A new study in the journal Scientific Advances shows that overall, the world’s seven sea turtle species are increasing, mainly due to conservation efforts undertaken over the last half century, reports Joanna Klein at The New York Times.
An international team of researchers led by Antonios Mazaris of Aristotle University of Thessaloniki in Greece looked at 4,417 annual estimates of sea turtle nesting numbers collected from around the globe, dating back between six and 47 years. The researchers found that the number of turtles was increasing in 12 turtle management units around the globe and decreasing in five. The most increases occurred along the Atlantic coasts of North and South America while the Asia Pacific region saw declines.
“There's a positive sign at the end of the story,” Mazaris tells Seth Borenstein at the Associated Press. “We should be more optimistic about our efforts in society.”
Currently, six of the seven species of sea turtle on Earth are listed as vulnerable, endangered or critically endangered, according to the International Union for the Conservation of Nature. The seventh species, the flatback turtle, whose range is limited to the waters off northern Australia, does not have endangered status because there is too little information on its population to determine its current state.
Turtles numbers have plummeted during the last century for many reasons, Klein reports. The turtles often died after being caught as bycatch by fishing trawlers or after getting tangled in fishing gear. The commercial trade in turtle meat and the popularity of turtle soup also devastated populations. Development along nesting beaches disrupts turtle breeding, as do bright lights from nearby settlements.
It takes loggerhead turtles 12 to 30 years to reach sexual maturity and up to 50 years in green turtles. So it is often challenging for the turtles to remain alive long enough to reach breeding age and help maintain the population.
People began intervening to prevent continued decline in the 1950s. And in recent decades, the situation has improved: governments and conservation groups have protected nesting areas; the commercial turtle harvesting industry has ended; and many fishing vessels are equipped with turtle-saving devices. As Kate Sheridan at Newsweek reports, the uptick in turtle populations may be the fruits of these efforts, which are allowing more turtles to reach breeding age.
For instance, Borenstein reports that in the 1940s there were about 40,000 Kemp's ridley sea turtles in the southern U.S. and Mexico. By the 1970s, the population was down to about 1,200. But changes to fishing equipment and the establishment of protected nesting areas has led to slow but steady 10 to 15 percent increase in the population every year.
“People are seeing lots and lots more turtles,” David Godfrey of the IUCN Marine Turtle Specialist Group and executive director of the Sea Turtle Conservancy tells Sheridan. “You can’t continue to say that the sky is falling when it’s clear that good things are being done.”
The positive news, however, doesn’t mean the problem is solved. Klein reports that leatherback sea turtles in the Pacific still continue to decline, and a removal of protected status, conservation funding or resumption of egg or meat hunting could wipe out any gains very quickly. “Sea turtles are bellwethers. They're flagships that we use to tell the story of what's going on in the oceans," Roderic Mast, co-chairman of the IUCN Marine Turtle group tells Borenstein. “And that's why people should care about turtles.”
Another reason to care? It's extremely relaxing to watch them glide through the deep.