The conservation and restoration of archaeological sites is the collaborative effort between archaeologists, conservators, and visitors to preserve an archaeological site, and if deemed appropriate, to restore it to its previous state. Considerations about aesthetic, historic, scientific, religious, symbolic, educational, economic, and ecological values all need to be assessed prior to deciding the methods of conservation or needs for restoration. The process of archaeology is essentially destructive, as excavation permanently changes the nature and context of the site and the associated information. Therefore, archaeologists and conservators have an ethical responsibility to care for and conserve the sites they put at risk.
Archaeological sites go through many phases.
These phases may be repeated and may occur in a different order.
Weathering is the source of most of the deterioration of archaeological sites. Wind, rain, freeze-thaw, and evaporation are extremely common and can cause erosion. Natural disasters, such as floods, fires, earthquakes, and volcanic eruptions, can cause the complete destruction of a site. The most effective way to protect archaeological sites from these larger events is to formulate a risk management plan. Archaeologists and conservators should assess threats to the site and determine material susceptibility.
Climate projections also show that changes in rainfall (intensity and frequency), increases in temperature and frequency of heatwaves, rising sea levels and groundwater fluctuations, warmer seas and ocean acidification will also result in changes to flora and fauna, ground conditions (on and below the surface) will affect archaeological deposits and structures. Human responses to the climate crisis also impact archaeological sites.
Modern development poses a great risk to archaeological sites. Vibrations from construction can cause instability and cracking of structures. An example of the effects of modern development can be found at an ancient Puebloan site in Arizona, that dates to A.D. 900-1350. It was damaged by construction activities while putting in a new road. After the damage was assessed, it was determined that the site was not eligible for the National Register of Historic Places. This determination was made due to construction activities destroying any information that was important in prehistory or history that was remaining at the site.
While development cannot be discontinued simply to protect archaeological sites, having a basic understanding of what might be impacted before development takes place could help protect sites and at least the information they can provide. The Arizona Antiquities Act of 1960 is an example of some ways in which archaeological sites can be protected.
Vandalism is also a prominent force of damage to archaeological sites. A range of actions can be considered, including graffiti, carving, deconstruction, and burning. These can be intentional or unintentional. Intentional vandalism occurs when visitors know that there is an archaeological site and still choose to deface it in some way. Unintentional vandalism happens when the visitor vandalizes while not realizing they are at an archaeological site, such as accidents.
To protect an archaeological site from vandalism requires a combination of techniques. The most effective course of action is educating the public. This does not just entail explaining the harms of vandalism—but to educate them on the importance of these sites, and what could be lost if it is vandalized. Signage should be posted at the site to alert visitors. Another possible measure to prevent vandalism is the addition of barriers, patrols, or even full-time observation and security.
Looting is the theft of artifacts from archaeological sites. Looting is often the main source of artifacts that enter into the antiquities market, in which objects are sold domestically or exported internationally. In the United States, there are laws for the protection of archaeological sites that contain penalties for those who choose to loot or cause disturbances. The act of looting serves as a disservice to both stolen objects and the sites themselves, as objects lose their historical context and sites lose record of even having that object in the first place. Archaeologist Arthur G. Miller states, “our very strong concern is because the looting of archaeological remains destroys those sites without any record whatsoever, let alone any record of the context from which artifacts are wrenched. It is as if a few particularly attractive pages were ripped from the books of a library, and the remainder burnt. In a word, the context is destroyed without record, so that most of the information vital to the fullest study and reconstruction of the past is irremediably lost to the world."
Throughout history, war has been the source of destruction of many archaeological and historical sites. During World War II, the Nazi's destroyed many buildings during the planned destruction of Warsaw, including several palaces and other buildings dating back to before the 13th century. The prevention of destruction due to war is almost impossible without large-scale strategies. Efforts by the Monuments Men during World War II is an example of an organized plan to protect the art and history of Europe from destruction at the hands of the Nazis. The Monuments Men played a significant role in attempts to repatriate art stolen during World War II. The Rape of Europa is a book, turned documentary that explains the Nazi's systematic theft and destruction of art during the war, and the implications for international museums and art collectors that followed.
In recent times, the Taliban destroyed a sacred Buddha statue in Afghanistan.
