Conservation of Key Underground sites: the database

The group was established at the AC4 as the IWG on "Transboundary programme – habitats: Data compilation" 
texts and maps compiled by Tony Mitchell-Jones, updated by the Secretariat in 2016

Introduction

Underground habitats

Underground habitats, such as caves, mines, fortifications and tunnels, play a vital role in the life-cycle of many European bat species, which use them as hibernation, breeding and transitional roost-sites, including during migration. Particularly in the latter case, it is often difficult to establish the importance of sites, owing to the transitory nature of their occupation. However, such sites may often be key to the survival of a species in a particular region of the continent. The significance and threats to such sites have been highlighted in the IUCN Microchiroptera Action Plan (2001).

Recognising the importance of underground habitats and the many threats they face, Eurobats Resolution 2.4 (Bonn, 1998) set in place a project to identify and list the most important underground habitats across the Agreement area. Listing is considered an important step towards ensuring that important sites are appropriately protected and managed to maintain their continuing value to bats. In parallel with this data-gathering project, the Advisory Committee was instructed to prepare guidelines on the protection and management of underground habitats. These were published in 2007 as EUROBATS Publication Series No 2.

Guidance on the selection of important underground habitats by Parties and Range States, including a description of the information required,  was prepared and adopted by the Advisory Committee in 2000 (see here), with Parties encouraged to submit data using a standardised data structure. The importance of this work was reiterated in Resolution 4.3 (Sofia, 2003), which also called on Parties to ensure that listed sites are protected by law and, where appropriate, physically protected against unauthorised entry. Given the uneven distribution of both bat species and populations, as well as underground habitats, across the Agreement area, Parties and Range States were asked to use their own judgement to select their most important sites.

Sites submitted by Parties and Range States

By the time of the 7th Meeting of Parties (Brussels, 2014) 1,895 sites had been submitted for inclusion in the list.
Totals for Parties and Range States are shown in the table below (Parties are shown in bold Italic):

In order for these nationally-important sites to benefit from listing, it is essential that their value is widely recognised. Resolution 6.16 (Prague, 2010) implements the Eurobats Conservation and Management plan for 2011-2014 and includes an instruction that:  “The list of internationally important underground sites for bats identified by Parties and reviewed at the 15th Meeting of the Advisory Committee and site assessment criteria should be published in a suitable format and be accessible through the EUROBATS website.”

List of internationally important underground sites

Site lists

The Eurobats underground sites database contains details of 1,891 sites across the Agreement area. The amount of information available for sites varies, but each has a name, geographic coordinates (of varying precision) and an indication of the type of site. Many sites also have information about the main way in which the site is used by bats, whether the site is physically protected against unauthorised access and whether there are threats to the site. Information about the bats occupying the site is also variable in detail. Some sites have only a figure for the number of bats using the site, others have dated (year) counts of each species present at the site and there are many variations between these two extremes.
 

Publication format

Sensitivity

Recognising the need to balance the value of publication against the sensitivity of some underground sites to disturbance and the threat posed by uncontrolled tourism, the Advisory Committee offered Parties and Range States the option of restricting publication on a site by site basis. Three options were offered:
 

A  -  Publication of standard details (site name, location, species list)
B  -  Limited publication; no site name, location degraded to 1° (approx. 111 km)
C  -  No publication
 

The table below shows the number of sites in each category:

Details published

For each country, an outline map showing the location of each site is provided. For each site, the published data consist of the site name (or ‘Underground site’, where the name is not to be published), the type of site, geographic location and a list of species recorded at the site.
 

Summary data

The Eurobats database is the largest international collection of data on underground sites for bats in Europe and so contains a unique insight into the way in which bats use underground sites across this area. The following sections summarise some of this data:
 

Type of site

The table below shows the proportion of each site type held in the database:

The same data are illustrated on the map below, which shows the importance of cave sites, particularly in the foothills of mountain ranges. In northern Europe, or in areas without significant mountain ranges, mines, fortifications or other types of underground site become more important.

The boundaries shown on the map do not imply official endorsement or acceptance by the United Nations.

Species of bats

Although data are incomplete, sufficient data are available to give a fairly detailed picture of the extent to which different species use underground sites.

The table below is dominated by the two widespread and cave-dependent Rhinolophus species, Greater and Lesser horseshoe bats. These species use underground sites for both breeding and hibernation, though in the northern part of their range they typically seek out buildings for breeding.

The Greater mouse-eared bat Myotis myotis, another widespread cave-dependent species, uses underground sites in a similar way to the horseshoe bats, typically breeding in churches or other large building in the northern part of its range.

Schreiber’s bat Miniopterus schreibersii has a more southerly distribution and uses caves, or other underground sites throughout the year. It forms particularly large colonies and sometimes makes seasonal long-distance movements between caves.

The following maps show internationally important underground sites for the Lesser and Greater horseshoe bat as well as for Schreiber's bat. The shaded areas represent the distribution area of the respective species as described in the European Mammal Assessment (IUCN).

The boundaries shown on the following maps do not imply official endorsement or acceptance by the United Nations.

Underground sites with most bat species

The importance of any particular underground site needs to take into account not only the species and number of bats present, but also the location of the site. For example, underground sites with small numbers of bats in Scandinavian countries may be important in a national or even regional context, as they provide an essential resource for the bats in that region. Nevertheless, sites with very large numbers of bats are undoubtedly of European importance and deserve the highest level of protection.

The table lists all 34 sites with 10,000 or more bats recorded.

These sites are distributed across Parties and Range States as shown:

Main usage by bats

Although some sites are occupied by different species at different times of the year, contributors were asked to indicate the main usage of each site. The table is dominated by sites used primarily for hibernation, though all-year and maternity sites become more important in the Mediterranean region (see map).

Site lists for each Party or Range State that submitted data can be found by clicking on the country name. For each country, an outline map showing the location of each site is provided. For each site, the published data consist of the site name (or ‘Underground site’, where the name is not to be published), the type of site, geographic location and a list of species recorded at the site.

The boundaries shown on the following maps do not imply official endorsement or acceptance by the United Nations.