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Management challenges at a complex geosite: the Giant’s Causeway World Heritage Site, Northern Ireland

Défis pour la gestion d’un géosite complexe inscrit au Patrimoine Mondial de l’Humanité : la Chaussée des Géants, Irlande du Nord
Bernard J. Smith
p. 219-226

Résumés

Dans cet article, on explique la géologie et l’importance de la Chaussée des Géants, site inscrit au Patrimoine Mondial de l’Humanité. Le site est remarquable pour ses formations volcaniques héritées de l’ouverture de l’océan Atlantique, ses paléosols inter-coulées d’importance scientifique internationale, et l’extrême beauté des colonnades et entablements basaltiques évoluant en falaise vive sur la bordure maritime du plateau d’Antrim. Il est démontré que la protection légale du site s’est concentrée sur la désignation des habitats à conserver pour la faune ou la flore et sur les roches ou les colonnes de la Chaussée actuelle. Par conséquent, l’importance du site pour les sciences de la Terre au sens large est faiblement reconnue. Il est également démontré que la reconnaissance de la dynamique de la côte  de la Chaussée des Géants a permis une meilleure appréciation du rôle joué par les processus géomorphologiques dans la formation et le maintien de la caractéristique fondamentale de ce site inscrit au Patrimoine Mondial de l’Humanité.

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Errata

Article reçu le 4 septembre 2004, accepté le 7 juin 2005

Texte intégral

Introduction

1The 40,000 basalt columns of the Giant's Causeway are located on the north coast of County Antrim, Northern Ireland (fig. 1), and for over two hundred years they have been an important tourist attraction, which today attracts approximately 500,000 visitors per year. The Causeway itself is owned and managed by the National Trust and, together with its adjacent coastline, the area is renowned for its geology, geomorphology, and associated habitats that contain important plant and animal communities. These habitats include: maritime cliffs and slopes, coastal saltmarsh, coastal vegetated shingle, lowland heath and littoral communities. It is for these reasons, but primarily because of its geological significance, that the Causeway was inscribed as a natural World Heritage Site in 1986. Because of this early inscription, there was no requirement at the time to produce a management plan for the site. However, it is now UK policy that all of its World Heritage Sites will have management plans in place by 2005/2006 so as to satisfy UNESCO reporting requirements. The plan for the Giant’s Causeway is currently in preparation. However, at an early stage it identified a number of competing factions and priorities that will have to be accommodated if an holistic management strategy is to be achieved. This paper identifies and discusses some of these conflicts. It is not with the intention of finding generic solutions, but in the spirit of sharing information with others who seek to manage multifaceted geosites. This is in the belief that solutions to complex management issues must understand their origins. First, however, it is necessary to know something of the site itself.

Fig. 1 – Location map for the Giant’s Causeway World Heritage Site.
Fig. 1 – Localisation de la Chaussée des Géants, site inscrit au patrimoine mondial de l’Humanité.

Fig. 1 – Location map for the Giant’s Causeway World Heritage Site.Fig. 1 – Localisation de la Chaussée des Géants, site inscrit au patrimoine mondial de l’Humanité.

Geological background to the Giant’s Causeway

2The story of the Causeway landscape began some 62 million years ago with extensive volcanism linked to the opening up of what is now the Atlantic Ocean. Although there is some evidence of early explosive activity associated with volcanic vents, the period was dominated by multiple flows of basalt lavas. The total area of these flows is now much reduced, but they still represent, with an area of 3,800 km2, Europe’s most extensive lava field. In the literature, the lava flows of the Antrim Lava Group have been divided into three main phases of activity, separated by two extended periods of quiescence or limited, local activity. During these intervening periods the upper surfaces of the preceding flows were exposed to climatic conditions that were both warm and wet enough to weather the rock to a depth of several metres. This produced soils and weathered regoliths redolent of those found in the present-day Humid Tropics and which appear today as two, largely red coloured, ‘Interbasaltic Beds’ separating the Lower, Middle and Upper Basalts. The landscape of the World Heritage Site is cut into the Lower and Middle Basalts and the lower of the two Interbasaltic Beds (Lyle, 1996).

