The world’s biggest cities are sinking. Is yours one of them?

Global cities, including New Orleans, Mexico City, Jakarta, and Rome, are sinking at an alarming rate, according to a comprehensive new study published in Nature Cities. Researchers utilized satellite radar to monitor 465 urban areas with populations exceeding one million since 2014. The findings reveal that subsidence, or land sinking, is not just a local issue for a few cities but a global urban concern.

The study, led by Guoquan Wang, a geophysicist at the University of Houston, highlights that subsidence, caused by factors such as the weight of buildings or excessive groundwater extraction, is particularly severe in Southeast Asia, West and Central Asia, and North America. However, it also affects South America and Africa, regions often less studied in relation to land subsidence.

Groundwater extraction, a primary driver of subsidence, leaves the soil unsupported, causing it to sag. The uneven nature of sinking poses significant risks, as varying subsidence rates within a city can lead to structural damage, sewer line disruptions, subway system failures, and exacerbated flooding. In extreme cases, such as Jakarta, Indonesia, the sinking is so severe that the government is constructing a new capital city on Borneo Island.

While the consequences of subsidence are irreversible once they occur, cities have successfully halted further subsidence. Tokyo, for example, experienced rapid sinking until it implemented policies to limit groundwater pumping and promote surface water use. Similarly, Beijing and Tianjin in China ceased groundwater extraction, leading to a halt in subsidence in certain regions.

Experts emphasize that cities still have time to act, but prompt action is crucial. With a subscription to Scientific American, readers can support the publication's efforts in delivering high-quality, impactful science journalism about the discoveries and ideas shaping our world today.