Contrasting trends in climatic and ecohydrological aridity over one-fifth of global drylands

Climatic aridity interplays with ecohydrological aridity, generally showing synchronous increasing trends under global warming. However, these changes can be decoupled and even exhibit contrasting temporal variations. The spatial patterns and underlying mechanisms of such contrasting aridity changes remain poorly understood. Utilizing satellite and climate data, we demonstrate that nearly one-fifth (22.3%) of global vegetated drylands showed contrasting trends in climatic and ecohydrological aridity over the past four decades. Approximately 60% of these areas experienced an increase in climatic aridity but a decrease in ecohydrological aridity, while others exhibited opposite temporal trends. These divergences stem primarily from elevated atmospheric CO₂ levels, which exert opposite effects on ecohydrological aridity via vegetation structure and canopy stomatal conductance. These findings highlight the nonlinear nature of vegetation-climate interactions in drylands and provide new insight into water and carbon cycling in global drylands under climate change.