Wildfires diminish vegetation control on surface runoff.

Wildfires are increasingly reshaping global terrestrial ecosystems, yet their impacts on the fundamental coupling between vegetation and the hydrological cycle remain poorly understood. Here, we present a global-scale assessment of how wildfire disturbances alter the sensitivity of surface runoff to vegetation dynamics using multidecadal satellite observations and reanalysis datasets. We developed a spatially explicit framework to quantify pre- and postfire runoff-vegetation sensitivity across climatic gradients and fire regimes. We show a widespread and systematic weakening of vegetation control on runoff after wildfires, indicating a fundamental decoupling of hydrology-vegetation interactions. This attenuation is notably modulated by aridity and fire intensity, with the most pronounced sensitivity losses occurring in fragile drylands. These findings expose a critical blind spot in traditional hydrological models that overlook disturbance-driven vegetation shifts. Our study provides a mechanistic understanding of how compound climate-fire perturbations accelerate terrestrial water flux instability, suggesting that increasing fire frequency will exacerbate ecosystem vulnerability and threaten water security in a warming world.