Divergent ecohydrological impacts of agricultural and urban expansions across global drylands

Global drylands face compounding threats from climate change and rapid human expansion, yet satellite observations paradoxically show widespread vegetation greening. This study investigates the divergent ecohydrological impacts of agricultural and urban expansions across 8,507 global dryland basins from 2000 to 2022. By integrating cloud-based, multi-source Earth observation data with a Spatial Durbin Model, we decouple the local footprints and spatial spillover effects of human land-use on surface water loss. The results unveil a pervasive Greening Illusion associated with cropland expansion, where gains in vegetation productivity are strictly sustained by the severe depletion of surface water bodies, affecting 43.33 % of the studied basins. In contrast, urban growth consistently triggers simultaneous ecological and hydrological degradation. Crucially, the spatial econometric analysis (spatial interaction coefficient ρ = 0.616) demonstrates that the indirect spatial spillover effect of agricultural expansion on water loss is significantly positive (+0.0584) and vastly overpowers its non-significant direct local footprint (‒0.0051) under the baseline k = 6 specification. This massive spatial contagion is structurally robust, exhibiting a 16.0-fold magnitude over the local footprint under physical basin contiguity, which validates a beggar-thy-neighbor dynamic, indicating that localized water withdrawals propagate severe water scarcity to hydrologically connected ecosystems. Our global functional diagnosis identifies 6,679 desiccated hotspots globally that have experienced near-complete surface water desiccation. These findings challenge the assumption that vegetation expansion universally benefits drylands and highlight the urgent need for integrated basin-scale governance, strict regulation of land conversion based on finite hydrological carrying capacities, and transboundary water-sharing frameworks to mitigate systemic ecohydrological risks.