99% of these sea turtles are turning female - here’s why you should worry

By: Irene Lorenzo
Date posted: 9 January 2018

Green sea turtles from the Pacific Ocean’s most important green sea turtle rookery in the northern Great Barrier Reef now outnumber males by at least 116 to 1.

Green turtle
© Brocken Inaglory

This is a problem that sea turtle conservationists have been aware of for some time now. There is evidence that some turtle populations are gradually adapting to climate change by shifting their breeding seasons to cooler seasons, but for many populations this won’t be an option

Peter Richardson,
Head of Ocean Recovery
Marine Conservation Society

If temperatures continue to rise as a result of climate change, these populations could become all female in the near future, pushing this endangered sea turtle even closer to extinction, scientists warn.

New research published today has shed some light into the ratios at which females and males hatch in the largest green sea turtle rookery of the Great Barrier Reef. For over two decades now, sea turtle hatchlings monitored at the Great Barrier Reef have turned out to be female.

While it’s a well-known fact that the sex of sea turtles is determined by the temperature of the sand when the eggs are incubating, no research had been carried out to look at how significant the impact of warming sands is becoming, already today.

“This is a problem that sea turtle conservationists have been aware of for some time now. There is evidence that some turtle populations are gradually adapting to climate change by shifting their breeding seasons to cooler seasons, but for many populations this won’t be an option”, said MCS Head of Ocean Recovery Peter Richardson.

The new research, published in the journal Current Biology, showed how 99% of the young green sea turtles hatched in warmer beaches were female. Sea turtles hatching in cooler beaches had less of a female sex bias, at around 69%. The temperature that produces an exact 50/50 gender split is passed down from parent to offspring but the range resulting in all-male or all-female populations varies by few degrees. As global temperatures continue rising, these sea turtles will continue producing offspring in warm nesting beaches that might result in the feminisation of the entire population – posing a serious threat to the survival of the species.

This new research also has implications for the other six species of sea turtles, as well as for other species where sex is determined by temperatures such as iguanas, alligators and even some fish species.

“Sea turtles are a very successful group of animals, having survived catastrophic environmental changes in the past. Can they successfully adapt to the alarming pace of human-induced climate change? We don’t know, but only through concerted conservation now will we give them a fighting chance,” concluded Richardson.

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