Last month, a paper published in the journal Science Advances announced a conservation success: Imperiled sea turtle populations were, in general, rising. For example, from 1973 to 2012, the number of green turtles nesting on a Hawaiian beach grew from 200 to 2,000. Hawaiian green turtles are now listed as a subpopulation of "least concern" by the International Union for Conservation of Nature.
But the recent report was not all good news. The populations of leatherback turtles in the North Atlantic continue to drop, and some species, like flatback turtles, remain "data deficient," meaning that researchers have very little information with which to estimate the size of the population.
There are seven species of sea turtles around the world, each with a unique biology and habitat that faces different threats. Even small differences between populations and species can change how well they recover, says Margaret Lamont, a biologist with the United States Geological Survey. Lamont is also a researcher at the University of Florida's Archie Carr Center for Sea Turtle Research, and has studied several species of sea turtles. She says that understanding which conservation efforts work and don't work is particularly challenging, because the animals live for so long.
Oceans Deeply spoke with Lamont about why some species of turtles are recovering at different rates than others and why good data on these animals is so challenging to collect.
How different are populations and species of different sea turtles from one another? How much can the data that we have on one species be reasonably applied to another?
If you're comparing a sea turtle to a black bear, then I would say [sea turtle species] are similar. [But] I'm not sure I would say that they all face generally the same threats. The leatherback is probably the most different, the most unique, when you are just looking at the sea turtle species. Leatherbacks utilize deeper waters, they're further out to sea, often. That introduces them to issues with longline fishing. Particularly in the Pacific, there's issues with that threat impacting the leatherback populations.
If you're slightly closer to shore, if you're slightly deeper, if you're eating a species like a blue crab that's commercially valuable, those variations can have huge impacts.
The Science Advances paper states that, for flatbacks specifically, there was a lack of data. Is that true generally? And why is it so difficult to collect the right data on these animals?
That is a big question. Flatbacks are unique. They nest in one place, it's a pretty small area, and it's harder to find them. Sea turtles live in the water, so you can't go out and just sit and watch them or observe the mating patterns. Where even are they? What are they doing? [You can't answer] basic questions.
We've had to develop new technologies, like satellite tracking, in order to just know where [the nesting ones] are going, and that's only adult female turtles. Then you say what are the males doing? There’s just multitudinous questions, multitudinous challenges, to studying these animals.
The other issue is that they're long-lived. I've been studying turtles almost 25 years and that's not even one generation. When we start seeing an increase in nests, you attribute that to, what? Those adults were juveniles 20 years ago. You have to look back and go, "20 years ago we did something." There's this big lag so it's hard for us to know what action actually has a direct impact that helped with recovery.
Has there been talk about what happened 20 years ago?
It's probably the No. 1 issue and question that's talked about. There are arguments and there's great discussions that say it was this protection or that protection.
The Kemp's ridley is a really great case study. That species nested, historically, on one general beach in northern Mexico. That was the only spot it nested in the world, and it started declining to the point where it was one of the most endangered species in the world. So the managers got together between Mexico and the U.S. and decided to try to relocate some of the nests to South Padre Island, in hopes of starting a second group there. Over a 40-year period, they have successfully done that. The Kemp's ridley is still endangered, but not to the point where in 10 years it's going to be extinct.
One of the big factors that is difficult to [understand] is climate change. We've seen the increase in green turtle nesting. Green turtles are considered tropical species, so the fact that the oceans may be warming may be benefiting them to some extent, or allowing a range expansion. But it's difficult on the broad scale to really nail that down.
Do you have other concrete examples of policies or efforts that might have caused this increase in population?
Well, definitely in the Gulf [of Mexico] and the southeast U.S., the increased use of turtle excluder devices, which most people call TEDs, have been used primarily on shrimp trawlers. The use of these TEDs allows fishermen to keep capturing shrimp, but allows the turtles to escape the nets.
Turtles were killed in the tens of thousands before the use of these TEDs. The use of TEDs has really helped protect the Kemp's ridley and the loggerhead. Those are two species that people can point to and say there's been a big increase in the number of nests.
With so much data being so difficult to collect, how confident is the scientific community about the results from this latest paper?
People are optimistic. I think people feel good about it. I think people are confident, but there's also that it's as confident as a sea turtle biologist can get. There's always that level of, let's wait—10 years from now, are we going to be celebrating? No one's going out and being like, "Woo-hoo, we're done!" There's always going to be that hold back just because we're scientists. You know that you're not getting an absolute answer.