3Of the three units that comprise the coastal cliff sequence at the Causeway, the most distinctive are the Middle Basalts, which are also known as the Causeway Tholeiite Member (CTM). These are a series of thick, fine-grained, olivine-poor lavas that average c. 18 m in thickness. However, the most striking feature of these basalts is their distinctive structure. S.I. Tomkeieff (1940) first likened the structure of the Middle Basalt lava flows to architectural elements of a classical building. Using this terminology, each lava sequence is seen to comprise a colonnade of regular vertical columns, capped by an entablature of narrower, more irregular and often curved columns. The most accessible example of the colonnade/entablature junction is to be found at ‘The Organ’, where the 12 m-high columns are the colonnade of flow 1 of the CTM. This structure derives in part from the thickness of individual flows that ponded in river valleys cut into the Lower Basalt landscape. One such valley was located at what is now the Giant's Causeway, where the first flow is almost 100 m thick and where its colonnade forms the columns of the Causeway itself (fig. 2).

Fig. 2 – Basalt columns of the Middle Causeway. Columns are approximately 50 cm wide. (picture taken by B.J. Smith).
Fig. 2 – Colonnes de basalte de la Chaussée moyenne. Les colonnes ont environ 50 cm de diamètre (cliché B.J. Smith).

Fig. 2 – Basalt columns of the Middle Causeway. Columns are approximately 50 cm wide. (picture taken by B.J. Smith).Fig. 2 – Colonnes de basalte de la Chaussée moyenne. Les colonnes ont environ 50 cm de diamètre (cliché B.J. Smith).

The wider significance of the Giant’s Causeway site

4Although the Causeway was initially inscribed for its geological value (Department of the Environment, 1985), it was acknowledged that there were numerous additional features of interest – even if these are not always apparent in the information available to visitors. This lack of explanation, and a transport system that delivers many visitors directly to the causeway stones, has fostered two common misconceptions. First, that the only area of interest is the Giant’s Causeway itself – when there are many kilometres of spectacular coastline to the east and west of it. Second, the view that the landscape as we see it was formed 60 million years ago by volcanic activity. Although the building blocks of the Causeway did form at this time, and continue to exert a major influence on the landscape, the detailed features we see today are much younger. Indeed, it was only approximately 15,000 years ago that the coastline emerged from beneath a cover of ice. Since this time, a series of landscape adjustments has not only produced the three promontories that comprise the Giant’s Causeway, but also a stunning coastal landscape. This landscape owes its existence to the interactions of a variety of factors, including a complex late- and post-glacial history that included ice retreat from the area and relative sea levels rise and fall. The para-glacial adjustment of marine cliffs has seen the development of a wide array of active and relict slope failures (Carter, 1991; Knight, 2002), and long-term exposure to high-energy coastal conditions has worked with the underlying geology to erode and emphasise the distinctive embayed nature of the coastline (Smith and Ferris, 1997). Lastly, the character of the site also reflects an ongoing history of human intervention. This includes stone extraction, footpath construction, road building, the construction and demolition of various buildings, and the running of a high profile transport system (Smith et al., 1994; Smith and Hughes, 1999). Thus, whilst the majority of visitors are drawn to the site by iconic images of interlocking basalt columns, they are confronted on arrival with a spectacular, dynamic coastal landscape of Atlantic waves, rugged cliffs, secluded bays, and magnificent views.

5The value of this environment is recognised through its various inscriptions and designations that identify it as having regional, national and international importance for its ecology (National Nature Reserve, candidate Special Area of Conservation (SAC) and Area of Special Scientific Interest), its landscape value (Area of Outstanding Natural Beauty) and its geology and geomorphology (World Heritage Site), not to mention its economic and cultural significance as a major tourist destination. A consequence of this multiple recognition is, however, a proliferation of stakeholders within the site, all of whom proclaim a degree of ‘ownership’ and, in many cases, claim primacy in determining the direction that site management should take. The majority of these conflicts are social, political and/or economic in nature and their solution must lie in negotiation between the concerned stakeholders. However, there are two areas of debate, between the biological and Earth Science communities and, within the Earth Sciences, between geologists and geomorphologists, which are of wider scientific  concern.

