For this project, more than 2,000 mollusc species (over 1,200 terrestrial molluscs from selected families and 854 freshwater species) have been assessed. According to the latest census available, geographical Europe (excluding Russia) is inhabited by more than 3,373 species (Fauna Europaea 2011). This means that 2/3 of the molluscan fauna of Europe is covered by the project, which can thus claim to be representative in a statistical sense. The addition of species from European Russia (defined as up to the Ural Mts but not including the Caucaus) is likely to only slightly change this figure.
The nomenclature and checklist for the non-marine molluscs follows Fauna Europaea (Bank et al. 2006), with subsequent additions of new species from the period 2005-2011, as well as various nomenclatural changes, which have been through a peer-review process and are largely based on published papers. It should be noted that subspecies were not individually assessed as part of this project.
A small number of species (approximately 1%) are introductions from outside Europe and have not been assessed as part of the European Red List.
More than 75 experts gathered species specific information, obtained from primary literature, museum collection and personal knowledge, and provided a preliminary assessment for all the native European mollusc species included in this project. For every mollusc species the following data were compiled:
All species had their global status assessed according to the 2001 IUCN Red List Categories and Criteria: Version 3.1.
The preliminary assessments were evaluated through review workshops and correspondence with relevant experts. New information was added to the species summaries and maps, and corrections to existing data were made.
Two workshops were organised to cover the freshwater mollusc species: the Balkans and south-east Europe species were reviewed from 23 to 27 November 2009, in Budapest (Hungary), whilst species occurring in northern Europe and the western Mediterranean regions were considered from 1 to 5 February 2010 in London (UK). The remaining freshwater species were dealt with by correspondence and meetings with the relevant experts. Another workshop was dedicated to threatened terrestrial molluscs, from 28 September to 2 October 2010 in Bern (Switzerland). The list of non-threatened terrestrial species was agreed during the latter workshop and these species were only evaluated through correspondence.
Following the review workshops, the data were edited, and outstanding questions were resolved through communications with the workshop participants. The post-workshop draft categories and criteria were also made available to allow the participating scientists to make any final corrections.
Facilitating staff from the IUCN Red List Unit and the IUCN Regional Office for Europe reviewed the assessments to ensure they complied with the guidelines for application of the IUCN Red List Categories and Criteria and included the most up-to-date comprehensive information. The resulting finalized IUCN Red List assessments are a product of scientific consensus concerning species status and are backed by relevant literature and data sources.