Regionally divergent drivers behind transgressions of the freshwater change planetary boundary

Human-driven freshwater change relates to elevated Earth system risks, which motivates analysis to better understand its global characteristics. Here, we analyse global and regional patterns of anomalous conditions and their drivers in streamflow (blue water) and soil moisture (green water), building on the recently updated planetary boundary for freshwater change (PB-FW). Our data consist of updated scenario simulations from a large ensemble of global hydrological models covering years 1901-2019. During the early twenty-first century, PB-FW transgression has increased across its blue and green water components. Climate has increasingly become the dominant global influence on dry and wet streamflow and soil moisture deviations from pre-industrial-like baseline conditions. Amongst the regionally variable change in blue and green water, direct human forcings (encompassing land and water use changes) intensify particularly dry deviations, whereas wet deviations are mainly climate-driven. Regional unpacking of the global PB-FW transgression improves understanding of the extent, degree and drivers of global freshwater change, guiding mitigation and adaptation strategies in response to it, and is a notable advancement for analysing PBs across scales.