Habitat conservation versus Earth Science protection

6It is perhaps ironic that a site of world significance for its unique geology should draw most of its legal protection from regional and national designations targeted at its habitat role. This highlights two issues. First, the imbalance between the protection afforded to biodiversity as opposed to geodiversity within organisations such as the European Union, and hence within member countries. For example, failure to satisfy UNESCO that the Giant’s Causeway is being appropriately managed might eventually lead to it being named and shamed on a list of sites at risk. Failure to maintain habitat quality under SAC designation can lead to fines running into millions of Euros until the situation is rectified. It is to be hoped that this situation may eventually be rectified. For example, the Council of Europe recently appeared to acknowledge that biodiversity is in large part underpinned by geodiversity, when, at a meeting on 13th September, 2002 of its committee in the field of biological and landscape diversity, it agreed to establish a working group on geological heritage. In January 2003, this working group decided to proceed with the preparation of recommendations on the “Conservation of the Geological Heritage and Areas of Special Geological Interest”. It is to be presumed that the ultimate intention is to translate these recommendations into an ‘Earth Science Convention’ that is equivalent to the Landscape Convention that is currently undergoing ratification within the EU. However, this is symbolic of landscape and Earth Science designation catching up with, rather than taking the lead in, environmental protection.

7The second issue is that in relatively economically deprived regions such as Northern Ireland, government support for economic development can sometimes appear to take precedence over spending on environmental protection. Limited resources for protection tend to be focused on satisfying legislative requirements that are largely habitat driven. Consequently, themes such as landscape protection and Earth Sciences that suffer from a legislative deficit are woefully under-resourced within Northern Ireland (CNCC, 2004). Indeed, within the Environment and Heritage Service (EHS), the responsible body for Northern Ireland, only half of one person’s time is allocated to Earth Science conservation. The other half, together with several support staff, is dedicated to ornithology. This situation is compounded by EHS policy of relying upon the existing body of knowledge when identifying and designating sites, rather than commissioning research that could identify new sites or add to the understanding of well-known locations. This is especially important in regions such as Northern Ireland where in comparison to Great Britain, existing geomorphological surveys and research are sparse.

8The effect of this lack of investment in understanding Earth Science heritage is amply demonstrated at the Giant’s Causeway, where limited site interpretation is directed overwhelmingly at the stones of the causeway itself and where mythology supersedes rationality in the explanation of specific features such as ‘The Giant’s Boot’ and ‘The Irish Harp’. As a consequence, the wider scientific importance and the landscape history of the site go largely unexplained – at least in a format accessible to the general public. This is despite the fact that, even within the original inscription, it was acknowledged that much of the site’s scientific value lies beyond the visually impressive stones of the causeway. This includes: (1) volcanic features associated with the opening up of the Atlantic Ocean at the end of the Cretaceous / beginning of the Tertiary; (2) internationally important exposures of iron- and aluminium-rich Interbasaltic Beds that provide a unique, time-constrained opportunity to evaluate climatic conditions at the beginning of the Tertiary (Migon and Lidmar-Bergstrom, 2002); (3) an excellent example of the contrasts between older olivine basalt flows and later, quartz basalt or tholeiitic flows; (4) varied suites of late-formed zeolite minerals that infill former gas filled cavities; (5) notable exposures of NW-trending basalt dykes that are instrumental in shaping the characteristic embayed coastline; (6) hyaloclastite material in the form of flow-foot breccias at Port na Spaniagh (Lyle and Preston, 1993) that provide evidence of abundant water in the eruptive environment of the Causeway tholeiites.

9The site has also played an important role in the development of scientific ideas concerning basalt terrains. It was, for example, important in the advancement of the concepts of volcanology in the late 18th and early 19th centuries when the water colours of Susanna Drury and the letters of the Reverend W. Hamilton (1786) made it one of the best known geological localities in the world. Subsequently, S.I. Tomkeieff’s (1940) architectural terminology has also achieved widespread international usage.

Dynamic landscape or geological museum?

