Planetary Boundary Nr 6: Freshwater consumption and the global hydrological cycle

The freshwater cycle is both a major prerequisite for staying within the climate boundary, and is strongly affected by climate change. Human pressure is now the dominating driving force determining the function and distribution of global freshwater systems. The effects are dramatic, including both global-scale river flow change and shifts in vapour flows from land use change. Water is becoming increasingly scarce and by 2050 about half a billion people are likely to have moved into the water-stressed category. A water boundary related to consumptive freshwater use has been proposed to maintain the overall resilience of the Earth system and avoid crossing local and regional thresholds ‘downstream´.