|IPA Factsheet - Shetland|
Site Description Ronas Voe is located in Northmavine, in the North Mainland of Shetland. Ronas Voe IPA component site consists of an extensive area of upland to the north of Ronas Voe, including Ronas Hill itself (the highest point in Shetland at 450 m), the North Roe plateau and the Beorgs of Housetter, Skelberry and Uyea. The site is characterised by an open landscape of heathland, bogs, pools, lochs and impressive coastal scenery. The summits and upper slopes of Ronas Hill, Mid Field and Roga Field have extensive areas of granite gravel or ‘fell-field’ created by the action of wind and frost. Freezing and thawing of the gravelly soil has produced a range of landforms known as peri-glacial features (formed under extremely cold climates). They include wind stripes, boulder field and solifluction terraces. Some of these are relict (i.e. no longer active), possibly dating from the end of the last ice age, others are still forming. The higher ground supports arctic-alpine plant communities. At lower altitudes on Ronas Hill and across the North Roe plateau the vegetation consists of a mosaic of European dry heath, North Atlantic wet heath and blanket bog depending on the nature of the soil and particularly its drainage characteristics. The northern part of the site has numerous water bodies, ranging from dystrophic (acidic and nutrient-poor) pools to clear-water lochs with low to moderate nutrient levels. Arctic water flea Eurycercus glacialis is found in small lochs on the scord between Mid-field and Ronas Hill. This is one of only two sites in Great Britain where it is known to occur, and is of international importance. The peatlands of North Roe hold a rich community of breeding moorland birds including Arctic and great skua, dunlin and golden plover. The site includes the second densest breeding aggregation of red-throated divers in Britain. Keen of Hamar Keen of Hamar lies to the north-east of Baltasound on the east coast of Unst, the most northerly island of Shetland. It comprises the fenced lower Keen and upper Keen (western and eastern compartments respectively) separated by a ‘cattle corridor’, Hagdale chromite quarry and the coastline from Geo of Hagdale to Muckle Geo of the Keen. The site is noted for its geological interest: chromite mineralisation (ferrous chromate, FeCr2O4) is present at Hagdale quarry and the Wick of Hagdale, and for the serpentine soils of the Keen of Hamar which support a patchwork of calaminarian grassland (vegetation growing on soils containing heavy metals) with associated plant rarities and species-rich serpentine heath. Whiteness Whiteness is a peninsula lying between Whiteness Voe and Stromness Voe. South Whiteness lies on the largest continuous outcrop of crystalline limestone in Shetland. The limestone rocks here produce calcium-rich, fertile soils in parts of the site and the Whiteness peninsula is one of the few areas in Shetland which is not influenced by water draining from acidic rocks nearby.
Botanical Significance Description and Botanical Significance: (From SSSI Citation) Shetland is a sub-arctic archipelago of Scotland that lies north and east of mainland Great Britain. The islands lie some 80 km to the northeast of Orkney and 280 km southeast of the Faroe Islands and form part of the division between the Atlantic Ocean to the west and the North Sea to the east. The total area is 1,468 km2 and the population total 22,210 (2009). The largest island, known simply as "Mainland", has an area of 967 km2, making it the third-largest Scottish island and the fifth-largest of the British Isles. There are an additional 15 inhabited islands. The archipelago has an oceanic climate, a complex geology, a rugged coastline and many low, rolling hills. Over one million birds of 70 different species breed in the islands. Many of these are of national and international significance. As well as breeding birds, Shetland is of great importance to migrating birds with over 430 species recorded in the islands. Shetland, with its dramatic coastline and wealth of wildlife, is unique and boasts a range of habitats, from moorland to serpentine rocks. The vegetation is largely blanket bog dominated by heather, cotton grass, dwarf shrubs such as crowberry and bilberry and sphagnum moss. The numerous freshwater lochs, pools and marshes also contain a variety of aquatic plants. The lower lying land consists of pasture, grasslands and coastal heath. Many of these grasslands have had no or very little agricultural improvement. Shetland has