A study published in the journal, Nature Climate Change, has demonstrated that hotter sands, the product of climate change, could cause more turtles to be born female, which will increase their numbers in the short term but ultimately threaten their extinction. The study examined a loggerhead turtle rookery at Cape Verde in the Atlantic ocean that is one of the largest in the world.
In humans and other mammals, the gender of offspring is the result of sex chromosomes, but in turtles, it has been known for decades that this is determined by the temperature of the sand in which eggs are buried. So warmer temperatures = more females.
The temperature of sand is strongly dependent on its colour: the darker it is, the more heat it will absorb. Light-coloured beaches already produce 70.1 percent females while dark ones produce 93.5 percent.
At what the researchers termed the “pivotal temperature” of 84 degrees Fahrenheit, the turtle sex breakdown is 50:50. Sand as hot as 88 degrees Fahrenheit will produce almost nothing but females. At 82 degrees Fahrenheit, it’s males that pop out.
Professor Graeme Hays, Chair of Marine Science at Deakin University and one of the lead authors of the study, explained, “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 females but not enough males to fertilise all those eggs.”
Turtles could compensate by laying eggs in a cooler season. As Professor Hays warned, the excess of females “will be end of story without human intervention.” But humans could intervene by moving turtles to colder areas, avoiding development of lighter beaches and creating shade for nests.
Turtles are reptiles, and other reptiles whose sex is the result of temperature might also be affected. This includes alligators, crocodiles and many species of lizard, although warmer temperatures lead to more male alligators.
Timothy Chilman used to work in IT. Once, in Sydney, he was turned down for a job because he was “too flamboyant” (“Someone who wears green tartan suspenders to a job interview probably isn’t going to fit in here”). Timothy then became an English teacher. University students in Bangkok complained that he was “too enthusiastic” and company students in Prague complained that he was “too theatrical.”