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Global Warming Is Turning 99 Percent Of Northern Queensland's Turtles Female

12 January 2018

Because incubation temperature of turtle eggs determines the animal's sex, a warmer nest results in more females. That means the temperature surrounding on the beach, also known as a rookery.

"For example, putting shade cloth onto key nesting beaches, which can reduce the sand temperature ... will produce more male turtles in a clutch of eggs", Mr O'Gorman said.

Green sea turtles are considered endangered by the International Union for Conservation of Nature.

However, the temperatures on islands in Australia's northern Great Barrier Reef have increased significantly since 1990s and are contributing to dramatic changes in sex ratio of turtles here.

A study published Monday in the journal Current Biology about green sea turtles that nest along island beaches near Australia's Great Barrier Reef found that turtles born in areas most heated by climate change are 99.8 percent female. At this temperature, the resulting young turtle population is relatively evenly split between males and females.

That was an increase in more females being born over time, because the adult population has an 86.7 per cent female bias. Researchers still do not know the ideal ratio, or how many males to females it takes to effectively sustain the population, Jensen said.

In one population towards the southern end of the reef, the turtles skewed 65-69% female, according to the researchers.While that's bad for that populatio' survival rate, it's not almost as alarming as what the researchers found in a genetically distinct population in the warmer areas toward the northern tip of the Great Barrier Reef.

The pivot temperature where a population will turn out 50 percent females and 50 percent males is based on genetics and varies with species and even individual nesting groups, the researchers wrote. As such, turtle populations from the northern Great Barrier Reef differ sufficiently from southern Barrier Reef turtles that the researchers were able to distinguish them by DNA analysis, says Jensen. The findings provide a new understanding of how warming temperatures are affecting sea turtle populations and how they will respond to climate change.

Biologist David Owens, a professor at the College of Charleston who was not involved in the study, agrees.

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This is extreme - like capital letters extreme, exclamation point extreme.

A sea turtle's sex is determined by its nesting environment.

"Is this species liable to go extinct? We won't see the effects of what's happening today for several decades", she said.

"That transitional range, from 100 percent males to 100 percent females, spans a very narrow band of only a couple of degrees", Jensen said.

As a result scientists and conservationists have warned that as, Australian turtle populations face "complete feminisation" in the near future.

"I'm virtually positive this is happening elsewhere", she said.

Sea turtles are the "lawn mowers of the ocean", according to Camryn Allen, an author of the new study and a marine biological researcher with the Joint Institute for Marine and Atmospheric Research - University of Hawaii and located at NOAA in Hawaii.

So strong is this fidelity to home that populations of turtles from different origins are thought to only rarely interbreed.

Mansfield told HuffPost that it's not clear yet how sea turtles will adapt to climate change, but she pointed out that the rate at which their habitats are changing is unprecedented.

Global Warming Is Turning 99 Percent Of Northern Queensland's Turtles Female