A satellite-radar survey tracking 465 cities with more than one million residents from 2014 to 2023 found that urban land is sinking around the world, reaching several inches per year in some places.

Published in Nature Cities, the study examined small areas within cities and detected subsidence across Southeast Asia, West and Central Asia, North America, South America and Africa; nearly half of the cities had not previously been surveyed for subsidence using satellite radar.

Groundwater extraction by utilities, industries and other users is the most common cause: as water is removed, the soil above can settle. The weight of buildings compressing soft ground is another factor, as seen in New York City.

Uneven sinking can put serious strain on infrastructure, cracking building foundations, breaking sewer lines, damaging subway systems and worsening floods. Severe subsidence and flooding in Jakarta have contributed to Indonesia’s decision to build a new capital on Borneo.

Although subsidence accumulates and is largely irreversible, cities can stop further sinking by managing groundwater use and turning to surface water. Tokyo curbed subsidence by restricting groundwater pumping, while Beijing and Tianjin stopped pumping and began using water piped from the Yangtze River basin; sinking has halted in parts of the region.

Researchers say many cities still have time to respond, but action is needed to prevent continued subsidence.