Cadair Idris

Site details

UK map showing location of Cadair Idris Special Area of Conservation/Site of Community Importance.
Location of Cadair Idris SAC/SCI/cSAC


When undertaking an appropriate assessment of impacts at a site, all features of European importance (both primary and non-primary) need to be considered.

Annex I habitats that are a primary reason for selection of this site

3130 Oligotrophic to mesotrophic standing waters with vegetation of the Littorelletea uniflorae and/or of the IsoŽto-Nanojuncetea
Within the Cadair Idris range, Llyn Cau is a mountain lake representative of this type, located in an upland cirque. The lakeís conical basin, which reaches a water depth of almost 50 m, results from glacial scour of Ordovician volcanic and sedimentary rocks. Quillwort Isoetes lacustris is abundant and shoreweed Littorella uniflora occurs frequently. The boulder-dominated shore has abundant growths of liverworts and mosses, including Sphagnum denticulatum and Rhytidiadelphus squarrosus. There are distinct associations of I. lacustris, starwort Callitriche hamulata and bulbous rush Juncus bulbosus var. fluitans, the latter being most abundant adjacent to inflow streams. The water is moderately acid with low conductivity but relatively high nitrate concentrations for an upland lake. A lake sediment study did not reveal any evidence of acidification. It has been classified as a type 1 (dystrophic lake) on the basis of its vegetation but its water transparency is very high with a distinctive blue colour. It stratifies with a thermocline at 10-15 m depth. Brown trout Salmo trutta fario are present.
8110 Siliceous scree of the montane to snow levels (Androsacetalia alpinae and Galeopsietalia ladani)
Cadair Idris is the most southerly site in the UK selected for high-altitude siliceous scree and as such is not as species-rich as more northerly examples. Much of the rock is dry and unstable, but on the extensive screes on steep slopes U21 Cryptogramma crispa Ė Deschampsia flexuosa vegetation is well-distributed, and on the boulder screes, lemon-scented fern Oreopteris limbosperma can be found together with a range of characteristic bryophytes and lichens.
8210 Calcareous rocky slopes with chasmophytic vegetation
Cadair Idris is one of three Welsh sites representing Calcareous rocky slopes with chasmophytic vegetation. It is the highest mountain in the south of the Snowdonia National Park and has a number of cliffs and rock outcrops with base-rich exposures, with the moist, north-facing cliffs supporting a number of notable bryophytes. Many of the higher plants are clustered below the tall-herb ledge vegetation where water streams down from above and include species such as green spleenwort Asplenium viride and purple saxifrage Saxifraga oppositifolia.
8220 Siliceous rocky slopes with chasmophytic vegetation
Cadair Idris is one of three Welsh sites representing Siliceous rocky slopes with chasmophytic vegetation. Cliffs and rock outcrops are abundant on the site, with many supporting characteristic assemblages of lichen and bryophyte communities, particularly on the steep, moist, north-facing cliffs. Vascular plants include Wilsonís filmy-fern Hymenophyllum wilsonii, starry saxifrage Saxifraga stellaris and fir clubmoss Huperzia selago.

Annex I habitats present as a qualifying feature, but not a primary reason for selection of this site

4010 Northern Atlantic wet heaths with Erica tetralix
4030 European dry heaths
6410 Molinia meadows on calcareous, peaty or clayey-silt-laden soils (Molinion caeruleae)
6430 Hydrophilous tall herb fringe communities of plains and of the montane to alpine levels
7130 Blanket bogs (* if active bog)  * Priority feature
7230 Alkaline fens
91A0 Old sessile oak woods with Ilex and Blechnum in the British Isles

Annex II species that are a primary reason for selection of this site

Not applicable.

Annex II species present as a qualifying feature, but not a primary reason for site selection

1065 Marsh fritillary butterfly  Euphydryas (Eurodryas, Hypodryas) aurinia
1393 Slender green feather-moss  Drepanocladus (Hamatocaulis) vernicosus

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