A recent study published in the journal Current Biology and led by the National Oceanic and Atmospheric Administration (NOAA), entitled ‘Environmental Warming and Feminization of One of the Largest Sea Turtle Populations in the World,’ found that 99% of Green Sea Turtles born along the east coast of Queensland, Australia, were female. This natural phenomenon, the article states, is due to our earth’s warming temperatures.
Gender is usually determined during fertilization, however, in many reptiles, including turtles, gender is determined after fertilization occurs. For most turtles, the temperature of the nesting environment determines the gender of the offspring.
According to the study published at the beginning of the year, the warmer the beaches, the more females born and if climate change continues to occur, a complete feminization of sea turtle populations is possible.
In the northern Great Barrier Reef the gender ratio of the Green Sea Turtle population is about one male for every 116 females, according to the study. Luckily on the southern edge of the reef, the gender ratio is about one male to two females. This is due to the fact that temperatures have not increased as significantly in this area.
Green Sea Turtles are currently considered endangered by the International Union for Conservation of Nature. Even though it is not clear yet what will happen to these populations, it is clear that climate change is posing a serious threat to not only Green Sea Turtles, but the ecosystem to which they belong.
Green Sea Turtles graze on seagrass beds, which allows the beds to be more productive. Without this constant grazing, seagrass beds will become overgrown. Sea Turtles also have a finely serrated beak, that plays a major role in maintaining the health of coral reefs, because it allows sea turtles to scrape and eat algae off of different surfaces. When sea turtles eat algae off of the coral, they help keep them healthy!
Green Sea Turtles may seem far away, but climate change is affecting species in our own backyard! Residing from southern Canada to northern Mexico and from the Atlantic to the Pacific, Painted Turtles could also face a complete feminization if temperatures become warm enough.
In 2013, Telemeco et al published a research study in The American Naturalist, stating that average temperatures in the Midwest only need to rise by 1.1 C to produce nests of all-female hatchlings. This fate may not be too far away, since NASA announced that 2017 was the second hottest year since 1880.
This would not only harm the turtles, but the entire ecosystem they live in. Since these turtles are in the middle of the food chain, both its prey and predators would be affected. Known predators include raccoons, northern river otters, american minks, and red foxes could face a lack of food without the turtles, causing their population to decline.
Painted turtles are omnivores, eating fish, insects and algae! If turtle populations decline, the populations of all of these prey species may increase. This could be disruptive to the ecosystem, especially if algae populations become overgrown.