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Turning up the heat on sea turtles

Female Olive Ridley Sea Turtle nesting in Northern Australia ©Cathy Cavallo 2012

Female Olive Ridley Sea Turtle nesting in Northern Australia ©Cathy Cavallo 2012

Sea turtles have existed on earth, relatively unchanged, for around 180 million years. Modern humans arose only 40,000 years ago, meaning we have only been around for approximately 0.1% of the entire existence of marine turtles. Yet our civilisation is posing a major threat to turtles, with the majority of the seven species listed as globally endangered on the IUCN Red List. Not only is their habitat rapidly declining due to overfishing, coastal development and pollution of the oceans, but scientists are predicting catastrophic effects on populations due to global warming.

As cold-blooded animals, the life cycle of sea turtles is very closely linked to environment. Sea turtle biologists are predicting that global warming will detrimentally impact turtles at all stages of life, with changes in air and sea temperatures, sea level rise, storms and ocean acidity posing the biggest risks. The Marine Turtle Research Group released a review in 2009 that outlines the major threats posed to turtles from climate change. Since then, sea turtle biologists have been attempting to predict the damage that will occur to different populations around the globe, including the large population of Green Turtles that live and nest along the coast of Northern Queensland in Australia.

In particular, research has focused on the nesting phase of sea turtles, to which global warming poses a specific set of risks. Sea turtles, like many other reptiles, exhibit temperature dependent sex determination (where the temperature that the eggs experience in the nest determines the sex the hatchlings become). Consequently, scientists predict the warming of sand temperatures over the next century will damage sex ratios. As warm nests lead to females and cooler nests produce males, global warming is likely to lead to a great many more females being produced. Some studies have even predicted that under extreme emission scenarios, many beaches will be so hot that only females will hatch. Clearly, this would have a terrible impact on the dynamic on sea turtle populations, and would eventually lead to a population crash.

This is only one small piece of the puzzle. As sea levels rise in the coming century, the amount of beach available for nesting will be further reduced. Add to this the predicted increase of catastrophic storms that can wipe out hundreds of nests overnight, and the viability of sea turtle reproduction is looking dire. Not to mention the multitude of other threats that will impact turtles while they forage and mate out at sea.

So is there any hope for these majestic sea giants? On a local scale, wildlife managers may be able to protect key nesting beaches and cool nests to ensure the continuation of the reproductive cycle. However, considering this is a global issue, our only hope is that legislators will get their act together before the damage we have done to the earth becomes irreversible.

Failing this, we will have to put our faith into the turtles themselves. As mentioned earlier, they have been swimming around in our oceans for 180 million years. They have weathered climatic fluctuations and sea level shifts in the past and may indeed be able to shift their time and place of nesting to suit the new conditions. But climate change induced by humans is likely to be a lot quicker than anything experienced before and scientists are unsure as to how many species, sea turtles included, will cope without our help.

Please visit the IUCN Marine Turtle Specialist Group for more information.

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