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Forecasting Change: Warmer climate producing 99% female sea turtles in Florida

Increasing temperatures impacting ratio of male, female turtles, causing higher mortality rate

ORLANDO, Fla. – Many of us call Florida home because of our beaches. But, sea turtles are also calling Florida home.

According to the Sea Turtle Conservancy, about 90% of all sea turtle nesting in the U.S. happens on Florida beaches.

Joel Cohen is a volunteer with the Sea Turtle Preservation Society and has been keeping an eye on some of those nests in Brevard County, working with other volunteers to count and analyze every nest possible.

By the end of August, researchers across Florida reported a record number of loggerhead and green turtle nests this season, totaling more than 200,000 on our beaches.

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These nesting records along the Florida beaches are proof that conservation can be successful. Much in part because of the passing of the Endangered Species Act in 1973, providing protection to animals like green sea turtles and loggerheads.

“The nesting numbers are wonderful, absolutely great. We should celebrate them. But we can’t stop it there because that will give us the wrong story,” Cohen said.

A story that stems from a quickly warming climate, warming the ocean and the sand. In Melbourne, the last 10 years have all ranked as the top 10 hottest years on record with 2023 on track to do the same.

Unlike humans, the sex of sea turtles is determined by the temperature of the sand surrounding the eggs, making them especially vulnerable to changes to the climate.

Research shows that turtles that incubate in a nest with a temperature of 81.8 degrees Fahrenheit or cooler will be male. But eggs with a nest temperature over 88.8 degrees will likely hatch female.

“The normal rate is six females to every one male. Right now, in Florida, Australia and some other Caribbean islands, it’s 99 to one and in some cases 100% female,” Cohen said.

A skewed ratio that can have a negative outcome for sea turtles years from now, as they can take 25-30 years to reach reproductive age.

“They’ve adapted through climate change before, but it’s happening at such a high pace. Now, the rate of change with climate change is faster than the research can prove it.” Cohen said.

One of those researchers is Jeanette Wyneken from Florida Atlantic University, who has been studying this issue for the last two decades.

“We’ve calculated out how often do we need to have a good male year and when I say a good male year, I’m talking about around 25% of the other production is male. And it has to happen about every three to four years. And we haven’t been even coming close to approaching that,” Wyneken said.

Increasing temperatures are not only impacting the ratio of male and female turtles but also causing a higher mortality rate.

“Most of them can’t make it, and all of the clutch (number of eggs in a nest) dies. And if you have, like this year, record numbers of nests out there, you should have record numbers of hatchlings coming out. And we’re just not seeing that. And the reason why we’re not seeing them is because the embryos are getting too hot and or too dry to survive. This is a problem, if it’s too hot for the embryos, it’s too hot! And if we didn’t have air conditioning or shade, we wouldn’t be OK either,” Wyneken said.

“That’s why these studies are so important. You learn from the animals; they’re canaries in the coal mine of your their indicator species. So the indicators are not looking good. They’re scary alarms going off that we need to pay attention to,” Cohen said.

Ways to protect sea turtles:

  1. Do not disturb sea turtles: Never approach or touch a nesting sea turtle. If she is disturbed or spooked, she might not be able to lay eggs or may leave before completely covering up her nest.
  2. Hands off hatchlings: Hatchlings need to crawl on their own to the ocean to survive in the water. During their trip from nest to ocean, they also imprint on the beach, so one day they can return to the same area to nest. Do not remove hatchlings or eggs from a nest.
  3. Lights out for sea turtles: Brevard and Volusia counties have a “Lights Out Ordinance” effective May 1- Oct. 31 that requires all lights visible to be covered, blocked or turned off from 9 p.m. to 5 a.m. Sea turtles use the moonlight to navigate to and from the ocean, any artificial lighting can disrupt their ability to find their way back.
  4. Remove obstacles on the beach: Put away beach chairs and umbrellas at night. Before leaving the beach, fill in any holes and knock down sandcastles. These barriers can pose a threat to adult sea turtles and their hatchlings from making it back to the ocean.

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