Boston II

Greater Boston, with a population of about 4.5 million, is located at low elevations and is thus highly vulnerable to rising sea levels, says Pilkey, who adds that cities will likely have to abandon low-lying portions and build seawalls and tide gates to protect against rising waters.

According to a U.N. study, other highly vulnerable low-lying cities include New York; New Orleans; Tokyo; Rotterdam, Holland; and Virginia Beach, Va.

In the same study, the U.N. urged cities and national governments to consider threats posed by environmental degradation and global warming in their urban planning and to come up with innovative ways to address the changes.