Florida sea turtle numbers up, but climate change poses threat

Ludmilla Lelis / Orlando Sentinel /

Published Sep 8, 2012 at 05:00AM

NEW SMYRNA BEACH, Fla. — Canaveral National Seashore and neighboring beaches in central Florida are reporting record numbers of loggerhead sea turtle nests, a promising change from a decade-long drop.

But now a new threat is looming: rising temperatures. Summers are gradually getting warmer at Canaveral. And with climate change scenarios projecting the trend to continue, there’s increasing concern it might get so hot that the eggs literally fry.

This could mean trouble especially for the male of the species, which is already at a disadvantage in Florida. Sea turtle biologists have long used the adage “hot mamas, cool dads” as a reminder that loggerhead sea turtles become male or female based on the temperature when their eggs incubate — higher temperatures make them females.

With the prospect of even hotter weather as a backdrop, the interplay between temperatures and sea turtle eggs is the basis for a study by University of Central Florida graduate student Monette Auman, who is tracking nest temperatures and hatching success of some loggerhead sea turtle nests at Canaveral National Seashore.

“It’s an interesting subject to discuss because there are questions like, what does an overabundance of females mean to the population?” Auman said. “And what happens if rising temperatures put sea turtles in a more precarious situation?”

From 2001 to 2011, average temperatures at Canaveral were 1.3 degrees Fahrenheit higher than they were from 1961 to 1990, according to a new study released by two environmental groups, the Rocky Mountain Climate Organization and the National Resources Defense Council.

Climate change scenarios suggest that average temperatures could continue to increase an additional 1.8 to 4 degrees by 2060, the report said.

Loggerhead sea turtles are protected under federal law as a threatened species, and Florida beaches are home to 90 percent of the nation’s loggerhead nests, making the state’s shoreline crucial to the species’ survival. The marine turtle nests are closely tracked, and regulations protect them from human interference.

In recent years, scientists have been concerned that the loggerheads may be in trouble. Though nest counts steadily increased during the 1990s, those numbers plummeted 40 percent to record lows in 2007.

This summer could be the turtle’s comeback season, though. Archie Carr National Wildlife Refuge, about 60 miles south, is one of the world’s most important nesting beaches and has had 18,425 nests to date. Volusia County, which includes New Smyrna Beach, has had a record-setting 902 loggerhead nests. Canaveral National Seashore also has topped its prior record with more than 5,700 nests.

When loggerhead nesting declined from 1999 to 2007, “it seemed that something was seriously wrong with the population,” said David Godfrey, executive director of the nonprofit Sea Turtle Conservancy. “Yet nesting is skyrocketing this year, and it reminds you as a turtle conservationist that we don’t know everything that is affecting turtle behavior or nesting patterns.”

Scientists have long known that temperature can have a strong effect on the cold-blooded reptiles. A winter freeze can shock young turtles into paralysis, as happened to thousands of young green sea turtles in 2010.

On the flip side, heat can speed up egg incubation, make all the turtle eggs turn female and, at the extreme, cause the eggs to fail. Some studies estimate that 80 percent to 99 percent of Florida hatchlings may be female, while the nests at beaches in Georgia and the Carolinas tend to produce more males.

Rising temperatures, and other effects of climate change, pose a great threat to the sea turtle and its habitat at Canaveral, the study by the environmental groups says.

“If the trend continues, we’ll have more females and fewer males, and at some point, we may have nothing but females,” said Stephen Saunders, president of the Rocky Mountain Climate Organization.

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