2020 Conservation Outlook Assessment
Total Page:16
File Type:pdf, Size:1020Kb
IUCN World Heritage Outlook: https://worldheritageoutlook.iucn.org/ St Kilda - 2020 Conservation Outlook Assessment St Kilda 2020 Conservation Outlook Assessment SITE INFORMATION Country: United Kingdom of Great Britain and Northern Ireland (UK) Inscribed in: 1986 Criteria: (iii) (v) (vii) (ix) (x) This volcanic archipelago, with its spectacular landscapes, is situated off the coast of the Hebrides and comprises the islands of Hirta, Dun, Soay and Boreray. It has some of the highest cliffs in Europe, which have large colonies of rare and endangered species of birds, especially puffins and gannets. The archipelago, uninhabited since 1930, bears the evidence of more than 2,000 years of human occupation in the extreme conditions prevalent in the Hebrides. Human vestiges include built structures and field systems, the cleits and the traditional Highland stone houses. They feature the vulnerable remains of a subsistence economy based on the products of birds, agriculture and sheep farming. © UNESCO SUMMARY 2020 Conservation Outlook Finalised on 02 Dec 2020 GOOD The overall conservation outlook for St Kilda site is good. The natural values for which the site are inscribed are of overall low concern with low level threats. The main issues of concern – declines in some seabird population sizes and breeding success (except gannet Morus bassanus and northern fulmar Fulmarus glacialis) - seem likely to largely reflect natural variation in the wider marine environment. However, if the longer-term population trend is for a decline, there is more cause for concern about this value, especially in the uncertain context of climate change given that addressing this threat lies outside immediate site level management control. A buffer zone in which fishing is restricted could help, as could a potential Marine SPA, however the establishment of this is uncertain in the context of UK's exit from the European Union as previously this may have been achieved through EU directives. Despite this, protection and management within the World Heritage site remains highly effective. All the other values seem in overall good condition and likely to remain so if the current situation prevails. IUCN World Heritage Outlook: https://worldheritageoutlook.iucn.org/ St Kilda - 2020 Conservation Outlook Assessment FULL ASSESSMENT Description of values Values World Heritage values ▶ Significant marine and maritime plant communities Criterion:(x) The combination of exposure to oceanic swell, deep ocean currents along the continental slope, water depth and clarity produce a diverse range of marine communities and species of both northern and southern provenance at the extremities of their range (World Heritage Committee, 2013; StKMPlan; Posford Duvivier Environment, 2000). Unique ecological conditions also result in diverse coastal and inland plant communities and species, making the maritime grassland turf and underwater habitats integral elements of the total island setting (World Heritage Committee, 2013; StKMPlan; Love, 2009). ▶ Significant populations and colonies of seabirds Criterion:(x) A number of significant populations of seabird species inhabit St Kilda including the oldest and one of the largest Northern Fulmar (Fulmarus glacialis) colonies in the UK, a significant proportion of the UK population of the Atlantic Puffin (Fratercula arctica) and one of the largest Northern Gannet (Morus bassanus) colonies in the world (World Heritage Committee, 2013; StKMPlan; Mitchell et al., 2004; Love, 2009; Murray & Wanless, 1997; Wanless et al., 2005; Murray et al., 2014). ▶ Important seabird station Criterion:(x) St Kilda is one of the largest seabird sites in the North Atlantic and Europe with over half a million birds present in the breeding season (World Heritage Committee, 2013, Murray 2002, Mitchell et al 2004), utilizing the range of breeding sites and ecological niches offered by the local topography in combination with the rich productivity of the surrounding sea (World Heritage Committee, 2013). ▶ Outstanding array of species in diverse terrestrial Criterion:(ix) communities The islands are home to an outstanding array of species in diverse terrestrial communities, including a number of endemic sub-species such as the St Kilda wren and St Kilda fieldmouse, following genetic divergence since their ecological colonisation. Additionally, the ancient breed of Soay sheep, descendents of the most primitive domestic sheep found in Europe roam the isle of Hirta (World Heritage Committee, 2013). ▶ Complex ecological dynamic in the marine zones Criterion:(ix) There is also a complex ecological dynamic in the three marine zones present at the site that is essential for the maintenance of both marine and terrestrial