The goal of archaeologists in the conservation of excavation sites is "to preserve the physical remains of our past and to employ them in perpetuating our historical heritage”. This goal can be reached by ensuring that there is thorough documentation of archaeological sites, where details of the physical characteristics of the site itself and the excavations it has endured are written down. In the case that a site is destroyed, thorough documentation can preserve the memory of how it once existed. Archeologists are turning to other methods to preserve sites and use excavation techniques that impact sites as little as possible and save their natural features. Partial excavations are currently being conducted in place of full excavations to answer research questions without causing unnecessary deterioration to sites. A previous technique involved reconstructed walls and other site features to resemble their original structure. However, this method has mostly fallen out of use, and archaeologists and conservators are now focused on preserving the site in its present state
Conservators are the other leading voices for the advocacy and guidance of archaeological site conservation. It is these specialists that are needed to formulate the most sustainable and effective plan for the successful preservation of sites and they do so using the help of the expertise of the archeologists that know the sites up close and personally from their own excavations as well as their own experience and knowledge. Martha Demas (2004) has created an outline that conservators can rely on to create the most effective plan:
Identification and description
Aims: What are the aims and expectations of the planning process?
Assessment and Analysis
Visitors can have an impact on the conservation of archaeological sites themselves and not necessarily always positive ones. Their simple actions during visitation, even just visiting a site can be harmful to it, even serving as an agent of deterioration on their own. An example of this happened at Recapture Canyon in Utah. In 2007, the United States Bureau of Land Management (BLM) had to close access to the canyon to off-road vehicles due to the damage it was causing to local archaeological sites. However, several visitors ignored this closure and actually created a wider trail through the canyon. In May, 2014, a large protest was held in this same canyon, which consisted of hundreds of people riding off-road vehicles through the canyon itself. Owing to the large number of people going through it in such a short amount of time, it is very possible that the protest itself caused further damage. While this was an example of people acting as physical forces, they can also act as other agents such as vandals/thieves or pollutants by stealing pieces of sites or artifacts, defacing the sites, or leaving waste/trash nearby.
To combat further damage, archaeological sites that are open to the public are given trails that do not impact the site while still giving visitors good views. It is important for visitors to understand their own impact on archaeological sites they visit and be mindful of how they can contribute to their deterioration if they are not careful. Such sites open to the public should educate and inform visitors of such impacts if they wish for them to be truly aware, as many are likely unaware of how easily they can become damaged. If there is a designated path, they should remain on the path and restrictions should be set for the distance between visitors and artifacts/movable parts of the site and they should be guarded well.
The purpose of any technique used on an archaeological site is to strengthen its ability to resist damage and/or reinstate its cultural significance and ability to teach about its history.
Restoration is the "returning of the existing fabric of a place to a known earlier state by removing accretions or by reassembling existing components without the introduction of new material." The biggest difficulty in this technique is the lack of introducing new material. Ideally, this is the primary technique to strengthen the site from further damage.
Reconstruction is "returning a place to a known earlier state; distinguished from restoration by the introduction of new material into the fabric." The aim of reconstruction is to "preserve and reveal the aesthetic and historic value of the monument and is based on respect for original material and authentic documents."
There is also debate on whether this is conservation work or not, due to potential over-reconstruction. The appropriateness of this technique is highly dependent upon the region, the amount of known knowledge of the site itself, as well as the actual condition of the site. The older a site, the more difficult it is to be confident in the reconstruction. Reconstruction should also be identifiable upon inspection as well as reversible. A common form of reconstruction is the re-plastering of floors and walls. Due to weathering, the plaster that originally protected surfaces has eroded away and left the surfaces vulnerable. The re-plastering then adds that layer of protection back and in many cases was at least the same technique as originally even if it isn't exactly the same material.
Re-creation/renovation is the "speculative creation of a presumed earlier state on the basis of surviving evidence from that place to other sites, and on deductions drawn from that evidence using new materials." This is the least favorable option as it is less likely to reinstate the originality of the site, and many times includes destroying existing authentic materials in order to add new materials. It is deemed justifiable if it is the only form of effective conservation available, or if conservation measures prove to be unfeasible.
An example of this can be seen in the work of Sir Arthur Evans at the ancient city Knossos, an archaeological site on the Greek island of Crete. Evans, a British archaeologist, excavated the site beginning in 1901 and was able to preserve and restore much of the original architecture. The restorations, carried out by three different architects, included the reinforcement and reconstruction of buildings, rooms and frescoes. Yet, these renovations have faced criticism throughout the years and “what is restored does not accurately reflect what was found. Instead, a grander, and more complete, experience is presented. For example, when you visit Knossos, because of the way it is reconstructed, it is very easy to believe that all that was ever found there was a Late Bronze Age palace”, instead of a place that stood well into the Roman era.
Relocation is a dramatic form of conservation which involves the physical movement of the site or part of the site itself. This should only take place if the site would be heavily damaged or even eliminated if it were to not be moved. A famous example of this is the move of the Abu Simbel temples. The movement of these temples was expensive as well as challenging, but if the move did not take place they would be completely underwater due to the construction of the Aswan High Dam.