Hurricane Sandy confirmed what Irene and Katrina had suggested: We will retreat from the edge of the sea. We should do so in a planned, organized manner that protects citizens' interests and the ecological, economic, recreational and aesthetic values of our coasts.

Coastal storms have killed thousands of people and have caused more than $250 billion in damages in the past 12 years. Costs are increasing with each storm because more and more people live, and build infrastructure, in risky places. For example, hundreds of thousands of people live on barrier islands along the East and Gulf coasts. The nature of these low-lying sand islands is to move. Winds, waves and currents, independent of hurricanes, cause barrier islands to roll toward the shore and migrate along the coast. Put another way, they naturally migrate from under buildings placed on them. The population density of U.S. coastal counties increased 28 percent from 1980 to 2003, to about 153 million. Clearly, coastal development must be rethought.

Billions of dollars have been spent building seawalls, jetties, beaches and dunes in efforts to control water flow and sediment movement and, ultimately, to stabilize dynamic shorelines to protect people and property. Since 1922, "renourishment" sand has been pumped on more than 3,700 miles of beach in the United States. That's equivalent to the distance from Bangor, Maine, to Miami and back. Unfortunately, these efforts have often failed. All engineered solutions, whether "hard construction" such as seawalls or "soft construction" like dunes and beaches, have a limited life and have to be rebuilt repeatedly.

In addition to human and monetary costs, attempts to stabilize naturally dynamic shorelines have ecological costs. Many coastal plants and animals have adapted to eroding, shifting shorelines. They are integral parts of the food webs that support fish and wildlife species important to commerce, recreation and aesthetics. If humans succeeded in stabilizing the shoreline, many species, and the ecological, recreational and economic benefits they produce, would be at risk of extinction.

For decades, federal, state and local agencies have made legislative and regulatory efforts to address these concerns. But the levels of destruction wrought by Hurricanes Katrina, Irene and Sandy show that efforts to date have been wrongly directed or insufficient.

Data show that the sea is rising. Moreover, the frequency and intensity of Atlantic tropical cyclones are projected to increase. Lands that support many homes and other infrastructure are likely to be underwater or increasingly vulnerable to storm surges in 100 years. Other near-shore lands will be uninhabitable by people, because of the effects of the sea.

Retreat from the sea will be painful no matter how it is executed, but it will hurt most if Americans continue to try to protect all existing infrastructure until the sea destroys it and if we repeatedly rebuild in the same places.

Planning for the coming reality must be a collaborative effort of the multiple stakeholders with diverse interests in coastal values. We offer these suggestions as a starting point.

• Federal, state and local coastal policies should encourage people to develop in low-risk, environmentally robust areas, not high-risk, environmentally sensitive places.

• Planning should begin to depopulate high-risk areas now, rather than waiting for disasters to cause further loss of life and property.

• Certain things should be recognized as dependent on shorelines, such as shipping terminals, fishing ports, beach recreation, and shorebird and fish habitats. Shoreline dependence should be an important criterion as trade-offs among land uses are evaluated.

• The sea should be walled off only to protect shoreline-dependent infrastructure and only when no other protective actions are possible. Soft walls (dunes) may be necessary for short-term protection in areas where retreat is planned and ongoing.

• The coast should be recognized as a limited natural resource that provides ecological, economic, aesthetic, recreational and cultural benefits. New policies should provide a fair balance between the public and private costs of managing the coast and the benefits derived from this resource.

James D. Fraser, Sarah M. Karpanty and Daniel H. Catlin are coastal ecologists in Virginia Tech's College of Natural Resources and Environment.

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