The advocacy of preserving archaeological sites in situ has been politically galvanized internationally and certainly within Europe through a number of conventions: the European Convention for the Protection of Archaeological Heritage 1969 (The London Convention), updated in 1992 as the Valetta Convention.Footnote1 The treaty aims to protect the European archaeological heritage ‘as a source of European collective memory and as an instrument for historical and scientific study. All remains and objects and any other traces of humankind from past times are considered elements of the archaeological heritage. The notion of archaeological heritage includes structures, constructions, groups of buildings, developed sites, moveable objects, monuments of other kinds as well as their context, whether situated on land or under water’. In particular, Articles 4ii and 5vii respectively seek the conservation and maintenance of archaeological heritage preferably in situ and to make provisions for in situ conservation, when feasible, in connection with building/development work. In terms of underwater archaeology, the Annex (General principles, Rule 1) of the international 2001 UNESCO Convention on the Protection of the Underwater Cultural HeritageFootnote2 recommends that the protection of underwater cultural heritage through in situ preservation shall be considered as the first option.
It was the advent of the Valetta Treaty, increasingly backed up by national legislation that made preservation in situ the preferred option for dealing with archaeological evidence on sites being developed, that began to see concentrated efforts within Europe to investigate the feasibility and efficacy of in situ preservation. The results of much of this research have been presented in the international conferences that have collectively become known as the PARIS conferences (Preserving Archaeological Remains In Situ). The first and second conferences were organized and hosted by English Heritage and the Museum of London in the United Kingdom in 1996 (Corfield et al., Citation1998) and 2001 (Nixon, Citation2004), and the third by the Vrije University in the Netherlands in 2006 (Kars and van Heeringen, Citation2008). The fourth conference was organized and hosted by the National Museum of Denmark in Copenhagen in 2011. The conference was made possible with grants and goodwill from the National Museum of Denmark, the Farumgaard Foundation, the National Cultural Heritage Agency of Denmark, English Heritage, the Viking Ship Museum in Denmark, the Danish Palaces and Properties Agency, and the Museum of Copenhagen. The conference attracted over a hundred participants. An interesting development for the conference was the geographic broadening of participants and the research presented, with delegates coming from Denmark, Sweden, Norway, the United Kingdom, Germany, the Netherlands, Belgium, Eire, Finland, France, Belgium, Italy, Portugal, Croatia, Turkey, USA, Australia, and New Zealand.
The key aim of the conference was to present and discuss the latest knowledge, yet focusing on long-term studies of degradation and monitoring of archaeological sites preserved in situ in urban, rural, and marine environments. One of the strengths of the PARIS conferences is their multidisciplinary nature bringing together scientists, heritage managers, and policy makers. Building on this, focus was given to presentations from both practitioners (scientists and archaeologists) and stakeholders (cultural resource managers) to cover the four following themes, taking into account the benefit of hindsight of almost twenty years’ research.
| 1. | Degradation of archaeological remains. Can we quantify the degradation rates and what rates are acceptable? | ||||
| 2. | Monitoring and mitigation studies — with special focus on long-term projects. How and how long should sites be monitored? | ||||
| 3. | Protocols standards and legislation for monitoring and management. Is it realistic to make multinational standards when the sites and national legislations are so variable? | ||||
| 4. | Preserving archaeological remains in situ. Can we document the effectiveness of in situ preservation after nearly two decades of research? | ||||
The four themes were covered through a total of forty-six oral and poster presentations. Each theme was chaired by a practitioner and a stakeholder in order to try see ‘both sides of the coin’. The conference was closed with a round table discussion, with panel members from the scientific committee. The full transcript of the round table is available on the conference home pageFootnote3 and key points have been included as part of our editorial.
Theme 1. Degradation of archaeological remains. Can we quantify degradation rates and what rates are acceptable?
This theme included twelve presentations at the conference (ten oral presentations and two posters) with nine papers in these proceedings. The papers represent different approaches to studying degradation and quantifying degradation rates. A literature-based approach using carbon budgets was presented by Durham et al. (wetlands in the UK). Field studies focusing on environmental monitoring and the state of preservation of archaeological material was presented by Martens et al. (urban deposits in Norway), and field studies of degradation processes were given by Ricci et al. (underwater bioerosion of stone) and by Huismann (impact of piling and compression); however, these studies did not include estimates of actual degradation rates. Repeated visits to field sites using standardized documentation and monitoring was suggested by Heumüller (erosion of lake dwellings in Lake Constance). Model experiments were presented by several authors as a useful supplement for measuring degradation rates: microcosms in the laboratory were used by Gelbrich et al. (decay of wood), whereas modern replica samples were used in the field by Richards et al. (marine corrosion). By combining both model experiments, field monitoring, and descriptions of the archaeological objects Saheb et al. (corrosion of iron under anoxic conditions) studied corrosion mechanisms and estimated degradation rates that were validated by ground truthing. Overall, the presentations showed a whole range of different tools to study the degradation of archaeological remains, and also that it is necessary to combine several tools if degradation rates shall be estimated and validated. None of the presentations discussed what rates are acceptable.
