The nation's biggest cities are sinking, according to data from a new study.
Known scientifically as land "subsidence," the most common cause of the sinking is "massive ongoing groundwater extraction," say the study authors, though other forces are at work in some places. The cities include not just those on the coasts, where sea level rise is a concern, but many in the interior.
In every city studied, at least 20% of the urban area is sinking – and in 25 of 28 cities, at least 65% is sinking.
He added that the study "offers critical information for urban planning, infrastructure adaptation, and hazard preparedness."