Disentangling the impacts of changes in climate and vegetation on hydrological processes across 2,252 global catchments

Understanding large-scale hydrological responses to climate and vegetation change is critical, yet most studies focus on basin or regional scales. Here, we analyzed 2,252 unregulated catchments worldwide to disentangle climate and vegetation change effects by employing the HBV-PML hydrological model, which features enhanced representations of evapotranspiration processes. The model robustly simulates eight streamflow signatures, achieving a median Kling-Gupta Efficiency (KGE) of 0.65. Sensitivity analysis reveals: (i) Increasing Leaf Area Index (LAI) enhances interception and transpiration but suppresses soil evaporation, decreases streamflow magnitude and dynamics, shortens high-flow durations, and increases low-flow frequency/duration, indicating reduced water availability. (ii) Precipitation alters water availability, exerting effects on streamflow signatures opposite to those of LAI. (iii) Temperature modulates hydrological processes via rain-snow partitioning, soil evaporation, and evaporation from intercepted vegetation. The impacts of climate and vegetation change are magnified as they propagate through hydrological processes. Notably, the relative changes of key hydrological variables increase over longer temporal durations. Contribution analysis identifies precipitation as the dominant driver of streamflow signature changes (73.6 ± 10.5% of catchments). Contributions vary by climate zone and signatures: median precipitation contributions exceed 60% in equatorial zones, while temperature dominates (61.4–73.6%) low-flow changes in polar zones. This study provides global insights into hydrological responses under environmental change and offers an essential process-based understanding of impact propagation mechanisms for water resources management.