Yr Wyddfa (Snowdon) is considered to be of European importance for its upland habitats and species. Details of the main habitats and species are found below. For further details on the Snowdonia National Park Biodiversity Plan, go to Conservation/ Biodiversity.
Acidic Scree is a particular form of scree, occurring in the uplands at moderate altitudes where summers are cool, winters cold and rainfall high. These screes form from fragments of acidic rocks such as sandstones, granite and quartzite and can cover small or extensive slopes, often beneath cliffs from which they were derived. The stability of the screes varies, with some being relatively mobile and others more stable. They support a colonising vegetation community, usually dominated by ferns such as parsley fern (Cryptogramma crispa) with fir clubmoss (Huperzia selago), mosses such as woolly fringe moss (Racomitrium lanuginosum) and the liverwort (Diplophyllum albicans). Small tufts of grasses including wavy hair-grass (Deschampsia flexuosa) and sheep’s fescue (Festuca ovina) can commonly occur, together with occasional flowering plants such as, foxglove (Digitalis purpurea) and heath bedstraw (Galium saxatile). Parsley fern, which characterises the community, tends to grow in more stable but nevertheless active screes, supporting larger rock fragments than are found in the more active sections. Where a scree becomes very old and stable, a vegetation type dominated by heather (Calluna vulgaris) and bilberry (Vaccinium myrtillus) can become established.
Crevice communities in the uplands are found on rocky slopes and cliffs, growing in fissures and crevices where there is sufficient accumulation of soil and organic matter, together with drainage water, to support low growing arctic-alpines, ferns, mosses and lichens. The habitat most resembles the alpine rock gardens situation, but the vegetation varies depending upon whether the rock substrate is basic or acidic in nature. Basic rocks often support rare arctic-alpine species, for example arctic saxifrage (Saxifraga nivalis) together with ferns such as maidenhair spleenwort (Asplenium trichomanes) or the brittle bladder fern (Cystopteris fragilis). Rocks with a more acidic nature can also support rare arctic-alpines such as the fern Woodsia ilvensis and a number of mosses and liverworts. This vegetation type has been less directly influenced by man than most others.
Montane Heath and Montane Acid Grassland
Montane heath and montane acid grassland occur on the siliceous soils of high mountain summits, ridges and, plateaux above the natural tree line, where they represent some of the most natural and undisturbed habitat in the UK. Montane heath and montane acid grassland comprise dwarf-shrub heath, moss-heath and acid grassland (a derivative of dwarf-shrub heath and/or Racomitrium moss-heath through injudicious grazing). Generally, examples to the south of the Scottish Highlands lack the extent and diversity of associated montane vegetation which characterise stands further north.
In Snowdonia, montane acid grassland accounts for the majority of this vegetation, with moss-heath less well represented by the stiff sedge-woolly fringe-moss (Carex bigelowii-Racomitrium lanuginosum moss heath) (NVC community U10), and only fragments of dwarf-shrub heath. Grasses, sedges and mosses tend to characterise this vegetation in Snowdonia. Montane heath and montane acid grassland support a number of nationally important, uncommon or endangered species, including a number of rare/scarce invertebrate species, namely the sawfly (Pontania crassipes), a species solely dependent on dwarf willow (Salix herbacea) as a food plant, the spider (Micaria alpina) and two ground beetles, (Nebria nivalis), a species recorded only from Snowdon in Wales and (Leistus montanus), a species largely restricted to Racomitrium summit heath. Dotterel (Charadrius morinellus) has also bred on this habitat in Snowdonia in the past 30 years. Plant species of interest include the arctic alpine dwarf willow (Salix herbacea), a priority local BAP species, stiff sedge, and woolly fringe-moss.
Upland Dwarf Shrub Heaths
Upland Dwarf Shrub Heaths includes open, infertile ground usually above 250-300m and below 600-750m. The vegetation is dominated by the following species, alone or in various combinations: ling heather (Calluna vulgaris), bell heather (Erica cinerea), bilberry (Vaccinium myrtillus), crowberry (Empetrum nigrum) and western gorse (Ulex gallii). Scattered trees and scrub also occur. At least two distinct types of upland heath exist. Dry heath is dominated by dwarf shrubs such as the above, which thrive on dry often rocky soils. Wet heath is found on damper soils and, in addition to some of the above, supports species which require a degree of moisture in the soil. The most common species are deergrass (Scirpus cespitosus), purple moorgrass (Molinia caerulea) and cross-leaved heath (Erica tetralix). Botanical variation between and within these two broad community types is influenced by climatic and environmental factors and management practices including grazing and burning.
Upland Dwarf Shrub Heath frequently occurs in a mosaic with other habitats such as mire and blanket bog (vegetation on deep peat), acid grassland and bracken. Diversity of vegetation structure, caused by different growth stages of heather and areas with scrub and woodland regeneration, and mosaics of contrasting habitat provide important niches for associated species of invertebrates, reptiles, birds and mammals.
