Rising seas mean shrinking South Florida future, experts say

 

Under current projections, the Atlantic would swallow much of the Florida Keys and Miami-Dade in a century, according to experts at a sea-level rise summit

cmorgan@miamiherald.com

The subject of global warming has become so politically unpalatable over the last few years that neither party mentions it much anymore.

A conference on climate change sponsored by Florida Atlantic University made it clear that ignoring the threat has done nothing to slow it down — particularly in South Florida, which has more people and property at risk by rising sea levels than any place in the country.

The two-day summit in Boca Raton, which wrapped up Friday, painted a bleak and water-logged picture for much of coastal Florida.

Under current projections, the Atlantic Ocean would swallow much of the Florida Keys in 100 years. Miami-Dade, in turn, would eventually replace them as a chain of islands on the highest parts of the coastal limestone ridge, bordered by the ocean on one side and an Everglades turned into a salt water bay on the other.

Ben Strauss, chief operating officer of Climate Central, an independent research and journalism organization, warned that much of the southern peninsula south of Lake Okeechobee would be virtually uninhabitable within 250 years.

“There’s good reason to believe southern Florida will eventually have to be evacuated,” Strauss told some 275 scientists and climate and planning experts from government agencies, insurance companies, construction experts and other businesses likely to be impacted by rising seas.

While scientists can’t yet predict with certainty how fast and high seas will eventually rise, there is no disputing South Florida will be ground zero for the earliest major impacts, said Leonard Barry, director of FAU’s Florida Center for Environmental Studies.

“The sky is not falling, but the waters are rising,” he said. “We need to recognize that, prepare for that and begin to address it.’’

Four counties — Miami-Dade, Broward, Palm Beach and Monroe — have begun to do that under a 2009 agreement to work together studying how to mitigate and adapt to the myriad ripple effects of rising seas.

Though it might take a century or more to flood people out, scientists warned that potential impacts will come long before in the form of increasing damage from hurricane storm surge and flooding, rising insurance rates and shrinking freshwater supplies as sea water taints coastal wells.

If the rate of rise increases, as some new studies suggest, all those impacts could come sooner — in decades, not centuries.

University of South Florida oceanographer Gary Mitchum said data from worldwide tide gauges suggest the sea level rise might be speeding up, jumping from about two millimeters a year from 1950 to 1992 to three millimeters since.

That amount, a little bit more than a tenth of an inch, adds up quickly in low-lying South Florida, according to expert analysis.

Six more inches, for instance, would compromise half of the South Florida Water Management flood control gates at high tide, potentially worsening flooding losses. Seven inches would consume 30 percent of Big Pine Key. At a foot, 60 percent of Monroe County’s land would disappear. At three feet, 85 percent would be inundated — along with a large swath of coastal Miami-Dade and Broward.

Overall, according to a “Surging Seas” report produced earlier this year by Climate Central, Florida easily ranks as the most vulnerable state to sea-level rise, with some 2.4 million people, 1.3 million homes and 107 cities at risk from a four-foot rise, according to the report. Louisiana, by comparison, has 65 cities below the four-foot mark.

Miami-Dade and Broward alone have more people at risk than any state except Florida and Louisiana, Strauss said. Lee and Pinellas counties also are at high risk.

It’s not just coastal areas either. Low-lying inland cities like Hialeah and Pembroke Pines could be flooded out by a rising, saltier Everglades.

Daniel Williams, an architect and post-disaster planner, said he envisions a future where Miami-Dade would be confined to islands on the highest points of an ancient coastal ridge that runs along the coast. Inundated homes and building along the coast might be left behind to serve as reefs.

The Climate Central study projects that under current trends, the most vulnerable areas could see increased flooding as early as 2030. The Intergovernmental Panel on Climate Change, an international science panel, estimates the average sea level could rise from seven inches to about 24 inches by 2100 but notes it could be higher under some scenarios.

James Beever, a principal planner with the Southwest Florida Regional Planning Council, said the changes can already been seen in Florida’s landscape.

Some salt marshes, he said, had already moved inland by the length of a football field. In the Everglades, mangroves have also marched inland, as salt water transforms freshwater marshes.

“The things you read about in the literature that this is going to happen, it’s already happening,’’ he said.

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