Methods trialled to stop heat turning green turtles female in Queensland’s north

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A trial of ways to cool turtle nests is underway in Queensland’s Far North as global warming threatens turtle populations throughout the tropics. (Credit: Veronica Joseph / WWF-Australia).

MILMAN ISLAND: A trial of ways to cool turtle nests is underway in Queensland’s Far North as global warming threatens turtle populations throughout the tropics.

The nest cooling project is a partnership between the University of Queensland, the Queensland government, and WWF-Australia and is supported by Australian furniture company Koala.

Researchers from the University of Queensland and WWF Australia are testing a range of nest cooling techniques including pouring seawater nightly on a small number of nests and shading others with structures made from palm fronds.

The project was prompted by research indicating that more than 99% of green turtles being born in the northern Great Barrier Reef are female, causing concern for the future of that population.

Scientists say hotter sand, linked to climate change, is to blame. A turtle’s sex is determined by the incubation temperature of eggs with higher temperatures producing more females.

In the Far North, nest temperatures above 29.1°C generate mostly females, while sand temperatures above 34°C are fatal.

Temperature data loggers buried in the nests will indicate whether temperatures were kept cool enough to produce a healthy ratio of males and will be compared to temperatures in a control nest left in full sun.

Queensland government scientists have monitored nesting green and hawksbill turtle populations on Milman Island since 1990 in one of the longest running monitoring projects in the western Pacific.

The tiny island was chosen as the trial site so that researchers could test cooling methods on the nests of both species and because it is a suitable location to test shade structures.

On Raine Island, 120 kilometres south, the large numbers of green turtles coming ashore each night would knock over any shade structures.

Of all the green turtles nesting in the northern Great Barrier Reef, up to 90% nest on Raine Island or surrounding cays.

“If our project is successful cooling techniques could be trialled on Raine Island – the largest green turtle rookery in the world,” project lead Melissa Staines from the University of Queensland said.

A shade structure made from palm fronds and drift wood is also being tested as an alternative cooling method for islands that lack the resources to build an irrigation system or have no access to shade cloth and other materials.

“Climate change is real. It’s at our door, killing our reef and wildlife. We believe businesses need to get off the sideline and be a part of the solution. That’s why we work with experts like WWF and have given over $1 million to conservation in three years,” Koala founder Mitch Taylor said.

“Turtles have survived for millions of years but now they are in trouble because of pressures caused by humans,” WWF-Australia Marine Species Project Manager Christine Madden Hof said.

“If we can increase the numbers of male hatchlings we can give these magnificent creatures a chance,” she said.