St Kilda

Country
United Kingdom of Great Britain and Northern Ireland (UK)
Inscribed in
1986
Criteria
(iii)
(v)
(vii)
(ix)
(x)
The conservation outlook for this site has been assessed as "good" in the latest assessment cycle. Explore the Conservation Outlook Assessment for the site below. You have the option to access the summary, or the detailed assessment.

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.

Current state and trend of VALUES

Low Concern
Trend
Stable
The overall condition of the site is of low concern and stable, with a few specific issues requiring more investigation. Terrestrial biodiversity seems to be stable and of healthy status, whilst the scenic values of the site are improving through the ongoing work around buildings and infrastructure on the site. Of greatest concern is the decline in numbers and breeding success of some seabird species, however as the drivers of these are likely to be wider marine issues, the degree to which this may be addressed at the site level is low. The relative lack of data relating to the site's terrestrial and marine biodiversity also highlights the the need for a systematic monitoring system in the coastal and inshore marine ecosystems.

Overall THREATS

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. Visitors numbers have increased in recent years, but are still within acceptable levels and easily controlled under the existing management arrangements. The threats are low overall. The potential threat of closure of the military base and the impacts thereof on the continued operation of the World Heritage Site are recognized and covered in detail in the Management Plan. Wider issues such as climate change and overfishing might be considered to be higher threats but are at present rated low because their specific impacts on the site will need to be further evaluated.

Overall PROTECTION and MANAGEMENT

Highly Effective
The protection and management of the site is mostly effective. Management is well-guided by the management plan, and implemented to the extent possible given the remote nature of the site and with cooperation with all the relevant stakeholders, including the Ministry of Defence. Staff are relatively well-resourced, with adequate training to deliver the objectives of the management plan, however additional funds could improve this situation, especially in light of increased visitation in recent years. The terrestrial integrity of the site is well protected by effective protection and management and national legislation, with some limitations arising in the marine environment.

Full assessment

Click the + and - signs to expand or collapse full accounts of information under each topic. You can also view the entire list of information by clicking Expand all on the top left.

Finalised on
02 Dec 2020

Description of 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 communities

Criterion
(ix)
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)

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).
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

