PACIFIC NORTHWEST MOLLUSKS

With names like “knobby rams-horn,” “masked duskysnail” and “Hoko vertigo,” Pacific Northwest mollusks may have an amusing image, but they’re also some of the most intriguing invertebrates in the world. Crucial to the integrity of Pacific Northwest ecosystems, they’re expert recyclers of nutrients in soil and water, improving water quality in springs and rivers and enriching soils in old-growth forests. Mollusks are also important prey for a wide variety of animals, from mammals to birds to snakes to fish, and their sensitivity to environmental pollution makes them excellent indicators of overall ecosystem health.

Unfortunately, at least 32 mollusk species occurring in western Washington, Oregon and Northern California are in danger of extinction. Seventeen aquatic species and 15 terrestrial species are gravely endangered by a long list of threats including logging, grazing, wildfire, dams, pollution and climate change. Augmenting these dangers are the species’ extremely limited distributions, as well as life-history characteristics that make them especially vulnerable to dying out, such as low reproductive rates. Seven of the 32 species are known from only one or two sites, and nearly half the mollusks occur at 10 or fewer sites, making recovery from habitat loss difficult or even impossible for some species.

Yet the destruction of the Pacific Northwest’s waterways and woodlands continues, and despite these mollusks’ imperilment, none of them are listed on state or federal endangered species lists. Long protected under the Forest Service and Bureau of Land Management’s Survey and Manage Program, that program was suspended by the Bush administration, leaving crucial mollusk habitat unsurveyed and unprotected from ground-disturbing activities. Happily, after a lawsuit by the Center and allies, that program was reinstated in 2011. But while 22 of the 32 imperiled mollusks are included in either the Forest Service or Bureau of Land Management’s Special Status Species Program, this program provides no tangible protections for either the mollusks or their habitat.

To make sure the Pacific Northwest isn’t robbed of 32 of its rarest mollusks, the Center petitioned to list these species under the Endangered Species Act in March 2008. When the U.S. Fish and Wildlife Service failed to move forward on protections as it should have, in December 2009 we filed a notice of intent to sue to stop the delay. 

Finally, as part of a landmark victory for 757 species in July 2011, we reached a settlement with the feds that requiring initial listing decisions for all 32 mollusks. In October of that year, the Fish and Wildlife Service determined that 26 species of the snails and slugs might warrant protection.

CASE STUDIES: PACIFIC NORTHWEST MOLLUSKS

Cinnamon juga
This river snail has a near-black, cinnamon-red shell and is known from only four to eight sites in the Shasta Springs complex in the upper Sacramento River drainage — all of which are near railroad tracks that have substantially modified the species’ aquatic habitat. This snail is also threatened by spraying, water diversions, water pollution, grazing, development and recreation. Although the species is critically imperiled, and research shows that the loss of a single site may cause its demise, the cinnamon juga is not included in the Special Status Species Program, and there are no protected locations for the species.

Evening fieldslug
One of the least-known slugs in the western United States, the evening fieldslug once had an extensive range in the West but is now distributed only in northwestern Oregon, the northern Olympic Peninsula, and the northeast coast of Vancouver Island. Called “a truly rare species” in the 2004 Survey and Manage species assessment, this slug is included in both the Bureau of Land Management and the Forest Service’s Special Status Species Program, but it has experienced drastic declines of 50 percent to 75 percent.

Shasta sideband
The Shasta sideband is a very rare, terrestrial snail confined to a narrow range near Shasta Lake in Northern California, known from only nine scattered locations. It is specifically threatened by timber harvest, road construction and maintenance, pesticides, fire and recreation, but is hurt by any activity that alters the integrity of its habitat, including soil conditions, ground temperature and food supply. Though this species is included in the Forest Service’s Special Status Species Program, none of its known sites are protected.