"The pivotal temperature for sea turtle populations where they produce 50 per cent male and 50 per cent female is about 29 degrees Celsius".
Both marine biological researcher Ms Allen and Mr Limpus said they were optimistic that the turtles might adapt to the warmer temperatures.
The research examined two genetically distinct populations of turtles on the reef, finding the northern group of about 200,000 animals was overwhelmingly female.
Green sea turtles are considered endangered by the International Union for Conservation of Nature.
Using a new, non-invasive hormone test, the researchers from the U.S. National Oceanic and Atmospheric Administration (NOAA) Fisheries Department and the Queensland Department of Environment and Heritage Protection found that while 65 -69 percent of the turtles from the southern region were female, between 86.8 and 99.8 of turtles tested in the northern region were female, depending on age.
"Combining our results with temperature data show that the northern [Great Barrier Reef] green turtle rookeries have been producing primarily females for more than two decades and that the complete feminization of this population is possible in the near future", the study's co-authors wrote.
Warming temperatures are turning one of the world's largest sea turtle populations in Australia's Great Barrier Reef nearly entirely female, running the risk that the colony may not sustain itself in coming decades, a study has found. Sand temperatures determine the sex of turtle hatchlings, with warmer temperatures resulting in more females.
"But for this population we were quite surprised to find this result, because this is one of the largest sea turtle populations in the world and we would expect them to be doing very well". "Eggs, when they are laid, can become either male or female", explains biologist Jeanette Wyneken of Florida Atlantic University who also was not involved in the research. One population breeds at the southern end and the other nests in the Far North, mostly at Raine Island and Moulter Cay.
The team made this discovery after analyzing hundreds of green turtles (Chelonia mydas) of different ages at their foraging grounds on the Great Barrier Reef.
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David Owens, a professor emeritus from the College of Charleston in SC, was not involved in the new study but said he has dreamed of doing such research for years.
There's been something happening over the past 20 years, and if it's not climate change, I'm not sure what it is.
This is extreme - like capital letters extreme, exclamation point extreme. However, she says it could be the start of a decline in green sea turtle populations. Common sense tells you: "One male and a hundred females ― that's going to be a very exhausted boy". "The disconcerting thing is that we can now see how changes in the climate could affect the longevity of this and other sea turtle populations around the world".
If the trend continues, it could lead to the risk of producing all females or perhaps embrynoic death in many sea turtle populations.
"The pace of change affecting these populations is probably unlike anything they have experienced before", research biologist Camryn Allen, Ph.D., of NOAA Fisheries' Pacific Islands Fisheries Science Center, and a coauthor of the new research, said in a statement.
Mr O'Gorman said it was yet another indicator that climate change was having negative impacts on the Great Barrier Reef.
"The degree of temperature and habitat change that has happened is likely unprecedented due to how quickly these changes are happening now with the rapid warming of the earth", she told HuffPost in an email. If green sea turtles go extinct, we all lose.
Sea turtles play an important role in maintaining a healthy ecosystem in the ocean. "Without sea grass beds, many marine species humans harvest would be lost, as would the lower levels of the food chain".
"This is the first paper that's shown this multigenerational effect", influencing the gender of juveniles, older adolescents and adults, Wyneken said.