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One of the world’s largest green sea turtle populations turns majority female due to climate change

By Johnny Lieu, January 9, 2108

Climate change has been disastrous for coral on Australia’s Great Barrier Reef.

It’s also spelling trouble for the more than 200,000 green sea turtles which make the area home, one of the world’s largest populations.

Researchers are seeing young populations in the Great Barrier Reef turn almost entirely female, according to a study published in Current Biology.

Unlike humans and most other mammals whose development of sex is determined by chromosomes, the sex of reptiles (such as turtles) is determined by an egg’s incubation temperature.

Queensland Governement

Warmer temperatures results in a female being born, while cooler temperatures means males. For an exact number of female and males to be born, scientists refer to the pivotal temperature which sits at 29.3 degrees Celsius (84.74 degrees Fahrenheit) for the green sea turtle.

But here’s the thing: There’s a range of only a few degrees separating the possibility of 100 percent males or females. Certainly a concern, as global warming continues.

« This research is so important because it provides a new understanding of what these populations are dealing with, » the paper’s lead author and NOAA marine biologist, Michael Jensen, said in a statement.

« Knowing what the sex ratios in the adult breeding population are today and what they might look like 5, 10 and 20 years from now when these young turtles grow up and become adults is going to be incredibly valuable. »

There are two distinct populations of green sea turtles along the Great Barrier Reef. On warmer northern nesting beaches, researchers noted 99.1 percent of juveniles, 99.8 percent of subadults, and 86.8 percent of adults were female.

Down in the cooler south, the population was 65 percent to 69 percent female. Left unchecked, the lack of males in future could be detrimental to green sea turtle populations.

« First back-to-back mass coral bleaching and now we find that virtually no male northern green turtles are being born, » WWF-Australia CEO Dermot O’Gorman said in a statement.

« Finding that there are next to no males among young northern green turtles should ring alarm bells, but all is not lost for this important population. Scientists and wildlife managers now know what they are facing and can come up with practical ways to help the turtles. »

In the case of the endangered loggerhead turtle, Queensland’s Department of Environment have experimented with shade cloths help keep nests cool and produce more males.

Ultimately, as O’Gorman notes, more needs to be done to achieve ambitious climate change targets — something much of the world is proving to be not good at committing to, so far.


Source : Mashable