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Researchers at AAAS Pacific Division Meeting Trace the Mass Extinction of Hawaiian Land Snails
Achatinella sowerbyana on a fingertip
[Photo © and courtesy of Bjorn Erickson]
WAIMEA, Hawaii—Animal-loving tourists come to Hawaii for spinner dolphins, sea turtles and the scarlet I'iwi bird and not, generally, for its native land snails. Brenden Holland is an exception. While he concedes that most people find the snails "boring and gross," Holland is working with a small band of fellow malacologists in an increasingly urgent bid to save them from extinction.
Native Hawaiians call some of the species pupu kani oe, or pupu hinuhinu—singing snails. The snails once flourished here, 750 species which served as a rainbow-colored testament to the creative power of natural selection. But during the annual meeting of the AAAS Pacific Division, some of the world's top snail experts described how humans and non-native predators—including rats, pigs, and voracious meat-eating snails—are wiping out species that evolved over millions of years into exquisitely beautiful creatures that may play a key role in island ecosystems.
Already, as many as 80% of the species are gone, and others are endangered. Such broad losses are a signal that Hawaii's luxurious but fragile natural environment is under severe stress, said Michael G. Hadfield, a professor of zoology at the University of Hawaii at Manoa.
"You knock out one species, and you knock out another species, and you knock out another species—at some point, something is going to happen," Hadfield said in an interview. "There is going to be a shift and that ecosystem is not going to be what it was before. And whether that's the first step or the third step in the collapse of that ecosystem, we don't even know.
"But the snails are the canary in the coal mine—they're telling you that's something isn't right."
The speakers at the AAAS Pacific Division symposium on endangered Hawaiian snails were: (standing, l-r) Wallace Meyer; Michael Hadfield; Bjorn Erickson; Meaghan Parker; and Kevin Hall; (front row, l-r) Brenden Holland and Kenneth Hayes
Hadfield was among more than 300 researchers, teachers, students, and science aficionados who attended the Pacific Division's 89th annual meeting from 15-20 June. The meeting was held at the Hawaii Preparatory Academy in the rolling pastures below the dormant Mauna Kea volcano on the Island of Hawai'i (the Big Island); it featured dozens of symposia, workshops, talks, and poster sessions. There were field trips to observatories, volcanoes and lush island reefs, and a performance by the duo of John Keawe a Grammy-winning slack-key guitar player, and his wife, hula dancer Hope Keawe.
The meeting ranged across disciplines, and included sessions on astrobiology; science education; U.S.-Asia scientific cooperation; hidden health threats to Asian American women; and the neuroscience of indigenous people in Hawaii and Alaska. But the recurring theme of the meeting was the health of Hawaii and other Pacific islands, and how they serve as an environmental barometer for the rest of the earth.
Terence M. Gosliner, the outgoing president of the Pacific Division and senior curator in the Department of Invertebrate Zoology at the California Academy of Science in San Francisco, described the sort of biodiversity found on the Pacific islands as humanity's "money in the bank"—a foundation of genetic information that could be crucial to future production of food and medicine.
Biodiversity "helps humans survive," Gosliner said. "It could be the thing that makes or breaks our own survival.... We are the stewards of the planet, and since we've created so many of the changes on the planet, we have a moral responsibility and an aesthetic responsibility—beyond the practical reasons—for preserving it."
The history of land snails offers a microcosm of the islands' natural and human history.
In geologic terms, the islands are relatively young—the first island in the chain emerged about 5 million years ago. The ancestral snails likely were brought to the islands by floating logs, storm winds, or birds. Over millions of years, in a nurturing climate with varied ecosystems and no predators, they spread, evolved to suit their surroundings, and thrived.
The first humans arrived around 500 C.E. from Polynesia; they may have brought other snails and rats, and over the centuries they used the native snail shells for leis and clothing. But the human impact on the islands deepened in the 18th century, when Europeans arrived (with rats in the holds of their ships).
Hadfield is among the world's most influential authorities on Pacific island snails, and he has taught, mentored or employed several of the scientists who made presentations in a four-hour snail conservation symposium 16 June. He has focused much of his study over the past three-plus decades on a snail called Achatinella. Its oblong shells range from 17-24 millimeters long (roughly as much as an inch); the elegant tapered shape and bright, seemingly hand-painted designs made them especially attractive to collectors.
