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Climate Change Could Turn Over 90% of Green Turtles Female by 2100

“It’s hard to say whether it’s good or bad but it’s big and it could have a lot of cascading consequences. Though it does seem a little scary.”

Due to an unusual biological trait of turtles, warmer temperatures can affect the resulting gender of turtle hatchlings. Currently, about 52 percent of hatchling green turtles, one of the seven sea turtle species, is female but that number could grow into an overwhelming majority of females as temperatures rise around the world.

Unlike most mammals, green sea turtles do not develop into males or females by sex chromosomes, but rather, the temperature outside of the egg determines the sex of the embryo. Warmer temperatures contribute to females and cooler temperatures to males.

According to a study done by Portugal’s Marine and Environmental Sciences Centre and the University of Exeter, 76-93 percent of turtle hatchlings will be female if a prediction of warmer temperatures by the Intergovernmental Panel on Climate Change (IPCC) is correct.

Dr. Rita Patricio, a marine ecologist at the Centre for Ecology and Conservation at the University of Exeter’s Penryn Campus in Cornwall, said, “Green turtles are facing trouble in the future due to loss of habitats and increasing temperatures.”

Although the study was specific to Guinea-Bissau, West Africa, researchers say that the results would be similar globally. The researchers also predict that 33-43 percent of current turtle nesting areas will be engulfed by rising sea levels.

Green sea turtles can live as long as 60 to 70 years. Biologist David Owens, a professor emeritus at the College of Charleston, told the Washington Post last year, “Oh yes, there are a few males remaining, and there will be for decades to come. But they will eventually die off. I predict that very soon the population will start to see reduced fertility at the nesting beach if it is not already happening.”

The most prominent nesting place for green turtles in Africa, the Bijagós Archipelago, is also the chief breeding ground for the species in the South Atlantic.

Patricio continued, “Our results suggest the nesting population of green turtles [sic] the Bijagós Archipelago, Guinea-Bissau, will cope with the effects of climate change until 2100. Cooler temperatures, both at the end of the nesting season and in shaded areas, will guarantee some hatchlings are male. Although rising temperatures will lead to more female hatchlings – and 32-64% more nesting females by 2120 – mortality in eggs will also be higher in these warmer conditions. As temperatures continue to rise, it may become impossible for unhatched turtles to survive.”

Climate change resilience of a globally important sea turtle nesting population,” the paper published by Patricio and her colleagues with the results of the study, was published in the journal Global Change Biology. The MAVA Foundation funded the research.

By 2100, as much as 93 percent of green turtle hatchlings could be female. What that would mean for the turtle population is unclear.

A single male turtle can impregnate multiple female turtles, as such the loss of the male population isn’t likely as devastating as a loss of the female population. However, an overwhelmingly disproportionate gender population is worrisome.

“It’s hard to say whether it’s good or bad but it’s big and it could have a lot of cascading consequences,” said Rory Telemeco, a biologist at California State University Fresno, to the Washington Post. Telemeco is not affiliated with the research, but studies temperature and reptile development.

“Though it does seem a little scary,” Telemeco added.

Leighanna Shirey

Leighanna graduated with a degree in English from Pensacola Christian College. After teaching high school English for five years, she decided to pursue her dream of writing and editing. When not working, she enjoys traveling with her husband, spending time with her dogs, and drinking way too much coffee.

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