GREENHOUSE-EFFECT AND SEA-LEVEL RISE - THE COST OF HOLDING BACK THE SEA

Previous studies suggest that the expected global warming from the greenhouse effect could raise sea level 50 to 200 cm (2 to 7 ft) in the next century. This article presents the first nationwide assessment of the primary impacts of such a rise on the United States: (1) the cost of protecting ocean resort communities by pumping sand onto beaches and gradually raising barrier islands in place; (2) the cost of protecting developed areas along sheltered waters through the use of levees (dikes) and bulkheads; and (3) the loss of coastal wetlands and undeveloped lowlands. The total cost for a 1-m rise would be between $270 and $475 billion, ignoring future development. We estimate that if no measures are taken to hold back the sea, a 1-m rise in sea level would inundate 30,000 sq km (14,000 sq mi), with wet and dry land each accounting for about half the loss. The 1500 sq km (600-700 sq mi) of densely developed coastal lowlands could be protected for approximately $1000 to $2000 per year for a typical coastal lot. Given high coastal property values, holding back the sea would probably be cost-effective. The environmental consequences of doing so, however, may not be acceptable. Although the most common engineering solution for protecting the ocean coast, pumping sand, would allow us to keep our beaches, levees and bulkheads along sheltered waters would gradually eliminate most of the nation's wetland shorelines. To ensure the long-term survival of coastal wetlands, federal and state environmental agencies should begin to lay the groundwork for a gradual abandonment of coastal lowlands as sea level rises.