10In addition to its detrimental effect on wider geological understanding, the focus on the Causeway stones has also drawn attention away from the coastal geomorphology that is central to the overall significance of the site and was integral to its inscription. The dynamism of the site, and the importance of natural erosion processes in maintaining its character, was most recently noted by a UNESCO/IUCN mission that reviewed the site in February 2003. They recognised it as a dynamic geological site with ongoing geological processes and coastal erosion phenomena, which have to be managed as such. Included within the ‘geological processes’ are a variety of active and recent slope failures. These have a geomorphological significance in their own right, but their continued action is crucial for maintenance of the rugged nature of the coastline and its biodiversity through the regular exposure of bare soil and rock that also provides new geological exposures for scientific study (fig. 3). These failures range from shallow, translational mudflows to large scale rotational landslides and block falls that vary from individual boulders to major failures measured in hundreds of tons (Smith et al., 1994). The final trigger for these failures is often a period of prolonged and/or intense rainfall, but underlying factors include the undermining of cliffs by marine erosion, excavation of the Interbasaltic Bed to create a footpath and the gradual weathering and weakening of the geology. In their report for the Environment and Heritage Service on slope failures at the Giant’s Causeway, B.A.M. McDonnell and B.J. Smith (2000) drew attention to two areas within the site that have particular geomorphological significance.

Fig. 3 – Shallow flowslide over stabilised scree within Port Noffer in 1994 – approximately 10 m wide.
Fig. 3 – Glissement superficiel sur un éboulis stabilisé à Port Noffer en 1994 – largeur environ 10 m.

Fig. 3 – Shallow flowslide over stabilised scree within Port Noffer in 1994 – approximately 10 m wide. Fig. 3 – Glissement superficiel sur un éboulis stabilisé à Port Noffer en 1994 – largeur environ 10 m.

These failures are a regular occurrence and quickly re-vegetate, but they are important for maintaining biodiversity (Picture taken by B.J. Smith).
Ces phénomènes sont récurrents et rapidement revégétalisés, mais ils sont importants pour le maintien de la biodiversité (cliché B.J. Smith).

11The ‘Amphitheatre’, together with the cliffs above Lacada Point, has consistently been identified as the most active and hazardous cliff section within the World Heritage Site (Smith et al., 1994). The headland is especially prone to the toppling of basalt columns and deep-seated rotational failures through the Interbasaltic Bed that runs along the cliff at mid-height. Within the Amphitheatre is a superb example of an active scree.

12Port Noffer is the location for numerous shallow translational slides and flows above and within vegetated screes around most of the embayment (Smith et al., 1994; Smith and Warke, 2001). The mudflows, in particular, are valuable for maintaining a level of vegetational variety through the regular re-colonisation of new erosion scars.

13The slope failures, together with other associated erosion processes, do, however, present a number of challenges for the successful and sustainable management of the site. It is clear, however, that these challenges can be addressed positively. For example, in 1994, a series of slope failures caused effectively irreparable damage to the then lower footpath (fig. 4), and resulted in the closing off of the remaining sections to the general public – whilst retaining access for scientific study. Subsequently, closure of the lower-cliff path was used to argue for EU funding to upgrade other elements in the path network, and produced an overall improvement in access to the coastline as a whole.

Fig. 4 – Large slope failure below Chimney Tops in 1994, where the lower cliff path was excavated into an inter-basaltic bed and undermined the overlying Middle Basalt.
Fig. 4 – Grand glissement sous Chimney Tops en 1994, là où le chemin des falaises inférieur a été excavé dans une couche interbasaltique, provoquant la déstabilisation des basaltes moyens sus-jacents.

Fig. 4 – Large slope failure below Chimney Tops in 1994, where the lower cliff path was excavated into an inter-basaltic bed and undermined the overlying Middle Basalt. Fig. 4 – Grand glissement sous Chimney Tops en 1994, là où le chemin des falaises inférieur a été excavé dans une couche interbasaltique, provoquant la déstabilisation des basaltes moyens sus-jacents.

This 10-m-wide landslide triggered the closure of the path and has continued to shed basalt debris (Picture taken by B.J. Smith).
Ce glissement de 10 mètres de largeur a provoqué la fermeture du chemin et continue de produire des débris de basalte (cliché B.J. Smith).

14The closure of the lower-cliff path was not undertaken lightly and research into the long-term viability of the path (Smith et al., 1994) considered a range of options, including engineering intervention, for re-opening the path. In particular, the Geo-Conservation Committee of the Geological Society of London took a particular interest in the path closure and lobbied strongly and publicly for the reconstruction of the path involving major engineering works. The basis for their argument was the vital importance of maintaining the existence of and access to existing exposures. However, the halt in path maintenance revealed how active the cliffs are and detailed mapping of the path identified the extent to which the repeated cutting of the path into the Interbasaltic Bed had created large areas of potential instability – especially around the near-vertical headlands. Because of this it was concluded that the intervention required to ensure path stability and visitor safety would need to be on a scale that was inimical to maintaining the visual integrity, dynamic character, natural drainage and biodiversity of the cliffs. Moreover, it was felt that engineering intervention would inevitably mask or destroy existing geological exposures, prevent new exposures from appearing and that solutions that involved tunnelling and cantilevered walkways would do little to improve opportunities for scientific study. This view was endorsed at the time by all key stakeholders and at a public meeting.

