Habitat account - Rocky habitats and caves


8310 Caves not open to the public 

Background to selection

Distribution of SACs/SCIs/cSACs with habitat 8310 Caves not open to the public.  Click image for enlarged map.
Distribution of SACs/SCIs/cSACs with habitat 8310 Caves not open to the public. Click image for enlarged map.

Description and ecological characteristics

 

Caves are formed by the erosion of soluble rocks, such as limestones. They typically form the subterranean components of a distinctive ‘karst’ landscape, and are associated with various topographic features, including gorges, dry valleys, 8240 Limestone pavements, and dolines (surface depressions and hollows). Caves not open to the public is interpreted as referring to natural caves which are not routinely exploited for tourism, and which host specialist or endemic cave species or support important populations of Annex II species.

 

Caves lack natural illumination, and therefore support species which are adapted to living in the dark. Microclimatic conditions vary widely within and between caves, and this determines the composition of the fauna and flora. Many species feed on detritus derived from the surface; others are carnivorous. Cave-dwelling species (cavernicoles) can be divided into three categories:

 

     

  1. Troglobites – obligate cave-dwellers which typically display morphological adaptations, such as reduced pigmentation and regressed eyes.
  2. Troglophiles – facultative cave-dwellers which may have permanent populations in caves but which are also found in other suitable habitats.
  3. Trogloxenes – species which are found in caves but only for part of their life cycle.

 

The cavernicolous flora and fauna of the UK and other parts of northern Europe is highly impoverished compared to southern Europe. The reason for this is that most karst areas in the UK (except for parts of southern England) were glaciated during the Pleistocene, and many species are therefore recent colonists. Southern Europe escaped glaciation and consequently has a richer fauna of highly-specialised relict troglobites.

 

Cavernicoles in the UK include bacteria, algae, fungi and various groups of invertebrates (e.g. insects, spiders and crustaceans). Characteristic troglobites and troglophiles include Porrhoma rosenhaueri (a blind cave spider), Trechus micros (a ground beetle), Niphargus glennei (an amphipod, only known from Devon in the UK), and Arrhopalites pygmaeus (a springtail). Some caves are important hibernation sites for bat species, including all four Annex II species found in the UK.

European status and distribution

 

Caves not open to the public are widely distributed in Europe but are most frequent in the extensive limestone regions of southern Europe. The cavernicolous fauna of southern European caves includes a large number of troglobites, many of which are endemics. Notable species include amphibians, such as the blind cave salamander Proteus anguinus. An assessment of the occurrence and protection of the habitat throughout Europe was provided by Juberthie (1995).

UK status and distribution Click to view UK distribution of this habitat

 

In the UK, caves are particularly characteristic of the limestone areas of the North Pennines, the Peak District, the Mendips, south Wales, and County Fermanagh. Examples also occur in Devon, north Wales and Scotland.

Site selection rationale

 

Because of the impoverished nature of the cavernicolous fauna in the UK, Caves not open to the public is not a primary reason for the selection of any SACs. However, the habitat occurs at a number of sites selected for other features, typically Annex II bat species, and where appropriate it has been treated as a qualifying interest feature.

 

Only natural caves have been selected. Sites that are entirely artificial in origin, e.g. mines and tunnels, are excluded from the Annex I definition, even though in some cases the species present may be similar to those of more natural sites.


Site accounts

No data currently available

SACs/SCIs/cSACs where this Annex I habitat is a qualifying feature, but not a primary reason for site selection

Limestone Coast of South West Wales/ Arfordir Calchfaen de Orllewin Cymru East Wales, West Wales and The Valleys
Mells Valley Dorset and Somerset
Mendip Limestone Grasslands Dorset and Somerset, Gloucestershire, Wiltshire and Bristol/Bath area
North Somerset and Mendip Bats Dorset and Somerset, Gloucestershire, Wiltshire and Bristol/Bath area
South Hams Devon
Usk Bat Sites/ Safleoedd Ystlumod Wysg East Wales, West Wales and The Valleys
 

Many designated sites are on private land: the listing of a site in these pages does not imply any right of public access.