The green sea turtle population near the northern tip of Australia’s Great Barrier Reef has scientists seeing pink.
New research has found female hatchlings are outnumbering males by a staggering ratio thanks to rising temperatures, accounting for over 99 per cent of the local juvenile population. The study published in the journal Current Biology suggests the gender imbalance linked to climate change poses a serious threat.
The Great Barrier Reef is home to one of the largest green sea turtle populations in the world, with an estimated 200,000 nesting females. The endangered reptiles are only a few centimetres long when they are born. Adults can span 1.5 metres and weigh up to 400 pounds. Estimates suggest they live for about 80 years.
Scientists have known for decades that the temperature of the sand where green sea turtles bury and incubate their eggs alters the sex of the developing clutch. Hotter sand ups the odds of more females. This latest research by the U.S. National Oceanic and Atmospheric Administration (NOAA) and the Worldwide Fund for Nature-Australia is the first time the phenomenon has been documented directly in a major wild population.
The research, led by Michael Jensen from the NOAA, compared two genetically distinct turtle populations near the Great Barrier Reef, one at the north and one at the south.
While the cooler southern nesting beach yielded a 65 to 69 per cent female bias, young turtles from the warmer north were found to be 99.1 to 99.8 per cent female. More than 400 turtles were studied in total.
“Combining our results with temperature data show that the northern Great Barrier Reef green turtle rookeries have been producing primarily females for more than two decades, and that the complete feminization of this population is possible in the near future,” the study’s authors wrote. “Furthermore, extreme incubation temperatures not only produce female-only hatchlings, but also cause high mortality of developing clutches.”
Vancouver Aquarium veterinarian Martin Haulena said he is worried by the study’s findings.
“The warmer it is, the more females are born,” he told CTV News. “If that population becomes all female, that is detrimental.”
According to the World Wildlife Fund, green sea turtles are under significant threat from fishing activity and habitat destruction on top of the risks of increasing egg mortality and female-only offspring highlighted by this study.
Some conservation observers have suggested using cloths to shade nesting sites and reduce sand temperatures. Others believe efforts to ensure mature breeding-age males are not caught in fishing gear need to be bolstered. Both are stop-gap solutions for the obvious cause of the problem -- heat.
“With average global temperature predicted to increase 2.6 C by 2100, many sea turtle populations are in danger,” the study’s authors wrote.
The problem could be larger than the giant turtles. Kirsten Zickfeld, a climate researcher at Simon Fraser University, worries the dire situation facing green sea turtles is indicative of bigger problems.
“There are ecosystems that are very sensitive to changes in temperature,” she said. “Some ecosystems may actually be very close to that critical point.”
The researchers behind the green sea turtle study said their findings raise new concerns about how rising temperatures impact climate-sensitive species, and underscore the need for action.
“Our study highlights the need for immediate management strategies aimed at lowering incubation temperatures at key rookeries to boost the ability of local turtle populations to adapt to the changing environment and avoid a population collapse, or even extinction,” they said.
With a report from CTV’s British Columbia Bureau Chief Melanie Nagy
