PRINCETON, N.J., March 14 (UPI) -- Rising seas in the next century could threaten up to 4 million Americans living in a combined area larger than the state of Maryland, researchers say.
A study published in the journal Environmental Research Letters reports more than 12,000 square miles of land in the United States lies just 3 feet above the high tide line.
Within this area are 2.1 million housing units where 3.9 million people live, the researchers said.
With a predicted sea level rise of 3 feet or more by the end of the century, the U.S. government's currently designated flood zones should not be considered stable, they said.
"The sea level rise taking place right now is quickly making extreme coastal floods more common, increasing risk for millions of people where they live and work," researcher Ben Strauss of the organization Climate Central said.
"Sea level rise makes every single coastal storm flood higher. With so many communities concentrated on U.S. coasts, the odds for major damage get bigger every year."
The findings suggest there are significant exposures to sea level rise impacts on every coast, the researchers said.
A study by researchers at Climate Central and the University of Arizona found areas surrounding the Gulf of Mexico to be the most vulnerable, while in terms of population Florida is the most vulnerable, closely followed by Louisiana, California, New York and New Jersey.