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.

In Iran, about 60% of the water supply comes from underground aquifers. To study what effects this is having on the surface, Jessica Payne, a doctoral candidate in the School of Earth and Environment at the University of Leeds in the U.K., and her colleagues used radar data from the European Space Agency’s Sentinel-1 satellite constellation to map how the ground level in Iran has changed over eight years between 2014 and 2022.

The researchers found 106 regions of subsidence covering a total of 12,120 square miles, or about 2% of the country.

“The rates of subsidence in Iran are some of the fastest in the world,” Payne told Live Science. “We found about 100 sites across Iran where subsidence is faster than about 10 millimeters [0.4 inches) a year. In Europe, case studies are considered extreme if they exceed 5 to 8 millimeters [0.2 to 0.3 inches] a year.”

The ground is sinking due to groundwater extraction, she said, with 77% of incidences of subsidence faster than 10 mm per year correlating with the presence of agriculture.