Tall Herb and Ledge Communities
Tall herb and ledge communities in the uplands are found in rather inaccessible situations, for example on cliff ledges or in ravines, where the broken topography provides protection from grazing and burning, allowing the often luxuriant growth of its palatable herbs. Consequently the stands are usually small and fragmented and often have a locally distinctive composition. Great woodrush (Luzula sylvatica) dominates this community, but the presence of other species depends on whether the underlying rocks and soil are base-rich or base-poor. On the latter, bilberry (Vaccinium myrtillus) is the main associate, with heath bedstraw (Galium saxatile) and wavy hair-grass (Deschampsia flexuosa) also commonly occurring (NVC U16).
On more base-rich soils, the community is more species rich, with larger herbs predominating and giving the vegetation the appearance of ‘hanging gardens’ high on mountain ledges (NVC U17). The species most frequently occurring in NVC U17 include, wild angelica (Angelica sylvestris), roseroot (Sedum rosea), ladies mantle (Alchemilla glabra), goldenrod (Solidago virgaurea) and mountain sorrel (Oxyria digyna). Ferns, moses and liverworts can locally be abundant and arctic-alpine plant species are often found around the less shaded margins of the ledges. Small bushes and saplings of rowan and birch sometimes become established on the larger ledges.
Blanket bog is a general term for peat-forming ecosystems where the ground is periodically or permanently waterlogged by high rainfall, poor drainage and a high water table. Found usually between 250-700 metres they are seldom found on slopes greater than 15 degrees. The vegetation is dominated by heather (Calluna vulgaris), cross leaved heath (Erica tetralix), deer-grass (Scirpus cespitosus), the cotton grasses (Eriophorum vaginatum and E. angustifolium) and purple moorgrass (Molinia caerulea). These species are found in various combinations and dominance depending on the altitude and the degree of waterlogging and drainage.
Blanket mire often occurs in a mosaic with rock outcrops, acid grassland and upland dry heath. In some parts of Snowdonia, blanket bog is subject to erosion and degradation resulting in the breakdown and fragmentation of the habitat.
The presence and variety of associated plants, birds, invertebrates and lower plants, particularly species of bogmoss (Sphagnum spp.), are important indicators of this habitat’s quality. Notable species include bog rosemary (Andromeda polifolia), hen harrier (Circus cyaneus), merlin (Falco columbarius), skylark (Alauda arvensis), golden plover (Pluvialis apricaria), short eared owl (Asio flammeus) and the nationally scare large heath butterfly (Coenonympha tullia) which is confined to this habitat.
Oligotrophic waters are nutrient poor and are typical of northern and western Britain although they also occur in some southern heathland sites. Their waters are clear due to low biomass of plankton and have low productivity of aquatic plants and invertebrates. They are important for invertebrate groups such as mayflies and caddisflies and fish, including brown trout (Salmo trutta) and arctic char (Salvelinus alpinus). Llyn Cwellyn contains six-stemmed waterwort and floating water-plantain. A genetically distinct form of the Welsh race of arctic char is also found. The bivalve Pisidium conventus, a species of UK conservation concern, is found in lakes in the Yr Wyddfa SSSI.
The composition of the ground flora varies in relation to a number of factors including soil fertility, drainage conditions and whether or not grazing is present.
Bluebells (Hyacinthoides non-scripta), brambles (Rubus spp.) and ferns tend to be most common where the soil is rich, with heather (Calluna vulgaris), bilberry (Vaccinium myrtillus) and mosses becoming more prominent on soils which are acid and deficient of nutrients. Upland oakwoods and especially ravines within them are especially important habitats for mosses, liverworts and lichens, and the oceanic climate of the humid western woods is favourable for many internationally rare species. Woodlands once covered most of Snowdonia but now only a fraction remains. Clear-felling of upland oak-woods is rare nowadays but a range of other factors threaten the quality and area of this habitat.
Floating water plantain is an aquatic plant of clear, oligotrophic, still or slow moving water. It has horizontal stems, which can be floating or submerged, bearing both blunt, elliptical, floating leaves on long stalks and linear, submerged leaves. The solitary flowers arise from the leaf axil and have three white petals with yellow spots at the centre.
The Snowdon Lily (Lili’r Wyddfa) is a delicate, white flowered arctic-alpine plant with grass-like leaves. It has a widespread distribution in alpine and arctic regions in the northern hemisphere where its typical habitat consists of gently sloping, alpine tundra above the treeline. In Snowdonia, it grows high in the mountains on north/north-east facing cliffs, but not commonly in association with other arctic-alpine species, being less demanding of base rich substrates, and can be found in some sites growing alone out of cracks and crevices in the rock. In Britain, Lloydia has never been recorded outside Snowdonia and its current distribution is similar, but somewhat more restricted, to that indicated by previous records since its discovery in Snowdonia by Edward Llwyd in the late seventeenth century.
The small Snowdon beetle has a brightly coloured red, gold, green and blue striped elytra which accounts for its European name, the Rainbow leaf beetle. Snowdon beetles live on base-rich scree where grasses such as Agrostis capillaris and Festuca ovina grow alongside the beetle’s main food plant, wild thyme (Thymus polytrichus). The adult beetles lay their eggs on grass blades. Despite a relative abundance of similar habitats, the beetle is found at only a very few sites on Snowdon and, perhaps, in Cwm Idwal.
Historical records suggest that the Snowdon population may once have been ‘extinction-resistant’ supporting the distribution of new colonies in the region. However, recent evidence indicates that this once resistant population is now in serious decline, with a population of approximately 1000 adults only.