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Facts on Biodiversity & Human Well-being
 

 

Protected Areas and World Heritage

The St. Kilda archipelago has preserved ecosystems intact for thousands of years virtually unchanged by man; also a well preserved well documented primitive settlement. These remote and scenically dramatic islands have some of the highest cliffs in Europe which provide a refuge for some of the most important colonies of seabirds in the north-eastern Atlantic, and is a major breeding site for puffins and northern gannets. The local Soay sheep is the most primitive domesticated animal in Europe, dating unchanged from Neolithic times. St. Kilda is also of national importance for its geology, flora, other fauna, marine interest and ancient vernacular buildings.

COUNTRY  United Kingdom

NAME  St Kilda (Hirta) National Nature Reserve

IUCN MANAGEMENT CATEGORY 

St Kilda National Nature Reserve        IV         (Habitat/Species Management Area)             
Natural World Heritage Site, inscribed in 1986                       (Natural Criteria  iii, iv)

Extension to site in 2004 to become a Mixed (Natural & Cultural) World Heritage Site.
Natural Criteria  i, ii, iii, iv / Cultural Criteria  iii, iv, v.

BIOGEOGRAPHICAL PROVINCE  Scottish Highlands  (2.31.12)

GEOGRAPHICAL LOCATION  The World Heritage site comprises a  group of four small islands located on the Atlantic continental shelf, off the  coast of the Outer Hebrides, 165 km west of the mainland of northern Scotland. The site is contained within a square with the coordinates 57°54'36"N / 08°42'W, 57°46'N / 08°42'W, 57°46'N / 08°25' 42"W, 57°54'36"N / 08°25'42'W.

DATES AND HISTORY OF ESTABLISHMENT
Declared a National Nature Reserve by the Secretary of State for Scotland under Section 1 of the National Parks and Countryside Act;

1979:   Listed under the Ancient Monuments and Architectural Areas Act;

1981:   Declared a National Scenic Area by the Secretary of State for Scotland;

1984:  Designated a Site of Special Scientific Interest under Section 28 of the Wildlife & Countryside Act; also a Geological Conservation Review Site;

1992:  Designated an E.U. Special Protection Area for its wildfowl and a Special Area of Conservation for its cliffs, reefs and sea caves.

AREA
Total areas of 24,201.4ha, comprising land: 854.6ha and sea: 23,346.8ha (measured above and below the mean high water spring mark). Hirta, 628.5ha, Soay, 96.8ha, Boreray, 86.5ha, Dun, 32ha, and six islets, 10.8ha.

LAND TENURE
The islands were bought in 1931 by an ornithologist, the 5th Marquess of Bute, who bequeathed them in 1957 to the National Trust for Scotland (NTS) which has managed the reserve since May 2003 on behalf of Scottish National Heritage (SNH). Rights to the foreshore between high and low tide levels are vested in NTS. 3ha on Hirta was subleased to the Ministry of Defence (MOD) in 1957 for a small radar tracking station for the Benbecula missile range. This is controlled by very strict lease agreements.

ALTITUDE  Sea-level to 425.8m (Conachair).

PHYSICAL FEATURES
The archipelago comprises four small islands: Hirta, Soay, and Dun, with Boreray 7.5km northeast, plus the islets of Stac an Armin, Stac Lee, Levenish and two stacks off Soay. They are the remains of a Tertiary ring volcano, weathered, glaciated and carved by violent storms into a precipitous and dramatic landscape of cliffs. The cliffs of Boreray and Soay rise sheer to over 370m and the north face of Conachair on Hirta is 426m high. Two rock stacks off Boreray are the highest in the British Isles: Stac an Armin 191m and Stac Lee 165m. The steep island coasts are riddled with caves, arches, stacks, geos and blowholes formed by frost, ice and wave action. Hirta has two deep bays in Village Bay (Loch Hiort) and Glen Bay.

The igneous rocks were intruded about 55 million years ago above a platform of PreCambrian rock, cut by seas at earlier far lower levels into terraces at 80m and 120m down. The islands' steep cliffs continue under water another 40m to rock rubble and 70m to the first platform thinly veneered with gravels and sands.  The rocks of Hirta are predominantly a complex of dolerite and microgranites with gabbro along the castellated west coast, intruded by basalt dykes.  Soay and Boreray are formed of a breccia of gabbro and dolerites. The cold surrounding waters are clear, allowing sunlight to penetrate deeply and a rich marine life to flourish among submarine caves, tunnels and arches. Geologically this assemblage of unusual forms of contact metamorphism with simultaneously intruded acidic and basic magmas is unique in the British Tertiary Volcanic province. The soils are acid and peaty but are balanced by guano, sheep dung and salt-spray which imparts a pH of 5.8 - 6.2 and by organic manure behind the village.

