The extraction of water from aquifers in Iran is causing an area the size of Maryland to sink, exposing an estimated 650,000 people to the risks of subsidence and freshwater depletion.

The depletion of Iran’s underwater aquifers is driving the ground to sink rapidly throughout the country, new research shows.

More than 12,120 square miles (31,400 square kilometers) of the country — an area roughly the size of Maryland — is now moving downward faster than 0.39 inches (10 millimeters) per year. In a more extreme example, the ground level has dropped by over a foot (34 cm) per year near the city of Rafsanjan, in central Iran.

This sinking, known as subsidence, exposes an estimated 650,000 people to a higher risk of other threats caused by changes in ground level, such as water scarcity and food insecurity, experts say. And part of the cause is ongoing drought in the country.