New York City is sinking under the weight of its massive buildings, leaving it more vulnerable to rising seas, a new study finds.
Most coastal cities are slowly sinking as the earth beneath them settles and groundwater is drained away. In some metropolises, the weight of large, concrete-and-steel skyscrapers may be hastening this slump, but experts rarely, if ever, account for the mass of large buildings in projections of future sinking.
For the new study, scientists tallied the weight of every building in New York, which they put at 842 million tons, and estimated the downward force of these structures across the city. They found that buildings are leaving a bigger imprint in areas rich in clay than in areas where sand or bedrock predominate.
“The softer the soil, the more compression there is from the buildings,” lead author Tom Parsons, of the U.S. Geological Survey, told The Guardian. “It wasn’t a mistake to build such large buildings in New York, but we’ve just got to keep in mind every time you build something there you push down the ground a little bit more.”
Accounting for the weight of buildings, scientists estimate that New York is sinking by around 1 to 2 millimeters yearly, though some areas are sinking much faster. Their findings were published in the journal Earth’s Future.
Parsons said that cities must plan for future sinking, which will exacerbate the impact of rising seas. “It’s not something to panic about immediately,” he said, “but there’s this ongoing process that increases the risk of inundation from flooding.”