The round table discussion on this theme was opened by Jim Williams from English Heritage and Mark Pollard from Oxford University. They pointed out that we already have many of the tools necessary to investigate degradation rates, and there are already a lot of data available from deterioration/preservation research and other research fields. However, we really need to ground truth the predictions from these tools and models. The question about ‘what rates are acceptable’ was discussed, but in general people were reluctant to give fixed limits as it depends on the sites in question. At this stage it is necessary to quantify, publish, and compare decay rates from a large number of different sites and different conditions in order to gain more experience with decay rates. We need to know what we can expect in the ideal and non-ideal situation before setting limits or goals.
Theme 2. Monitoring and mitigation studies — with special focus on long-term projects. How and how long should sites be monitored?
This theme included sixteen presentations (ten oral presentations and six posters) at the conference with fifteen papers in these proceedings. The case studies covered monitoring and mitigation strategies on a gamut of archaeological sites and environments. These ranged from: underwater sites (Richards, Pascoe, Petriaggi and Davidde, and Bjordal et al.); waterlogged rural sites (Jones and Bell, Lillie et al., Tjelldén et al., Dal Ri and Fruet); waterlogged urban sites (de Beer et al., Petersen and Bergersen), an arctic site (Hollesen et al.), the remains of built heritage sites (Goodburn Brown, Bai, De Mattia) and a complete country (de Lange et al.).
Many of the papers which discussed monitoring, especially those sites on land, discussed the variety of methods available for classifying and assessing the physical, chemical and biological environment. Aside from the description of the methods, it was also interesting to see progress in the interpretation and presentation of monitoring results. Of particular note was the development and use of models, modelling software, and geographical information systems (GIS) to come to grips with the great wealth of information modern dataloggers provide. This was highlighted particularly in the presentations by Bjordal et al. where GIS had been used to look at the spread of shipworm in the Baltic. De Beer et al. showed the hydrodynamic and geochemical modelling and 3D presentation of the conditions around the world heritage site of Bryggen in Bergen Norway. De Lange et al. showed the development of a predictive 3D model to assess the effects of compression of archaeological soils and sediments. This could be used to assess the likely effects of any building/development work around sites in the Netherlands. In the round table discussion, chaired by Jane Sidell, English Heritage, and Hans Huismann, the Dutch Cultural Heritage Agency, it was commented that perhaps the theme should have included not only how should we monitor but what should we monitor. This entails focusing upon what the aim of monitoring is: it may be purely intellectual archaeological questions; questions of establishing a baseline, monitoring the trend of decay, monitoring information loss. Petersen’s and Bergersens paper on monitoring in Trondheim addressed this in part and showed the use of the Norwegian standard for monitoring (see Theme 3). The question of what to monitor was perfectly illustrated in Pascoe’s paper concerning the monitoring of the wreck of the Sterling Castle in England, which was in part monitored using 3D marine geophysical techniques. This showed that the wreck was in a very dynamic environment being covered and uncovered due to sediment transport, with each episode leading to more loss of information both in terms of artefacts and archaeological context. Richards’ and Patriaggi and Davidde’s paper may offer some possible solutions to mitigation for the deteriorative processes in the marine environment as they discussed the in situ stabilization of the wreck of the James Matthews in Australia and the restoration and display of ancient underwater sites in Italy. On land, Goodburn Brown’s and Bais paper discussed mitigation methods for re-buried and upstanding monuments on land.
The round table discussion also picked up on the consequences of monitoring and mitigation. The current editors have argued for a process-oriented approach to in situ preservation — what are the threats to a site, regardless of its environment, how can these be assessed and quantified (monitoring). Based on this baseline data, is the site safe or are mitigation measures required? However, if monitoring shows that the site is at risk of deterioration and mitigation methods are not the optimal solution, what happens then? How do we prioritize what should be preserved?
Theme 3. Protocols, standards, and legislation for monitoring and management. Is it realistic to make multinational standards when the sites and national legislations are so variable?
This theme included eight presentations (six oral presentations and two posters) at the conference with seven papers in these proceedings. The papers demonstrate the variability in monitoring and management in different countries. From Norway, Loska and Christensson presented a Norwegian Standard describing in detail how archaeological deposits shall be documented and monitored by standardized methods during and after development projects at urban sites. The methods included visual description, laboratory analyses and field monitoring with automated equipment. From the Netherlands, Os et al. suggested a simple method for assessing the burial environment based on visual observations during excavations. From Belgium, Goeminne described an organization that monitor the condition of the archaeological heritage, mainly based on visual observations, and from Turkey Kökten described how practical problems sometimes hinder a continued monitoring and maintenance of floor mosaics. From Croatia, Plěse described the management of a Roman site, however, without giving details on the monitoring. Overall the presentations represented a whole range of different approaches to monitoring — from detailed instrument based monitoring at individual sites, visual observations during excavation, to visual registration from the soil surface during systematic visits to a large number of sites — and all these approaches are probably needed in a standard monitoring scheme.
