Since figuring out the sex of buried eggs is too hard, researchers chose to catch sea turtles and use genetic tests to find out where they'd come from.
In Australia alone, there are seven regional populations of green turtles that nest in different areas; the southern Great Barrier Reef, the northern Great Barrier Reef, the Coral Sea, the Gulf of Carpentaria, Western Australia's north-west shelf, the Ashmore and Cartier Reefs and Scott Reef.
"With average global temperature predicted to increase 4.7 Fahrenheit (2.6 Celsius) by 2100, many sea turtle populations are in danger of high egg mortality and female-only offspring production", said the report.
Of green turtles from warmer northern nesting beaches, 99.1% of juveniles, 99.8% of subadults, and 86.8% of adults were female. As sands warm, more females will hatch relative to males; if the sand temperature tops 84.7 degrees during incubation, only females will emerge.
Sea turtles have a long lifespan and therefore might not be able to adapt to drastic changes in the environment so quickly. Warmer nests, which are dug into beaches, mean more females.
Researchers release an adult green sea turtle after it was caught during the survey. Heat up the eggs, and only females are born.
Clownfish are all born male, with most dominant male of the group will become female.
This research is so important because it provides a new understanding of what these populations are dealing with.
"I'm virtually positive this is happening elsewhere", she said.
Green sea turtles are not the only creature to be affected like this. "If this happens everywhere, we'll probably see a slow decline".
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.
Allen comes to this conclusion from the team's analysis of recorded air and sea temperatures from one of the nesting sites of the northern population from 1960 to 2016. Many other animals determine their sex by temperature such as alligators, iguanas, and fish.
It is possible that they could lay their eggs earlier in the season, instead of waiting for the hottest weeks of the year, but Jensen said there is no evidence to suggest that such a shift has or could occur.
Sea turtles play an in maintaining a healthy ecosystem in the ocean. If they are lost, other species that depend on the same habitat will also be harmed.
Wyneken was confident that other green sea turtle populations are experiencing the same thing.
When the researchers looked at sand temperatures from those beaches, they found the green sea turtle nests in those areas have been incubated above the temperature that produces a balanced sex ratio since the early 1990s.
More fun facts. The not-so-fun fact?
Allen said the government of Australia has started to take steps toward helping sea turtles, such as funding the Raine Island Recovery Project to study and support the local turtle population.
The study's authors believe that their research points to a dim future for this population of north Great Barrier Reef turtles. Using a combination of endocrinology and genetic tests, researchers identified the turtles' sex and nesting origin.
Wyneken agrees. "If nothing changes, then it's going to be a problem", she says. "But we do know they don't have sex chromosomes like humans do".
They found that populations, who live on cooler beaches in the South were only about 65 to 69 percent female.
The researchers expressed concern that in the future, the lack of males could leave many females unable to find a mate and "eventually impact the overall fertility of females in the population".
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