Humanity’s modification of the water cycle has pushed the world further beyond a safe operating space for continued life on Earth, say scientists. A reassessment of the planetary boundary for freshwater that now includes rainfall, soil moisture and evaporation — so-called “green water” — found the boundary to be “considerably transgressed,” with the situation likely to worsen before any reversals in the trend will be observed. Previously, researchers had only considered rivers, lakes and groundwater in their evaluations.

“Green water modifications are now causing rising Earth system risks at a scale that modern civilizations might not have ever faced,” according to researchers from the Stockholm Resilience Centre in collaboration with colleagues from Germany, Netherlands, Finland, Austria, Australia, the U.S. and Canada. The findings were published  in the journal Nature Reviews Earth & Environment.

Based on the findings, water is now the sixth boundary to be transgressed, out of the nine identified by the Planetary Boundaries Framework. Published in 2009 and updated regularly, the framework demarcates a safe operating space for humanity, beyond which civilization could collapse, and life altered as we know it. The other boundaries already transgressed are climate change, biosphere integrity, biogeochemical flows (nitrogen and phosphorous pollution), land-system change, and also since 2022, novel entities, which includes pollution by plastics and other humanmade substances.

Until now, the freshwater boundary had been considered to be within the safe zone. The so-called “freshwater use” boundary was based on allowable human consumption, and set at 4,000 km3/year of water utilized and not returned as runoff. It evaluated water extracted from rivers, lakes and groundwater, so-called “blue water.”

The journal article published in Nature Reviews Earth & Environment can be read here.

Further information from the Stockholm Resilience Centre can be found here and  further information on this story is here.