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
(Climate change )
Data Deficient
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
(Excessive visitor pressure )
Low Threat
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. 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
(Grazing by feral sheep flock )
Very Low Threat
Inside site
, Scattered(5-15%)
The Soay sheep on Hirta have always fluctuated in numbers from 500 to 2000, and ahead of the periodic population crashes, the vegetation become overgrazed. The issue is subject to a very detailed study by various universities and is not thought to be a serious or long-term problem (Jewell at al 1974, Clutton-Brock and Pemberton 2004 and their Annual Research Reports). Annual monitoring will reveal any deleterious change immediately.
War, Civil Unrest/ Military Exercises
(Obtrusive installations )
Very Low Threat
Inside site
, Localised(<5%)
The impact of buidlings and some infrastructure has been present ever since the military base was established in 1958. However, recently actions have been taken to minimise these impacts. A project to construct a new accommodation block and energy centre and demolish the existing buildings was begun in 2017 , albeit with its completion delayed by Covid 19.  The buildings occupy a smaller footprint, have a turf roof and larch cladding, minimising their impact on the landscape (IUCN Consultation, 2020). 
Low Threat
Several potential threats are identified, most of which are considered at to pose very low threats. There has been a recognisable decline in some breeding numbers and success of some seabird species. However this seems to be a product of impacts outside the site and by factors that appear to be multinational, even global. It would appear that these are being addressed at a governmental level with little firm data available at present. A higher threat would be presented by the closure of the military base making many of the management aspirations and functions more difficult to sustain. However, the recent investment to rebuild the military base indicates a commitment to retain the facility for the near to medium term.
Fishing / Harvesting Aquatic Resources
(Overfishing out at sea and unsustainable fishing methods )
High Threat
Outside site
Small scale crustacean creeling continues as it always has and is not considered to pose a threat. Longline and trawl fishing takes place out at sea subject to EU Fisheries Regulations. This could severely impact fish stocks and therefore food supplies for the seabirds nesting on St Kilda. Poor breeding seasons have been recorded for kittiwakes, puffins and other auks, shags, and probably Leach’s storm petrels (Murray 2002, Mitchell et al 2004, NTS Seabird Warden/WIM Reports). The designation of the West of Scotland MPA in 2020 (JNCC, 2020) should mitigate against this potential threat, although as the MPA is recently established its effects are yet to be determined. 
Shipping Lanes
(Moored vessels going aground )
Very Low Threat
Inside site
, Localised(<5%)
Ship wrecks have occurred on and around St Kilda for hundreds of years (Love, 2009) and so far no rats have appeared on the archipelago; however, two recent incidents have caused concern – the supply vessel Elektron grounded in Village Bay, Hirta in Oct 2000, and a fishing boat Spinningdale was wrecked in Village Bay in Feb 2008. Monitoring and mitigation measures for rats/mink were refreshed and improved as a result. (NCC/SNH and NTS Wardens/WIM reports, StKMPlan). A new biosecurity plan was adopted during the construction of the new MOD facility due to the increased frequency of shipping. 
The National Trust for Scotland are working to develop a new biosecurity plan as part of a national project s for all SPAs (IUCN Consultation, 2020).
Flight Paths
(Helicopter straying out of corridor )
Very Low Threat
Inside site
, Localised(<5%)
A few incidents of low-flying aircraft and helicopters have been reported in the past (NCC/SNH Wardens/ NTS Ranger Reports), and more recently occasional drone use, causing panic in the sheep flocks and disturbance to seabird colonies (IUCN Consultation, 2020). Private operators are difficult to trace, but military and regular supply flights adhere to an established code of practice.
Water Pollution
(Oil slicks )
Low Threat
Outside site
In Dec 1981 the empty 100,000 ton tanker Maersk Angus lost power temporarily and drifted perilously close to St Kilda but no incident took place (Love 2009). Since the Braer went aground in Shetland in January 1993 laden tankers are encouraged to take the outside route, west of the Hebrides which renders St Kilda, vulnerable to oil spillages etc. of which a major spill could have a potentially catastrophic impact on seabirds and other marine life. (StKMPlan)
Industrial/ Military Effluents
(Accidental fuel spillage )
Very Low Threat
Inside site
, Extent of threat not known
Periodic supply vessels offload fuel for the Base during the summer months. QuinetiQ (who operate the base on behalf of the Ministry of Defence, Western Isles Council Emergency Planning Department) have measures in place to cover spillages (SKMPlan)
Temperature extremes
(Sea temperatures affecting fish stocks/ seabird food resources )
Data Deficient
Outside site
It is thought that climate change affecting sea temperatures and ocean circulation patterns, potentially exacerbated by overfishing, might be implicated in declines in fish stocks and impacts on seabird breeding numbers and success but there is insufficient data to assess this adequately. However, a data logger to measure salinity and temperature was planned to be installed in the site in November 2020 to address this issue (IUCN Consultation, 2020). 
War, Civil Unrest/ Military Exercises
(Closure of the Base and its facilities )
Low Threat
Inside site
, Scattered(5-15%)
The future of the military base and therefore its facilities are reviewed periodically by the Ministry of Defence and QuinetiQ. Closure would seriously undermine the operation of the World Heritage Site. The closure of the base would remove all human presence and surveillance in the winter months leaving the World Heritage Site vulnerable to vandalism, and remove some of the logistical support for current monitoring.
However, the recent investment to rebuild the military base indicates a commitment to retain the facility for the near to medium term and the matter is addressed fully in the NTS Management Plan (IUCN Consultation, 2020).
Invasive Non-Native/ Alien Species
(Potential introduction of invasive species )
High Threat
Inside site
, Extent of threat not known
