In an hourlong debate that brought together scientists and coastal community leaders, Suffolk County Executive Steve Bellone, a Stony Brook University oceanography professor, a small-town New Jersey mayor and two others debated the inevitability of human retreat from flood-prone areas.

It's an issue of heightened importance -- and sensitivity -- for coastal dwellers on Long Island and across the metropolitan area since superstorm Sandy slammed their shores in October 2012, taking scores of waterfront homes with it.

"Retreat is a very difficult word -- it's people's lives, it's our homes, it's our livelihoods, it's our communities," moderator Marilyn Jordan Taylor said in an introduction. The afternoon panel was one of nine Friday at the Waldorf-Astoria in Manhattan for the Regional Plan Association's 2015 assembly on urban planning and infrastructure. Taylor, an urban designer and architect, is on the association's board.

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The panelists, including a Columbia University scientist and a member of the Fairfield, Connecticut, Business Council, agreed that eventually, humans will have to move from low-lying areas or take serious and expensive steps to reinforce shorelines. They differed on timeline and who should be responsible for making changes.

"As Americans, generally speaking, we are great at responding to a challenge, but it's only when it becomes an absolute crisis . . . that we are willing to take the collective action necessary to make something happen," Bellone said.

Because of the sharp political divide on climate change, sea-level rise and forcing people from coastal homes, Bellone said he could not envision a near-future scenario in which "it is possible to build a consensus to achieve managed retreat." Bellone also said that market forces, such as sky-high insurance rates, will be more influential than the government in causing an eventual retreat.

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But Columbia special research scientist Klaus Jacob and Stony Brook Professor Malcolm Bowman, who studies storm surges, contested that.

Jacob said an institutional framework would eventually have to be created to make retreat a reality in places like Sea Bright, New Jersey -- his comments coming after Sea Bright Mayor Dina Long told the panel about her 1,000 residents who were evacuated for 10 days after Sandy and the 182 homes that still sit uninhabitable.

"We can talk about the time scale in which you're not sustainable -- but you're not sustainable," Jacob told Long. "So we have to start to think in terms of setting an institutional and financial framework."

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Bowman said the government will have to get involved as the stakes rise. "Where does the political will come from to make these capital investments? It comes from loss of human life," he said. "Something like 85 people drowned in Sandy."

After 1,833 people perished in Hurricane Katrina and its aftermath, he added, "that provided the political will to do something about the city of New Orleans, whether or not it was wise to rebuild that city. It can be done, and it can be done quickly."