European Red List of Terrestrial Molluscs: Snails, Slugs, and Semi-Slugs Least Concern
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EUROPEAN RED LIST OF TERRESTRIAL MOLLUSCS: SNAILS, SLUGS, AND SEMI-SLUGS LEAST CONCERN LC The semislug Vitrinobrachium breve (LC) shown here at Elfenau, close to Bern in Switzerland. A species of forests and woodlands, it is widespread in Central and Southern Europe. © Beat Pfarrer B European Terrestrial Molluscs Europe has one of the most highly fragmented year as more research is undertaken, especially landscapes of all the continents, with only a tiny in under-researched regions of the world such fraction of its land surface – largely the Arctic as the tropics. However, even within the relatively regions – considered as wilderness. Over the last well-studied European region, new species are 5,000 years, much of the European landscape constantly being described, and the status of has been shaped by human activity through many species names, as either valid species food, timber and fuel production. Currently within or as synonyms of other species, needs further Western Europe, more than 80% of the land taxonomic study. The actual number of extant area is under some form of direct management species of Mollusca globally is uncertain. Molluscs (European Environment Agency, 2007). can be found in almost all habitats, from the Consequently, European species are to a large bottom of the oceans to mountain-tops and extent dependent upon semi-natural habitats across tundra regions. They are very diverse, not created and maintained by human activity, only in size and shape but also in their lifecycle, particularly traditional, non-intensive forms of lifespan and habitat. They are an important land management. Over the last century, these food source for birds, fish, mammals and other habitats have come under increasing pressure invertebrates, and in some cases for humans, from agricultural intensification, urban sprawl, too. Together with such groups as the fungi and infrastructure development, land abandonment, saproxylic beetles, Mollusca play a key role in acidification, eutrophication and desertification. soil-generation and the recycling of nutrients Many species are directly affected by in natural ecosystems. Because of their often overexploitation, persecution, and impacts of alien specific habitat requirements, they can be good invasive species, and climate change is set to indicators of environmental quality, especially for become an increasingly serious threat. Europe is ancient woodlands, grasslands, wetlands and a vast, diverse region and the relative importance subterranean habitats. Farmers and gardeners of different threats varies widely across its usually view terrestrial molluscs as pests that biogeographic regions and countries. This report damage plants and the subsequent control of is one of a series of reports on the conservation terrestrial molluscs can cause problems from a status of animals and plants in Europe, focussing conservation perspective. However, these ‘pest’ on terrestrial molluscs in the Class Gastropoda – species actually represent only a very small slugs, snails, and semi-slugs. fraction of the species that occur in the European region. Indeed, many of the globally significant The Phylum Mollusca (snails, slugs, clams, pest species were exported from Europe to other mussels, chitons, tusk shells, monoplacophorans, parts of the world. polyplacophorans (chitons), Caudofoveata, Solenogastres, squids, cuttlefish and octopuses) Terrestrial molluscs utilise a very wide range of contains an estimated 94,000 extant species microhabitats – taxa have evolved to exploit these worldwide. This figure comprises ca. 55,000 niches, with some having very specific ecological marine gastropods, ca. 10,000 marine bivalves, at requirements, such as interstitial spaces within least 25,000 terrestrial and freshwater snails and subsoil, living on trees, found only on rock-faces 1,300 freshwater bivalve species. The remaining or restricted to pristine forest habitats. The groups embrace considerably fewer numbers of assemblage of molluscs found at a particular site species, ca. 800 cephalopods, 1,100 chitons, is influenced by historical geographical isolation 600 tusk shells and 420 Caudofoveata and and glaciation, altitude, degree and duration of sun Solenogastres (currently known and estimated exposure, the quantity and duration of rainfall and numbers taken from MolluscaBase). The overall the frequency of habitat disturbance (i.e., forest number of described species increases each fires or clear-cutting, amongst many other factors). 