Rising temperatures could cause a shift in the gender of sea turtle populations

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(PNJ.com) - Loggerhead sea turtle populations are set to become increasingly female as global temperatures continue to rise as a result of climate change, possibly to the point of threatening the species' survival, a new study suggests.

The study, published recently in the journal Nature Climate Change, warns that as global temperatures tick upward, more and more sea turtles, whose sex is determined by the average temperature during the incubation process, will be born female.

Initially, the researchers say, this will mean a spike in sea turtle populations as there will be more females laying eggs. However, they warn, if left unchecked, climate change could push turtle populations to the brink of extinction if not enough males are born to fertilize the increasing number of eggs.

Such a threat is more than a century away, according to the study, "Effects of rising temperature on the viability of an important sea turtle rookery." However, significant shifts in male to female birth ratios could be seen within the next 30 years.

However, Mark Nicholas, district biologist with the Gulf Islands National Seashore, said he is skeptical that climate change could truly threaten sea turtles' extinction given the animals' long history on the planet.

"The Earth was warmer in the past than it is right now, and turtles made it through," Nicholas said. "Turtles have been around for millions of years. They've lived through ice ages and warm spells, so they've got some kind of coping mechanism."

Though, should a shift in sex ratio of turtles begin to be seen, Pensacola and nearby beaches could become some of the most important turtle habitat.

At about 84 degrees Fahrenheit, developing sea turtles have an equal chance of being born either male or female.

Because of the cooler white sands that line coast of the Florida Panhandle, much of the Gulf of Mexico's male turtle population comes from Panhandle beaches, according to Gary Appelson, policy coordinator with the Gainesville-based Sea Turtle Conservancy.

"The Panhandle beaches are so important because they produce a different ratio of male to female than the southern beaches," he said.

The study was conducted on a sea turtle colony in the Cape Verde Islands off the coast of Africa.

While the same species of turtle as those studied, Panhandle loggerheads are importantly different, said Florida Atlantic University's Jeanette Wyneken.

"(Panhandle turtles) are genetically distinct from other nesting assemblages and so are a source of genetic diversity," she said in an email. "Genetic and geographic diversity are part of any species' resilience."

No matter what happens with climate change, sea turtles biggest threat, Appelson said, will remain the same — us.

"They've never been around when the beach was lined with steel and concrete," he said. "When a 40 year old sea turtle comes back to nest, when that hatching left there were no high rises, no bright lights, no 100 million tourists. The continuing erosion of Florida's beaches up against the line of development is certainly our biggest concern."

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