Sea levels are rising on average a quarter inch per year on populated coasts, and nearly half comes from sinking land in cities like Jakarta and Houston. This sinking, called subsidence, is driven mainly by groundwater withdrawal compacting sediment underground. Southeast Asia is sinking fastest, but U.S. cities including Houston, Philadelphia, and New York are dropping 2 to 4 millimeters a year, compounding the risk of coastal flooding and infrastructure damage.