Hunting bans and other conservation efforts
may be paying off — though warming oceans remain a serious threat.Sea turtle
survey shows the endangered animals are making a comeback.
A new survey of sea life in the Pacific Ocean
suggests that some
endangered sea turtles are making a comeback. The survey showed that
populations of green sea turtles along dozens of coral reefs in waters around
Hawaii and other nearby regions either remained stable or increased from 2002
to 2015.
“You often hear such bad and challenging news
about the threats that our ocean faces,” said Kyle Van Houtan, chief scientist
at the Monterey Bay Aquarium in Monterey, California, and leader of the team of
researchers that conducted the survey. “There are places where there are a lot
of sea
turtles very close to shore. And that’s good news.”
Once hunted for their meat, green sea turtles
were designated an endangered
species in 1978. They're now protected under U.S. law and international
treaties.
The same survey suggested that populations of
hawksbill turtles, another protected species that is even more endangered,
remain perilously low.
The survey effort began almost by accident,
according to Van Houtan. On a research expedition to count fish living on
reefs, divers with the National Oceanic and Atmospheric Administration found
themselves counting turtles, too.
As it turns out, counting turtles in the
water is more reliable than counting them on land, where only egg-laying
females and their hatchlings are visible. “Really understanding
the dynamics of turtle populations requires more attention to different age
classes, and that means getting out on the water,” David Godfrey, executive
director of the Sea Turtle Conservancy in Gainesville, Florida, told NBC News
MACH in an email.
So Van Houtan and his colleagues decided to
formalize the count. Over 13 years, divers trained to count green sea turtles
and hawksbills visited 53 reefs across the Pacific, including spots in Hawaii,
the Marshall Islands and American Samoa. Towed along by a slow-moving boat for
a total of more than 4,500 miles, the researchers tallied more than 3,400
turtles.
The research represented a “Herculean
effort,” Van Houtan said, adding, “This is the kind of data and the kind of
study we’ve wanted for so long.”
Analysis showed that what the scientists call
"turtle density" — the estimated number of animals per kilometer
based on the survey counts — had increased by as much as 8 percent each year in
some areas.
Turtle density increased the most in areas
that tended to have few turtles at the start of the census period, including
the Hawaiian Islands. The greatest turtle density was seen In the Pacific
Remote Island Areas, uninhabited islands west of Hawaii, with an average of
3.62 green turtles per kilometer.
Hawksbill turtles, meanwhile, were
outnumbered by green turtles by 11 to 1. “Their numbers have not really come
back,” Van Houtan said of the hawksbills.
The highest turtle densities were seen in
regions with plenty of seagrass and algae for the turtles to eat; minimal human
presence; and, most important, water temperatures at 80 to 82 degrees
Fahrenheit. Sea turtles flourish in that "Goldilocks" environment,
which is neither too hot nor too cold.
But as the world's climate continues to warm,
turtles and other marine species may be forced to relocate. “As the ocean
warms with climate change, that ideal temperature is going to move toward
the poles and away from the equator,” Van Houtan said. “As the temperatures
change, those distributions are going to change.”
While Van Houten is wary of the effects this
move will have on the greater coral reef ecosystem, he’s optimistic about the
turtles’ odds for survival.
“They’re very resilient animals, and they’ve
lived for millions of years,” he said. “The turtles aren’t going to roll over
and die.”
Credit: CC0 Public Domain
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