Can we really vacation with endangered animals and say it's for their own good? (Erik S. Lesser/EPA)

As the sun set, 25 boats converged on a small patch of reef just a few hundreds yards from the shore of Kona, Hawaii. With only four moorings, most of the boats illegally dropped anchor on the coral, dangerously tied themselves to other boats, or simply kept their engines running: a serious hazard if there are people in the water. And boy, were there people in the water. Between the snorkelers and us divers, there were a few hundred, all of whom made a frenzied dash for the water as soon as darkness fell. The chaos on the surface overwhelmed us, and we anxiously waited for chains of snorkelers to move away from our boat so we could descend below it.

Underwater, things got even worse. Lights in all directions from the dozens of dive groups disoriented us, and we were tossed this way and that by the high surge as our dive master attempted to move large, venomous urchins out of the way with tongs so we could sit on the reef. She instructed us to hold tight to the coral — even though touching the coral can kill it — as the water pushed us this way and that.

[Scientists discover an unexpectedly beautiful rainbow of fluorescent corals in the Red Sea]

I tried to remind myself that some of the money paid by all of these people would be used to conserve this place, to protect the majestic animals we anxiously awaited. But looking around, it was hard to believe that any of this was going to help the manta rays.

Manta rays, with wingspans in excess of a dozen feet, are some of Hawaii’s biggest attractions. Manta ray ecotourism brings in $3.4 million a year to the small town of Kona, which is big business for the rural island of Hawaii. And ever since the discovery in the 1970s that the rays will feed on plankton drawn by bright lights, turning and flipping acrobatically as they filter in the microscopic food, business has been booming. But according to many who’ve been there for decades, greed has changed the once-conservation-minded industry. Behind-the-scenes drama among tour owners, selfish operating practices and a lack of regulation are placing both the mantas and the tourists that come to see them at risk.

[Ever wondered what it would be like to ride a sea turtle through the Great Barrier Reef?]

My bad experience has become a common one, explained Martina Wing, a professional photographer and owner of Manta Ray Advocates, who has been filming manta dives for more than a decade. “It’s way too dangerous. It’s out-of-control dangerous … [and] the state of Hawaii is liable,” Wing said. A recent safety assessment commissioned by the Department of Land and Natural Resources (which is responsible for oversight) went so far as to state that “existing data and observations suggest that a severe accident is mathematically inevitable.”

It’s not just the tourists who are in danger. Wing has videotaped anchors dragging on the reef, destroying the fragile ecosystem that supports the plankton that the mantas come to feed on. She has images of mantas with deep cuts from boat collisions because avaricious operators have begun to install lighting on the vessels themselves, which works a little too well when it comes to attracting mantas. Even anchor lines sunk into the water by careless boat operators can leave the rays tangled and injured.


A manta ray injured by an anchor line. (James L. Wing and Martina S. Wing)

Wing helped create a "Green List" which points potential tourists in the direction of the most ecologically-minded tour operators, hoping to drive tourism dollars to the most responsible hands. There’s not much else she can do — reporting offenses has proven ineffective, as the Department of Land and Natural Resources claims they don’t have the manpower or funding to police the manta ecotourism. Now, even the legislature is getting involved, but formal regulations, if imposed, are still years away.

[The world’s most beautiful greenhouses are underwater, and growing strawberries]

Ecotourism is the fastest-growing sector of the tourism industry, but while operators often tout lofty conservation goals to lure customers, little oversight or evaluation actually ensures that such goals are being met. The manta dive industry off Kona is just one example of how such ventures are failing to live up to the “eco” in their names. Just last month, ecotourists in Costa Rica were slammed for overcrowding beaches where sea turtles were attempting to nest, preventing the animals from safely laying their eggs. And according to a new paper published in Trends in Ecology and Evolution on Oct. 9, even seemingly benign ventures may be putting wildlife at risk.

“We love our natural areas and wildlife and plants to death,” said senior author Daniel Blumstein, professor and chair of the Department of Ecology & Evolutionary Biology at University of California Los Angeles. “I think one has to always realize that you can't observe a system without influencing it.”

[Humans may be loving one type of shark too much]

Blumstein and his colleagues reviewed published literature on human-wildlife interactions from around the world, and came to the conclusion that when animals become habituated to our presence, they lose some of their life-saving instincts. “Animals become tame around people, and this may increase their vulnerability to predators,” Blumstein said.

Though Blumstein is quick to note that the paper lays out the potential for harm rather than documenting cases of it, he said that the review is intended to stimulate further study. “We think we're doing something that's good, and if it's having a potentially bad outcome, that should give us pause and drive more research to understand what's really going on.”

And while the change in vulnerability from ecotourism-related habituation might be small in many cases, “it doesn't take a lot of extra predation to take a population, particularly a fragmented small population, from a sustainable trajectory to an unsustainable trajectory," he said. “It’s not as though this is going to be the cause of extinction of wildlife, but many of the problems we face are additive or synergistic, a death by a thousand cuts.”

Ecotourists around the world may be inadvertently causing more harm than good, and that certainly seems to be the case in Kona. No one knows how the mantas’ behavior has been altered by the nightly interactions with humans and the artificial plankton aggregations created by their lights. It’s exactly the kind of situation that Blumstein and his colleagues warn about: The Kona industry might be “taming” the rays, causing unforeseen harm — in addition to the damage to the reef and rays already documented.

“Last time we did a survey, we figured it was about 50,000 people per year diving and snorkeling with manta rays. That number has probably doubled,” said Keller Laros, founder and president of the nonprofit Manta Pacific Research Foundation. The foundation hopes to further study Hawaii’s ray populations to begin to understand how ecotourism affects the mantas. “Having been diving with them for 30 years, I'm really concerned with the longevity of the manta rays.”

But Laros and Wing and other conservation advocates, though critical of current practices, are simultaneously hopeful that manta ecotourism can be made sustainable through regulation and oversight. For while they are worried about the rays, they recognize that there are benefits to such ventures that are more important than financial gains.

“People see a manta ray and they come away from it changed,” Laros said. “All of a sudden they're curious about marine ecology and they're passionate about marine conservation. These animals change peoples' lives. They changed mine.”

Christie Wilcox is a freelance science writer and postdoctoral researcher at the University of Hawaii at Mānoa. She pens the award-winning blog Science Sushi for Discover magazine and can be found on Twitter as @NerdyChristie. Keep an eye out for for her first book, "Venomous," published by FSG/Scientific American Books, which will hit shelves in summer 2016.

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