CLIMATE
The climate is oceanic, of a cool Atlantic type with extremely high humidity and strong winds from the southwest and south particularly in the winter months. These average 110 kph and can gust over 185kph, carrying salt spray as high as 60 meters. The tidal range averages 2.9m and the ocean swell generates 2- meter waves most of the year but 5-meter waves for 10% of the year, often making access impossible. The average rainfall is 1400mm, evenly spread but heavier in winter and less between mid-April and mid June. The mean temperature in January is 5.6°C and in July 11.8°C.  Studies of the pollen profile reveal 6000 years of climatic change in an environment relatively undisturbed by man.

VEGETATION
The vegetation is typical of oceanic islands with a cool north Atlantic climate. This is modified by the prevailing high humidity, giving peaty soils and a wide distribution of oceanic plants such as liverwort Frullania teneriffae, by the effect of salt spray even hundreds of metres inland, resulting in Plantago-dominated swards on cliff tops, and by the fertilising effects of vast numbers of nesting seabirds which create a rich turf. Over 182 species of vascular plants have been recorded from the islands, 162 species of fungi, 194 lichens and 160 bryophytes, but no trees. The full range of habitats includes dwarf shrub heath, dwarf shrub moss tundra, low bog, meadow, freshwater marsh lair grassland, maritime communities and twelve grassland associations. Pollen analysis shows that the islands were partially covered with birch-hazel scrub between 5200 and 6400 years ago. Subsequent climatic change led to the extinction of tree cover and the expansion of halophytic communities. However, Salix herbacea is still present. After the evacuation of Village Bay, there was an increase in heather moorland. There is little intertidal vegetation due to the extreme exposure of the shores. The sub-littoral supports wrack, Fucus spp., Alaria esculenta and a   dense forest of kelp Laminaria hyperborea and below it, parks of kelp as deep as 35 meters. These shelter a great variety of unusual species of invertebrates which also blanket rock walls. The water is so clear that pink algae thrive at 70 meters, and, even at that depth, the effect of the ocean swell is felt.

Salt tolerant plants such as sea pink Armaria maritime, sea campion Silene uniflora and sea plantain Plantago maritimus, Asplenium marinum and Grimmia maritima occur even inland. Much of the grassland, as on Soay and Boreray, has a sub-maritime character consisting of Holcus lanatus, Agrostis stolonifera, A. capillaris, Festuca rubia and Anthoxanthum odoratum. The less maritime communities occurring on Hirta are mainly a range of acid-loving species: poor submontane grassland and heaths consisting of ling and cottongrass Calluna vulgaris - Eriophorum vaginatum bog, extensive mixed Nardus-Calluna-Rhacomitrium lanuginosum heath with Luzula sylvatica grassland dominant on the summit of Conachair. Northern Atlantic species include Botiychium lunaria, Ophioglossum vulgatum, Gentianella campestris, Ligusticum scoticum and Sedum rosea with Arctic-Alpine montane species such as Silene acaulis and Saxifraga oppositifolia. Mediterranean-Atlantic liverwort Fossombonia angulosa also occurs here, at its northernmost locality. The Agrostis-Festuca grassland of Hirta, Boreray and Soay is heavily grazed by sheep. Soay has dry cottongrass bog with Holcus lanatus.  Dun is species-poor but has been ungrazed for 75 years and has a rich Festuca and Rumex sward.

FAUNA
The seabird population, with 330,000 breeding pairs of 17 species, including migratory birds, is the largest seabird colony in the British Isles and one of the largest concentrations in the North Atlantic. A total of 228 sea and water bird species have been recorded though only 140 species have been seen over the course of one year. This includes the world's largest colony of northern gannet Morus bassanus - 60,428 pairs in 1999/2000, 23.6% of the northeastern Atlantic population; the largest and oldest British colony of northern fulmar Fulmaris glacialis (67,000 pairs); and 30% of the British population of the Atlantic puffin Fratercula arctica (135,732 pairs). This species was formerly estimated at two to three million pairs but numbers have dropped substantially. Predation by a small but growing number of skuas Catharacta skua (170 pairs) may be partly responsible. The islands are also one of the very few European breeding stations of Leach's storm petrel Oceanodroma leucorhoa, with 92% of the British population (45,433 pairs), and also of the European storm petrel Hydrobates pelagicus (1,121 pairs, NTS, 2003). The numbers of common guillemot Uria aalge (23,378) are also very high. However, the total populations recorded fluctuate from year to year.

