Sea turtles laid a record 52,500 nests in Florida but 99% are female

• Sea turtle nests hit record highs in Florida this year, tripling last year's numbers.
• Most new turtles are girls, because a turtle's sex depends on the temperature they sit in as an egg.
• This is probably a symptom of climate change, and may spell disaster for future turtle populations.

Baby sea turtles are back in Florida in record numbers, but it's not time to celebrate just yet.

Almost 99% of new turtles are female, which means future generations could be in trouble, Joel Cohen, the director of communication at the Sea Turtle Preservation Society, told Insider.

That's because the sand where turtles nest is warmer than usual due to the abnormally warm temperatures this summer related to climate change. And temperature is what determines these turtles' sex.

"It's really overwhelmingly bad that we've done this amazing conservation work and brought this species back to record nesting," Cohen said, adding, "And now we are seeing this overwhelming problem of climate change."

"The alarm bells are going off," he later said.

The turtles laid 52,500 nests this year along the Space Coast, an area of eastern Florida named for its proximity to NASA's Kennedy Space Center. That's three times the amount of nests from the previous record set in 2022, ABC News reported. 

But even amongst all these record numbers, from 2018-2022, scientists studying the hatchlings found no male sea turtles, Lucy Hawkes, an ecologist who studies turtle sex ratios from the University of Exeter, told Insider in 2022. 

How does this happen

For most animals, sex is determined by preset genetic codes. But for many turtles, alligators, and crocodiles, sex is determined by the temperature they're incubated at.

If the sand surrounding a turtle's eggs is 81.8 degrees Fahrenheit or lower, all or most of the turtles will be male, but if it's above 88.8 degrees F, the turtles will be female. If temperatures fluctuate between this range, then there will be a mixture of male and female turtles, according to the US National Oceanic and Atmospheric Administration.

The turtles bury their eggs in sand, but they don't dig deep enough to avoid the influence of the ever-warming surface, Cohen explained. This past summer, parts of the sand in Florida's Miami South Beach — about 225 miles south of Space Coast — reached as much as 137 degrees F, USA Today reported.

So in a world that continues warming, the ratios of female to male turtles could continue to skew. This could eventually spell trouble for future generations of turtles looking to reproduce. 

"If you ran out of all males, it would threaten the population — but we don't think that's going to happen too soon," Hawkes said. 

How they may adapt

Despite these concerns, Cohen remained optimistic, pointing out that the sea turtles have survived over 230 million years, withstanding multiple mass extinctions, according to the British Natural History Museum. They're surprisingly durable. 

Some of the turtles have begun to act differently, in what could be interpreted as an effort to adapt to the heat. Cohen said that some turtles have been moving farther north, into the cooler sand of the Carolinas, to nest. 

Others have begun nesting earlier than normal, beginning to climb ashore in February, a month ahead of their typical breeding pattern. Cohen said that the data on these behaviors is sparse, but that to him, it's still encouraging. 

"They are amazing animals. And they have ways to deal with all kinds of things that have been thrown at them," Cohen said.