A rosy wolf snail eating a Bradybaena similaris while climbing an aquarium wall
[Photograph © and courtesy of Bill Frank of jaxshells.org]
As late as the 19th century, Hadfield told the audience, many species of Achatinella were widespread, but by the 1950s, the decline was evident. Collectors, fascinated by the coiled, colorful beauty of the shells, took a huge toll on the snail populations. Hungry rats and feral pigs were to blame, too. And when forests were cleared for sugar cane or cattle pastures, snail habitat was lost. Later, giant African snails introduced to the islands became pests, and a carnivorous snail called Euglandina rosea (rosy wolf snail) was imported from the Southeastern United States in hopes of controlling their enormous cousins. But that effort failed—Euglandina much preferred Achatinella and other native Hawaiian snails.
Now, Hadfield reported, 21 of 42 Achatinella species are or appear to be extinct, and the number may be as high as 31. The 11 species under study in the wild are endangered and "rapidly declining," he said.
Hadfield and other researchers have embarked on ambitious efforts to save the snails, but the efforts are early and the outcomes uncertain. For example, researchers described projects in which the habitat of endangered snails was sequestered with electronic and other barriers to keep rats and Euglandina snails out.
A collection of Achatinella shells assembled ca. 1933
Kevin Hall, who works with Hadfield in the University of Hawaii Department of Zoology, described how tiny transmitters could be attached to the snail's shell to permit tracking around the jungle. Björn Erickson, a researcher at the University of California-Davis who also has worked under Hadfield, discussed successful programs to breed the endangered snails in laboratories.
For both Hall and Erickson, the goal is to assess how to use genetic studies to help make a successful reintroduction of lab-bred snails bred into the wild. "It's not just one big snail population out there," Erickson said. Hall concurred that it is a delicate calculation: If snails are too inbred, their fitness can be compromised, but too much genetic diversity also can pose problems.
And yet the stakes could be high—not just for snails, but for many island species, including Homo sapiens. Hadfield and his colleagues suspect the snails perform some specific function in the forest ecosystem; the snails "scrape" the fungus from the leaves of host trees. Thus far, the utility of that is not clear. But the fear is that if the snails fail, the forests may eventually fail, too. And if mountain forests fail, that can lead to degradation of lowland watersheds that are fed from the mountains.
To many people, the relationship between small snails and the purity of water supplies is not immediately evident. According to Holland, Hadfield and others, that means the importance of Achatinella is not immediately clear, either.
"I get that question all the time—'Who gives a damn about snails?'" Hadfield said. His response is both scientific and deeply passionate.
"These snails have been evolving with the plants and trees and everything else in that ecosystem for 5 million years or longer," he says. "So I suppose part of that answer is, do you care whether we keep these ecosystems?
"The biodiversity issue is big, too... Are we going to find medicine from snails? I don't know—I doubt it, but it could be possible.
"But you know, they're also a cultural resource. Hawaiian tree snails have been part of Hawaiian song and legend since the beginning of time. The snails I work with are called pupu hinuhinu or pupu kani oe, which means 'singing snails.' The Hawaiians are totally convinced that the snails sit up there in the mountains and sing. So it's a cultural resource. And they're beautiful in their own right.... It's a major loss when you consider the incredible, incredible variety of things that have been decimated en masse, in so many different ways."
"Had Darwin known about the tree snails, I have no doubt that they would have been his example, rather than the Galapagos finches. He did know about them, actually. J.T. Gulick, who was an early American evolutionist in the 1800s, sent Darwin snails and described the diversity. Darwin was well aware of them and he was very interested. So they're teaching us about life and evolution and diversity. It's a lesson."
The AAAS Pacific Division includes more than 30,000 AAAS members from California, Hawaii, Idaho, Western Montana, Nevada, Oregon, Utah, Washington, the Canadian provinces of British Columbia and Alberta, and all other countries bordering or lying within the Pacific Basin, with the exception of mainland Mexico south to Panama.
The four regional divisions of AAAS—Pacific, Southwestern and Rocky Mountain, Arctic, and Caribbean—serve as regional networks for scientists, organizing meetings on regional issues and promoting publications from scientists active within the division. The Pacific is the oldest AAAS regional division, with a charter dating to 1914, followed by the Southwestern and Rocky Mountain Division (1920), the Arctic Division (1951), and the Caribbean Division (1985).
All AAAS members in good standing, and who reside within the specified boundaries of a regional division, are automatically included as members of that regional division.
8 July 2008