St Kilda is an outstanding example of the ecological colonisation of a remote island and of the genetic divergence caused by the isolation of small populations. For instance, the endemic St Kilda wood mouse Apodemus sylvaticus hirtensis (which survived the human depopulation where the house mouse did not), and St Kilda wrenTroglodytes troglodytes hirtensis (~230 pairs in 2002). The terrestrial avifauna of 10 species is impoverished but the terrestrial invertebrate fauna includes 200 species of fly, 150 beetles and over 280 lepidoptera.  Soay sheep Ovis aries, now free ranging on Hirta as well as Soay, is the most primitive domesticated animal in Europe, a living Neolithic artifact unchanged for thousands of years. Those introduced from Soay to Hirta in 1932 are subject to crashes in the population which ranges between 600 and 2000. A dense but healthy population averaging about 400 blackface-cross sheep on Boreray are quite unmanaged. Grey seals Halichoerus grypus now breed on the islands and 9-10 species of cetaceans are seen: among them minke Balaenoptera acutirostrata and killer whales Orcinus orca, harbor porpoises Phocoena phocoena and Risso's, whitesided and whitebeaked dolphins, Grampus griseus, Lagenorhyncus acutus and L. albirostris. The marine invertebrate fauna of sea anemones, sponges, bryozoans, corals, sea slugs and topshells is extremely diverse, encrusting caves and submarine cliffs. The relatively mild ocean temperatures result in some southern species finding their northern limit and some northern species their southern limit around the islands.

CULTURAL HERITAGE
St.Kilda's name probably derives from the islanders' pronunciation ("hilt") of its Gaelic name, Hiort (from skildar, the old Icelandic for shield). The islands have a wealth of archaeological remains including evidence of Bronze Age occupation, Vikings and early Christian carvings. They are believed to have been fairly continuously occupied for some 2,000 years with settlement concentrated at Village Bay with Gleann Mor for summer sheilings. 1,400 cleiteans, turf-covered stone storage huts, have been found all over the islands. For the last 800 years St.Kilda was owned mainly by the Macleods of Dunvegan. In 1724 smallpox decimated the population which, at the end of the century, was 180. The village was reestablished in a spirit of improvement in 1834 and 1861 with better housing ranged around the bay, the traditional blackhouses end-on to the sea being kept on for animals. But emigration in 1852 had left only about 70 inhabitants. The people grazed up to 2,000 sheep and harvested seabird colonies, mainly gannets and puffins, of which they took scores of thousands every year for oil, feathers, food and fertiliser, paying their rent with them. Their skill in climbing the cliffs to do this, not only for necessity, documented by a traveller, Martin Martin at the end of the 17th century and more recently, is seen as the first example of recreational rock climbing in Britain. For such a primitive community St.Kilda has been unusually well preserved and well documented, partly because of the 18th-19th century idealisation of the noble savage and sublime landscapes, which adds to its cultural significance.

LOCAL HUMAN POPULATION
In the late 19th century, tourists began visiting St.Kilda, for whom the islanders made goods for sale. But with increased contact with the world, which started with disease and puritanical religious missionising, the islanders' self-sufficiency and morale diminished and emigration increased. The islands were finally evacuated in 1930. Poorer crops may also have contributed to this, now attributed to toxic accumulation in the seabird bodies traditionally used to fertilise the fields. The few hectares previously cultivated have now reverted to grassland and heath, and bracken is encroaching. Some lobster and crab fishing is still carried out from the mainland. But St.Kilda remains the remotest British island to be inhabited since the siting in 1969 of a radar-tracking station for the Ministry of Defence, maintained by 12 civilians. In summer a nature warden and an archaeologist are also employed by Scottish Natural Heritage and the NTS jointly for six months and four months respectively, and up to 15 researchers may stay during the summer.

