Lessons from New Orleans could save other cities already at sea level, such as New York and Miami. Global-warming models indicate that sea level will climb one to three feet this century and increase the frequency and intensity of storms. "Even if you believe that sea level and storm activity are rising because of natural cycles," Williams says, "these cycles run for 25 to 30 years, and we are only eight years into the current one. And the cycle will return." The USGS has recently finished fine-tuning a formula, called the Coastal Vulnerability Index, which can predict how at risk an open coastline is to high seas.
Despite the urgency, experts say the U.S. should not rush to erect new protection around New Orleans. "Politicians want to act now," Weijers remarks, but "you need a long-term strategy." His counsel? "You must learn how to work with nature instead of defying it."