A new satellite-based study reveals that the 28 most populous cities in the United States—including New York City, Chicago, Dallas, and Denver—are gradually sinking at rates of 2 to 10 millimetres (0.08 to 0.4 inches) per year. Researchers at Virginia Tech used high-resolution radar measurements to map this ground subsidence across urban regions. In every city examined, at least 20 percent of the land area was found to be sinking; in 25 of the 28 cities, more than 65 percent exhibited measurable downward movement, posing serious long-term risks to urban infrastructure systems. As per the Nature Cities report published on May 8, cities in Texas showed the highest subsidence rates, with Houston being the most affected—40 percent of the city is sinking faster than 5 millimetres per year, and 12 percent exceeds 10 millimetres annually. Under the direction of Leonard Ohenhen, the researchers linked almost 80 percent of the urban subsidence to too high groundwater extraction, a process motivated by growing urban needs. While natural geological activity is important as well, human activity is now the dominant driver …