Climate change limits turtle's nests

James Cook University Science Alert 28 Jan 13;

A global map predicting where sea turtle nesting sites occur throughout the world has been developed by a James Cook University researcher, to help define where they lay their eggs and to help better protect their habitats.

Dr David Pike, from JCU’s School of Marine and Tropical Biology, said the project was an attempt to map sea turtle nesting habitat in coastal areas across the world.

The three-year study, "Climate influences the global distribution of sea turtle nesting", was the first step in predicting how sea turtles would fare under climate change, he said.

Dr Pike said sea turtles lived throughout the world, but only nested in tropical and subtropical regions of the world.

“Protecting nesting beaches is crucial towards conserving these species, but many areas of the world are difficult to access, and thus our understanding of where sea turtles nest is quite limited,” he said.

“My study used mathematical models to create maps of where sea turtles could nest under today’s climate.”

Dr Pike said he studied all seven of the world’s sea turtle species.

“The most important species here in Australia include green turtles (Chelonia mydas) and flatback turtles (Natator depressus).

“Flatback turtles nest only in northern Australia, so they are very important for Australian conservation even though relatively little is known about them. Green turtles are much different in that they nest in most tropical areas worldwide.”

The work involved computer modelling using global data on where sea turtles were known to nest and climate data such as temperature and rainfall, he said.

“All sea turtle eggs are vulnerable to temperature – nests that are too hot or too cold will not produce baby turtles.

“My study found that current climates, including temperature and rainfall, limit where sea turtles can nest, in terms of whether eggs will hatch, and some species can tolerate a wider range of nesting beach conditions than can other species.”

Dr Pike said that Australasia, the Caribbean Sea, and the Gulf of Mexico are important regions for sea turtle conservation because between three and six sea turtle species nest in these areas, and some individual beaches have several species nesting there.

“As the climate warms over the next several decades, we may begin to see signs of some nesting beaches becoming too warm for successful egg incubation, and other areas will become warm enough to produce baby turtles.”

Dr Pike said his main conclusion was that turtle nesting was highly dependent on climate, and that changing temperatures brought on through climate change could have a major impact.

“Turtles nest in areas with very distinctive climates that allow eggs to hatch, and whether these areas will remain suitable under climate change is the next big research question,” he said.

“The tight link between current geographic patterns of nesting and climate, along with the dependence of developing embryos on temperature inside the nest, imply that regional or global changes in environmental conditions could differentially influence the distribution of sea turtle species under climate change.

“Because sea turtles must nest on land, they must be able to continue nesting in areas that will produce hatchling turtles.

“If sea turtles are unable to find suitable nesting beaches, they may be unable to adapt to changing environmental conditions and decline as climate change takes hold.”

To view the maps online

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