been principally identified for its vascular plant interest including Shetland mouse-ear Cerastium nigrescens, Shetland mouse-ear hawkweed Pilosella flagellaris subsp. bicapitata and a large assemblage of eyebright Euphrasia spp.. Shetland mouse-ear Cerastium nigrescens is a tufted perennial herb confined to two adjacent hills on very exposed, sparsely-vegetated fell-field of shattered serpentine rock. It grows to an altitude of only 80 m and has a habitat with many similarities to more montane communities. Shetland mouse-ear hawkweed Pilosella flagellaris subsp. bicapitata is an endemic perennial herb of grassy limestone rocky outcrops, heathy granulitic gneiss and feldspathic rocky sea-banks in three localities in Shetland, where it was first described in 1962 (Online Atlas of the British and Irish Flora, 2012). Ronas Voe is located in Northmavine, in the North Mainland of Shetland. The crags overlooking Ronas Voe support several endemic species of hawkweeds including three which grow only on Ronas Hill: Hieracium breve, H. ronasii and H. subscoticum. The site is one of only three where Shetland mouse-ear-hawkweed Pilosella flagellaris subsp. bicapitata occurs. Keen of Hamar lies to the north-east of Baltasound on the east coast of Unst, the most northerly island of Shetland . Keen of Hamar has the largest surviving area in the UK of near-natural Calaminarian grasslands on serpentine. The site is rich in rare northern species, such as arctic sandwort Arenaria norvegica ssp. norvegica and northern rock-cress Arabis petraea, and includes the endemic Shetland mouse-ear Cerastium nigrescens, found only on serpentine rocks at this site. The site has ecological features and floristic composition similar to those of serpentine grasslands in Scandinavia, where the habitat type is also rare. The Whiteness component IPA site is located on the west coast of the Shetland Mainland, 12 km north-west of Lerwick. The influence of the calcium-rich rocks is most easily seen in the shallow soils around rock outcrops which support the main botanical interest. Some of the outcrops are too steep for sheep to climb and the absence of grazing allows some of the more interesting plant species on the site to flourish. The site is designated for the presence of Shetland mouse-ear hawkweed Pilosella flagellaris subsp. bicapitata, the global distribution of which is restricted to just three sites in Shetland. The peninsula also supports other important limestone plant communities of botanical interest. Shetland as a whole has a large assemblage of eyebright Euphrasia agg..The complex of cliff top turf and flushed habitats round most of the coast line supports Euphrasia with high morphological diversity and incipient speciation. E. arctica, confusa, marshallii, micrantha, scotica, foulaensis (Heslop-harrisonii on Foula) are all present. The roadsides in Sumburgh have good populations of E. arctica var. zetlandica (endemic to Shetland but not rare): a variant claimed to be of hybrid origin but not necessarily so. The complex of wet hay meadows at Cunningsburgh is possibly the only remaining site for Euphrasia arctica var. speciosa, an endemic taxon formerly widespread in Shetland (E. arctica ssp. arctica sensu Yeo). The flushed coastal area at Bridge of Walls supports, amongst other Euphrasia agg. a distinctive and uniform Euphrasia probably derived from E. foulaensis x scottica (resembles Heslop harrisonii). Ronas Voe Ronas Voe holds a large proportion of the remaining native trees in Shetland. These comprise all of Shetland’s surviving downy birch and numerous rowans, aspens and willows including, on one of the islands in Moosa Water, the only downy willow in Shetland. All these trees are vulnerable to grazing and so are restricted to sites that are inaccessible to sheep, particularly to islands in the larger lochs and the crags overlooking Ronas Voe. These crags also support several endemic species of hawkweeds including three which grow only on Ronas Hill: Hieracium breve, H. ronasii and H. subscoticum. The site is one of only three where Shetland mouse-ear-hawkweed Pilosella flagellaris subsp. bicapitata occurs. Keen of Hamar The site contains one of the finest examples of serpentine debris vegetation in Europe and supports a number of national plant rarities. It provides an interesting contrast to the other major serpentine outcrops in Britain such as the Lizard Peninsula in Cornwall and those in North-East Scotland. The unique flora is related directly to the unusual chromite-serpentine substrate and the