Climate turns up heat on sea turtles

The ancient mariners need beach temperatures that are just right to hatch their eggs. If it's too warm, only females are born – and a species could vanish.

from the June 21, 2007 edition

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But many scientists don't see direct human meddling in nature as a viable long-term solution.

"I think it will be inescapable that people will to try to work around these problems," says ecologist Carl Safina, author of "Voyage of the Turtle." "But constant intervention as a way of keeping a wildlife population in existence strikes me as probably a losing battle.

"If the expectation becomes that we will simply adjust to [climate change], ... I think we're just asking for an overwhelming slew of problems," he adds.

In pristine conditions, sea turtles might be able to adapt. Females lay several clutches of eggs each nesting season, on different areas of the same beach or different beaches entirely. Some scientists speculate that by dispersing her eggs, a mother turtle increases the chances of some eggs hatching.

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.

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