and human activity

Dryland degradation threatens ecosystem function and livelihoods across arid regions, yet its spatial extent and drivers remain poorly quantified in many African drylands. We investigated long-term trends in bare ground cover, a direct indicator of desertification, across northwestern Namibia from 1984 to 2023 using rainfall-adjusted remote sensing analyses. Temporal trends in residual bare ground were modelled against climatic, edaphic, topographic, woody cover, and anthropogenic predictors using Random Forest. Residual bare ground increased significantly across approximately 52% (29,000 km²) of the study area, whereas only 0.7% showed decreases. Increases were concentrated in the arid zone, between the hyper-arid and semi-arid zones. The final model explained 63% of the spatial variation in bare ground trends. Temperature-related variables were the strongest predictors, exceeding the influence of rainfall and anthropogenic factors. Bare ground expansion was greatest under relatively cooler, less temperature-variable conditions and intermediate rainfall. Increasing woody cover was negatively associated with bare ground trends, suggesting bush encroachment may partially mask herbaceous degradation. Anthropogenic factors had weaker but detectable effects, with greater desertification near areas of concentrated livestock activity. These findings indicate that climate-related processes, particularly warming, are the primary drivers of recent desertification patterns in northwestern Namibia.