One-third of snail species in Switzerland are threatened by extinction, the Swiss Association for the Protection of Birds has warned.
The updated red list of snails, due to be published in 2010, will show that two more species have become extinct since 1994, BirdLife Switzerland said on Tuesday.
There are around 200 species of land snails in Switzerland and 50 species of water snails. Around 80 of these are endangered.
The group said that despite their reputation as pests, snails are an important part of the food chain, and also contribute to the fertility of the soil. It attributed their decline to a number of factors, including habitat loss and climate warming.
BirdLife is currently overseeing Swiss participation in a European census of two common types of snails, which is due to run until September.
Members of the public have been asked to participate in the survey. The Swiss have proved enthusiastic snail observers: although they account for only two per cent of the population of Europe they have so far supplied ten per cent of the observations.