"You have species that might like to do something on that land - birds wanting to forage on beaches, horseshoe crabs wanting to lay eggs," said the report's lead author, James G. Titus, the Environmental Protection Agency's sea-level-rise project manager since 1982. "These structures that are continually getting built to protect people's homes tend to eliminate those systems."
"The idea of wetland ecosystems getting 'squeezed out' between encroaching seas and existing or future development and armored shorelines is the key message," said Christopher Linn, a coauthor of the study and senior environmental planner at the Delaware Valley Regional Planning Commission.
The report adds a new layer - a projection of where current land-development policies are likely to lead - to numerous studies that have looked at how low the coastal land is and how high the sea might rise.
"Sometimes, there's the implication that all this land will be underwater," Titus said. "We're saying that land won't be underwater because people will do things."
Linn said current estimates predict sea levels will rise up to a meter by 2100, or about three inches or more a decade, but estimates keep changing as more is learned about polar ice.
Most communities do not have specific plans for how they will deal with rising sea levels. They can choose between two main options: protect shorelines or retreat.
In the absence of such plans, the researchers looked at 131 land-use policies from Florida to Massachusetts, and projected where "business as usual" might lead.
It will lead to bulkheads, dikes, and similar structures made to hold back the sea.
Along the entire stretch of the coast, about 60 percent of land within one meter of the tides is developed or going to be developed. And, therefore, shore protection is likely to certain, Titus and his colleagues concluded.
