99% of These Turtles Are Being Born Female Because of Climate Change
Scientists think this is a clear consequence of climate change.
All-female societies in popular fiction are generally utopian — both “Wonder Woman” and Charlotte Perkins Gilman’s “Herland,” for example, involve places where peace is achieved through biological gender uniformity.
But what if turtles suddenly found themselves in an all-female society? Well, that’s happening to green sea turtles on Australia’s east coast, according to the Washington Post, and it could cause the population to vanish.
It’s not some fanciful imagination dreaming this unusual situation up, either.
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It turns out that climate change is causing 99% of newborn turtles to be female. Already, around 87% of mature turtles are female among this particular turtle population, according a new study published in the journal Current Biology.
And the link to climate change is fairly straightforward.
The turtles are becoming female at an overwhelming rate because the sex of this species is determined by the environmental temperature at the time of hatching, not through chromosomes, according to the study.
When sand temperature where eggs hatch are above what is known as the “pivot temperature,” turtles become female, and when the sand temperature is below the pivot temperature, turtles become male.
The pivot temperature for this species is roughly 85 degrees Fahrenheit. Historically, temperatures toggled fairly evenly above and below this range, according to the Post.
The scientists don’t know why the turtles have this temperature switch, but they think it has to do with the fact that bigger turtles grow in colder environments and it may be useful to have bigger males.
In recent decades, climate change has raised the average temperature of the sand and rigged the sex lottery in favor of females.
To determine the role of climate change, the scientists collected data on sea and atmospheric temperatures around the breeding areas beginning in the 1960s through recent years, according to the Post.
Starting in the 1990s, temperatures were consistently higher than normal and in recent years they have climbed even higher, which follows the global pattern of a hotter planet.
These days, there’s one male turtle born for every 116 females.
“If it's not climate change, then what is it?” Camryn Allen, a co-author of the new study, told the Post.
This skewing of the population is setting the turtles up for long-term decline, the research team thinks.
The turtles won’t suddenly cease reproduction, because there are still enough males, and males reproduce more frequently. But this ratio suggests that, overtime, males could disappear and the population could collapse.
However, the research team thinks that simple interventions like shading nesting areas and dumping cold sand on beaches can even out the ratio of males and females. And the Australian government is now working to address this phenomenon through the Raine Island Recovery Project.
The scientists point to turtles who breed to the south in a cooler environment where the sex ratio is closer to 1:1 to show that it’s still possible for stable populations to exist.
The green sea turtles are not the only animals who are being affected by climate change.
Various bird species, for example, are being driven from their normal migration routes because of climate change and many fish are shrinking in size because of warming oceans, disrupting food chains in the process.
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The sea turtles currently live in a vibrant ecosystem where they play an important regulatory role, according to the scientists.
In some ways, it’s a utopian environment of abundant food that’s relatively untouched by human development, the Post writes.
But for that utopia to continue, then climate change’s population control has to be stopped.
Sounds like the making of a comic book.