CONSERVATION

Freshwater snails are among the most imperiled groups of organisms in the world. Of the approximate 700 species in North America, 67 species (10%) are considered likely extinct, 278 (40%) endangered, 102 (15%), threatened, 73 (10%) vulnerable, and 26 (4%) have uncertain taxonomic status. The remaining 157 (26%) are considered stable. The primary factors responsible for the decline of freshwater gastropods are similar to those for freshwater mussels, fishes and aquatic insects. Aquatic snails respond negatively to anthropogenic disturbances to stream habitats, such as habitat destruction and environmental contamination, as well as invasions of exotic species. Causes of habitat degradation include damming , dam tail water modifications (e.g., temperature, dissolved oxygen, discharge alterations), channelization, erosion, excessive sedimentation, groundwater withdrawal, and multiple forms of pollution (e.g., salts, metals like Cu, Hg, Zn, untreated sewage, and agricultural runoff).

The vast majority of extinct freshwater gastropods (92.5%) were narrow endemics, with highly restricted ranges, occurring in a single river, spring, or lake. Habitat destruction in medium to large rivers caused by damming and channelization contributed to most extinctions (45 species, 67% of total), followed by drainage or diversions of lakes (8 species, 12%), alteration of springs (4 species, 6%), and possibly effects of exotic fish introduction (2 species, 3%). Only five species with historical distributions spanning multiple water bodies are extinct.

Conservation and recovery efforts for freshwater snails include artificial culture, water pollution control, and most importantly, habitat protection and restoration. Cleaning waterways not only improves the habitat for snails and other aquatic life, but it also improves the quality and supply of water for human consumption.