Turtles: the new clue to climate change?

Vesela Todorova, The National 1 Mar 10;

ABU DHABI // For as long as anyone could remember, hundreds of marine turtles used to make their way to the beaches of Abu Dhabi to lay their eggs between the middle of March and June.

For the past three years, however, the sea creatures have changed their breeding habits; their nesting season is now starting about two weeks later.

Scientists at the Environment Agency-Abu Dhabi (EAD) say they do not know exactly why this is happening. But they suspect it could be an early indication of how climate change is affecting the turtles and perhaps other species, as well.

“The nesting season has shrunk from 90 days to 75 days,” said Dr Himansu Das, an EAD scientist.

The agency has been monitoring sea turtles since 1999. For the past three years, the nesting season has started in April, instead of the second half of March, Dr Das said.

He speculated it was probably due to the fact the winter rains now last until the end of February and into March. The cooler, more turbulent seawater associated with storms delays mating and, therefore, nesting on the beaches.

Two kinds of marine turtles the green and the hawksbill live in UAE waters. Between 5,000 and 7,000 feed on seagrass and coral around the shores of Abu Dhabi. Of the two species, only the hawksbill is known to regularly nest here. So far, despite the changes to their nesting period, the population is stable; between 150 and 217 females come to Abu Dhabi each season, Dr Das said.

Dr Thabit al Abdessalaam, the director of the EAD’s biodiversity sector, said other species also seem to be affected. There is data that young kingfish are entering the fishery later that usual, which could indicate a delay in spawning.

“In Oman, they have noticed the same with yellow-fin tuna,” he said.

The scientists were making their comments ahead of this year’s turtle nesting season and two days after southerly winds caused sandstorms and thunderstorms.

Dr al Abdessalaam said more research was needed before a clear connection between climate change and the delay of the nesting patterns could be made.

“It is too early to say it is climate-induced,” he said. “Three years is a short period of time. We need a longer time series to confirm that. We need at least a decade of data.”

While the delayed turtle nesting season does not appear to be hurting the overall population, it appears to be having an impact on the gender of hatchlings.

If the temperature is between 29°C and 30°C, the number of male and female hatchlings will be roughly even, said Dr Das. But as the temperature gets higher, more females are hatched.

Because sea turtles are highly migratory, the negative connotations of gender imbalance are softened, he said.

“There are places in the Pacific where it is cooler and predominantly males are hatching,” he said. But Dr al Abdessalaam cautioned that the long-running implications on the population could be serious.

Turtles are known to travel thousands of miles around the ocean, and the details of their migrations are not clear to scientists.

“We do not know the long-term implications; no one has studied this so far,” Dr al Abdessalaam said.

In addition, as the weather gets hotter, the number of hatchlings produced and the health of the hatchlings are adversely affected. For example, said Dr Das, a nest studied in the middle of June showed a hatching success rate of zero.

“Temperature also affects the rate of growth of the embryo and hatchlings,” he said. Birth defects are also more common when temperatures are higher.

“What we need to do is find a mechanism to buffer this,” Dr al Abdessalaam said.

Buffers could include the creation of protected areas as well as measures to ensure the nesting habitats are not further affected by development.

Another option is to restore habitat on beaches already affected by development.

Also, environmental organisations will be cautioned to clean beaches by hand. Using machines for clean-up can compact the sand and remove native vegetation, destroying two important conditions for successful nesting.