Florida beach erosion has left many sea turtles with no place to dig a good nest

April 05, 1992|By Cory Dean | Cory Dean,New York Times News Service

ST. PETERSBURG, Fla. -- Every spring, the sea turtles begin returning to the beaches of Florida to lay their eggs.

Theirs is a treacherous journey. Shrimpers' trawls drown them, lights on ship and shore confuse them, and they are routinely ground up by dredging equipment.

But a more intractable problem awaits the females lucky enough make it to shore: in many places, erosion has left them with no place to dig a good nest.

Conservationists, oceanfront communities and state officials say they want to help the turtles, but they cannot agree how.

Every time someone proposes a remedy, someone else is quick to explain how it will only make things worse. Because the possible solutions involve access to the beach, a crucial part of Florida's lucrative tourism industry, the arguments are bitter.

And because all sea turtles in the United States are either endangered or threatened, the stakes are high, particularly for loggerhead sea turtles since 90 percent of the loggerheads in the Western Hemisphere nest in Florida.

The controversy centers on beach renourishment, a method of restoring an eroded beach by dredging sand from the ocean floor and pumping it onshore as a slurry. Many famous beaches, including Miami Beach, are maintained this way.

Short of requiring the turtles to bring their own sand, advocates say, renourishment is the only way to save them.

But the National Research Council reported last year that beach renourishment could result in "significant reductions in nesting success." The sand on renourished beaches is so tightly compacted that it is difficult for turtles to nest in it, the report stated.

Further, when the renourished beaches erode, they often form sharp scarps that the 250-pound turtles cannot climb over. Renourishment itself can destroy nests or leave them buried under so much sand that hatchlings never make it to the daylight.

So the state has proposed banning renourishment for up to eight months a year to give the turtles time to nest and the eggs time to hatch.

The proposal has provoked outrage among those who make their living in replenishment and those who rely on it to maintain their beaches.

Dredgers say they will not be able to renourish beaches in the winter months when it will be allowed. In winter's heavy weather the work is far more dangerous, they say, and so expensive that most projects will never be done, leaving the turtles with less and less beach each year.

Dredging and nesting can coexist, they say, if workers survey the beaches closely early each morning in nesting season, follow the trails of the nesting females, retrieve their eggs and incubate them on protected beaches or in hatcheries.

But conservationists who work with other kinds of turtles say they are not convinced that hatchery-born turtles can survive and reproduce in the wild. They say it is better to let the turtles take their chances with the beaches that remain.

The Florida Shore and Beach Preservation Association attempted to resolve the dispute at a conference here in February. The scores of government officials, dredgers, coastal engineers, geologists and biologists who attended could hardly agree on anything, except that fewer and fewer turtles return to nest each year.

In part the problem arises from the strict standards the turtles must meet as they lumber out of the surf in the darkness of a warm spring night and look for a spot to scrape out their nests.

Below the high water line, the eggs will be flooded; if the eggs are laid too close to the dunes, raccoons, crabs, ants and other predators will make a meal of them.

"Eroded and eroding beaches present one of the greatest long-term threats to the sea turtles," said Richard H. Spadoni of Coastal Planning and Engineering, a concern in Boca Raton, Fla., who advocates renourishment.

On one stretch of beach, he said, nest density rose from 90 per mile to almost 900 per mile after the beach was renourished.

But another speaker at the conference, Dr. Peter C. H. Pritchard, vice president of the Florida Audubon Society, said his research had left him doubtful that renourishment projects would help the turtles, especially if they involved moving turtle eggs.

He cited the Kemp's ridley turtle, a species that nests almost exclusively at a small portion of the gulf coast of Mexico, about 250 miles south of Brownsville, Texas.

In the 1940s, he said, at least 40,000 nesting females could be found on the beach on one day. Today there are probably only 600 females left and conservationists try to retrieve all their eggs for raising in hatcheries.

After almost three decades of this, he said, "the recovery of the species has been negligible."

The most likely -- and alarming -- explanation is that hatcheries are somehow turning out imperfect turtles that cannot compete and reproduce in the wild. But he added, "The effects of hatcheries and renourished beaches on turtles are unknown."

He said, for example, that scientists discovered only about 10 years ago that the sex of a baby turtle was determined by the temperature of its nest and that small differences could alter the ratio of females to males.

Randall W. Parkinson, a geologist at the Florida Institute of Technology, told the conference that a two-year project monitoring replenished and natural beaches at Sebastian Inlet, Fla., found no appreciable difference in nesting and hatching rates. Either the effects of renourishment were not significant, the study said, or they were not detectable in the time frame of the study.

Scientists do not know exactly how long sea turtles live in the wild or when they begin reproducing so some problems might not immediately appear. "We are so ignorant of sea turtle population dynamics," Mr. Pritchard said.

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