|Organisation / Company||Countryside Council for Wales|
Cadair Idris and its surrounding upland area are of interest for their geology, land form and biodiversity. There are corries, summit ridges, steep scree slopes and cliffs found on the massif itself. To the south-east is the large U-shaped glaciated valley containing the lakeTal-y-llyn. The area of Cadair Idris and Tal-y-llyn is of major importance for glacial landforms. It contains a number of cirques, including Cwm Cau which has been described as the finest in Britain. (Cirques, corries and cwms are names for the bowl-like depressions below summits, formed by erosion caused during ice forming processes that feed glaciers.) Today, nutrient-poor lakes occur in several of these depressions, Llyn Cau being the largest.
The site supports a wide range of upland habitats, with acid grassland as perhaps the most widely distributed. Other habitats include blanket bog, wet and dry heaths, lichen/bryophyte heath, broadleaved woodland and a range of grassland types. The area is typical of Welsh uplands in being fairly heavily sheep-grazed.
There is widespread but patchy development of blanket bog, dominated by Hare’s-tail Cottongrass, with Deergrass, abundant Purple Moor Grass and a little Heather and Cross-leaved Heath. Wet heath has Cross-leaved Heath as the major woody species, usually with Tormentil. Dry heath is characterised by much Heather, often with Bell Heather, and other woody species such as Bilberry and Crowberry, usually with Sheep’s Fescue or Mat Grass, but sometimes with the beautiful Wavy Hair-grass. Western Gorse occurs with Heather on the drier slopes.
On the northern and eastern fringes of Cadair Idris there are scattered woodlands with gullies and ravines. These woodlands, stream gullies and the mixture of base and acidic rocks, together with the high rainfall and clean air, have produced ideal conditions for a diversity of lower plants and ferns. Overall, the main tree species is Sessile Oak, although Pedunculate (or English) Oak occurs and the two hybridise to give almost continuous variation between the parents. Oaks occur with abundant Downy Birch, Rowan and Holly, frequent patches of Hazel and Hawthorn. Alder occurs locally in the wetter areas of woodland.
Cadair Idris is one of the most southerly high mountains in the UK, and many upland species reach their southerly limit in the UK here. The spectacular cwms, boulder fields and scree slopes support biogeographically important and fragile vegetation communities in the crevices and on ledges and rocks.
A population of the Lesser Horseshoe Bat uses the mines on Cadair Idris for hibernation. The abundance of Hazel in the woods provides good habitat for a population of the Common Dormouse to breed and forage. Otter, Brown Hare and Water Vole regularly use the site. Both Brook and River Lampreys, have been recorded. The rivers both upstream and downstream of Tal-y-llyn lake are spawning grounds for Salmon. Breeding birds of the open upland include Ring Ouzel, Wheatear (both summer visitors), Peregrine, Raven, Meadow Pipit and Skylark. The woodland and ffridd (the area just above the limit of agricultural improvement) support typical species, such as Wood Warbler, Pied Flycatcher, Spotted Flycatcher, Redstart and Tree Pipit (all summer visitors). The invertebrates of Cadair Idris include a number of uncommon species.