The negative impacts of global warming on the world’s oceans are well known. Ice caps are melting, coral is bleaching and sea turtles are all being born female. Wait, what was that last one?
The Science Of Sex Ratios
The sex of sea turtles is determined by the temperature of the sand in which the eggs incubate. Warmer sand means more females, but typically both sexes are represented in turtle nests. This is not the case anymore in Florida, where researchers have found that in 7 of the last 10 years 100% of the hatchlings were female.
Florida is of vital importance to three turtle species: leatherback, loggerhead, and green turtles. In recent years, all three of these species have been producing all female nests. This trend becomes even more striking when you consider that leatherback turtles nest early in the year, while green turtles nest closer to fall. These species should have more male offspring because they nest during cooler months, but even they have been affected by overall rising temperatures.
It’s Not Just Florida Either
Australia’s Raine Island is the biggest green sea turtle nesting ground in the Pacific. A 2018 study showed that the ratio of turtles born here was 116 females to one male. The study showed that 40 years ago, nests were also mostly female, but the ratio at that time was 6 to 1. In contrast, turtles born in the last 20 years were 99% female. A third study conducted with green turtles in Guinea-Bissau, West Africa showed similar results.
All Hope Isn’t Lost
Sea Turtles are an incredibly resilient species. They have existed in some form for 200 million years, withstanding multiple extinction events. The species is good at adapting to changes in their habitat, and one male turtle can impregnate many females. So the biggest question isn’t whether the species is capable of evolving, instead it is whether they can evolve as fast as the climate is changing.