Exacerbated global surface water stress under climate change

Abstract

Water stress is expected to intensify due to escalating atmospheric and surface dryness under global warming. Despite extensive research indicate that intensified dryness exacerbates water constraints on ecosystems, the dynamics and underlying mechanisms of surface water stress (SWS) under climate change remain poorly understood. In this study, we use annual evaporative stress as the surface water stress index (WSI) and provide a comprehensive analysis of historical and projected global terrestrial SWS, covering its characteristic changes, driving factors, and impacts on vegetation. Our results show a significant declining trend in WSI during 1982–2014 (-0.0033/decade, p < 0.01), indicating the enhancement of SWS concurrent with a rapid expansion of water stress intensified areas at a rate of 1.85 %/decade (p < 0.01). Using the Budyko-Penman budget framework, we found that the intensification of SWS was primarily driven by an increase in vapor pressure deficit (VPD) and a decrease in precipitation. Furthermore, the intensification of SWS contributed to a decline in vegetation growth, with the extent of areas experiencing increased vegetation water deficit expanding rapidly at a rate of 1.38 % per decade (p < 0.01). In the future, SWS is projected to escalate, with the proportion of areas experiencing intensified SWS increasing from 6.3 % to 24.3 % by the end of the century under the SSP5–8.5. Our study provides a comprehensive analysis of the drivers of SWS under climate change and its impacts on ecosystems, offering valuable scientific insights for the effective management of water resources.