Photo: National Geographic

Pollution, coastal development, toxic algae, and gillnets all pose a threat to the existence of sea turtles but climate change may pose the biggest threat of all. It turns out that the heat of the sand where eggs are buried ultimately determines whether a sea turtle becomes male or female. As NatGeo reported, since climate change is driving up temperatures around the world, researchers weren’t surprised that they’d been finding slightly more female offspring. In fact, in Raine Island, Australia—the biggest and most important green sea turtle nesting ground in the Pacific Oceans sand temperatures there had increased so much that female baby turtles now outnumber males 116 to 1.

NOAA researchers Camryn Allen and Michael Jensen have been studying turtles on Raine Island for quite some time yet this discovery was significant as older turtles that had emerged from their eggs 30 or 40 years earlier were also mostly female, but only by a 6 to 1 ratio. As NatGeo went on to explain, but younger turtles for at least the last 20 years had been more than 99 percent female. And as evidence that rising temperatures were responsible, female turtles from the cooler sands near Brisbane currently still only outnumber males 2 to 1.

However, after Allen and Jensen published their findings another research team studying loggerhead sea turtles in Florida published a paper revealing that temperature isn’t the only factor that affects sea turtle eggs and if sands are moist and cool, they produce more males. If sands are hot and dry, hatchlings are more female.

Why This Matters: Sea turtles have been around for 100 million years yet human influence may be causing their greatest challenge yet. It’s not totally clear how we can help turtles (aside from not dumping our waste in the ocean and causing climate change) with the disproportionate sex ratios of their hatchlings but researchers have found that providing shade for turtle nests to cool the sand has shown positive results. Protecting turtle habitat is crucial to preventing their extinction and that’s why the 30 by 30 campaign (a call for 30% of the planet to be managed for nature by 2030—and for half the planet to be protected by 2050) is so important for threatened and endangered species.