European regional assessment: Vulnerable (VU)
EU 27 regional assessment: Vulnerable (VU)

Based on the estimated loss of individuals in sites, combined with total loss of sub-populations from sites that have been well monitored since the Habitat’s Directive monitoring began and the lack of habitats in favourable condition as mentioned in recent EU reporting, this species is considered to be meeting the thresholds of 30% of population decline over the last 10 years. These declines are likely to become more severe in the future, as this species has most of its range in salt-marsh/coastal dunes, within fringing habitats of a gradient of groundwater levels (often marginal strips of vegetation less than 5 m wide), and these habitats lie where sea defence construction will take place (especially in regions concerned about climate change and increased frequency of storm-surges at spring tides), and as such further declines in areas with pristine habitats might be expected, thus this species is listed as Vulnerable (VU) A2ac+3c at the European level and at the level of the 27 member States of the European Union.

This is mainly a European species, but it extends through Turkey to Iran. It ranges from southern Scandinavia to the Mediterranean and from Ireland to the Caspian Sea. It has a scattered and often localised distribution in many countries (Cameron et al. 2003).

The population trend is thought to be decreasing. The UK has some of the biggest populations in Europe.

Evidence from Ireland, where a significant 3 year survey (2008 – 2010) was undertaken on known extant sites, found 1 of the 21 sites had been totally destroyed (Moorkens and Killeen 2011). A further 7 sites had declined to a situation that the snail may already be lost or is likely to be lost in the near future (5% loss in the last 5 years, and 30% sites showing decline in the last 5 years). It should be noted that site losses were in inland wetland habitats.

The Favourable Reference Population (FRP) is ‘the population in a given biogeographical region considered the minimum necessary to ensure the long-term viability of the species’ (European Commission 2006). Expert opinion considers that in order to conserve the long term viability of Vertigo angustior in the Republic of Ireland, the population Conservation Status should be based upon maintaining the current number of sites in favourable condition and not on number of individuals which is an unreliable measure (see above). Thus sites that were classified as being in unfavourable condition for population (based on assessment of snail presence) were assessed using best expert opinion as to how much more area of occupancy they would have if they were in favourable condition. As the Favourable Reference Population of the species is greater than the Current Population, the population status is currently considered to be unfavourable.

The snail is particularly vulnerable in Europe at wetland sites, which are difficult to protect, and in coastal sites which may be subject to increasing inundation. The UK sites are currently in good condition, but the future prospects are considered to be potentially poor as the vast majority of the population is found along sea wall defences and in estuarine habitats that are becoming increasingly vulnerable to inundation. Pressure to increase sea level defences with stronger, steeper walls could destroy the populations depending on the older more vulnerable defence bunds.

Evidence from elsewhere in the range is missing in its precision due to the absence of targeted studies across the range, but proxy evidence can be taken from reporting by member states under Article 17 of the Habitat’s and Species Directive. The last round of reporting was in 2007, and member states returned assessments on range, population, habitat, future prospects and overall assessment under an assessment of either (i) favourable (green), (ii) unfavourable declining (amber) or (iii) unfavourable bad (red). The following member states have published their results as follows (2007 assessment), for the overall status of the species: Germany, France and Belgium - unfavourable bad (red), Ireland and the Netherlands - unfavourable declining (amber) and UK - Unknown.

At a broad level, it appears to be present in a very wide range of habitat categories of maritime dune grassland and maritime or inland wetland (including fen, marsh, salt marsh and flood plain), but the micro-habitat within which it is restricted means that the exact conditions which its presence demands are rare, and a lot of habitat that is “almost correct” is devoid of the snail. Where fixed dunes have the correct habitat conditions, the snail may cover a large area of occupancy. Otherwise, it can be found in an often narrow transition zone between saltmarsh and dune, and in transition zones between grassland and wetland with short herbs, mosses and Iris. In Cumbria, it occurs in moss on limestone pavement. It is normally found on permanently moist but free-draining soils, not subject to prolonged inundation. Vertigo angustior is a groundwater-dependant species.

The main threats to this species is the modification of site hydrology, heavy grazing, lack of grazing, supplementary feeding of livestock, scrub encroachment, eutrophication, pesticides, exposure to leisure activities (especially on coastal sites) e.g. caravan parks and marinas, seawall construction and modification, managed retreat of coastal marshes, fragmentation of habitat, artificial planting on open ground, motorised vehicular damage to habitats, rise of temperatures and extremes, sea level rise and flooding.

This species is not used.

The species has been assessed as threatened in several European countries (e.g. GB, Ireland, Netherlands, Sweden, Denmark, Poland, most federal regions of Germany) (Cameron et al. 2003). While there now are a range of protected sites where this species is present, these require ongoing appropriate site management, and this should be enough to secure the species albeit at a smaller range of sites than at present (Moorkens, pers. comm, 2011), as losses are likely to continue at inland and marginal sites especially in western Europe. In the longer term, should there be loss of present habitat from sea-level rise, then many sites would not have space for movement into new areas and some of the larger populations in Western Europe would be threatened.