The round table discussion on this theme was opened by Jens Rytter from the Directorate of Cultural Heritage in Norway and Henk Kars from Vrije Universitet in Amsterdam. They pointed out that the standards need to be tested under different conditions, and to that end the Norwegian monitoring standard is currently being tested in England. As for international standards, Stub Johnsen from Denmark gave an overview of ongoing work to make CEN standards within the field of conservation, where he showed that the standardization procedure is relatively slow and it can be difficult to combine the needs in different countries. This was also emphasized in the round table discussion and overall it was concluded that the time is probably not ripe yet for making international standards for monitoring of in situ preserved archaeological sites — the national standards need to be implemented and their use evaluated first. It was suggested to work on ‘guidelines for good practice’ instead of rigid standards, as the latter are difficult to change when new knowledge has been gained.
Theme 4. Preserving archaeological remains in situ — can we document it works?
This theme included ten presentations (seven oral presentations and three posters) and all are presented in these proceedings. The majority of papers came from the UK (Sidell, Corfield, Brunning, Panter and Malim, and Williams), which may be understandable as systematic in situ preservation has been part of planning policy guides since the early 1990s. However, results of other long-term projects from Sweden (Godfrey and Bergstrand), Denmark (Gregory and Matthiesen) and the Netherlands (Huisman et al.) were also presented. Sidell’s paper bodes well for in situ preservation, where sites that had been excavated up to 150 years ago, many of which were in good condition upon re-excavation in the recent past. The question of testing the efficacy of mitigation and monitoring methods also arose with the question of the Rose Theatre (Corfield), which was one of the first attempts to systematically monitor and rebury an urban site. The site has been continually monitored and is due to be re-excavated, so it will be interesting to see how the site has fared after twenty years. Brunning’s, Panter and Malim’s, and Williams’ work brought together the pioneering work carried out in the UK over the past twenty years. Work on the Somerset levels, showed an excellent approach to systematic in situ preservation, particularly in terms of the efficacy of monitoring methods and also that in some areas it works and some areas it has not. This was reflected in the other papers from the UK and the Netherlands (Huisman et al.) and a general feeling was that monitoring methodology has improved significantly over the past twenty years. This was reflected in the round table discussion, chaired by Mike Corfield, former chief scientist for English Heritage, and Vicki Richards from the Western Australian Museum. However, both papers and the following discussion reflected that the aims and goals of in situ preservation should be better stated from the outset with thorough project planning, quality assurance and interdisciplinary involvement, and review of projects. It was also highlighted that the state of preservation of material on a site (both environmental and artefactual) should be a prerequisite when developing any in situ preservation strategy. One of the very interesting developments from previous PARIS conferences reflected in the aforementioned papers, and also by Godfrey and Bergstrand’s paper, was the need for better understanding and communication between all parties involved with in situ preservation (archaeologists, conservators, planners, heritage, and other government agencies with responsibility for the natural environment) and a good dialogue should happen from the outset of a project. Furthermore, there should be other options available if monitoring and mitigation methods show that in situ preservation is not optimal. Only in this manner can we ensure that preservation in situ is a viable and realistic option.
To conclude, the PARIS4 conference has been successful in bringing together stake-holders and practitioners working with in situ preservation in a large number of countries. The presentations and discussions were of a high quality, and it was remarkable how the level of knowledge has developed since the first PARIS conference in 1996. The next PARIS conference will take place at Lake Constance in April 2015 — further details may be found on <www.archaeologie.tg.ch> in due course. Hopefully, the knowledge level will have increased even more by then — there is still work to be done: quantifying degradation rates, improving mitigation methods, developing guidelines for best practice, and documenting when in situ preservation is a realistic option and when it is not.
Notes
Related Research Data
Bibliography
- Corfield M, Hinton P, Nixon T, Pollard M. eds. 1998. Preserving Archaeological Remains In Situ. Proceedings of the Conference of 1–3 April 1996. London: Museum of London Archaeology Service.
- Kars H, van Heeringen RM. eds. 2008. Preserving Archaeological Remains In Situ: Proceedings of the 3rd Conference, 7–9 December 2006. Amsterdam: Amsterdam: Institute for Geo and Bioarchaeology.
- Nixon T. ed. 2004. Preserving Archaeological Remains In Situ? Proceedings of the 2nd Conference 12–14 September 2001. London: Museum of London Archaeology Service.