Priorités régionales de conservation pour les Mollusques continentaux : un défi pour les taxons mal documentés

Barely 1% of continental molluscs, on a European or French national scale, have a protection status, although around 30% to 40% of the species are considered threatened according to the IUCN criteria. It therefore appears necessary to provide complementary tools for the management/planning of regional conservation strategies. The current study proposes a hierarchical list of species with conservation stakes built on a point-scoring method based on three criteria and an index linked to the current state of knowledge. Our dataset contains around 60 000 occurrence data for 227 target species for the Grand Est and Bourgogne-Franche-Comté, two administrative regions in eastern France. We observe significant disparities in the quantity/quality of available information not only between geographical sub-units but also among major taxonomic groups. The taxonomic biases can be explained by the intrinsic rarity of species, the difficulty in identifying taxa and/or the reliability of their descriptors, and the restrictive protection measures that unbalance the search for species in the field. The result of the prioritisation procedure indicates that 51% of the target species, 15% of which present a major risk of global or regional extinction, present a volume and quality of information deemed satisfactory in order to assess their level of prioritisation. The other species present a handicap in terms of taxonomic knowledge, identification and/or distribution that makes it impossible to rigorously assess their conservation priority. We therefore show that there is no good indicator – in the current state of knowledge – for the legislator and/or the curator to identify, evaluate and prioritise regional molluscs conservation plans. Our results do, however, make it possible to establish the basis for a regional strategy by separating real conservation issues from issues of improving knowledge.