|IPA Factsheet - Isle of Arran|
Site Description The Isle of Arran, Scotland is one of the most southerly Scottish islands and sits in the Firth of Clyde between Ayrshire and Kintyre. Arran is 19 miles long by 10 miles wide but has a remarkable diversity of landscapes and seascapes. Arran is regarded as a unique microcosm of Scottish geology. It encompasses, within a comparatively small area, a richness and diversity of rock types and formations that document many of the events in the last 700 million years of Scotland’s history. The profile of the north Arran hills as seen from the Ayrshire coast is a well-known sight referred to as the "Sleeping Warrior" due to its resemblance to a resting human figure. The highest of these hills is Goat Fell (874 m). There are three other relatively high mountains in the north east; Caisteal Abhail, Cìr Mhòr and Beinn Tarsuinn. Bheinn Bharrain is the highest peak in the north west (721 m). The largest valley on the island is Glen Iorsa to the west, whilst narrow Glen Sannox and Glen Rosa to the east surround Goat Fell. The terrain to the south is less mountainous than the north although a considerable portion of the interior lies above 350 m and the summit of A' Chruach reaches 512 m. Snow seldom lies at sea level and frosts are less frequent than the mainland. In common with most islands of the west coast of Scotland, rainfall is generally high at between 1 500 mm per annum in the south and west and 1 900 mm per annum in the north and east. The mountains are wetter still with the summits receiving over 2 550 mm annually Arran has a number of villages that are mainly found around the shoreline. Brodick is the site of the ferry terminal, several hotels, and the majority of shops. Lamlash is the largest village on the island and in 2001 had a population of 1,010 compared to 621 for Brodick. The main industry on Arran is tourism. Farming and forestry are other important industries. Forestry Commission are the one of the biggest landholders on the island, owning approximately 11,100 ha (or 25%) of the whole island. The Mountains in the north of Arran support a variety of habitats and species. The mountains, which include two nationally important geological areas of Ordovician and Tertiary Igneous rock exposures, support the largest and most diverse upland habitat assemblage in west central Scotland. The plant and animal communities show characteristics influenced by the maritime climate, acidic rock and soil formations, as well as altitudinal characteristics, not seen on the mainland of southern Scotland. The plant habitat assemblage includes blanket bog, subalpine wet dwarf-shrub heath, subalpine dry dwarf-shrub heath, alpine heath, and alpine moss heath. The north west supports an extensive area of birch woodland. The vascular plant assemblage includes endemic whitebeams and the Killarney fern. The upland moors of Arran, predominately within the southern half of Arran, comprise a nationally important example of an upland habitat assemblage which supports breeding hen harriers as well as a wider assemblage of breeding birds. Gleann Dubh lying 3km south west of Brodick comprises an assemblage of upland habitats that is unusual on Arran for the abundance and quality of the base-enriched subalpine flushes and rock ledge communities. Benlister Glen lying 2km west of Lamlash supports good examples of species-rich (‘tall herb ledge’) vegetation on limestone outcrops containing some plants otherwise scarce on Arran. The South Coast of Arran Site is noted for both geological and biological features. Arran Northern Mountains The mountains of north Arran are a south-westerly outlier of the South West Highlands, with landforms similar to those of the Highlands. The corries and cliffs are sharply defined, particularly in the Goatfell range in the east. The summits of the western heights of the Beinn Bharrain chain are less accentuated but still more pronounced than most other hills in southern Scotland. These two mountain blocks are separated by the wide glacial valley of Glen Iorsa. The vegetation displays the same kind of patterns seen on the higher mountains of western Scotland. Arran’s Northern Mountains support a variety of habitats and species and an uninterrupted sequence of plant communities from sea-level to mountain tops can be found over a short distance. The mountains, which include two nationally important geological areas of Ordovician and Tertiary Igneous rock exposures, support the largest and most diverse upland habitat assemblage in west central Scotland. This habitat assemblage includes blanket bog, subalpine wet dwarf-shrub heath, subalpine dry dwarf-shrub heath, alpine heath, and alpine moss heath. The north west of this area supports the most extensive area of birch woodland within the site. The vascular plant assemblage includes endemic whitebeams and the Killarney fern while the diverse upland breeding bird community includes hen harrier, peregrine and golden eagle. The invertebrate interest includes both dragonfly and water beetle assemblages. Arran Moors The upland moors predominately within the southern half of Arran, with a small, north eastern section, situated around Sannox, comprise a nationally important example of an upland habitat assemblage which supports breeding hen harriers as well as a wider assemblage of breeding birds. The upland assemblage consists of wet and dry heath; blanket bog; subalpine flushes; and acid grassland. There are also water bodies and mosaics of acid grassland with rush communities within some of the lowland areas. Small areas of broad-leaved woodland including areas of eared willow scrub are also present, typically associated