15The initial recommendation from the consultants was that means should be investigated for keeping the path open as far as Lacada Point. However, the decision to close it at Roveran Valley Head has since been justified by a major blockfall that obliterated the path within the Amphitheatre and a further landslide at Lacada Point. In closing the lower-cliff path, all parties concerned were aware of the geological significance of the cliffs and access to the remains of the lower-cliff path continues to be available through a normally closed gate for bona fide academic study.

Conclusion

16As indicated in the introduction, the World Heritage Site management plan for the Giant’s Causeway is currently in preparation. However, early drafts that have gone out to consultation have taken notice of comments emanating from UNESCO/IUCN and emphasised the importance of maintaining the dynamic nature of the site. Wide-scale engineering intervention would be extremely expensive and would not halt landscape change. Instead, change would be re-directed towards, for example, a decrease in slope angles, reduced exposure of bare rock, increased vegetation growth and widespread soil development. In short, this means the destruction of those very features that justified the site’s inscription. A welcome by-product of the recognition of the dynamic nature of the site is that it emphasises the importance of geomorphological processes as well as geological controls in shaping the landscape.

17Managing a dynamic landscape, or indeed any form of change, is fraught with difficulties. For it to be successful it is essential that managers have the support of stakeholders in taking decisions that can be politically sensitive, such as the closure of the lower-cliff path. However, as that closure demonstrated, apparently negative actions can be balanced by positive developments provided that funding is available. However, arguments deployed to placate geologists, such as the creation of new exposures, do not necessarily satisfy the biologist who is determined to preserve a specific habitat or specimen. Because of this, it can be foreseen that the multiple designation of the Giant’s Causeway could very well lead to conflict between a landscape policy that permits ‘managed retreat’ of cliffs and habitat designations that demand detailed defence of the statu quo.

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Bibliographie

Carter R.W.G. (1991) – Shifting Sands: A study of the coast of Northern Ireland from Magilligan to Larne. Countryside and Wildlife Research Series No.2, Belfast: HMSO. 49 p.

CNCC (2004) – Council for Nature Conservation and the Countryside Sixth Report 2000 – 2003. Belfast, 41 p.

Department of the Environment (NI) (1985) – Giant’s Causeway, Natural Site Nomination for UNESCO world Heritage List. Belfast, 20 p.

Hamilton W. (1786) – Letters concerning the northern coast of the County of Antrim, London.

Knight J. (ed) (2002) – Field Guide to the Coastal Environments of Northern Ireland. University of Ulster, Coleraine, 204 p.

Lyle P. (1996) – A Geological Excursion Guide to the Causeway Coast. Environment and Heritage Service (Department of the Environment NI), Belfast: HMSO, 90 p.

Lyle P., Preston J. (1993) – Geochemistry and volcanology of the Tertiary basalts of the Giant's Causeway area, Northern Ireland. Journal of the Geological Society, London, 150, 109-120.

McDonnell B.A.M., Smith B.J. (2000) – Slope failures at the Giant’s Causeway 1995–1998. Report for Environment and Heritage Service, 55 p.

Migon P., Lidmar-Bergström K. (2002) – Deep weathering through time in central and north-western Europe: problems of dating and interpretation of geological record. In Smith, B.J., Turkington, A.V. and Thomas, M.F. (Eds): The interpretation and significance of weathering mantles. Catena Special issue, 49, 20-35.

Smith B.J., Ferris T.M.C. (1997) – Giant’s Causeway: management of erosion. Geography Review, 11, 30-37.

Smith B.J., Hughes D.A. (1999) – Condition assessment of the Giant’s Causeway road and recommendations for remedial actions. Report for Environment and Heritage Service and DoE Roads Service, 28 p.

Smith B.J., Warke P.A. (2001) – Classic Landforms of the Antrim Coast. Geographical Association, Sheffield, 52 p.

