KEY LARGO -- You might not be able to hire a gondolier along U.S. 1 any time soon. But sea level rise could have portions of the Keys looking a little bit more like Venice in the coming decades.

That's was the message of University of Miami geologist Harold Wanless, who spoke about sea level rise before a packed crowd of more than 100 at John Pennekamp Coral Reef State Park last week. The lecture was part of the park's "Delicate Balance of Nature" series.

Wanless jokingly titled his lecture "The State of the Conch Republic Address" because he delivered it at the same time as President Obama's Jan. 27 State of the Union Address. According to his report, the Keys union is in some peril.

"What I am saying is don't think about your investment in coastal areas as something that is going to be passed down to your great grandchildren," Wanless said.

Since 1930, sea level in South Florida has risen nine inches, an eight-fold increase over the rate of the previous 2,000 years, Wanless said.

That might not sound like much, but in Key West it has been enough to transform roads that were once safely elevated a foot above the mean high tide into ones that are commonly flooded, city officials report.

To date, most sea level rise has been the result of water's tendency to expand as it warms. But experts expect sea level rise to accelerate as global warming melts the Greenland, Arctic and Antarctic ice caps. In 2007, the United Nations Intergovernmental Panel on Climate Change concluded that global sea levels will rise between seven inches and 1.9 feet by 2100. That estimate, however, did not allow for melting of the ice caps.

As the melting of the ice sheets has accelerated, studies in major scientific journals since then have concluded that sea level could rise five feet or more by 2100.

Wanless last week said that even with major worldwide reductions in greenhouse gas emissions, he expects such a scenario to unfold.

"People talk a lot about uncertainty," he said. "There isn't a lot of uncertainty. It's four to five feet this century."

With an average elevation of less than five feet, according to The Nature Conservancy, that could mean disaster for the Keys. Low-lying neighborhoods would be largely underwater.

In addition, coastal wetlands and mangrove environments would collapse, just as they have already along Cape Sable on the southern tip of the mainland.

"Miami-Dade and Broward will be diminished and risky places to live -- including all of the Florida Keys," said one slide Wanless presented at his lecture in reference to a three to five foot sea level rise.

The Wanless speech came as skepticism of climate change science is on the rise. A recent CNN poll found that the percentage of Americans who believe that global warming is caused by humans dropped from 54 to 45 percent between the summer and December.

The decrease came on the heals of this fall's "Climate-gate" scandal, in which hackers obtained thousands of e-mails from climate change scientists at the University of East Anglia in England. In some of the e-mails, the scientists appeared to be attempting to suppress information that did not fit with their conclusions.

Wanless urged attendees at his lecture to take global warming seriously.

"If you don't buy global warming, learn about it," he said. "It is too important. Don't listen to Rush Limbaugh. He is not a scientist."

Attendees on their way out of the lecture were convinced.

"Very informative," Islamorada resident Will Dunbar said. "I'm just going to be a grandfather. They're the ones that are going to be affected. They'll be the ones who'll inherit the earth."

rsilk@keysnews.com