Extremely sensitive to changes in temperature, the green sea turtle (Chelonia mydas) is one of the thousands of species which faces extinction due to climate change. This endangered reptile has a vast range, inhabiting tropical and subtropical seas all around our planet. These turtles spend most of their time in seagrass beds, salt marshes and coral reefs around coastal areas. However, with rising sea temperatures, their natural habitat (particularly coral reefs) may soon disappear.
Most adult green sea turtles are strictly herbivorous. Much of their diet consists of algae and sea grass. Their serrated jaw helps them gnaw through the vegetation. By biting off the tips of the seagrass, they help to keep the seagrass healthy and maintain ecological sustainability. Adult turtles have few predators – only humans and large sharks. In contrast, juveniles and new hatchlings feed a whole variety of coastal creatures, including crabs, small marine mammals and seabirds. The fact that these turtles play such a huge ecological role makes them a keystone species – their presence is vital to the survival and maintenance of coastal habitats.
Green sea turtles undertake lengthy migrations from feeding sites to nesting grounds throughout their life. Some swim more than 2,600 kilometres to reach their breeding grounds. These turtles return to the beaches on which they were born to lay their eggs. To lay their eggs, females haul themselves up onto the beach, dig a pit in the sand with their flippers and fill it with anywhere between 100 and 200 eggs. The female then returns to sea and the eggs will hatch within about 2 months.
Once the baby turtles have hatched, they face a perilous journey. During the darkness of the night, the babies instinctively head towards the sea. It is thought that they are drawn to the water by the ocean’s light. This comes with its own problem – the light produced by our cities is causing hatchlings to wander astray and towards our busy roads. If they manage to go in the correct direction, they still face predation from the aforementioned animals. It is estimated that only 1 in 1,000 hatchlings reach sexual maturity.
Classified as endangered by the IUCN (International Union for the Conservation of Nature), green sea turtles seem to have a bleak future. They are threatened by over harvesting of their eggs, hunting of adults, capture in fishing gear, plastic pollution, habitat loss and climate change. We are losing these creatures at an unsustainable rate because of our actions.
The incubation temperature of green sea turtle’s eggs actually determines offspring’s sex. Warmer temperatures are more likely to produce females whereas cooler temperatures are more likely to produce males. Increased temperatures caused by global warming are therefore producing more females than males. This threatens the genetic diversity and, ultimately, the survival of this species. A recent study conducted in the northern Great Barrier Reef found that of turtles from warmer nesting beaches, 99.1% of juveniles, 99.8% of subadults, and 86.8% of adults were female.
These threats not only endanger the survival of green sea turtles, but also the survival of entire ecosystems. There are many things we can do to combat the growing issue of climate change. Here are a few:
- Produce less waste – eat all the food you purchase and buy higher quality items that last for longer.
- Completely avoid air-freighted food – air freight emits more greenhouse gases per food mile than any other mode of transport.
- Reduce meat and dairy consumption.
- Make your voice heard – Homo sapiens are the reason for climate change but we can also be the ones who stop it.
Hennessy, K., Wiggins, V. (2014) Animal Encyclopedia: The Definitive Visual Guide. 2nd edn. London. Dorling Kindersley.