Spatiotemporal dynamics, future change trends, and risk zonation of global drylands under climate change

Under global warming, the expansion and structural reorganization of drylands have become increasingly evident, reflecting major shifts in terrestrial hydroclimatic conditions. However, the evolutionary characteristics of different dryland subtypes and their risk differentiation remain insufficiently understood. Using global aridity index data for 1981-2020 together with future scenario data from CMIP 6, this study examined changes in dryland extent, subtype evolution, and drought risk patterns at global and continental scales. The Results global drylands expanded overall during 1981-2020 and are likely to continue expanding in the future. This expansion was driven mainly by increases in semiarid and dry subhumid zones, particularly the latter, suggesting that current global aridification is expressed more through the outward growth of wet-dry transition zones than through uniform intensification of hyperarid cores. Between 1981 and 2000 and 2041-2060, total global dryland area increased by 9.78×106 km2 at a rate of 1.63×105 km2 yr- 1, including increases of 4.71×106 km2 in semiarid zones and 5.57×106 km2 in dry subhumid zones, whereas hyperarid zones decreased by 9.33×105 km2. At the continental scale, Asia contributed most to net global dryland expansion, whereas Africa accounted for the largest shares of permanent dryland and high-risk dryland zones. Risk zoning based on drought frequency and maximum consecutive drought years revealed a clear spatial gradient from permanent drylands to high-risk and then low- to medium-risk dryland zones, with Africa and Asia forming the core regions of persistent dryland zones and the main frontiers of future expansion. Overall, global dryland evolution shows pronounced structural and intercontinental heterogeneity. High-risk dryland zones and dry subhumid zones should therefore be prioritized in future drought monitoring, early warning, ecological restoration, and region-specific management. This study provides a scientific basis for dynamically identifying global drylands, managing vulnerable areas, and developing sustainable land-management strategies under climate change.