Conservation of Wetlands, or Conservation of Archaeological Materials: Maybe They’re One in the Same
In addition to being an inspiration for cautionary bedtime stories by Han Christian Anderson, bogs, also known as peatlands and wetlands, have produced some of the best-preserved sources of archaeological materials in northern Europe and the United Kingdom (Buckland, P.C., 1993:513). It probably doesn’t help the bog’s reputation that the incredibly preserved remains of individuals killed by stabbing or hanging and then dumped into swamps millennia before present continue to be found by archaeologists in these wetlands. But the very existence of other, similar, undiscovered archaeological materials in bogs has been and continues to be threatened by both natural and cultural formation processes. Moving past the ghostly perils and carnivorous plants, should archaeologists and conservators advocate along with environmental scientists for the preservation of bogs, peat deposits, and wetland ecosystems?
As of 1988, more than 120 sites have been identified containing preserved human remains and archaeological objects in bog deposits (Omar et al., 1988:101). Threats to the continual preservation of these deposits include development, decreases in the water table via drainage and water abstraction, peat abstraction and wastage, and other environmental factors including climate change. (Van de Noort et al, 2002:18)
Bogs are formed over long periods of time on both dry land and standing water when layers of moss and algae find suitable surfaces to grow on. The moss retains water very easily (on dry and wet land), and any soil under the moss eventually becomes saturated and waterlogged. As the accretion of moss continues to grow over time, enough water collects in the once soil covered area to become swampy and submerged in successive layers of moss and water. Conversely, when algae and moss grow on the surface of standing water in lakes and ponds, those same layers continue to grow until they fill up any remaining space, preventing other biological organisms from growing in the vicinity (Lobell and Patel, 2010:27).
The importance of peat in preserving ancient organic materials lies in its anaerobic, water logged, acidic environments. Colder temperatures can also help in the preservation of deposits in bogs. Lack of oxygen and microbial life prevents the destruction of delicate materials, like wood, textiles, and even the bodies of humans and animals (known as Bog Bodies).
According to authors Lobell and Patel in their 2010 publication of Bog Bodies Rediscovered, the chemical nature of bogs vary. The exact chemical composition and interaction for successful preservation is not understood, and while half of a body or object can preserve beautifully, another half might completely disintegrate. For instance, Tollund man, found in Denmark, retains only the bones of his hands, while his feet remained fully intact.
Tollund Man on display.
There are other problems behind wetland archaeology that cause scientists to hesitate before excavating in peat and water logged sites. Despite the enormous potential of these areas for preservation of archaeological materials, archaeologists are guilty of diving head first into excavation without thought for how to take care of their findings once they are removed from their protective bed of soil. For this type of excavation and preservation, a trained conservator must be present during the stages of the artifact’s life span after removal from the burial environment.
Early methods of conservation have included slurries (oak bark), and solutions of distilled water and various oils, or solutions alternating concentrations of ethanol – anywhere from 33 to 99 percent (Omar et al., 1989:101). Methods used today include freeze-drying. However, it was necessary before carrying out this process to determine what should be used to impregnate the body. PEG is a type of water soluble wax used today that is a popular treatment for waterlogged wood. An object or organic substance, when placed in a solution of PEG 400, will absorb the wax from the water solution, filling and providing structure to otherwise compromised and delicate organic finds with either plant or animal cell structures. Once the PEG has been completely absorbed, the body or object can then be freeze-dried, and later, put on display in stabilized, museum environments.
It was not immediately clear to conservation scientists whether or not a consolidant would be required in the preservation of Lindow Man However, options existed that were successful when used on waterlogged wood and leather. These solutions involved PEG or polyethylene glycol and was first applied to Lindow Man at Silkeborg Museum, Denmark. Before they applied this solution, however, a n experiment was carried out on peat buried and preserved samples of pig skin to determine what solution of PEG would work best on bog bodies (Omar et al., 1989:104). After being buried in peat, the pig skins were tested by submersing them in solutions of PEG 400 with 10 percent PEG 2000. White, waxy residues congealed on the surface of the PEG 2000 samples. From these results, it was decided that it would be safest in the long term to use PEG 400 as a consolidant on Lindow Man (Omar et al., 1989:104-105).
Lindow Man on display.
Before his consolidation with PEG, Lindow Man was stabilized over the course of a year, first by storage in a custom made icebox. Limited numbers of people were allowed in the room at the same time to prevent fluctuations in temperature, and the body was consistently sprayed with distilled water, to prevent dehydration. The environment in the box was kept at a constant four degrees Celsius, while the surface of Lindow Man were continuously covered and recovered in a combination of cling-wrap and a loose-weave cloth used by doctors to make casts for broken limbs. These were dampened with water to harden, and painted with pastes, and then covered with fiber glass materials to form a very hard, custom body cast. This casting was meant to help the body retain its form, and after being placed in its temperature controlled environment, was made more secure by layers of peat to copy the original burial environment, and to prevent the cast and body from sliding around (Omar et al., 1989:101-104).
The remnants of these bodies, and the details of their last few days or years can also be analyzed by scientists seeking to reconstruct the past. Without the proper conservation of these finds, they would very quickly dry, crack, and warp into an unrecognizable form; useless for display. This is why it is so important to not only have conservators present from the time of removal from the burial environment but also why archaeologists and conservators must pay attention to the threats placed on wetland ecosystems. If we allow these areas to be destroyed, we allow rich potential resources of archaeological data on the past to be destroyed as well.
Buckland, P.C. 1993 Peatland Archaeology: a conservation resource on the edge of extinction. Biodiversity and Conservation 2(5):513-527.
Van de Noort, Robert et al. 2002 Monuments at Risk in England’s Wetlands. University of Exeter. English Heritage Strategy for Wetlands.
Lobell, Jarrett A. and Patel Samir S. 2010 Bog Bodies Rediscovered. Archaeology 63(3):22-29.
Envionmental Protection Agency Water: Wetlands In North America. 2013. http://water.epa.gov/type/wetlands/bog.cfm
Omar, S. et al 1989 The Conservation of Bog Bodies by Freeze-Drying. Studies in Conservation 34(3):101-109.