Green water, wetlands, and atmospheric moisture recycling ‐ An emerging new paradigm for grassland science

Abstract

Grassland science has traditionally treated water as a local constraint, assessed through precipitation, soil moisture, or evapotranspiration at site to regional scales. Emerging insights from Earth system science challenge this view, revealing freshwater cycling as a connected, planetary‐scale process shaped by land‐atmosphere interactions. Recent work on planetary boundaries has identified a transgression of the green water boundary, defined by deviations in root‐zone soil moisture from Holocene variability, with profound implications for terrestrial ecosystems. In this perspective, we argue that grasslands occupy a central yet underappreciated position within this emerging framework. As one of the world's largest biomes, grasslands depend predominantly on green water while simultaneously contributing to atmospheric moisture recycling that sustains precipitation locally and in distant downwind regions. Within these coupled processes, wetlands function as critical hydrological regulators by sustaining evapotranspiration, buffering soil moisture variability, and stabilizing land‐atmosphere feedbacks. We therefore highlight how grassland degradation, land‐use change, and associated wetland loss can jointly disrupt moisture‐recycling pathways, amplifying hydroclimatic instability across scales. Conversely, sustainable grassland management together with wetland conservation can enhance resilience by stabilizing soil moisture, supporting evapotranspiration, and buffering climatic extremes. By integrating planetary green water boundaries, atmospheric moisture recycling, and the hydrological role of wetlands, this perspective calls for a conceptual expansion of grassland science. Recognizing grasslands as active components of a connected planetary water system is essential for understanding their resilience, governance challenges, and capacity to support ecosystem services in the Anthropocene.