VISITORS AND VISITOR FACILITIES
Since 1995 there have been between 1,500 and 2,000 visitors a year between mid-May and August, but the islands remain hard to reach and numbers may not increase. Seasonal volunteer working parties from NTS are housed in the restored cottages. Several charter companies run short trips but visitors remain on board at night (SNH pers.comm.,1995). Landings are controlled by the warden who will sometimes guide tours around the islands. The row of village houses with walled enclosures is the main exhibition though there is a small museum, a reconstructed house, a shop, bar and a small campsite. The challenging cliffs are valued by Scottish mountaineers who are campaigning to have them made accessible to the sporting public (MCOS, 2001). The clear water and striking submarine formations also provide the best diving sites in Britain.

SCIENTIFIC RESEARCH AND FACILITIES
Much intensive field work, mainly on Hirta, has taken place over the last 100 years: the large number of scientific publications attest to the value of the islands as an outdoor laboratory, and studies have been carried out by teams from seven or more universities.  Geological surveys were first made in 1927-8, and between the 1960s and 1980s. There has been some systematic recording of migrant birds since 1910, and an annual summer survey since 1957.  Scottish Natural Heritage monitors the flora and fauna, particularly the sea bird populations, and Soay sheep, on which detailed studies of their biology and population dynamics have been made for 25 years.  From 1958 onwards, volunteer work parties have restored ruins and annually since the mid 1980s, run archaeological excavations. The whole intact primitive crofting township is designated an Ancient Monument. Six restored cottages are used to provide dormitories, common room, kitchens and museum space.  SNH has recently run a 6-year research program on intertidal, sublittoral and benthic sites with surveys in 1997 and 2000. There is a high level of cooperation between the NTS and the MOD which has assisted the scientific programme in many ways by providing conservation and scientific teams with transport, laboratory facilities, accommodation and catering facilities.

CONSERVATION VALUE
The scenically spectacular St. Kilda archipelago has preserved its ecosystems intact for thousands of years virtually unchanged by human settlement. It is one of the most important seabird colonies in the world and one of the most important breeding sites in the North Atlantic. Some of the highest cliffs in Europe provide a refuge for colonies of rare and endangered bird species, for thousands of puffins and the largest colony of gannets in Britain. St. Kilda is also of national importance for its geology, flora, submarine life, and a well documented  fossilised cultural landscape with relict vernacular buildings.

CONSERVATION MANAGEMENT
The whole archipelago is leased to Scottish Natural Heritage who declared it a National Nature Reserve  and who, with funds from the United Kingdom government, are responsible for managing the islands under the Wildlife and Countryside Act of 1981 and the Natural Heritage (Scotland) Act 1991. It was also designated a National Scenic Area in 1981, a Site of Special Scientific Significance in 1984 and an EU Special Protection Area for seabirds in 1992. A large part of the main island of Hirta has been progressively scheduled as an Ancient Monument and the village has been restored to its 1957 condition. It is also considered a Geological Conservation Review site. As a National Scenic Area it is covered by additional development controls and any proposed development has to seek the advice of the Countryside Commission for Scotland as well as SNH. The NTS has enforced a byelaw prohibiting climbing to protect climbers, birds and flora which is currently being challenged by the Mountaineering Council of Scotland.

The NTS aim is to manage the islands as a model of integrated conservation balancing natural processes and historic conservation with minimum intervention. The wildlife has been undisturbed since 1930 and active intervention is not generally required to conserve the site's values. The seabirds are regularly monitored, the frequency depending on the species. A seasonal warden employed jointly by SNH and NTS is present from April to mid-September. All the islands except Dun are grazed by feral sheep. There is no planned management of the sheep population, or of past cultivations. The activities of the MOD station are strictly controlled. The National Trust for Scotland organises ongoing volunteer working parties in consultation with Historic Scotland, who restore the village ruins: from 1958, six cottages, the church, school house, many cleateans and walls have been rebuilt and drains cleared. These working parties are planned to continue, following detailed archaeological management and action plans. The surrounding marine area was recently incorporated and a five year management plan prepared by SNH in preparation for revised World Heritage status for marine and cultural values.  Management of the marine habitats around the islands which are increasingly popular with Scuba divers, has been started.

MANAGEMENT CONSTRAINTS
The three hectares occupied by the MOD as a missile radar tracking station has a local effect - the road up to the radar mast remains a scar - as have areas of derelict turf cutting and derelict cultivation. But in consultation with SNH and NTS, the MOD retains the right to construct within the leased area. The pressure of visitors is lessened by the remoteness and uncertain weather. The only notable threats are of the accidental introduction of rats and other alien species, of oil spills and polystyrene or nylon fishing lines which could kill seabirds feeding at sea.

