Satellite study maps sinking ground and changing rates in 465 cities
A Nature Cities study used satellite radar observations from 2014 to 2023 to map local land subsidence across 465 cities with populations above one million. Sinking slowed in some cities and accelerated in other areas, with major hotspots across Asia and the Americas. The maps can guide risk priorities, although motion corrections add uncertainty and the observations alone do not establish the cause of every local decline.
Science··Evening
One satellite method was applied to 465 cities
A Nature Cities study published on 12 October compared local ground movement from 2014 to 2023 in 465 cities with populations above one million. Radar observations from the European Space Agency’s Sentinel-1 satellites track small elevation changes across repeat passes over the same ground. EL PAÍS and scinexx report that the common method places cities previously examined at different scales into one comparable map.[1], [2]
The maps show clusters of severe sinking in some large cities. They also add measurements for cities studied less often before. Subsidence here means ground moving downward over years, not buildings suddenly collapsing. A citywide average can differ greatly from the rates measured in particular districts.[1], [2]
Local rates stand out in Mexico City
scinexx highlights sinking reaching 21.7 centimetres a year in parts of Mexico City. That figure describes specific areas, not an average for the whole city. EL PAÍS discusses groundwater extraction and rapid urban development as possible contributors in some places. The global map is not an experiment that isolates the principal driver in every neighbourhood.[1], [2]
Rates do not stay fixed over time. Researchers detected broad deceleration across many cities in Asia, while substantial urban areas in those regions continued to accelerate. That within-city contrast shows why one average may conceal places where infrastructure and flood hazards merit closer attention. The map identifies locations for more detailed local investigation.[1], [2]
Global motion correction adds uncertainty
The satellite radar first measures movement relative to a local reference. Researchers compared those results with a global vertical-land-motion product to approximate movement on a common scale. The Nature Cities paper says the broad geographic patterns persist after that adjustment, but the added data introduce uncertainty. A centimetre or millimetre value for one place therefore has to be read with its measurement and reference method in view.[1], [2]
The assessment includes cities above one million residents, it is not a complete inventory of ground problems in smaller settlements. Radar observations describe movement over the past decade and do not predict that each rate will stay constant through the next. The local examples in EL PAÍS and scinexx show that cities face the same type of hazard at different speeds. The map can be paired with local ground and groundwater evidence.[1], [2]