soils derived from this, which are deficient in phosphorous, nitrogen and potassium but contain high levels of heavy metals such as chromium, magnesium and nickel. The principal vegetation types are a sparse fell-field community on bare serpentine debris and a closed sward of short heather and grasses on soil derived from glacial till. The debris vegetation holds an unusual mixture of montane and maritime species and uncommon forms of some of these are present. Species including nationally rare Scottish sandwort Arenaria norvegica ssp. Norvegica, northern rock-cress Arabis petraea and Shetland mouse-ear Cerastium nigrescens - endemic to this site and nearby Nikka Vord. Cerastium nigrescens is the only known example of a serpentine endemic in North West Europe. Classic Euphrasia ostenfeldii eyebright is found on the shattered serpentine. Whiteness The flora of South Whiteness includes the Shetland mouse-ear hawkweed Pilosella flagellaris ssp. bicapitata, one of only three sites for this endemic subspecies. Other species of note include the locally rare stone bramble Rubus saxatilis and maidenhair spleenwort Asplenium trichomanes as well as species more typical of Shetland limestone flora such as fairy flax Linum catharticum, moss campion Silene acaulis, hoary whitlowgrass Draba incana, lady’s-mantle Alchemilla filicaulis, common milkwort Polygala vulgaris, meadowsweet and long-stalked yellow-sedge Carex lepidocarpa. The site also contains areas of acid grassland, marsh and heath and the only marl loch in Shetland. Marl is a category of freshwater which has a high concentration of calcium but is low in other nutrients. Plants on the site which are local or rare in Shetland include stone bramble Rubus saxatilis and early purple orchid Orchis mascula (the only place where it grows other than on serpentine soils in Unst).
General Habitat Description
Conservation Issues Ronas Voe Heathland and blanket bog are sensitive to grazing pressure. Successive reductions of sheep numbers on Ronas hill in recent years have significantly reduced the impact of livestock on vegetation. Sheep crossing frozen lochs to access islands pose a threat to relict scrub. Other activities likely to affect the site include large-scale mechanical peat-cutting, quarrying, excessive trampling and use of vehicles. The effects of climate change on the geology, habitats and species of Ronas Hill are uncertain. The geology, many of the habitats, and several of the species are strongly influenced by the Arctic-alpine conditions of Ronas Hill and under most models of climate change this influence will be expected to decline. Keen of Hamar The last condition monitoring found targets were met for Calaminarian Grassland and Serpentine Heath vegetation (October 2010). However, monitoring of northern rock-cress, Shetland mouse-ear and Scottish sandwort showed a decline in population numbers (April 2004 and August 2006). In the past concerns have been expressed about the fragility of the site and the potential for damage caused by trampling by visitors. The debris habitat is regularly subject to weathering and frost heave and the plant species growing there are adapted to cope with movement so trampling by the public is not generally thought to be a problem. Pedestrian access is therefore unrestricted across the reserve but formal routes may need to be established if trampling appears to have an adverse effect on debris habitat and rare plants. Should commercial exploitation of the Platinum Group Elements ever occur on Unst then considerable pressure to extract may eventually be placed on the Keen of Hamar. SNH however holds the mineral rights to the Reserve. South Whiteness The latest site condition monitoring found the Shetland mouse ear hawkweed population to be in favourable condition with regeneration taking place. This suggests current grazing levels are sustainable, however a reduction in grazing would be beneficial as it would give the plants more opportunity to spread from established areas. Prior to 1986, an owner of part of the site was approached regarding test drilling to determine the quality of lime for possible quarrying. This does not appear to have had any follow-up and any developments of this type would require careful consideration. The channel, dug to prevent stock gaining access to the saltmarsh, is being enlarged by tidal action and there is evidence of erosion on the saltmarsh. Although this does not appear to pose an immediate threat to the marsh there may be long term effects on the extent of the area.