BUDGET
Funds are received from the U.K. government to meet the SNH commitment. The rest is financed by the NTS St.Kilda Fund, by  Historic Scotland and by donations from the St. Kilda Club and other charities.

STAFF
The summer Warden is an experienced naturalist who oversees and sometimes guides visitors. He is backed by a staff of science graduates at the Reserve administrative office on South Uist. The summer Archaeologist, with NTS archaeological guidance, supervises the work parties. A regional building surveyor is responsible for maintenance and repairs.

LOCAL ADDRESSES
Warden and Reserve Administration, Sub-Area Office, Scottish Natural Heritage, 135 Stilligarry, South Uist HS8 5RS, Hebrides.

Area Manager, Western Isles, National Trust for Scotland, Benbecula, Hebrides.

National Director, National Trust for Scotland, 28 Charlotte Square, Edinburgh EH2 4ET.

REFERENCES

The literature on St. Kilda is extensive. Further information is also available from the NTS website www.kilda.org.uk

Boyd, J. (1981). The Boreray sheep of St. Kilda, Outer Hebrides, Scotland: The natural history of a feral population. Biological Conservation 20: 215-227.

Buchanan, M. (ed.) (1995). St Kilda: The Continuing Story. HMSO, Edinburgh.

Emery, N. (1996). Excavations on Hirta 1986-90 HMSO, Edinburgh. 

Emeleus, C. & Gyopam, M. (1992). British Tertiary Volcanic Province. Chapman and Hall for Joint Nature Conservation Committee, London.

Harman, M. (1996). An Isle called Hirte. Maclean Press, Isle of Skye.

Harris, M. & Murray, S. (1977). Puffins on St Kilda. British Birds 70: 50-65.

Harris, M. & Murray, S. (1989). Birds of St Kilda. Institute of Terrestrial Ecology & Natural Environmental Research Council, Monks Wood, UK.

Jewell, P., Milner, C. & Boyd, J. (1974). Island Survivors: the Ecology of the Soay Sheep of St Kilda. Athlone Press, London.

Kearton, R. (1897). With Nature and a Camera. London. Reprinted 1978, Melven Press, Inverness. 

Martin, M. (1698). A Late Voyage to St Kilda. London. Reprinted 1986, Mercat Press, Edinburgh

Martin, M. (1703). A Description of the Western Isles of Scotland. London.

Mountaineering Council of Scotland (2001). St.Kilda, National Trust of Scotland. Review of Management Plan.

Murray, S. (2002). Birds of St. Kilda in Scottish Birds, JSOC Vol.23 supplement. 64pp. [with updated bibliography].

National Trust for Scotland (2003). St.Kilda Management Plan  2003-2008. [Contains a selected    bibliography of 73 references.]

Quine, D. (1988). St Kilda Portraits. Downland Press, Frome 

Quine, D. (2001) St Kilda. Colin Baxter Island Guides, Grantoun, Morayshire.

Quine, D (ed.) (2001). Expeditions to the Hebrides by George Clayton Atkinson in 1831 and 1833. MacLean Press, Skye.

Ratcliffe,D. (1977). A Nature Conservation Review: A Selaction of Biological Sites of National Importance to Nature Conservation in Britain. Vol.2.  Cambridge University Press, U.K.

Scottish Executive (2003). Revised Nomination of St.Kilda for Inclusion in the World Heritage List. [Contains a very extensive bibliography.]

Seton,G. (1878). St Kilda Past and Present. Edinburgh. Reprinted 2000, Birlinn, Edinburgh.

Steel, T. (1994). The Life and Death of St Kilda  (2nd edition). Fontana, Harper Collins, London.

Stell, G. & Harman M. (1988). Buildings of St Kilda. Royal Commission on the Ancient and Historical Monuments of Scotland / HMSO, Edinburgh.

Tasker, M., Moore, P.& Schofield, R. (1988). Seabirds of St. Kilda UK 1987. Scottish Birds 15(1):21-29.

Walker, M. (1984). A Pollen Diagram from St Kilda, Outer Hebrides, Scotland. The New Phylologist 97: 99-113.

Williamson, K. & Boyd, J. (1960). St Kilda Summer. Hutchinson, London [extensive bibliography].

DATE  November 1986. Updated 5/1990, 7/ 1995, 11/2002, November 2p>