Climate Change Affecting Turtle Sex at Birth

It’s a moonlit night on the warm beach of Costa Rica. A figure can be seen, a researcher, huddled over what appears to be tens of little rocks crawling towards the water. She picks one up as it emerges from the ground, checking it before writing ‘female’ in her notebook. Another: female. And again, female. On the surface, everything seems normal, as several healthy turtles have just hatched. However, this situation is beginning to frighten conservationists and scientists alike more recently.  As more and more of one sex is hatched, less of the other is. Something is affecting the gender ratios of these turtles, messing with the population balance and causing a disruption in the ecosystem, but what?

The answer lies in something called temperature sex determination, or TSD. This is the process by which the temperature of an environment directly affects the sex of the produced offspring (1). In other words,  the environmental temperature can determine  whether a hatchling will be a male or a female. An egg that is incubated at a warmer temperature will hatch female, and an egg incubated at a cooler temperature will hatch male.1 These changes, however, do not occur for the duration of the incubation period, rather they occur during a critical period in development.

What separates TSD animals from others is their lack of sex chromosomes, explaining their reliance on temperature to determine a sex. These processes have been previously thought to be separate,  although according to Scientific American, it is possible that some species of reptiles may experience TSD and contain sex chromosomes. Evidence has been put forward that these animals can use TSD to “reverse the genotypic sex of an embryo” (Scientific American). Studies are still being conducted to better understand  this phenomenon.

Climate change is having a large impact on animals that utilize TSD (2, 3). As global temperatures rise, more female eggs are incubated, thus producing more females., This causes stress on the reproductive abilities of the population, leaving females to largely outnumber the reproductive capabilities of the males. This is the reason why conservationists are feeling increasingly helpless when it comes to saving species. Populations are already declining for a variety of reasons, including deaths by fishing nets, trash ingestion, and poaching. However, TSD animals are now being targeted because of climate change. Now more than ever, climate change is affecting these beautiful creatures.

The blight of these turtles shows just how important it is for us to take action. Turtles are “great scavengers,” crucial for keeping oceans free of dead animals. The nests they dig also provide homes to over 350 species  and keep the land and sea diverse by scattering seeds. Not only can we see the tangible good that turtles do, for centuries, they have also been a symbol of survival and peace. Turtles have evolved for over 200 million years, and if climate change is so seveer now that not even they can adapt, what is to come of the rest of us? There are small things that you can do to do your part, such as carpooling, biking to work, turning off the lights, and eating less red meat, but there are also big things (4). Encourage your school or company to divest in fossil fuel companies and elect politicians who prioritize addressing climate change. If everyone acts, we can make a difference and save the turtles and our beautiful earth.

(1): "How is the gender of some reptiles determined by temperature?" Scientific American. June 25, 2007. Accessed November 01, 2017. https://www.scientificamerican.com/article/experts-temperature-sex-determination-reptiles/.

(2): Morreale, Stephen J., Georgita J. Ruiz, James R. Spotila, and Edward A. Standora. "Temperature-Dependent Sex Determination: Current Practices Threaten Conservation of Sea Turtles." Science 216, no. 4551 (1982): 1245-247. http://www.jstor.org/stable/1688754.

(3): Hansen, J., Ruedy, R., Sato, M., & Lo, K. (2010). Global Surface Temperature Change. Reviews of Geophysics, 48(4). doi:10.1029/2010rg000345

(4): Faura, Romualdo, et al. “5 Ways to Curb Climate Change: You.” National Geographic, National Geographic, www.nationalgeographic.com/climate-change/how-to-fix-it/you.html.

Toby Frank