The world has entered an era of “global water bankruptcy” that is harming billions of people, a UN report has declared.

The overuse and pollution of water must be tackled urgently, the report’s lead author said, because no one knew when the whole system could collapse, with implications for peace and social cohesion.

All life depends on water but the report found many societies had long been using water faster than it could be replenished annually in rivers and soils, as well as over-exploiting or destroying long-term stores of water in aquifers and wetlands.

This had led to water bankruptcy, the report said, with many human water systems past the point at which they could be restored to former levels. The climate crisis was exacerbating the problem by melting glaciers, which store water, and causing whiplashes between extremely dry and wet weather.

Prof Kaveh Madani, who led the report, said while not every basin and country was water bankrupt, the world was interconnected by trade and migration, and enough critical systems had crossed this threshold to fundamentally alter global water risk.