Add sea turtles to the list of worries related to extreme heat.

Fewer than 1% of sea turtles hatching on Florida’s beaches are male. And that has grave implications for the species.

The issue is temperature. Like alligators and crocodiles, the sex of a sea turtle is not determined at fertilization, but rather hinges on the temperature of the sand in which the egg incubates. That’s called temperature-dependent sex determination.

Nestled in sand that’s below 81.86 degrees Farenheit, a male sea turtle will develop. But turn up the heat of the sand to 88.8 degrees or higher and the creature in the egg develops into a female, according to the National Ocean Service. In between those temperatures, either a male or female might be formed.

In 2019, Camryn Allen, a scientist with the National Oceanic and Atmospheric Administration in Hawaii, told National Geographic that a count of sea turtles hatching on an Australian beach showed females outnumbered males 116 to 1.

Bette Zirkelbach, manager of the Turtle Hospital in Marathon, Florida, told Reuters that “scientists that are studying sea turtle hatchlings and eggs have found no boy sea turtles, so only female sea turtles for the past four years.”

That’s a big problem for the future of sea turtles.

The National Ocean Service warns that hotter sand increases the ratio of female turtles. And climate change, it said, could lead to “skewed and even lethal incubation conditions, which would impact turtle species and other reptiles.”

If turtle hatchlings worldwide do “skew dangerously female,” The Washington Post said they may become “an unwitting gauge for the warming climate.”

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The article notes, “If the trend continues at the Intergovernmental Panel on Climate Change’s lowest projection, researchers estimate that fewer than 1 percent of the country’s sea turtles will be born male by the century’s end. Higher rises could wipe them out completely.”

Efforts are being made to not just study the issue, but to try to solve it. National Geographic said one group of researchers had some success by putting palm leaves on the beach to provide some shade that cooled the sand.

The Washington Post said others found “gently digging up eggs and moving them to shadier parts of the beach has proved to work. So do sprinkler systems and dividing offspring into smaller batches,” since eggs that are close together provide each other with heat.

“Once replanted, the hatchlings burst from the ground some 50 days later in 1-by-1-foot enclosures, crawling in circles until someone scoops them into a crate and carries them to the shore, where they scramble into the waves,” the article said.

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