Sea-level rise could imperil low-lying areas along the length of the Atlantic Coast, but people are still building beach houses and condominiums there, which could lead to hard decisions about what to save, according to a scientific study released Tuesday.

The study, published in the journal Environmental Research Letters, mapped coastal development from Florida to Massachusetts and found that about 60 percent of the lowest land along the shoreline is built up or probably will be. Thirty-three percent is rural land that might be developed in the future.