In Simple Terms
In many cities, the ground is slowly sinking, sometimes by several inches a year. Pumping too much water from underground is one of the main reasons. Uneven sinking can damage buildings and raise flood risks, but cities can slow or stop it by using less underground water and finding other sources.
A city may seem solid beneath the feet of people walking its streets every day. But the ground below buildings and roads can shift so gradually that residents barely notice. Satellite measurements show that this is not a rare problem confined to a single city: it is happening across continents, and its effects can build over time. In places such as New Orleans, Mexico City, Jakarta, and Rome, measurements have recorded land sinking by as much as several inches a year.
A Wide-Ranging Survey Reveals a Global Pattern
A study published in Nature Cities offers a broad view of the problem, drawing on satellite radar data collected between 2014 and 2023. The analysis covered 465 urban areas, each with a population of more than one million. Rather than assigning a single average rate to each city, the researchers examined relatively small patches of land—roughly the area covered by a few homes. That finer-grained approach revealed how sinking can vary from one part of a city to another.
The study, by a team of researchers that included Lejun Wang, was published online on October 12, 2026. Its findings show that land subsidence is a global urban problem, not an issue affecting only a handful of cities. One striking result is that nearly half of the cities in the dataset had never before been studied for this issue using satellite radar. The survey therefore did more than add detail about places already known to be sinking: it also provided an initial look at areas that had been missing from earlier research.
Sinking was especially pronounced in Southeast Asia, West and Central Asia, and North America. It was also detected in South America and Africa, regions where land subsidence has received less research attention. So the smaller number of documented cases in some parts of the world should not be taken as proof that the problem is absent there. It may instead reflect a lack of available measurements.
How Radar Detects Movement We Cannot See
Satellites take radar images of the same place at different times, and scientists compare the signals that bounce back. If the ground’s height changes—even by a very small amount—the time it takes for the signal to travel out and back changes too. By repeating these observations and comparing the results, researchers can estimate gradual movement at the surface. The method can detect changes on the scale of millimeters: a shift of about one twenty-fifth of an inch can affect the signal’s return time.
The advantage of this approach is that it can track large urban areas in enough detail to reveal differences in sinking from one neighborhood to the next. A citywide average might hide a district that is sinking faster than the surrounding area, or a patch of ground that is moving at a different rate from nearby neighborhoods. Roland Bürgmann, a geophysicist at the University of California, Berkeley, described the work as one of the most comprehensive and systematic efforts to explore land subsidence within cities. He did not take part in the study, but his comment highlights the value of bringing measurements from around the world together in one analysis.
A radar image alone cannot tell us that every place is sinking for the same reason. It can show where the ground is moving and how it is changing, but understanding the cause requires looking at local conditions, such as the type of soil and how water is used. That is why combining satellite observations with local information is useful: the first reveals the pattern and scale of the problem, while the second helps explain what is driving it.
Growing Cities Put Underground Water Under Pressure
Several factors can cause the ground beneath a city to sink. In New York City, for example, the weight of buildings can press down on soft soil below them. But according to the study and experts explaining its findings, the most common factor is water being pumped from underground by water utilities, industries, and other users who rely on wells.
Groundwater can be thought of as part of a system that supports soil grains and fills the spaces between them, much as air fills a cushion. When water is pumped out, the soil that held it changes. Layers of earth can gradually compress, lowering the land surface above them. This does not necessarily happen all at once or as a sudden drop people can see. The change may unfold slowly, with repeated measurements detecting it before it causes noticeable damage.
That is why the issue is not just how much water a city needs on any given day. It also depends on where that water comes from and how the city secures its supply over time. If homes, public services, and industries depend on pumping water from beneath the city, ongoing demand can put pressure on the ground itself. New York shows that the weight of urban development can also play a role, but each city has its own circumstances. There is no single explanation that fits every case of subsidence around the world.
