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Green sea turtle

The future is female for green sea turtles, but for an alarming reason: climate change


Turns out, there might be some literal truth to Beyonce's lyrics "Who run the world? Girls."

But that may not be such good news for green sea turtles.

According to new research published in "Current Biology," scientists discovered that 99 percent of young turtles coming from the Great Barrier Reef are mostly female. Unlike most animals, green sea turtles don't have sex chromosomes, so their sex is dependent on the temperature of the sand. That means that warmer temperatures produce females, while cooler ones produce males.

"When you look at the data for the temperatures at the nesting beaches that these turtles were coming from, the northern Great Barrier Reef, there's a really good correlation between the number of females increasing and temperatures rising. So we're pretty sure it's due to climate change."
Camryn Allen, Endocrinology researcher at NOAA

According to 2014 report compiled by the Australian Government, the average sea surface temperature in the Coral Sea, which is part of the northern Great Barrier Reef, has substantially increased. Since records have began, 15 of the 20 warmest years have been in the last 20 years, while the warmest five-year running averages of sea surface temperatures occurred in the past 15 years.

All those ecological changes are not only affecting coral health, but also, according to the latest research, having a significant impact on the sex ratio of green sea turtles--a population listed as endangered on the IUCN's Red List of Threatened Species.

Allen acknowledged that it's pretty common for sea turtle populations to exhibit a female bias, saying it's a unique trait that allows them to produce more hatchlings and increase population numbers. But the ratio of male to female green sea turtles they found during their research shocked them, nonetheless. Allen explained that the green sea turtle population is one of the best studied in the world, so she said her and her colleagues weren't banking on finding "anything huge."

"We were taken aback when we saw that finding. Nobody has ever seen it that extreme before," she told Circa. "There are places where the females way outnumber the males, but this is crazy. Almost no males are coming from the northern Great Barrier Reef, so that's very striking."

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Scientists discovered a clear generational gap among green sea turtles. To put it in perspective, the ratio among adults is one male to every seven female, but, with young turtles, that changes to one male to every 100 female.

"So it's about 20 years that we think that something's been going on."
Camryn Allen

Despite the alarming statistics, researchers aren't that concerned--at least yet--since the green sea turtle population is pretty large. But they do agree that management strategies can be taken if, and when, necessary, since green sea turtles don't sexually mature until they around 20 years old and they won't be looking for mates anytime soon. That gives scientists some time to determine if intervention is the next viable option.

"I like to think of sea turtles as the lawnmowers of the ocean," Allen added. "So they keep our quarries clean. They remove algae, and other species that live on the coral reefs rely on them to keep it clean, so they are important for the ecosystem and if we were to lose them, it could have cascading effects to other species in the ecosystem."

Check out these other environmental stories:
Seeds help farmers fill fields with crops. Can a similar sowing technique work for coral reefs?
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