Smith B.J., Ferris T.M.C., Hughes D.A., Greer J.V., Murray M.R. (1994) – Footpath and visitor management strategy for the Causeway Coastal Path Network. Report for Environment and Heritage Service, 110 p.

Tomkeieff S.I. (1940) – The basalt lavas of the Giant’s Causeway district of Northern Ireland, Bulletin Volcanologique, Série 2, 6, 89-143.

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Annexe

Version française abrégée

Les 40 000 colonnes de basalte de la Chaussée des Géants sont situées sur la côte nord du Comté d’Antrim en Irlande du nord. Elles constituent une attraction touristique depuis plus de 200 ans et en 1986, le site et la ligne de côte environnante ont été inscrits au Patrimoine Mondial de l’Humanité. Il s’agit d’un site complexe, reconnu à travers une série de classements pour ses valeurs écologique, paysagère, géologique et géomorphologique (Carter, 1991 ; Knight, 2002). Une conséquence de cette complexité est la prolifération d’acteurs aux objectifs conflictuels qui tous proclament un certain droit de « propriété » sur le site. La plupart des conflits sont de type politique et/ou économique. Deux sources de discussions, entre les biologistes et la communauté des sciences de la Terre d’une part, et à l’intérieur des sciences de la Terre, entre géologues et géomorphologues d’autre part, ont toutefois une connotation scientifique plus large. Cet article présente les principales caractéristiques de ces débats en vue d’un échange d’expériences avec les scientifiques dont l’activité consiste à gérer des géosites multifonctionnels.

Il est piquant de constater qu’un site d’importance mondiale pour ses caractères géologiques voit la majeure partie de la protection légale au niveau régional et national se rapporter à son rôle comme habitat pour les espèces. Cela met en évidence le déséquilibre existant entre la protection de la biodiversité par rapport à la protection de la géodiversité dans des institutions telles que l’Union Européenne. Il faut espérer que cette situation change dans un proche avenir. Le Conseil de l’Europe a ainsi récemment admis que la biodiversité est largement dépendante de la géodiversité et a décidé de préparer des recommandations pour la « Conservation du Patrimoine Géologique et des Zones d’Intérêt Géologique Spécial ». Cette situation est toutefois symbolique de la position des sciences de la Terre et du paysage dans le concert de la protection de l’environnement. Les impacts du manque de développement dans le domaine de la géoconservation sont bien mis en évidence dans la gestion de la Chaussée des Géants, où une place très limitée est offerte à l’interprétation géologique sur le site lui-même, et où la mythologie ou la superstition sont appelées en renfort pour expliquer certaines formes spécifiques tels que la « Botte du Géant » ou la « Harpe irlandaise ». L’importance scientifique du site et son histoire géomorphologique sont, par conséquent, largement inexploitées et peu mises en valeur, en tout cas sous une forme accessible à un large public.

Outre l'absence d’explications géologiques en général, la concentration des infrastructures touristiques sur la Chaussée a complètement détourné l’attention que l’on peut porter à la géomorphologie côtière, dont le rôle est central pour la formation et l’évolution du site. Cette dynamique et l’importance des processus d’érosion pour le maintien du caractère du site ont récemment été mises en exergue lors d’une mission commune de l’UNESCO et de l’IUCN en 2003. Le rôle de la dynamique côtière a été reconnu et le principe d’une gestion incluant la prise en compte de cette dynamique a été accepté. Sont ainsi considérés comme des « processus géologiques » les mouvements de terrain actifs et récents (Smith et Ferris, 1997), allant des coulées de boue superficielles et de type translationnel aux grands glissements rotationnels et aux éboulements (Smith et al., 1994 ; Smith and Warke, 2001). Ces formes et processus ont une importance géomorphologique intrinsèque mais ils sont également cruciaux pour le maintien de la biodiversité, ainsi que pour le dégagement de nouveaux affleurements géologiques. Les mouvements de terrain présentent toutefois une série de problèmes en vue d’une gestion durable du site. Ainsi, en 1994, un chemin d’accès, taillé dans la falaise basaltique, a dû être fermé en raison d’un glissement de terrain (Smith et al., 1994). Cette fermeture fut ensuite utilisée comme argument pour solliciter des fonds européens en vue d’améliorer le réseau restant de sentiers pédestres, ainsi que l’accès à la côte. La fermeture de ce sentier provoqua des conflits entre géologues et géomorphologues et le Comité pour la « géoconservation » de la Société géologique de Londres s’engagea ainsi fortement pour le maintien du chemin et la réalisation de travaux de stabilisation. Cet épisode révéla toutefois l’importance de la dynamique géomorphologique de la côte et il fut admis que les mesures à prendre pour stabiliser le versant et pour assurer la sécurité des visiteurs étaient incompatibles avec le maintien de l’intégrité visuelle du site, de son caractère dynamique et de son rôle pour l’hydrologie et la biodiversité des falaises. Cette conclusion fut adoptée par les principaux acteurs et lors d'une assemblée publique.