The Biggest Risk Is Uneven Sinking
It may seem that a city sinking by roughly the same amount everywhere would be less dangerous than one where different areas sink at different rates. As Bürgmann has pointed out, if an entire city descended smoothly by about one inch, that would not necessarily be a major problem. But when one neighborhood sinks faster than a nearby one, differences in elevation emerge, putting buildings and infrastructure under uneven strain. So it is not enough to ask how much a city is sinking overall; it also matters where the movement is happening and how much it varies from place to place.
As stress builds, building foundations can crack, sewer lines can be damaged, and subway systems can be affected. Changes in ground elevation can also make flooding worse, leaving lower-lying neighborhoods more vulnerable to water pooling. These kinds of damage do not have to appear all at once. The process may begin with a gradual shift, then become harder to manage as the differences between parts of the urban landscape grow.
Jakarta is a stark example of how sinking ground and flooding can compound each other. The problem became so severe that Indonesia began building a new capital on the island of Borneo. This does not mean every threatened city will need to relocate. But it shows how subsidence, when combined with other hazards, can grow from a slow geological process into a major challenge for urban planning and a city’s future.
Cities Have Managed to Stop the Sinking
Once layers of earth have compressed, restoring the ground to its former height can be extremely difficult. Wang describes subsidence as a cumulative process that is difficult to reverse. But that does not mean cities are powerless to influence what happens next. They may be able to stop the continued decline, even if the land cannot simply return to its previous state. Distinguishing between halting further damage and restoring what has already been lost is important when setting realistic goals for city policy.
Tokyo has faced sinking faster than the rates seen in many cities today. According to Manouchehr Shirzaei, a geophysicist at Virginia Tech and one of the study’s reviewers, the city managed to stop the ongoing problem by introducing policies to control groundwater pumping and shifting to alternative sources of surface water. The experience shows that managing water demand and supply can be part of the response, rather than treating subsidence as something that cannot be changed.
In China, Beijing and nearby Tianjin stopped pumping groundwater and replaced it with surface water transported from the Yangtze River basin. After the change, sinking stopped in parts of the region. This does not prove that transporting water is the right solution for every city, but it offers an example of how reducing dependence on groundwater can change the course of the problem in some places.
Early Warnings Give Cities a Chance to Act
One challenge with land subsidence is that its slow start can make it less noticeable than sudden hazards, even as damage accumulates over time. That makes repeated maps and precise measurements useful in practice. They can help identify neighborhoods that are moving faster and track whether actions taken by a city are reducing the sinking. Knowing how movement varies across an area can also help direct attention to places where infrastructure may be under greater strain.
Shirzaei believes most places still have enough time to respond, but making use of that time requires action. Cities can start by understanding where their water comes from, monitoring changes in the ground, and then reviewing pumping policies and looking for suitable alternatives where possible. The study does not offer one solution for every city, but it makes the scale of the problem clearer and shows that ignoring the measurements will not make it disappear.
Data from 465 urban areas, each with more than one million residents, also helps shift the discussion from local impressions to broader comparisons. Studying cities in different regions using the same approach over the period from 2014 to 2023 makes it possible to see that subsidence is not limited to a single geographic region. And the fact that nearly half of the cities had not been studied before does not mean the risk is limited to places where it has already been documented.
The Bottom Line
Satellite measurements reveal that land subsidence is affecting major cities around the world, from New Orleans, Mexico City, Jakarta, and Rome to urban areas across Asia, North America, South America, and Africa. The study, published in Nature Cities, analyzed 465 urban areas with more than one million residents each and tracked ground movement between 2014 and 2023, finding that some locations are sinking by several inches a year. The most important concern is that different neighborhoods can sink at different rates, potentially damaging buildings, sewer networks, and subway systems while worsening flood risks. Although restoring land after it sinks can be extremely difficult, experiences in Tokyo, Beijing, and Tianjin show that cities can stop further decline by regulating groundwater pumping and switching to other sources. The danger develops slowly, but early monitoring gives cities a real chance to act before the effects accumulate.