Coastal squeeze presents threats to sea turtles
By Dinah Voyles Pulver, email@example.com
Guided by an ancient instinct that isn’t fully understood, sea turtles visit Florida’s sandy beaches in droves each year between May and October to lay their eggs, making the state’s coastline one of the world’s leading turtle nesting areas.
Laden with ping-pong ball-sized eggs, tens of thousands of female turtles made the laborious crawl this year. An army of researchers, professional and volunteer, staked and marked the nests, in part to track how many hatchlings emerged to scramble to the sea. It was a banner year, and as nest numbers grew, they celebrated.
But then, powerful Hurricane Irma approached in early September. Turtle researchers waited with foreboding concern.
Sure enough, the hurricane’s powerful waves and storm surge washed away tons of sand, destroying thousands of nests, leaving eggs and nests exposed or saturated with sea water. On a few beaches, it washed in sand and buried sea turtle nests much deeper. The carnage left advocates, scientists and others pondering whether such losses could become more routine as sea levels rise.
Storms are natural, said Mariana Fuentes, a turtle researcher and assistant professor at Florida State University. “But if you start having more intense storms more often, then we have to start thinking about the cumulative impacts.”
If storm after storm heavily damages the beaches, and the impacts are coupled with rising seas, ongoing erosion and other factors, turtles will find fewer places to nest, said Kate Mansfield, a marine biologist and assistant professor who leads the University of Central Florida’s Marine Turtle Research Group.
Five federally protected turtle species nest on Florida’s beaches. Three are listed as endangered: leatherbacks, hawksbill and Kemp’s ridley turtles. Two — loggerheads and green turtles — are threatened.
That nesting is critical to the survival of sea turtle species throughout the world, said Gary Appelson, policy coordinator for the Sea Turtle Conservancy, an international conservation and research organization based in Gainesville. “The largest nesting aggregation of loggerhead sea turtles on earth is in Florida, along the Atlantic coast.”
One stretch of beach in the Archie Carr National Wildlife Refuge in Brevard County is only 20 kilometers long. But “that little postage stamp is incredibly important,” said Mansfield, of the beach UCF’s turtle research group has monitored since the early 1980s. “It accounts for about 15 to 20 percent of all loggerhead nesting in Florida and about 30 percent of all green turtle nests in Florida.”
Similar consequences could affect turtle populations worldwide, and researchers around the globe are asking the same questions: Will rising seas make it harder for the species to survive and thrive? And will there be enough protected oceanfront land to allow beaches and dunes to continue the natural cycles that have taken place on coastlines and barrier islands for centuries?
An ancient ritual
At first, it might seem that sea turtles wouldn’t be greatly impacted by rising sea levels. After all, sea turtles have nested on the world’s beaches for 100 to 125 million years.
“There have certainly been changes in sea levels over that course of time,” including previous rises and falls of the world’s oceans, said Dave Addison, a senior biologist with the Conservancy of Southwest Florida in Naples. Over time, turtles developed unique strategies for balancing natural disasters that wipe out their nests. They can dig several different nests over a summer, in different locations along the beach, increasing the survival chances for their eggs against high surf, predators and other natural events.
Addison has watched this nesting behavior for decades as the conservancy monitored five miles of beach at Naples and Keewaydin Island to the south. “Sea turtles are one of the great bet hedgers,” he said. “They lay nests over a long period of time. They’ve hit on this pattern that allows a lot of flexibility, so they can get past years when the nest success is terrible for whatever reason.
“They’re fascinating animals, the way they’ve worked out their life cycles and the way they cope with change,” he added. “But that doesn’t mean we shouldn't be concerned about what the future might hold.”
As sea levels rose and fell in the past, the beach advanced and retreated unfettered, eroding and then gaining sand over time. As seas rise this time around, it’s the first time sea turtles have had to contend with widespread human development that alters the way the beach erodes and recovers.
And, this time the changes may be coming “very rapidly,” said Mansfield. “We don’t know if the turtles can keep up.”
The basic issue is that turtles like to nest on nice beaches, and nice beaches are also places where people like to live, said Jeanette Wyneken, a professor at Florida Atlantic University. “There’s not a strong tendency to leave a lot of space between the view and the places people live.”
Building along the shore blocks the natural movement of beaches, contributes to erosion and, in some cases, slows the accumulation of sand on the beach, Wyneken said.
When homes, condos and hotels prevent the buildup of the beach, it means fewer places for turtles to nest, said Fuentes, who researches turtle nesting at St. George Island and St. Joseph State Park on the state’s northern Gulf Coast. That “coastal squeeze,” she said, will be the big issue going forward.
Beachfront property owners want to protect their property. But coastal armoring, in the form of seawalls and other structures, changes the way a beach responds to the ocean’s ebb and flow, said Wyneken and others. The beaches eventually become more narrow.
Over her 35-year career, Wyneken said, she has seen a decline in suitable habitat for beach nesting birds and sea turtles, as coastal residents tried sea walls and other measures to protect their properties.
“People who can afford to have houses on the beach have money and they have clout,” she said. “They want to restore the beach and put rocks up. I get it, but it’s not good for the animals that have used the beach for years and years.”
