MIAMI BEACH — In the most dire predictions, South Florida’s delicate barrier islands, coastal communities and captivating subtropical beaches will be lost to the rising waters in as few as 100 years.

Further inland, the Everglades, the river of grass that gives the region its fresh water, could one day be useless, some scientists fear, contaminated by the inexorable advance of the salt-filled ocean. The Florida Keys, the pearl-like strand of islands that stretches into the Gulf of Mexico, would be mostly submerged alongside their exotic crown jewel, Key West.

“I don’t think people realize how vulnerable Florida is,” Harold R. Wanless, the chairman of the geological sciences department at the University of Miami, said in an interview last week. “We’re going to get four or five or six feet of water, or more, by the end of the century. You have to wake up to the reality of what’s coming.”

Concern about rising seas is stirring not only in the halls of academia but also in local governments along the state’s southeastern coast.