How to

17 July 2017

Sea Turtle Population Threatened by Changing Climate

Climate change affects all species, from birds and fish to cows and humans, so it’s no surprise to hear that the sea turtle is also under threat from the warming global temperatures.

The problem facing these reptiles is two-fold, with one issue relating to the effect that heat can have on the gender of their offspring. Sea turtles experience what is known as temperature-dependent sex determination (TSD) where the temperature at which the embryo incubates decides whether it’s born male or female. If the temperature is below 29°C then it’s almost certain to be the former, while above 29°C would produce a majority of the latter.

Higher average temperatures could skew the proportion of males to females, although this may potentially be beneficial up to a point. According to Jacques-Olivier Laloë of Swansea University, the warmer incubation temperatures would “increase the natural growth rate of the population” because the rise of females born as a result of TSD “leads to more eggs being laid on the beaches”.

However, the risk of temperature-linked-in-nest mortality can pose a problem to the survival of the species if it becomes too hot, because the embryos struggle to survive. Sea turtle eggs can only develop in a thermal range of roughly 25-35°C, meaning that as the climate worsens and grows warmer, too many nests will fail. Even if they manage to hatch and make it to the water, the young can end up dying from heat stress before they’ve managed to find food.

What’s more, the sea level rising threatens to wash away the beaches that they use for nesting. Sea turtles have a special ability to remember where they hatched, allowing them to return there to repeat their nesting ritual. However, thanks to the continued melting of the ice caps bringing the sea level higher and higher, these beaches may no longer exist sometime in the future, posing an even greater threat to the species’ survival.

A recent research study carried out in Cape Verde – a popular loggerhead sea turtle nesting site – looked into the temperatures of the local sand over the course of six years. They compared their results with the survival rates of over 3000 sea turtle nests to identify how the heat impacted this, using local climate projections to then map out how the future looks for this struggling species.

Right now, the turtles are in a stable condition with the current temperatures promoting the growth of the population; however that is destined to change if climate continues to soar.

“We should really keep a close eye on incubation temperatures and the in-nest survival rates of sea turtles if we want to successfully protect them,” says Laloë. Doing whatever we can to reduce climate change is essential for ensuring the continued lifecycle of the sea turtle; otherwise they’ll be another species to add to the list of those that have already become extinct.

James Darvill

James is a passionate scriptwriter and reluctant poet with a talent for the dystopian. When he’s not staying up late watching the Simpsons he’s beating the world at Mario Kart, always with a glass of wine in hand.