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Global Warming Forces Innovative Sea Turtle Protection

Dave Sherwood in Playa Junquillal, Costa Rica
for National Geographic News
July 22, 2008
 
When nearly 900 endangered leatherback sea turtles emerged from the sand on this remote Pacific beach this spring, scientists rejoiced.

The near record hatch, up from just a handful the year before, signaled progress.

Absent from the headlines, however, was the fact the turtles were born in a fenced, shaded hatchery to protect them from predators and scorching sun.

Scientists here and elsewhere are increasingly finding they have no choice but to intervene as a warming Earth, changing ocean conditions, and coastal development threaten to outpace the sea turtles' ability to adapt.

"These are no longer natural problems," said Carlos Drews, who leads the marine turtle program for the World Wildlife Fund in Latin America. "We can't expect the turtles to adjust."

This realization has sparked a growing discussion among conservationists on how to help species cope with climate change.

"It's an experiment we've been forced into, and one we hadn't planned for," said Michael Coyne, director of SeaTurtle.org and chairperson of the International Sea Turtle Society.

Highly Endangered Long-lived animals, leatherback sea turtles can reach 6.5 feet (2 meters) in length and weigh up to 2,000 pounds (900 kilograms).

Found in the Pacific, Atlantic, and Indian Oceans and the Mediterranean Sea, the animals are highly endangered.

The Pacific population, for example, has declined to an estimated 5,000 animals, a 95 percent drop since 1980. Coastal development, poaching, and fishing bycatch are the main culprits.

(Related story: Rare Leatherback Turtles Gain Protection in Costa Rica [March 2008])

With climate change bringing additional burdens, turtles and their habitat must be carefully monitored, Coyne says.

This would allow biologists to react more quickly if a region's beaches suddenly become uninhabitable or food sources become unavailable.

"Sea turtles are … driven by temperature," Coyne said. "We need to track their movements as climate change progresses, then protect their new habitat."

Beaches "Too Hot"

Already close to extinction, climate change may prove the last straw for the Pacific leatherback. Warming temperatures on nesting beaches are the primary concern.

Unlike humans, sea turtles have no sex chromosomes. The temperature of beach sand surrounding an egg determines the sex of a developing turtle.

When temperatures top 85 degrees Fahrenheit (29.4 degrees Celsius), females predominate; under cooler conditions, males take over.

In places like Junquillal, beach sand temperatures inside nests regularly reach a lethal 104 degrees Fahrenheit (40 degrees Celsius), according to biologist Gabriel Francia, who leads a World Wildlife Fund project there.

Surface sand temperatures can be much worse, often cresting at 158 degrees Fahrenheit (70 degrees Celsius).

"If we leave these eggs in the sand to fend for themselves, they hard-boil and die. It is just too hot," Francia said.

Biologists and community members are planting native trees to restore natural vegetation—and shade—to the beach.

With the species at risk, the biologist has no choice but to transplant the nests. He says the few turtles that might hatch would be female, skewing the natural balance of sexes.

"We're tinkering with nature. And we don't know what effect that could have," Coyne said. "Ideally we can find a way to help turtles survive on their own in the long-term."

Only one in a thousand sea turtles is believed to survive the natural and human-made hurdles of life at sea—from hungry sea birds to offshore fishing nets.

Climate change may stack the odds even more for breeding turtles that return decades later to their natal beaches to nest.

"If the turtles return to these beaches and find them flooded, or too warm, we have to ensure that they have someplace else to go," Coyne said.

Ancient feeding patterns and migration routes may also be affected by changing ocean temperatures and rising seas.

Migrating Beaches

James Spotila, a turtle researcher at Drexel University in Philadelphia, Pennsylvania, says defending against such threats starts with protecting ocean beaches and the forest that backs them.

"Beaches can then migrate landward as ocean levels rise, continuing to provide habitat for nesting turtles," Spotila said.

Drews, of the World Wildlife Fund, says the challenge is deciding which beaches to protect.

Seeking refuge from heat, the adaptable turtles could push farther north or south, depending on rainfall and cloud coverage patterns.

"We have to develop a more flexible conservation model if these turtles are to survive. The rigid park boundaries of the past won't do," Drews said.

For now small victories, such as the bumper crop of turtles this year on Playa Junquillal, are a good start, he said.

"We need be sure every egg hatches, every baby leatherback lives, so that populations are best equipped to survive the new challenges they face," Drews said.
 

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