Introduction of invasive species represents a potential threat to the site's biodiversity values (IUCN Consultation, 2017). However steps are taken whenever possible to mitigate against this potential threat. For example, in 2017 a supply vessel was refused permission to enter the WHS as it’s port of origin had an outbreak of Carpet sea-squirt, this highlighted the need for an enhanced bio-security plan to include marine species (IUCN Consultation, 2020).
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. Visitors numbers have increased in recent years, but are still within acceptable levels and easily controlled under the existing management arrangements. The threats are low overall. The potential threat of closure of the military base and the impacts thereof on the continued operation of the World Heritage Site are recognized and covered in detail in the Management Plan. Wider issues such as climate change and overfishing might be considered to be higher threats but are at present rated low because their specific impacts on the site will need to be further evaluated.
Management system
Highly Effective
The comprehensive Management Plan is fully effective in its purpose. There is an excellent working relationship between National Trust for Scotland (NTS), SNH, Historic Environment Scotland, Comhairle nan Eilean Siar and Ministry of Defence. This Management group is highly effective in that it includes all key stakeholders who meet informally and annually to review progress and forward planning (StKMPlan).
Effectiveness of management system
Highly Effective
The management of the site is highly effective. A comprehensive Management Plan is in place and there is adequate monitoring of most values, although the monitoring of the marine features is carried out very rarely (IUCN Consultation, 2017).
Boundaries
Mostly Effective
The boundary in low water to mark the whole archipelago is clearly defined and well recognized. However the ultimate boundary out at sea is not obvious and not well known. Thus the boundaries are adequate to preserve the terrestrial values of the site, but no buffer zone exists and no effective legislative framework associated with it (World Heritage Committee, 2013, StKMplan).
Integration into regional and national planning systems
Mostly Effective
Comhairle nan Eilean Siar, as the local planning authority, and the Scottish Government are largely supportive in management, but coordination could be improved (State Party of the UK, 2002).
Relationships with local people
Highly Effective
There is no resident population and the nearest communities are on the Outer Hebrides (45+ miles away). Consultation meetings were held locally, also with online response, in the preparation of the Management Plan (StKMPlan). Elected councilors also inputted (World Heritage Committee, 2013). The current Management Plan is signed by all key stakeholders – the Council, Ministry of Defence, Scottish Natural Heritage and Historic Environment Scotland (IUCN Consultaiton, 2020).
Legal framework
Mostly Effective
The primary legislation that protects the archipelago and surrounding seas and their key attributes are: The Conservation (Natural Habitats. & C.) Regulations 1994, as amended; The Wildlife and Countryside Act 1981; The Land Reform Act 2003; Nature Conservation (Scotland) Act 2004; The Ancient Monuments and Archaeological Areas Act 1979; The Planning etc. (Scotland) Act 2006; and The Environmental Liability (Scotland) Regulations 2009.Land tenure is secure and the site has many conservation designations (WHS, NNR, SSSI, SPA, SAC, NSA) most with associated legal obligations. The capacity does exist to employ legislation effectively (World Heritage Committee, 2013).
Law enforcement
Highly Effective
Enforcement of the relevant laws and regulations is effective.
Implementation of Committee decisions and recommendations
Mostly Effective
Most or all of the management activities that can be are being implemented and monitored effectively, with the exception of the marine area (State Party of the UK, 2002).
Sustainable use
Highly Effective
Within Hirta itself the available resources are utilized effectively but difficulties of access to all the other islands and stacks limit any further exploitation, thus effectively preserving the conservation values (State Party of the UK, 2002, StKMPlan and pers obs).
Sustainable finance
Mostly Effective
The available budget and sources are laid out by NTS (mostly from rent and operator payments and are found acceptable but still with room for improvement to fully implement management needs. This is secure in the medium term and moves are afoot to have this extended (State Party of the UK, 2002).
Staff capacity, training, and development
Mostly Effective
Staff training could be enhanced to improve and enhance management outputs. There is a high standard of expertise and training but additional finance would permit full access to professionals in all disciplines and to improve research, interpretation, visitor management and administration. Equipment is well maintained and good use is made of volunteers.
Education and interpretation programs
Highly Effective
Guided walks are available from the ranger service, there is an excellent museum, comprehensive and attractive literature available and an excellent website. Other projects and exhibitions are constantly generated off site by outside or related bodies, schools etc. Twitter and Instagram accounts provide regular updates on day to day life and information on conservation (IUCN Consultation, 2020).
Tourism and visitation management
Highly Effective
The ranger service provides an adequate welcome and briefing for visitors, while provision for groups with their own guides are familiar with what is on offer, and usually with time ashore restraints. Guidelines are available stressing safety precautions etc and tour operators are highly sympathetic to the site values and co-operative. The site is large enough and visitor impact small enough to minimize deleterious impacts to the site values.
Monitoring
Mostly Effective
Terrestrial values are well monitored, especially seabirds by the seabird warden (sample breeding plots etc) with national surveys every 10 years or so. There are also monitoring programmes for vegetation, sheep, seals, migrant birds and and ad hoc monitoring of lepidoptera and cetaceans. Certain groups of invertebrate, geological and geomorphological features have been surveyed but there is no regular monitoring of marine habitats and species (constrained perhaps by the physical conditions of the site) (NCC/SNH wardens reports, WIM reports, Research team reports and publications, StKMPlan, State Party of the UK, 2002).

