Half of China's cities are sinking, putting most of the country's urban population at risk

Nearly half of China's major cities are sinking due to groundwater extraction and the sheer weight of urban buildings and infrastructure, a new study finds.

The affected cities, which include Beijing and Tianjin, are concentrated in the eastern part of the country and along the coast. Combined with sea level rise, falling cities could expose around 10% of China's coastal population — between 55 and 128 million people — to flooding and irreparable damage by 2120.

For the study, published Thursday (April 18) in the journal Science, researchers measured land subsidence in every Chinese city with a population of more than 2 million people over the period from 2015 to 2022. Of the 82 cities they examined, 45% are sinking by more than 0.1 inches (3 millimeters) per year, with 16% falling by more than 0.4 inches (10 mm) per year.  

These major cities are home to three-quarters of China's urban population, which totaled 920 million people in 2020 — the largest of any country in the world, according to the study.

"The subsidence appears to be associated with a range of factors such as groundwater withdrawal and the weight of buildings," the researchers wrote in the study. "High-rise buildings are sprouting up, road systems are expanding, and groundwater is being used, all at a rapid pace."

Related: East Coast cities are sinking at a shocking rate, NASA images show

While it was already known that Chinese cities are subsiding, the study provides a first snapshot of the problem on a national scale. The researchers used data from the Sentinel-1 satellites, which measure vertical changes in Earth's surface with Interferometric Synthetic Aperture Radar (InSAR) instrumentation, and combined these land motion results with groundwater assessments from monitoring wells and building weight data.