It's the end of men: sea turtle edition. As temperatures rise, finds a new study published in the journal Nature Climate Change, more and more of these creatures are being born female, creating a skewed sex ratio that could one day lead to the species' demise.
Unlike humans, whose chromosomes determine their sex, sea turtles' gender is dictated by an external factor: the temperature of the sand in which the mother turtle buries her eggs. As the sand gets warmer, more females are typically produced. Carrying that out to its logical conclusion, study author Graeme Hays explained to the Guardian, suggests that a warmer world will mean the end of male turtles:
At the “pivotal temperature”, 29C [84F], the gender ratio of turtle hatchling is approximately 50:50. The ratio is upset as the sand temperature increases, until it reaches around 31C [88F]. Sand that hot will “almost exclusively produce female hatchlings”, Hays said.
...“Over the next 20 to 30 years, it’s not going to create problems,” Hays said. “In fact there’s going to be a benefit to the turtles, because there’s going to be more females produced, which means more females laying eggs. More females will lead to a population expansion.
“But ultimately, if you extrapolate long enough into the future … once you get 100 years or more into the future, then things start to look serious. You have so few males left that it’s likely to be a problem. There will be heaps of female but not enough males to fertilise all those eggs.”
According to Hays' team, which carried out its research among one of the world's largest breeding colonies of loggerhead sea turtles; the species at large may be able to adapt to rising temperatures -- for example, by finding cooler or shadier places to nest. But add this to other threats facing the reptiles from climate change, like rising sea levels, shifting currents and more extreme storms, and it would seem they're going to need all the help they can get.