Monitoring of three Annex II species of Vertigo snail on Irish sites (2022-2024)

Brophy, John; Daly, Orla H.; Hamilton, Jessica J.; O'Neill, Fionnuala; Martin, James R.

Publication

Monitoring of three Annex II species of Vertigo snail on Irish sites (2022-2024)

Brophy, John
;
Daly, Orla H.
;
Hamilton, Jessica J.
;
O'Neill, Fionnuala
;
Martin, James R.

Citation

Brophy, J.T., Daly, O.H., Hamilton, J.J., O’Neill, F.H. & Martin, J.R. (2025). Monitoring of three Annex II species of Vertigo snail on Irish sites (2022-2024). Irish Wildlife Manuals, No. 159. National Parks and Wildlife Service, Department of Housing, Local Government and Heritage, Ireland

Abstract

All three Vertigo species listed in Annex II of the EU Habitats Directive (92/43/EEC) and present in Ireland were surveyed over a three-year period (2022-2024). These surveys were carried out in order to gather the information needed to prepare National Conservation Assessments for the three species for submission to the European Commission, as required every six years. The three species are the Narrow-mouthed Whorl Snail (Vertigo angustior), Geyer’s Whorl Snail (Vertigo geyeri) and Desmoulin’s Whorl Snail (Vertigo moulinsiana). The 2022-2024 surveys fell within the 2019-2024 Article 17 monitoring period. This is the third round of monitoring that has been carried out for these species, with the previously completed monitoring having been for the periods 2007-2012 and 2013-2018. During this most recent monitoring period, 60 monitoring sites within the Republic of Ireland were surveyed for the target species. These comprised 20 sites for V. angustior, 19 for V. geyeri and 21 for V. moulinsiana. With the exception of three new V. moulinsiana sites, all the survey sites had been surveyed during at least one of the previous monitoring periods. The survey revealed that the number of sites positive for V. angustior has declined by six since the previous round of monitoring, while V. geyeri was recorded from seven fewer sites and V. moulinsiana was recorded from one additional site (excluding the three new sites). Of the 20 V. angustior sites visited, the overall conservation assessment status has declined at seven since the previous round of monitoring. For V. geyeri, a decline was noted for six sites and an improvement noted for one. In the case of V. moulinsiana, there was a decline at four sites and an improvement at one. A range of pressures were recorded at the sites that are considered to be affecting their conservation status. The treatment of threats and pressures in this site-based report is more detailed than that in the Article 17 National Conservation Assessments for the three whorl snail species, which concentrate, by necessity, on the overall national situation for each species and deal with the threats and pressures that are significant at a national level. The main pressures include grazing intensity, hydrological changes resulting in drying out or fluctuating water levels (possibly due to climate change, or to other local factors) and drainage. While grazing can have positive effects depending on the species (V. geyeri in particularly benefits from a moderate level of grazing, particularly by sheep), drying out of habitat has negative effects for all three species. While positive pressures were noted for several sites, these were generally incidental benefits from existing land-uses (e.g. agricultural grazing). Occasional conservation measures directed at improving the habitat at Vertigo sites were aimed at the general habitat rather than specific measures for the relevant Vertigo species. Such measures included the installation of chestnut fencing at sand dune sites, farm plans managing grazing levels, native invasive species control and conservation grazing. A notable example of conservation measures achieving positive effects for a Vertigo site is VgCAM08 Sheskinmore, which has seen improvements to the site for V. geyeri leading to its overall conservation status becoming Favourable (green) from Unfavourable-Inadequate (amber) after the 2013-2018 round of monitoring. At this site, conservation grazing has been undertaken and the water levels of Sheskinmore Lough controlled using a sluice at the outflow. The continued decline in overall conservation status of the Vertigo species’ sites is of considerable concern and active intervention will be required to address the decline and return the species to Favourable Conservation Status. While measures to reverse climate change are beyond the scope of any actions that can be initiated at a site level, the resilience of the sites may still be improved by other measures, such as applying an appropriate level of grazing or blocking drains. While the European Union Nature Restoration Law focuses on habitats, the required management and restoration of habitats including fixed dunes, alkaline fens and reed and tall herb swamps in Ireland will have to take the needs of the three Annex II Vertigo species into account.