with incised water courses and river valleys. Arran moors is also an important component of the Aran Moors Special Protection Area (SPA), which is designated for the breeding Hen Harrier Circus cyaneus. South Coast of Arran The South Coast of Arran Site is noted for both geological and biological features. In terms of its geology, the site has important examples of dykes and sills. Dykes and sills are igneous intrusions which form when molten volcanic rock is forced upward to fill cracks which form in the Earth’s crust. The numerous dykes exposed along the southern coast of Arran, known collectively as the Arran Dyke Swarm, are of international importance. About 200 dykes, varying greatly in thickness up to 30 metres, were formed around 60 million years ago during the Tertiary geological period. At Bennan Head, the cliffs expose a sill of great interest, consisting of granite and basalt which in some places appear to have been mixed in a molten state. Ard Bheinn Ard Bheinn Site of Special Scientific Interest (SSSI), lying 7km south west of Brodick, is a prominent hill on the south flank of the Shiskine valley and is nationally important for its Tertiary Igneous geological interest and breeding hen harriers. The geological interest of Ard Bheinn covers the north-western part of the small Central Complex of Arran. This is unique in the Tertiary Igneous Province in containing the well-preserved remains of high-level Tertiary volcanic activity, which occurred approximately 60 million years ago, as well as deeper-seated intrusions; it is also unusual in possessing considerable development of volcanic rocks intermediate in composition between granite and basalt, both as laval flows and as pyroclastic debris. The site also shows unique foundered masses of Tertiary basalt lavas, chalk, sandstones, shales and other sediments that once covered Arran but have been eroded away elsewhere. Benlister Glen Benlister Glen lies 2km west of Lamlash on the Isle of Arran. It supports good examples of species-rich (‘tall herb ledge’) vegetation on limestone outcrops containing some plants otherwise scarce on Arran, while in the lower half of the site the open habitat gives way to wet woodland. Gleann Dubh Gleann Dubh lies 3km south west of Brodick and comprises an assemblage of upland habitats that is unusual on Arran for the abundance and quality of the base-enriched subalpine flushes and rock ledge communities. It is also important to the diversity of birds breeding within the site, which includes part of the internationally important populations of hen harriers for which the site is an important component of the Arran Moors Special Protection Area (SPA). The red deer population within the site is part of nationally important red deer refugium (i.e. the deer are protected from potential hybridisation). The geological interest within the site is also of interest as it involves portions of a small Tertiary complex showing the elaborate assemblage and intricate inter-relationships of rock types' characteristic of such a mass.
Botanical Significance Arran Northern Mountains The mountains support the largest and most diverse upland habitat assemblage in west central Scotland. Dry heath is common throughout the site on steep slopes. Where slopes level out, a transition community containing blaeberry gives way to blanket bog at lower altitudes. Purple moor grass, deergrass and hare’s-tail cottongrass are dominant in these bogs, with their composition varying with altitude and topography. At higher altitudes, on more exposed slopes the dry heath takes on a prostrate growth form and communities such as fescue-blaeberry heath and wind-clipped alpine moss heath (dominated by Racomitrium moss) with large patches of dwarf willow are found. Dwarf juniper Juniperus communis ssp nana is an important component of the wet heath community, below 600m. On north-east facing slopes immediately below ridges, such as on Beinn Bharrain, small areas of blaeberry snow-bed vegetation may be found. In the lower parts of several glens (e.g. Glen Sannox and Glen Rosa) bracken forms a mosaic with purple moor grass and heather over large areas. The most extensive area of native birch woodland on Arran is found in the north-west, between Lochranza and Catacol. The canopy is predominantly birch, although rowan, oak and ash are locally present. Throughout the site a few scattered trees can be found on the crags (usually rowan) but trees are more common on steep-sided river banks or gullies at lower elevations where rowan, birch and rarely aspen occur. The vascular plant interest within the site includes the nationally rare endemic whitebeams (the Arran service-tree Sorbus pseudofennica, the Arran whitebeam Sorbus Arranensis and the Catacol whitebeam Sorbus pseudomeinichii), which are listed as vulnerable in the British Red Data Book (RDB). These endemic tree species are restricted to the northern part of the island, growing in river gorges and are most abundant in Gleann Diomhan and the Allt nan Calman), where they are found growing with birch and rowan. Other plants in the assemblage include the gametophyte stage of the Killarney fern Trichomanes speciosum and the nationally scarce brown beak-sedge Rhynchpsora fusca and alpine enchanter's-nightshade Circaea alpina. Arran Moors The moorland, which is found especially in the more westerly and low-lying areas, is dominated by areas of ling/bell heather heath which frequently grades to drier heather/blaeberry heath at higher altitudes and more easterly locations. On wet soils with impeded drainage (such as the lower reaches of Machrie Water) deergrass/cross-leaved wet heath can be extensive. On water-logged