A mapping survey of marine habitats and species was carried out by SNH in 1997 and 2000 (Posford Duvivier Environment 2000). A monitoring survey of the sea cave feature was conducted in 2015 (Harries et. al, 2018), and marine monitoring surveys for sea caves are carried out every 12 years and a review of potentially damaging activities every 6 years (IUCN Consultation, 2020). Whilst marine monitoring is limited by a combination of weather conditions and the high cost of marine monitoring surveys, there is also a relatively low probability of human-induced impacts due to St Kilda's remote location (IUCN Consultation, 2020).
Research
Highly Effective
There is an effective research policy which is targeted and sympathetic to the values of the site which feeds into its management and decision making. There is, however, plenty of scope for development and extension in the future. Research has been and is being conducted into the impact of great skuas Stercorarius skua on Leach’s storm petrels. Research has been conducted into the impact of great skuas Stercorarius skua on Leach’s storm petrels and on the distribution and population of the St Kilda field mouse (Apodemus sylvaticus hirtenis). The well established research programme on the Soay Sheep of St Kilda make the population one of the best understood of its kind (Regan et al., 2020; Kentie et al., 2020; Hayward et al., 2019 etc.).
The protection and management of the site is mostly effective. Management is well-guided by the management plan, and implemented to the extent possible given the remote nature of the site and with cooperation with all the relevant stakeholders, including the Ministry of Defence. Staff are relatively well-resourced, with adequate training to deliver the objectives of the management plan, however additional funds could improve this situation, especially in light of increased visitation in recent years. The terrestrial integrity of the site is well protected by effective protection and management and national legislation, with some limitations arising in the marine environment.
Assessment of the effectiveness of protection and management in addressing threats outside the site
Mostly Effective
With no effective buffer zone identified, management recommendations outside the site and the powers of its managers are limited. Fishery pressure around the site including in the feeding areas of local seabirds was until now largely driven by EU policies, however it remains unclear how this will change in the context of Brexit (State Party of the UK, 2002; StKMPlan). Wider scale environmental fluctuations have increased in recent years, possibly as a result of climate change, which have resulted in some detrimental impacts on seabird populations within the site, which is difficult to manage at a site level.
World Heritage values