La version préliminaire du plan de gestion du site du patrimoine mondial met également l’accent sur la nature dynamique du site. Le rapport reconnaît le rôle complémentaire des processus géomorphologiques et des facteurs géologiques dans la formation de ce paysage. Toutefois, les arguments déployés pour satisfaire les géologues, tels que la création de nouveaux affleurements, ne satisfont pas nécessairement les biologistes, qui sont déterminés à préserver un habitat ou des espèces particulières. Cette multiplicité des fonctions du site pourrait ainsi déboucher sur des conflits entre la politique du paysage, qui ne contrecarre pas l’évolution de la falaise, et la politique de conservation des espèces et de leurs habitats, qui plaide plutôt pour le statu quo.

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Table des illustrations

Titre Fig. 1 – Location map for the Giant’s Causeway World Heritage Site.Fig. 1 – Localisation de la Chaussée des Géants, site inscrit au patrimoine mondial de l’Humanité.
URL http://journals.openedition.org/geomorphologie/docannexe/image/386/img-1.png
Fichier image/png, 104k
Titre Fig. 2 – Basalt columns of the Middle Causeway. Columns are approximately 50 cm wide. (picture taken by B.J. Smith).Fig. 2 – Colonnes de basalte de la Chaussée moyenne. Les colonnes ont environ 50 cm de diamètre (cliché B.J. Smith).
URL http://journals.openedition.org/geomorphologie/docannexe/image/386/img-2.png
Fichier image/png, 159k
Titre Fig. 3 – Shallow flowslide over stabilised scree within Port Noffer in 1994 – approximately 10 m wide. Fig. 3 – Glissement superficiel sur un éboulis stabilisé à Port Noffer en 1994 – largeur environ 10 m.
Légende These failures are a regular occurrence and quickly re-vegetate, but they are important for maintaining biodiversity (Picture taken by B.J. Smith).Ces phénomènes sont récurrents et rapidement revégétalisés, mais ils sont importants pour le maintien de la biodiversité (cliché B.J. Smith).
URL http://journals.openedition.org/geomorphologie/docannexe/image/386/img-3.png
Fichier image/png, 234k
Titre Fig. 4 – Large slope failure below Chimney Tops in 1994, where the lower cliff path was excavated into an inter-basaltic bed and undermined the overlying Middle Basalt. Fig. 4 – Grand glissement sous Chimney Tops en 1994, là où le chemin des falaises inférieur a été excavé dans une couche interbasaltique, provoquant la déstabilisation des basaltes moyens sus-jacents.
Légende This 10-m-wide landslide triggered the closure of the path and has continued to shed basalt debris (Picture taken by B.J. Smith).Ce glissement de 10 mètres de largeur a provoqué la fermeture du chemin et continue de produire des débris de basalte (cliché B.J. Smith).
URL http://journals.openedition.org/geomorphologie/docannexe/image/386/img-4.png
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Bernard J. Smith, « Management challenges at a complex geosite: the Giant’s Causeway World Heritage Site, Northern Ireland », Géomorphologie : relief, processus, environnement, vol. 11 - n° 3 | 2005, 219-226.

Référence électronique

Bernard J. Smith, « Management challenges at a complex geosite: the Giant’s Causeway World Heritage Site, Northern Ireland », Géomorphologie : relief, processus, environnement [En ligne], vol. 11 - n° 3 | 2005, mis en ligne le 01 octobre 2007, consulté le 16 décembre 2017. URL : http://journals.openedition.org/geomorphologie/386 ; DOI : 10.4000/geomorphologie.386

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