soils where there is movement of ground water alkaline fen occurs, supporting sedges, bog mosses and rushes. Some of the most extensive areas of blanket bog are in the central area of the site - especially around An Tunna, between Cnoc a’ Chapuill and The Ross, and between Tor Beag and Tor Mhaoile – with one small area at Lon nan Cuilc in the north. Along drainage lines and the margins of water courses, where there is a measure of nutrient enrichment, subalpine flushes have developed, typically dominated by two main communities: the soft rush/sharp-flowered rush-marsh bedstraw rush-pasture community; and the short-sedge acidic mire community dominated by the star sedge-sphagnum bog moss mire. Acid grasslands, consisting mainly of the sheep’s fescue-common bent-heath bedstraw community, but also the mat grass-heath bedstraw grassland community on higher ground, are a frequent feature of the moorland mosaic. South Coast of Arran This site is of biological interest for its vegetated shingle and maritime cliff habitats. Shingle beaches occur in a number of locations, most notably by the mouth of the Torrylinn Water, but also in smaller areas at Port a’ Ghille Ghlais, south of Levencorroch and near Auchenhew. It is in the former location that the principal area of vegetated shingle occurs. Here, the shingle is vegetated to varying degrees, with a more stable grassland and scrub community developed on the landward side, and a transient, pioneer community towards the shore. The pioneer community supports a colony of the nationally scarce oyster plant Mertensia maritime, one of the largest in south-west Scotland. The maritime cliffs and steep slopes in the western part of the site support grassland and scrub communities which contain numerous locally uncommon plants, such as adder’s-tongue Ophioglossum vulgatum, carline thistle Carlina vulgaris, wood vetch Vicia sylvatica, and narrow-leaved everlasting-pea Lathyrus sylvestris at the northern limit of its natural range in Britain. The maritime cliff habitat has not been formally monitored yet. There are other coastal habitats of interest within the site. Intertidal habitats include many rock pools and extensive kelp beds which support an unusual diversity of marine life. Landward, habitats include a narrow stretch of sand dune and coastal grassland extending from the western extremity at Torrylinnwater Foot to the burn at Torran Riabhach, and which contains a variety of species typical of this habitat. Further to the east, from the Bennan Head cliffs to Levencorroch Burn, the vegetation shows a transition from beach head saltmarsh, through fen and wet grassland on the wave cut platform, to willow scrub at the base of the cliff. Ard Bheinn Ard Bheinn supports free draining slopes that give rise to an extensive mosaic of oceanic dry heaths interspersed with patches of wet heath, flushes and upland grasslands. These moorland habitats are a continuous extension of the habitats found within the adjoining Arran Moors SSSI and together they represent one of the best examples of upland habitat within North Ayrshire. The predominant habitat type is the heather-cross-leaved heath Calluna vulgaris-Erica cinerea heath. In hollows and shallower slopes, particularly on the eastern side, this gives way to wet heath communities dominated by deer grass-cross-leaved heath. In the extreme south east, the peat soils increase creating a small area of blanket bog. This is hydrologically linked to the adjacent central Arran moorland where it becomes much more expansive. Eared willow Salix aurita scrub can also be found along several of the watercourses and in their lower stretches and in the larger incised valleys there is a transition to scattered birch woodland. This is particularly well developed in Glen Craigag. Benlister Glen Tall herb ledges are found on steep slopes adjoining the upper reaches of the Benlister Burn and its tributaries, where limestone outcrops support relatively luxuriant and species-rich vegetation. Here, dominant species include greater woodrush Luzula sylvatica and various ferns, including green spleenwort Asplenium viride, while other species present include mountain sorrel Oxyria digyna and the Nationally Scarce alpine enchanter’s nightshade Circaea alpina. Wet woodland occupies the lower section of the site and is dominated by alder and birch with some rowan, ash and willow. Its understorey is well developed and the ground flora includes a number of species commonly associated with base enrichment, for example false brome Brachypodium sylvaticum, dog’s mercury Mercurialis perennis, sanicle Sanicula europaea and yellow pimpernel Lysimachia nemorum. Gleann Dubh The upland assemblage contains a variety of habitats. These include plateau areas to the west and south covered by ombrogenous bog vegetation. An ombrogenous bog is one in which the water component originates through rainfall. The vegetation here is dominated by heather, cottongrass and deer-grass. The steeper valley sides support dry heather heath with frequent bilberry, scattered patches of acidic grassland and dense stands of bracken. Subalpine flushes of a variety of types are found throughout. Downy birch and eared willow dominate the wooded fringe adjacent to the conifer plantations. Exposed rock, which is nearly vertical, is a very significant feature within the upland assemblage with occasional cracks and ledges which support rare or uncommon plants such as roseroot Sedum rosea, green spleenwort Asplenium viride, alpine enchanter’s-nightshade Circaea alpinum, rock whitebeam Sorbus rupicola, stone bramble Rubus saxatilis, alpine meadow-rue Thalictrum alpinum and alpine saw-wort Saussurea alpine.
