Atmospheric water recycling an essential feature of critical natural asset stewardship

Non-technical summary In this paper, we explore how critically important ecosystems on the land provide evaporation to the atmosphere, which will later fall as precipitation elsewhere. Using a model-based analysis that tracks water flowing through the atmosphere, we find that more than two-thirds of the precipitation over critically important ecosystem areas is supplied by evaporation from other land. Likewise, more than 40% of the evaporation from critically important ecosystems falls as precipitation on other land. We conclude our work by discussing the policy implications for how these critically important ecosystems connect spatially distant wild and working lands via the atmospheric water cycle. Technical summary Global ecosystems are interconnected via atmospheric water vapor flows. Land use change can modify evaporation from land, altering atmospheric moisture recycling and potentially leading to significant changes in downwind precipitation and associated ecological impacts. We combine insights on global ecosystem-regulated moisture recycling with an analysis of critical natural assets (CNA, the 30% of global land providing most of nature's contributions to people) to reveal the sources and sinks of atmospheric water cycle regulation. We find that 65% of the precipitation over CNA is supplied by evaporation from other land areas. Likewise, CNA regions supply critical moisture as precipitation to terrestrial natural ecosystems and production systems worldwide, with 44% of CNA evaporation falling on terrestrial surfaces. Specifically, the Congo River basin emerges as a hotspot of overlap between local atmospheric water cycle maintenance and concentration of nature's contributions to people. Our results suggest global priority areas for conservation efforts beyond and in support of CNA, emphasizing the importance of sparsely populated managed forests and rangelands, along with wild forests, for fostering moisture recycling to and within CNA. This work also underlines the manifold benefits associated with achieving United Nations Sustainable Development Goal #15, to sustainably manage terrestrial life and conserve biodiversity. Social media summary Critically important ecosystems are essential for connecting distant landscapes via the atmospheric water cycle.