As is true for most currently endangered animals, humans are the root cause behind the population drop for hundreds of snail species. Whether from habitat destruction, introduction of invasive species, global warming or pollution, almost a thousand snail species are listed as endangered worldwide.
Endangerment from Habitat Destruction
When humans build on once-fertile land, block up waterways with dams, or cut down forests to harvest wood, snail habitats are sometimes ruined. New Zealand is home to over 20 different species of Powelliphanta land snail, many of which are endangered due to development and industrialization. The Powelliphanta snail populations are also decimated by animals like rats and possums. In the case of Powelliphanta snails, pesticides can actually be beneficial—poisoning possums, which have come to consider the Powelliphanta their favorite food.
At Risk from Invasive Species
Sometimes an "old woman who swallowed the fly" situation arises when a new species is introduced to an ecosystem. About two dozen species in the genus Partula are listed as endangered and are extinct in their natural habitat—the Polynesian Islands—because of introduced species. Partula snails have been nearly wiped out by the carnivorous rosy wolfsnail (Euglandina rosea), which was brought in to help control the giant African land snails (Achatina fulica), also an introduced species. The giant African land snails were originally brought to the island as a food source for humans, but didn't prove lucrative and so were released into the wild, where they became an agricultural pest. Instead of controlling the GALS population, the rosy wolfsnail decimated the Partula snails, which actually offer great opportunities for scientists researching evolution. Now only a tiny sample of Partula snails remain alive after being transferred to the London Zoo. The London Zoo is also rearing a population of Bermudan land snails (genus Poecilozonites), which have nearly gone extinct in their native habitat.
Victims of Global Warming
Snails living in unique ecosystems are especially vulnerable to the effects of global warming. The Iowa Pleistocene snail (Discus macclintocki) lives only in one particular environment: the algific talus slopes, which are kept cool and moist by underground glacial ice. Pleistocene snails thrive in ground temperatures below 50 degrees F in summer and above 14 degrees F in winter. As global temperatures rise, conditions become increasingly unfavorable for the Pleistocene snail. In addition to climate changes, D. macclintocki is also at risk from human activities such as logging, quarrying, road building, livestock grazing and the use of pesticides.
Threatened by Pollution
Snails are sensitive creatures that easily absorb toxins into their bodies. If just a sprinkle of salt or a squirt of soap can kill a snail, it's easy to imagine that pollution, pesticide use and the dumping of toxic waste can have a devastating effect on snail populations. In Alabama, modifications to the Coosa-Alabama River system, the only place the Tulotoma (Tulotoma magnifica) calls home, are considered the primary reason the snail's numbers have declined sharply since it was first catalogued in the 1830s. Several dams have been built along the river, and runoff from local communities pollutes its once-pristine waters. Mitchell's rainforest snail of Australia (Thersites mitchellae) and the Stock Island tree snail (Orthalicus reses) of Stock Island in the Florida Keys are also at risk of extinction due to habitat destruction and the use of pesticides.
- Proceedings of the Biological Society of Washington: Rediscovery of Tulotoma Magnifica (Conrad) (Gastropoda: Viviparidae); Hershler, Robert; Pierson, Malcolm; Krotzer, Stephen R. [PDF]
- Earth's Endangered Creatures: Endangered Species Search by Group: Snails
- U.S. Fish & Wildlife Service: Iowa Pleistocene Snail (Discus macclintocki)
- BBC News: Mission to Save Endangered Snails
- ZSL: Polynesia: Partula Snail
- U.S. Fish & Wildlife Service: Stock Island Tree Snail [PDF]
- Treehugger: Slow, But Disappearing Fast: 10 Endangered Snails From Around the World (Slideshow)
- Science on NBCNews.com: Tiny Snail, Thought Extinct, Rediscovered in Alabama
- Global Post: New Zealand: 800 Endangered Snails Freeze to Death in Conservation Mishap
- WorldWatch Institute: Degraded Habitats Push More Species to Extinction
- New Zealand Department of Conservation: Threats to Powelliphanta Snails
- Hemera Technologies/AbleStock.com/Getty Images