Significant marine and maritime plant communities

Data Deficient
Trend
Data Deficient
Noting a limited degree of baseline data available from a mapping survey for marine communities carried out in 2000 (Posford Duvivier Environment, 2000) and a proposed monitoring plan for sea cave communities (IUCN Consultation, 2020), no structured monitoring programme is in place for either marine nor coastal/maritime terrestrial systems, partly due to logistical difficulties. Therefore it is difficult to assess any change.

Significant populations and colonies of seabirds

Low Concern
Trend
Deteriorating
The site remains a stronghold for the northern gannet and still holds one of the largest colonies of the species in the world. However, populations of other seabird species have experienced consistent and medium-term population declines, evidenced by erratic breeding success with occasional complete failures in recent decades in puffins and steadily deteriorating populations trends in fulmar. Despite this, the most recent survey data suggest that such declines are stabilizing with good productivity figures in the last two years for puffins and an increase in apparently occupied sites (AOS) in northern fulmar (IUCN Consultation, 2020).

Important seabird station

High Concern
Trend
Deteriorating
Regular national surveys and sample monitoring by NTS Seabird wardens have indicated a decline in some species such as shag (Phalacrocorax aristotelis), northern fulmar (Fulmarus glacialis) and auks (Alcidae), as well as growing threats such as predation on Leach’s storm petrel by great skuas. No firm data yet on the causes of any seabird declines, however links have been established with climate change (National Trust for Scotland, 2018). 

The site as an important breeding ground for kittiwakes (Rissa tridactyla) is of particular concern, who in the most recent count of 448 nests across the St Kilda archipelago in 2016 indicated an 88.5% decline since the previous census in 1999. Kittiwake numbers at the archipelago are now at their lowest in recorded history and there is a tangible risk of the species vanishing from St Kilda’s cliffs in the near future (IUCN Consultation, 2020), with unknown knock on community effects. 

Outstanding array of species in diverse terrestrial communities

Good
Trend
Stable
Whilst there is little ongoing structured monitoring of terrestrial biodiversity in the site, the active management of the site alongside the well established research program on Soay Sheep have not reported any significant decline in this value (NTS Ranger/WIM Reports, Booth 1996, Crawley 1993).

Complex ecological dynamic in the marine zones

Low Concern
Trend
Stable
There is a need for further monitoring but the subtidal habitats seem in a good state and there is no evidence to suggest that they have varied signficatnly since baseline data was obtained (Posford Duvivier Environment, 2000). There is little information, however, on the current state of marine biodiversity, especially in light of declining seabird populations being attributed anecdotally to shifting marine prey species availability in some instances (National Trust for Scotland, 2018).

Diverse seabird communities

Low Concern
Trend
Deteriorating
Despite a decline in some species, and the as yet unknown community effects of shifting population dynamics, biodiversity will likely remain uncompromised in the short to medium term (StKMPlan). There has been no obvious decline in terrestrial habitat quality, however recent report suggest a growing threat of climate change impacting seabird communities on St Kilda (StKMPlan; National trust for Scotland, 2018), however these impacts are still poorly understood.

Outstanding natural features and island scenery

Good
Trend
Stable
The scale of the features is such that little can be done to improve them. While largely in a good state, certain aspects should be addressed to improve the scenic quality at the main access point. Discussions have begun regarding the possible removal of the coastal defences and landscaping of the main access point. The rebuild of the Military of Defence accommodation block and energy centre was completed in the summer of 2019.  Works to demolish the old buildings and reinstate the ground are scheduled for 2021 (IUCN Consultation, 2020).
Assessment of the current state and trend of World Heritage values
Low Concern
Trend
Stable
The overall condition of the site is of low concern and stable, with a few specific issues requiring more investigation. Terrestrial biodiversity seems to be stable and of healthy status, whilst the scenic values of the site are improving through the ongoing work around buildings and infrastructure on the site. Of greatest concern is the decline in numbers and breeding success of some seabird species, however as the drivers of these are likely to be wider marine issues, the degree to which this may be addressed at the site level is low. The relative lack of data relating to the site's terrestrial and marine biodiversity also highlights the the need for a systematic monitoring system in the coastal and inshore marine ecosystems.
Assessment of the current state and trend of other important biodiversity values
Good
Trend
Stable
St Kilda field mouse and St Kilda wren rated good and populations appear to be stable (NTS Ranger/WIM Reports). A study has been undertaken into impact of great skua on Leach’s storm petrels, with ongoing study of petrel breeding using nest boxes.