biodiversity (World Heritage Committee, 2013). The highly diverse range of species, many of which are rare or absent elsewhere, mean that local marine communities are exceptional in terms of biodiversity value (World Heritage Committee, 2013; Posford Duvivier Environment, 2000) ▶ Diverse seabird communities Criterion:(ix) Densely packed seabirds nest on cliffs in a relatively small area (World Heritage Committee, 2013; Murray, 2002; Mitchell et al., 2004). Seabirds successfully utilize the range of breeding sites and ecological niches offered by the local topography (World Heritage Committee, 2013) IUCN World Heritage Outlook: https://worldheritageoutlook.iucn.org/ St Kilda - 2020 Conservation Outlook Assessment ▶ Outstanding natural features and island scenery Criterion:(vii) The scenery of the St Kilda archipelago is spectacular, reflecting its volcanic origin and subsequent weathering and glaciation to produce a dramatic island landscape. Marine erosion of the hard igneous rocks has produced cliffs extending underwater to produce dramatic sea caves, spectacular sea cliffs and stacks (World Heritage Committee, 2013). Other important biodiversity values ▶ Leach’s storm petrel St Kilda harbours the largest breeding colony of Leach’s storm petrel (Oceanodroma leucorhoa) in the North East Atlantic (Mitchell et al., 2004). ▶ St Kilda field mouse The St Kilda field mouse is an endemic subspecies evolved in isolation, demonstrating ecological isolation and subsequent biological evolution on islands (StKMPlan; Love, 2009). ▶ St Kilda wren The St Kilda wren is an endemic subspecies evolved in isolation, demonstrating ecological isolation and subsequent biological evolution on islands (StKMPlan; Love, 2009). Assessment information Threats Current Threats Very Low Threat The remoteness and isolation of the site grants natural protection from direct human induced threats. As such, the existing current threats are currently at very low levels under the current Management prescriptions, with little immediate prospect of deterioration in the site values. Visitor numbers have increased in recent years, but are still within acceptable levels and easily controlled under the existing management arrangements. However, the effects of climate change on the site can be seen to be affecting multiple values of the site. Recent reports indicate significant pressure of climate change on breeding success of seabirds, and subsequent population declines and likely community and ecosystem level disruptions. Whilst the threat of climate change is likely to be growing within the site the degree to which this can be mitigated at the site level is low. ▶ Habitat Shifting/ Alteration, Temperature extremes Data Deficient (Climate change ) Inside site, throughout(>50%) Outside site The effects of climate change on the site can be seen to be affecting multiple values of the site. Recent reports indicate significant pressure of climate change on breeding success of seabirds, and subsequent population declines and likely community and ecosystem level disruptions (National Trust for Scotland, 2018). In addition, it has been identified that the Soay sheep may also be shrinking in size, possibly due to changing climatic factors. However, no systematic assessment on the overall impacts of climate change on the values of the site is available. ▶ Tourism/ visitors/ recreation Low Threat (Excessive visitor pressure ) Inside site, localised(<5%) Visitor numbers are monitored annually and have increased over the years, from around 1000 in 1986, to 1518 in 2004 to to 5136 in 2019 (IUCN Consultation, 2020). The increase is mainly due to day visitors from several small charter vessels in recent years, and to small expedition cruise ship passengers whose numbers may vary greatly. This is still within acceptable levels and easily controlled under the existing management arrangements and is limited by weather conditions which may inhibit landings. IUCN World Heritage Outlook: https://worldheritageoutlook.iucn.org/ St Kilda - 2020 Conservation Outlook Assessment Recreational diving has always been a popular pursuit around the islands, but is assumed to have negligible impact. In recent years there have been more requests by rock climbers to scale the stacks and cliffs which would cause serious disturbance and damage to breeding Gannets, particularly on Stac Li and Stac an Armin (Murray et al 2013). Recent access legislation in Scotland makes it difficult to prevent ad hoc landings on islands and stacks other than Hirta, but these are still very few and controlled by voluntary codes of conduct, difficult/limited landing places and, principally, by weather (NCC/SNH and NTS Ranger reports, WIM Reports) ▶ Livestock Farming / Grazing Very Low Threat (Grazing by feral sheep flock ) Inside site, scattered(5-15%)