Green Turtle Numbers On The Up In Pacific Coral Reefs

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Amidst the tide of plastic pollution, beached whales, and dwindling coral reefs, some good news has just come out of our oceans. Green turtles, an endangered marine turtle species named for the layer of green fat under their shells, are on the up in Pacific coral reefs.

The new study, published in the journal PLOS ONE, assessed numbers of both green and hawksbill turtles, a critically endangered species that has been vastly exploited by humans for its beautiful tortoiseshell. Both species have suffered from habitat loss, while green turtles have also been hunted for meat.

The researchers looked at data incorporating 13 years’ worth of in-water visual surveys that recorded turtle numbers near 53 islands, atolls, and reefs in US Pacific waters.

So how do you go about counting turtles? You attach two divers to the back of a slow-moving boat, of course. The divers, about 15 meters (50 feet) down, record any sea life they spot as they peer beneath the waves. The surveys analyzed by the team covered a total of 7,300 linear kilometers (4,500 miles) and recorded 3,400 turtles.  

In-water surveys are useful as they record turtle abundances in the habitats where they spend most of their time. Many studies record turtle numbers on land when the reptiles arrive on beaches to lay their eggs. Underwater surveys can help confirm numbers recorded on land.

For years conservationists have been working to protect turtle species, and the researchers found that for green turtles, this work has paid off. During the 13-year sample period (2002-2015), green turtle populations either remained constant or increased. The animals were most abundant in the Pacific Remote Islands Area, where few people live, about 1,600 kilometers (1,000 miles) south of Hawaii. Meanwhile, population growth was highest around Hawaii’s islands, despite this being the area with the lowest population density overall. Hence, conservation measures in Hawaii appear to be working.

Sadly, it is not such good news for the hawksbill turtle. They were most abundant in the waters of American Samoa but overall, they made up just 8.3 percent of turtle sightings.

“This suggests that green turtles are nearly 11 times more abundant than hawksbills across the entire survey area, providing further empirical evidence of the rarity and conservation plight of hawksbills,” the researchers wrote.

It seems the mounting threats of fisheries, pollution, tourism, climate change, and drilling for oil and gas are too much for this turtle to fight back against. Illegal trade in their shells also exists to satisfy the “eager market” for tortoiseshell in Asia. The animals are also very dependant on highly threatened coral reef habitats where they survive off sponges and invertebrates. As we lose these coral reefs, we lose the turtles too.

While green turtle populations appear to be stable or increasing in Pacific coral reefs, this is not the only habitat in which these creatures are found. They live throughout the world’s tropical and sub-tropical waters, so the pattern found in the Pacific may not be echoed elsewhere. Still, with the majority of sea turtle species at risk of extinction thanks to humans, increasing green turtle numbers in the Pacific certainly comes as welcome news.

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