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Forecast: The Florida Keys are sinking

Part 1: Why America should care.

Key West resident Thomas Sakarizon holds his dog while standing in a flooded garden in Key West, after Hurricane Wilma hits Florida's southern west coast, Oct. 24, 2005. (Carlos Barria/Reuters)

Florida is slipping under water. And as global climate change steadily encroaches upon the Florida Keys, the Nature Conservancy is wondering why it should even bother saving land that will end up under water.

KEY WEST, Florida — Jody Thomas’s Key West home lies just across the street from the town cemetery, the island’s highest point.

That it sits just 18 feet above sea level is an indication of just how low-lying — and thus how vulnerable — this stretch of islands off Florida’s southern coast are.

Across the world, the temperature at the surface of the sea rose nearly 1 degree Fahrenheit during the 20th century.

As the waters continue to warm, they will expand.

Thomas, the director of the Nature Conservancy’s Southern Florida Conservation Region, and a colleague, Chris Bergh, rolled out a laminated chart on Thomas's wooden floor and showed why they’re worried.

The map showed the elevation of Big Pine Key, a low-lying island up the Keys where Bergh lives and where the Nature Conservancy, a nonprofit dedicated to protecting nature and preserving wildlife, is a partner in a deer refuge.

Four smaller maps showed the same island under different levels of rising water.

The first depicted the expected sea level rise by the end of this century under the most optimistic conditions, a scenario that assumes the world cooperates to aggressively fight climate change. Under that scenario, the seven-inch rise had flooded 16 percent of the island. Water would be sloshing through some streets and presumably the ground floor of many houses.

The next two maps were based on more realistic assumptions, and in these projections the sea rises accordingly.

Under a scenario of rapid world economic growth with little attention to climate change — the track the planet is currently on — waters would rise two feet.

In this scenario, waves would wash over more than half the island.

Bergh’s final map reflected the work of the German climatologist Stefan Rahmstorf, who junked the computer models and simply projected current trends to the end of the century. In this case, Big Pine Key was almost entirely under the sea, just a grid of rooftops and a scattering of highlands rising above the waves.

“The important thing is that we don’t know where we’re going to fall on this spectrum,” Bergh said. “And storm surges and abrupt changes could make it happen much more quickly.”