Climate turns up heat on sea turtles

Indeed, for years, puzzled scientists have observed leatherbacks mysteriously nesting in southern Baja California where temperatures weren't quite warm enough for incubation. The effort seemed a waste. But in the context of climate change – and sea turtles have survived past climate shifts – these northerly nests take on a new function.

"It will be those eggs that will hatch as the climate warms," says Carlos Drews, the World Wildlife Foundation's marine and species coordinator for Latin America and the Caribbean. "That gives them an adaptive window."

But turtles must live in a human-dominated world. Shifting north is not so simple: People and turtles tend to like the same sandy beaches. And while people and turtles can coexist – look at Juno Beach, Fla., says Dr. Safina, with "thousands of people and thousands of turtles" – people can alter beaches in ways that are harmful to turtles. Humans remove the vegetation immediately behind the beach to build houses, inadvertently causing erosion. They try to stabilize the beach with metal, stone, and concrete reinforcement. With predicted sea level rises – and stronger storms – the beach cannot migrate, and inevitably shrinks.

People also replenish shrinking beaches with sand dredged from offshore. Some ecologists think that this sand, high in fine clay particles, could suffocate hatchlings as they try to dig out of the nest.

"As climate changes, these turtles are going to have to find other beaches to nest on," says Frank Paladino, a professor of biology at Purdue University's campus at Fort Wayne, Ind. But human development "will have destroyed their ability to adjust and adapt to changing climatic conditions."

But the gravest threat may be on beaches where turtles already nest. Of the 13 nests counted on a recent May patrol here in Tortuguero National Park, eight nests – or 75 percent – had been poached. Even without human interference, only 1 in every 1,000 leatherback hatchlings makes it to adulthood.

"If you had a healthy population, the populations would have a better chance of adapting," says Emma Harrison, CCC's scientific director in Costa Rica. Already stressed, sea turtles have a greater chance of disappearing from a changing climate, she says. Helping turtles adapt ultimately means changing people's ways – showing those who live near nesting sites that turtles are worth much more alive.

In Costa Rica, as in many countries where turtles nest, custom has it that eggs eaten raw enhance male virility. But after Dr. Drews's team began an antipoaching campaign in communities near Junquillal in 2005, poaching dropped from almost 100 percent to near zero in one year. Residents saw that tourists would come to see the turtles, bringing money. Those who might have been poachers are now rangers, he says. They have a stake in the turtle's wellbeing.

When the project ends in a few years, "we want full appropriation by these young people," says Drews. "So the community will be the owners forever of the turtles."

Scientists aren't sure what would happen if sea turtles disappeared. But they suspect that whatever the turtles feed on will proliferate. Leatherbacks, which can weight up to a ton, eat jellyfish, lots of them. Jellyfish eat the young of fish species consumed by people. If you remove leatherbacks, one of the few jellyfish predators, the outlook for fish, an important source of food for humans, grows grimmer.

But while Safina sees these impact assessments as important, he says they don't capture the entirety of what is lost if such an ancient and mysterious creature disappears.

"This is a really wondrous world," he says, "and to eliminate [the] various opportunities to discover things that are wonderful [such as sea turtles] – even if you never see them – it, to me, greatly diminishes the prospects for being alive and for being a fully human being."

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