Post-Irma photos along north Florida beaches tell the tale, she said. “The beaches are missing.”
The most serious issue facing sea turtles, said Appelson of the Sea Turtle Conservancy, is the loss of nesting habitat due to chronic erosion — erosion that will be “exacerbated by sea level rise.”
About half of Florida’s 825 miles of sandy beach were considered critically eroded even before Hurricane Irma.
“What that really means is half of our beaches already need renourishment, perpetually, forever, irrespective of any future sea level rise," Appelson said. About a third of Florida’s beaches are already “replenished” with new sand every several years, he said, at a cost of between $70 and $100 million a year.
“From the Panhandle to northeast Florida, extreme beach erosion is an ongoing problem, which severely impacts sea turtle nesting and the public’s ability to recreate on the beach,” Appelson said. “It’s absolutely getting worse.”
When it’s time for a sea turtle to nest, she returns to the same region where she was hatched anywhere from 20 to 30 years earlier, depending on the species. Their lifespans are thought to range from 50 to 80 years. Scientists believe a combination of genetics, memory and navigation using the earth’s magnetic field helps sea turtles travel thousands of miles to foraging and breeding grounds and then to return to the beaches near where their mothers nested.
When a turtle arrives on a beach, she has no way of knowing whether that beach has been eroded or not, or that she could go two or three miles up or down the beach and find a better nesting site, said Melissa Bernhard, a staff biologist with Mote Marine Laboratory in Sarasota, which monitors 35 miles of beach in Sarasota and Manatee counties, including Longboat Key, Lido, Siesta and Venice.
As the beach shrinks, there’s only so high the turtles can go, because the dunes are lined with houses, swimming pools and walkovers, said Sharon Maxwell, founder of the South Walton Turtle Watch in Walton County. She also fears saltwater intrusion from a higher water table may impact nests on eroded beaches, as well as inundation from higher tides.
“Our beaches are very eroded. Even a high tide with a south wind,” she said, will push the Gulf up and over turtle nests.
Gulf County is among the Florida counties where homes have been condemned over the past year because of the erosion, said Jessica Swindall with the St. Joseph Peninsula Turtle Patrol. She worries a push to establish more sea walls could force turtle nests closer to the tide.
But with critical erosion putting both turtle nest areas and multi-million homes and properties at risk, what needs to be done?
“That’s the $64,000 question,” Appelson said. “There’s no simple answer to long-term beach protection.”
Coastal communities are in a real bind just with normal changes wrought by storms and seasonal tides, said Addison, the Southwest Conservancy biologist, but they’re caught “between a rock and a hard place” with rising seas.
If homes and other buildings were farther away from the beach, it would protect those properties and provide more area for the beach to adapt, said Fuentes and Wyneken. However, both researchers said they see resistance to that concept.
Some local governments have stronger setbacks than the state, including some that prevent sea wall construction, Appelson said, but those are “few and far between.”
Cape San Blas, on a barrier island in the Panhandle west of Apalachicola, is “one of the most erosive beaches in the state of Florida,” he said. And yet, “we continue to still line the beach there with development, and the beach keeps washing away.”
Finding a balance
Researchers are still trying to quantify the impact sea level rise could have on turtles and seeking long-term solutions to the challenges.
Addison, semi-retired, says he’s not going to be around to see the outcome in the years ahead. “But it’s not going to be pretty.”
Fuentes hopes for “a balance between protecting property and the natural environment.”
The value of having turtles in an ecosystem could be debated back and forth, Bernhard said. “But just the fact that these animals have been around for millions of years and have been able to overcome all sorts of obstacles over time makes it a shame we could be such a detriment to an animal like that, and have such an impact on this species,” she said. “To think they could overcome everything but humans is pretty sad.”
Even if sea turtle eggs can survive the surging seas and sand erosion, the eggs will have to contend with warmer temperatures and warmer water, which some scientists believe could leave the species without enough male turtles to be successful.
The sex of a sea turtle hatchling is determined while the embryo is growing in its sandy bed. The middle third of a turtle egg’s incubation period determines the sex of the turtle inside. Research shows the temperature of the sand may influence the sex of hatchlings. Some research has indicated the warmer the sand, above 81.8 degrees, the higher the ratio of female hatchlings, according to the National Oceanic and Atmospheric Administration. Imbalances between the ratio of female to male turtles, researchers said, could impact reproduction.
Wyneken and others have looked at whether conditions beyond temperature, such as moisture in the sand, may also influence the sex of hatchlings.
State wildlife officials also are among those looking into the potential impacts of a changing climate and rising seas on wildlife. The agency “continues to investigate and consider effects that climate change will have on Florida’s wildlife and habitats and identify possible adaption strategies,” stated Katie Purcell, an agency spokeswoman. In one report, the agency states rising seas are “one of the most important threats to Florida.”
Decisions could be made about how to rebuild the coastline or how to protect it, said Mansfield. “We really do have to think long-term when we’re considering sea turtle conservation issues.”
It will be interesting, she said, to see what the turtles do over time — and what Floridians do.