When scientists consider the possible effects of global warming, there is a lot they do not know. But they can say one thing for sure: sea levels will rise. This rising water will be felt along the artificially maintained beaches of New Jersey, in the vanishing marshes of Louisiana, even on the ocean bluffs of California.

According to a 2000 report by the Heinz Center for Science, Economics and the Environment, at least a quarter of the houses within 500 feet of the United States coast may be lost to rising seas by 2060. There were 350,000 of these houses when the report was written, but today there are far more.

"If it is as bad as people are saying, at some point it will be a crisis," said Thomas Tomasello of Tallahassee, Fla., a lawyer who represents many owners of coastal property. But he does not dwell on it. "I cannot deal with sea level rise," he said. "That is such a huge issue."

Though most of the country s ocean beaches are eroding, few coastal jurisdictions consider sea level rise in their coastal planning, and still fewer incorporate the fact that the rise is accelerating. Instead, they are sticking with policies that geologists say may help them in the short term but will be untenable or even destructive in the future.

Florida is a good example. To prepare for hurricane season, which began June 1 and has already brought Tropical Storm Alberto, Floridians were still repairing storm damage from 2005 and even 2004, building or repairing walls to shield beachfront buildings.

Until May 1, when turtle nesting season forced them to stop, they were also pumping hundreds of thousands of cubic yards of sand onto eroded beaches. Florida has relied on this approach for decades, but after the past few storm seasons, there has been an increase in applications for sea wall permits, many from Mr. Tomasello s clients. "If you have a house or a condo that is threatened, it is really the only alternative," he said.

Maintaining eroding beaches with artificial infusions of sand is difficult and costly, and as sea levels rise, it may become economically impractical or even impossible. "The combination of sea walls and rising sea level will accelerate the rate of land loss in front of those sea walls," said Peter Howd, an oceanographer who conducts shoreline research for the United States Geological Survey in St. Petersburg. "So people with a sea wall and a beach in front of it will end up with just a sea wall."

Many people "want to disagree" that global warming is a threat to the coast, said Daniel Trescott, a planner on the staff of the Southwest Florida Regional Planning Council, one of 11 such boards in the state. "But the first place you see these impacts is on the beach."

The council is participating in a federal program to map areas that are vulnerable to rising sea levels, identify crucial infrastructure there and assess how much will probably end up protected by armor. Mr. Trescott said he hoped that the effort would put sea levels "on the radar, to start addressing how we are going to respond to this rise."

Elsewhere, scientists are studying data from ancient sediment formations to predict how the barrier islands that form most of the East and Gulf Coasts will respond to rising seas. "As scientists, and especially as federal agency scientists, it is our responsibility to think long term," said S. Jeffress Williams, a coastal geologist at the United States Geological Survey in Woods Hole, Mass., who is organizing a session on sea level rise at a meeting of coastal scientists next year. "What are the cumulative impacts we can expect over the next 50 to 100 years?"
(Por Barbara P. Fernandez, The NY Times, 20/06/2006)