Additional information

Cultural and spiritual values,
History and tradition
The story of the former community, its unusual seabird economy, and its ultimate evacuation in 1930, is well known and contributes to the great public interest in the WHS.
Cultural and spiritual values,
Sacred natural sites or landscapes
The combination of natural and cultural is powerful in affording the site both wilderness and iconic status.
Health and recreation,
Outdoor recreation and tourism
Difficulties of access due to expensive, limited transport and weather, with the need to avoid facilities impacting on the very values of the site, will always impose a ceiling on direct tourism but those that do visit (via cruise and charter vessels, and to a lesser extent yachts) find the experience hugely rewarding, while those that cannot visit can access some of the experience at visitor centres and exhibitions in the Hebrides and elsewhere, media interest, online through websites and through many and diverse publications. Small, local charter vessels and accommodation outlets in the Hebrides benefit from the attraction of the site.
Knowledge,
Importance for research
The important aspects of geology, marine and terrestrial biology, island biogeography and evolution, feral sheep, seabirds and mice offer outstanding opportunities for research, not least monitoring of seabirds to inform debates on fisheries and global change. More work required on little-known species e.g. especially Leach's and European storm petrel and Atlantic Puffin
Knowledge,
Contribution to education
The WHS has generated a huge corpus of published material, and media interest over two centuries. Websites now make this accessible to a huge global audience.
St Kilda immediately captures the interest and imagination of all who encounter this remote archipelago and its natural attributes (both actual and virtual). It has much to offer the world of science and politics in the way of research and education. The effective management structure between the owners and diverse other stakeholders provides a useful model for other similar sites, while the whole package offered by St Kilda enhances the profile of its dual World Heritage status and ethos.
Organization Brief description of Active Projects Website
1 Nature Conservancy, various universities since 1957, esp Cambridge (T.Clutton-Brock) and Edinburgh (J Pemberton) Detailed study of feral Soay Sheep; numbers, breeding strategy, parasites, genetics etc.
www.zoo.cam.ac.uk www.soaysheep.biology.ed.ac.uk
2 M Crawley (Imperial College) Detailed study of vegetation, esp. sheep grazing impacts
www.imperial.ac.uk
3 National Trust for Scotland (Seabird wardens) Seabird populations and productivity, including guillemot feeding studies, puffin productivity and Leach’s petrel productivity using artificial nest boxes
www.kilda.org.uk
4 Universities of Edinburgh, Aberystwyth, Sheffield and Liverpool, Humbolt University Berlin, the Moredun Research Institute and the James Hutton Institute Role of gut ecosystems in the ecology and evolution of wild animals.
www.soaysheep.biology.ed.ac.uk/ecologywithin

References

References
1
Booth A (1996) A National Vegetation Classification Survey of Hirta and Dun. Commissioned Report to Scottish Natural Heritage, Edinburgh< Perth and Inverness.
2
Clutton-Brock T C and Pemberton J (2004) Soay sheep: dynamics and selection in an island population. Cambridge University Press (Annual Research Reports also produced, distributed by J Pemberton, University of Edinburgh)
3
Crawley M (1993) The Flora of St Kilda. Unpublished. Imperial College, Silwood Park.
4
Harries, D.B., Moore, C.G., Porter, J.S., Sanderson, W.G., Ware, F.J. & Kamphausen, L. (2018). The establishment of site condition monitoring of the sea caves of the St Kilda and North Rona Special Areas of Conservation with supplementary data from Loch Eriboll. Scottish Natural Heritage Research Report No. 1044.
5
Harris M P & Wanless S (2011) The Puffin. T & AD Poyser, London
6
Harris M P Murray S & Wanless S (1998) Long-term changes in breeding performance of puffins on St Kilda. Bird Study v 45
7
Hayward, A., Pilkington, J.G., Wilson, K., McNeilly T. and Watt, K. (2019). Reproductive effort influences intra-seasonal variation in parasite-specific antibody responses in wild Soay sheep. Functional Ecology, 33, pp.1307-13. doi.org/10.1111/1365-2435.13330
8
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