October 6, 2017 at 9:24 AM
Scientists have monitored the nests of green sea turtles along a stretch of central Florida’s coast for 35 years, and the trend over that time has been up, up, up.
In the 1980s, nests recorded each year numbered in the dozens. About a decade ago, there were more than 5,000. This spring was a record-breaker: The turtles laid eggs in 15,744 nests.
Then came Hurricane Irma.
University of Central Florida researchers who run the monitoring project said that more than half the green sea turtle nests along the 13 miles of Archie Carr National Wildlife Refuge — a crucially important U.S. spot for both green and loggerhead sea turtles — were washed out by the storm surge last month. Loggerhead turtles, which nest and hatch earlier in the season at the same site, got off a bit easier: 24 percent of their nests were lost.
“We spend an entire summer on the beach counting all the nests and keeping track of what’s hatching, and who hasn’t hatched yet, and interacting with the adult females,” said Kate Mansfield, an assistant biology professor who directs the university’s Marine Turtle Research Group. “It’s kind of a bummer to have all of that wiped away in a day and a half.”
Unusually high tides are now compounding the troubles, she said, because the eggs in remaining nests, and in those that green turtles have made since Irma, aren’t likely to do well when submerged under saltwater.
How bad is it? It could take 25 years or so to really know, Mansfield said. That’s about how long it takes for sea turtles to reach sexual maturity, at which point females mate offshore and then typically head back to the beach where they were born. There, they use their flippers to dig cavities, drop out more than 100 eggs the size of ping-pong balls, and then cover them up. Tiny turtles hatch after 45 to 70 days and head to the ocean.
Mansfield joked that this cycle means she’ll know around the time she retires whether Irma killed off a significant number of females in 2017. But the turtles’ large clutch size gives them a certain resilience, she said.
“One hurricane in the grand scheme of things is not going to cause a population crash,” she said, provided Irma isn’t the harbinger of a more storm-heavy future. Frequent lashing hurricanes, along with coastal erosion or efforts to “armor” beaches against erosion that interfere with turtles’ access to the nesting grounds, could spell problems for Florida’s sea turtles.
“We need to make sure that this trend continues, and is sustained over time,” she said of the turtles’ recovery. Both loggerhead and green sea turtles are listed as threatened under the Endangered Species Act.
In normal times, what Mansfield refers to as a “small army” of researchers and interns plies about 29 miles of central Florida coast in ATVs to observe the turtle terrain. During the May through August nesting season, they concentrate on the southern section, where the density of nests is higher and “gives us the pulse on the populations of loggerheads and green turtles in the Atlantic,” she said.
And those populations have been looking up — especially for green sea turtles, who were once killed in large numbers for their meat. This year, however, the researchers are likely to wrap up their work earlier. There simply aren’t as many nests to count, Mansfield said.
“We’re having a difficult time even just doing surveys . . . We can’t even access the beach in some places,” Mansfield said. But, she added, “hopefully in two years or so we’ll get green turtles back and nesting again in high numbers.”