1 Assessment Scope This IUCN European Red List provides an Criteria (IUCN, 2001; IUCN, 2012a), which is assessment for the 2,480 species of terrestrial the global standard for measuring extinction mollusc species known to be present in the risk. For species not endemic to the EU European region at the start of 2019. Of these Member States, the Guidelines for Application species, 11 are considered Not Applicable of IUCN Red List Criteria at Regional and (NA) for assessment as they are not native to National Levels (IUCN, 2003; IUCN, 2012b) the European region. The number of species were applied. constantly changes as their taxonomy is revised and new species are described; a Red List assessments were made at two further 15-20 species have been described regional levels: geographical Europe (‘Pan for the European region since this Red List Europe’), and the Member States of the assessment was completed. Updates can be European Union. In the first stage of the found on the MolluscaBase database, which European Red List of Non-marine molluscs represents the taxonomic backbone used in (Cuttelod et al., 2011), the species were this project. assessed at the level of the then 27 Member States of the EU (Croatia joined the EU in The data presented in this report comprises 2013), whilst in the second stage assessments 1,233 species assessed between 2009 and (2015-2018), the species were assessed at 2011 (Cuttelod et al., 2011) and a further 1,261 the EU 28 level, with the addition of Croatia. species that were assessed between 2015 For Pan Europe, the scope is continent-wide, and 2018 (of which 14 were first assessed in extending from Iceland in the west to the Urals the first phase but reassessed as the result of in the east, and from Franz Josef Land in the significant new data or changes in taxonomic north to the European Macaronesian Islands concept). All the assessments were made in the south. The Caucasus region is not following the IUCN Red List Categories and included. LEAST CONCERN LC The slug Milax verrucosus (LC) is thought to be endemic to the Stara Planina Mountains in Bulgaria. It occurs in mountains, in shaded valleys, and fairly damp places, in deciduous and mixed forests rich in litter. There are no widespread threats and it is Least Concern. © Ivailo Dedov 2 Levels of Endemism in Europe The level of endemism (92%; 2,268 species) 742 endemic species), and saproxylic beetles within the terrestrial molluscs of the European (32.4%; 224 endemic species). There are region is much greater than in many other very few terrestrial mollusc species present in taxon groups. In vertebrates, for example, Europe that are not endemic to the European the reptiles are 52.1% endemic (73 endemic region, and most of these have ranges that do species), mammals 26.9% (61 endemic not extend far into North Africa or Asia. Only species), and amphibians are 76.3% endemic a few species are proven to have a holarctic (61 endemic species). There are an estimated distribution pattern. As a consequence, 100,000 invertebrate species in Europe, with Europe and in particular those countries six groups assessed for the European Red with single-country threatened species have List. The dragonflies and damselflies have a a responsibility to ensure the long-term low level of endemism (12.2%; 16 endemic conservation of these species. species), compared to Orthoptera (69.9%; Threat Status Overall, 21.8% and 22.5% of the 2,469 native In Europe, 97 species (3.9%) have been species of terrestrial mollusc are considered assessed as Critically Endangered, and of these, threatened (species assessed as Critically 23 species are considered Possibly Extinct Endangered, Endangered or Vulnerable) in (CR(PE)). A further 90 species (3.6%) have been Europe and in the European Union Member assessed as Endangered and 296 (12.0%) as States (EU 27/28), respectively. These are the Vulnerable (Table 1 and Figure 1a). A further 14% mid-point values – assuming that a similar relative (345 species) are considered Near Threatened. proportion of the Data Deficient (DD) species are There is a very slightly higher proportion of likely to be threatened – and provide the best threatened species in the EU 27/28 (4.1% estimate of the proportion of threatened species Critically Endangered (23 species are CR(PE)), (IUCN, 2016). For Europe, the percentage of 3.7% Endangered and 12.3% Vulnerable), with threatened species ranges between 19.6% 12.3% Near Threatened (Table 1 and Figure 1b). (if no DD species are considered likely to be threatened) and 29.8% (if all DD species were Including the Near Threatened species, 37.4% to be assessed as threatened). The equivalent of mollusc species present in the region of figures range from 20.1% to 30.8% for the Europe – for which sufficient data exist – can EU27/28 Member States. be considered to be of elevated conservation concern. Nearly half (47.0%, 655) of all the extant For just over one-tenth (250 species – 10.1%) species in the Member States of the European of the species in Europe there was insufficient Union, are of conservation concern (threatened information to evaluate their risk of extinction and and Near Threatened categories). they were assessed as Data Deficient (DD). In the EU Member States, 240 species (10.6%) were At present, five species are considered assessed as DD, which is considerably lower to be extinct in the European region, all than the level of data deficiency for the freshwater previously endemic to the Member States of molluscs (24.7%) (Cuttelod et al., 2011).