KEY WEST — Treasure salvors searching for an 18th century wreck in the Florida Straits a few years ago made a fascinating but little-noticed discovery. Not buried treasure. Buried land.
Some 35 miles west of Key West, in 45 feet of water under a 5-foot layer of dense mud, lay an 8,500-year-old shoreline not unlike today's coast of the Florida Keys. There were well-preserved mangroves, pine cones and pine tree pieces, some amazingly still fragrant when brought to the surface.
"Looking at it, I was thinking: 'Wow, this could be the shoreline of Big Pine Key,' " said Corey Malcom, director of archaeology for the Mel Fisher Maritime Heritage Society.
The prehistoric past paints a sobering picture of what many experts see as an all-too-near future for the string of low-lying islands that make up the Florida Keys.
"South Florida is on the front line against sea-level rise in the United States, and the Florida Keys are ground zero," said Evan Flugman, who co-authored a Florida International University report on the importance of Monroe County tackling the issue now.
By 2100, under the best-case predictions by an international climate panel of a 7-inch sea-level rise, the Keys would lose about 59,000 acres of real estate worth $11 billion, according to the nonprofit Nature Conservancy.
Under the panel's worst-case projection of ocean waters rising 23.2 inches, about 75 percent of the Keys' 154,000 acres and nearly 50 percent of its $43 billion property value could become submerged. Consequences also include the loss of habitat for many endangered plants and species, including Key deer.
And the panel's predictions are conservative compared to some scientists' calculations.
The eye-opening projections were presented at a June meeting in Marathon to urge Monroe County Mayor George Neugent, other Keys leaders and residents to develop long-term plans to deal with climate change. Unlike Miami-Dade and Broward counties, the Keys do not have a climate change task force.
The charts displayed at the meeting, which depicted disappearing land, weren't intended as scare tactics. As Chris Bergh, the Nature Conservancy's director of coastal and marine resilience for Florida, said: "Nobody is going to drown from sea-level rise."
In the past century, waters in the Keys gradually rose 9 inches, an amount that caught the attention of scientists but few others. But if a growing consensus of climate predictions for this century prove true, rising waters will become impossible to ignore.
"This presentation is not to make anybody panic and run out and sell their property; I live on Big Pine and am trying to add on to my home," Bergh said. "It's designed to make people think and get better information."
During the presentation, Patrick Gleason, a geologist and member of the Broward County Climate Change Committee, noted that South Florida is among the world's more vulnerable areas, due to low elevation and a porous limestone base.
A Nature Conservancy study mapped out the potential ecological and economic consequences of rising seas for the Keys, particularly Big Pine Key. Yet the FIU study concluded that little has been done to plan for climate change in the Keys.
"If we are the canary in the coal mine, let's start tweeting," said Alison Higgins, the Nature Conservancy's Florida Keys conservation manager, who also serves as president of the Keys' nonprofit Green Living Energy Education.
James Murley, appointed by Gov. Charlie Crist as chairman of the Florida Energy & Climate Commission, said Monroe County should take advantage of its state designation as an area of critical concern. He said the county should seek help from the state and nearby climate change task forces.
Murley, who lives part time in Key West, acknowledged that "there are still a lot of science questions out there. But go with what you know and start making plans, which you can adjust."
Experts at the Keys meeting said any plan to address rising seas should include mitigation to help reduce greenhouse gases that are accelerating sea-level rise, and adaptation to cope with the consequences.
"Some people think, 'Let's put up sea walls, build New Orleans-type dikes and levees,' " Bergh said. "But that won't work for the porousness of rock and sand in the Keys."
Residents attending the meeting offered their own suggestions. One said the Keys should clean up toxic sites that could pollute the sea. Another suggested raising the roadbeds every time a road is repaved.
Already, though, scientists say the Keys have seen the results of climate change, from coral reef bleaching to loss of land. Standing in about a foot of saltwater that now fills a 1950s mosquito-control ditch on Big Pine Key, Bergh showed how the sea already has saturated the once-dry spot. Pointing at a dead tree, he said: "The pines tell the story."
Under the international climate panel's best-case scenario, Big Pine Key would lose 16 percent of its land to the sea and an additional 11 percent of upland habitat for the endangered Key deer and other rare species and plants.
Under the worst-case prediction, the sea would claim 51 percent of Big Pine Key, and leave only 4 percent of the island's pine forest and hardwood hammocks intact.
"Whatever we do, we are just buying time," Bergh said. "Ultimately, the sea will cover this whole place."