For the first time in recorded history the system that moves water around the planet is off balance.
Water moves in "atmospheric rivers", evaporating from ground level and spreading across the world as vapour before cooling, condensing and returning to the Earth as rain or snow.
But decades of destructive land use and water mismanagement, combined with climate change, have put "unprecedented stress" on the cycle, according to a landmark report from the Global Commission on the Economics of Water.
This "rapidly accelerating water crisis" means that more than half the world's food production will be "at risk of failure" within the next 25 years, according to The Guardian.
The study differentiated between "blue water", found in rivers and lakes, and "green water", contained in soils and plant life, and released into the atmosphere via transpiration. Green water accounts for about half of all global rainfall, but crucially it has been overlooked.
A vicious cycle is at play: a steady supply of green water is essential for supporting vegetation that can store planet-heating carbon, but the destruction of wetlands and forests is "depleting these carbon sinks" and "accelerating global warming", said CNN. The "climate change-fuelled heat" is then "drying out landscapes, reducing moisture and increasing fire risk".
Disruptions to the water cycle are "already causing suffering", with nearly three billion people facing water scarcity. Several cities are also sinking because of the loss of below-ground water.
The huge distances that water can travel means actions in one country can disrupt rainfall in another, so the report's authors have called for a collective effort, saying that world governments must recognise the water cycle as a "common good". | 
