Many of Florida’s Sea Turtle Nests Were Destroyed by Hurricane Irma

https://www.nytimes.com/2017/10/06/science/hurricane-florida-sea-turtle-nests-irma.html

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In addition to wiping out homes and businesses, Hurricane Irma swept away a large number of sea turtle nests as it tore across Florida last month.

The state is a center of sea turtle nesting, and this year was developing into a very encouraging year for the endangered leatherback turtles, the threatened loggerheads and green turtles, said Kate Mansfield, a marine scientist and sea turtle biologist at the University of Central Florida. The hurricane suddenly dashed those hopes.

An official statewide picture of the damage to sea turtles won’t be available until Nov. 30, because the nesting season runs through at least the end of this month, said Simona Ceriani, a research scientist with the Florida Fish and Wildlife Conservation Commission. But it’s clear that nests in many areas of the state were destroyed by Irma, she said.

The northwest Atlantic region is one of the world’s two largest loggerhead nesting areas, and 89 percent of those animals are hatched in Florida, Dr. Ceriani said, citing a 2015 assessment.

At the Archie Carr National Wildlife Refuge, just south of Cape Canaveral, more than half of the green turtle nests laid this season and a quarter of the loggerheads were lost as the storm tore up beaches, said Dr. Mansfield, whose program monitors turtles in the refuge.

Endangered leatherbacks lay their eggs earlier in the season, so none of their nests were lost in the refuge.

Sea turtles, which take 25 to 30 years to reach reproductive age, lay their eggs in the open beach, under vegetation or at the base of a dune. The hurricane eroded key nesting beaches, washing away nests or flooding them with rainwater or seawater, Dr. Mansfield said.

Along two stretches of beach south of Cape Canaveral, more than 90 percent of incubating loggerhead nests were destroyed by the storm, representing about 25 percent of the season’s total.

Sea turtle eggs take 45 to 70 days to incubate in the sand and are more vulnerable early in development, she said.

Sea turtles may lay eggs several times a season. Loggerhead nesting tends to wrap up by August or September, while green turtle nesting may continue through part of the peak hurricane season, Dr. Mansfield said.

Loggerheads have laid only eight new nests at the refuge since the storm, while green turtles have laid 466.

Green turtles typically lay more nests in alternate years. Last year, Hurricane Matthew wiped out many nests, but it was a light laying season for the greens, so there were fewer nests to destroy, Dr. Mansfield said.

This year, with record numbers of green turtle nests on the northeastern coast of Florida — with 12,000 north of Cape Canaveral and more than 15,000 a bit farther south — huge numbers were lost, Dr. Ceriani said.

Hurricane Nate, which is bearing down on Florida’s Gulf Coast, is unlikely to have a huge impact, because the loggerheads that are more common in that area have already laid their nests for the season.

There may be some impact on remaining green turtle nests on the Atlantic coast if the storm hits hard on those beaches, “but I don’t expect it would be bad,” Dr. Ceriani said in a follow-up email.

Although the losses this year are significant, sea turtle populations will survive as long as the hits don’t keep coming, Dr. Mansfield said.

But with hurricanes expected to intensify and increase in frequency, Dr. Mansfield worries about the longer-term health of the populations.

“I’m just hoping with two hurricanes like this in a row that we don’t have another few,” she said, “because we need a break.”