General Habitat Description Key organisations: SNH NTS Scottish Water Forestry Commission Armed Forces (HMS Gannet and the Territorial Army)
Conservation Issues Arran Northern Mountains In 2006 the condition of the upland assemblage feature overall was determined on the basis of the extent of the component habitats (blanket bog; subalpine dry dwarf-shrub heath; alpine heath; and alpine moss heath) and therefore the condition was assessed as favourable. However, the individual habitat components were also looked at in more detail at a number of sample points to give a better idea of the effects of current management. This highlighted a number of concerns with the actual condition of the individual habitat components. There were areas of eroding soil, associated with trampling on the spur extending northwest from north Goatfell, although it is unclear whether the damage is due to walkers or herbivores. Extensive burning was also evident on the north face of Suidhe Fhearghas, a subalpine dry dwarf-shrub heath area of high sensitivity. It is thought that past grazing and burning regimes may have facilitated the spread of bracken on the lower slopes which is affecting the areas of dry heath. Areas of blanket bog and wet heath have also been damaged due to cumulative grazing pressure and there has been a very wide spread outbreak of heather beetle. In order to improve the condition of all components of the upland assemblage feature it will be necessary to review some management measures. The upland birch woodland feature is in an unfavourable, declining condition (2008) as although there was no loss in the area of woodland, the feature has a very open canopy cover in places due to the historic overgrazing (by a combination of deer and sheep). The presence of invasive species such as bracken and rhododendron are also threats to this feature, suppressing natural regeneration. The vascular plant assemblage is considered to be in favourable condition as populations of all the target species were found. The assemblage was originally considered to be unfavourable as marsh clubmoss Lycopodiella inundata was not found during the monitoring visit. As this species has not been recorded on Arran since 1988 and is considered locally extinct, it has been removed from the vascular plant assemblage. Recreational pressure, by mountaineers, ridge-walkers and ramblers, is evident on the established footpaths to the summits with water damage from poor drainage exacerbating erosion. Arran Moors The upland habitat assemblage is considered to be in favourable condition (2006) however, bracken encroachment was noted as a problem within some areas of the wet and dry heath. Some areas of wet heath also showed signs of undergrazing. South Coast of Arran Authorised and unauthorised shingle extraction has occurred over a number of years to the east of the Torrylinn Water. Unauthorised extraction in particular, and associated vehicle use, are likely to have caused declines in the abundance and distribution of oysterplant in this area. Although non-native species are generally scarce, Japanese knotweed occurs towards the west of the site and has the potential to encroach on vegetated shingle to the detriment of oysterplant. Careful eradication and monitoring of Japanese knotweed will prevent any adverse effects. Benlister Glen The tall herb ledge feature is considered to be in favourable condition (2008), as there is a good variety of typical plants with little evidence of browsing damage. The wet woodland is considered to be in favourable condition (2002) as there has been no noticeable decline in the extent of the woodland. Indeed, the woodland appears to be expanding onto adjacent open ground, encouraged by low levels of grazing. Gleann Dubh The condition of the upland assemblage comprising subalpine dry dwarf-shrub heath, blanket bog, subalpine flushes and tall herbs is considered to be favourable, maintained (2006) as all the component habitats for which minimum area targets were applicable reached or exceeded those targets. However when the site is next monitored the site condition will also depend on the condition of the individual components.