Climate change means more than 99% of green sea turtles in some areas of the Great Barrier Reef are now female, researchers have said.
With such a profound lack of males for around 200,000 nesting females to reproduce with, the population of the creatures off Australia’s Queensland coast could crash, a study has found.
The sex of green turtles is influenced by temperatures during their incubation period and a difference of just a few degrees in the temperature of nests – which are dug into beaches – can result in a population that is 100% male or female.
Researchers collected 411 turtles from the southern barrier reef, where waters are cooler, as well as from the warmer northern reef to determine how the population was affected by temperature changes.
While in the southern waters, they found a moderate bias towards females of 65%-69%.
But where temperatures were higher, females made up 99.1% of the juvenile population and 99.8% of the population between juveniles and adults.
Among adult green sea turtles, the total proportion of females was 86.8%.
Published this week in the journal Current Biology, the report said: “With average global temperature predicted to increase 4.7 Fahrenheit (2.6 Celsius) by 2100, many sea turtle populations are in danger of high egg mortality and female-only offspring production.
“It is clear that climate change poses a serious threat to the persistence of these populations.”
Michael Jensen, the report’s leader author, said the trend of feminisation had been happening for two decades.
Climate change is not the only threat to green sea turtles, which are classified as an endangered species.
The creatures are also under pressure from loss of habitat, fishing nets and pollution.
A recent global by the University of Exeter found that more than 1,000 marine turtles were dying after becoming entangled in rubbish every year, while another found that 90% of young green turtles had plastic waste in their gut.
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