Wetlands are some of the most important environments in the world. From the Everglades of Florida, USA to the Mekong Delta, Vietnam to Lake Titicaca, Peru, wetlands are instantly recognisable landscapes across the globe. Inland waters represent a tiny fraction of the total water on the planet, but they are some of the most biologically diverse ecosystems, and crucially represent the source for most of world's drinking water, now and in the past. For this reason they have also been the target of human exploitation for our species' entire history. Inland waters take a range of different forms and the forms impact on the kinds of archaeology that you find, both in terms of the human activity taking place there and the quality of preservation conditions encountered.
Preservation of material is the unifying theme of wetland archaeology. Any and all kinds of material evidence of the human past ends up in wet locations, but preservation of organic material normally lost to archaeologists is frequently encountered in waterlogged contexts. Wetland settlement sites probably contain more archaeological material than any other site-type in the world.
Alongside classic excavation techniques, modern surveying and geoarchaeological methods are granting access to the archaeology of inland water in ever increasing detail. For example, developments in methods like XRF analysis and landscape scale photogrammetry are opening aspects of wetland archaeological sites to investigation that were previously impossible (or prohibitively expensive). The wealth of archaeological information that is contained in wetlands across the globe will only continue to become more accessible presenting great opportunities and great challenges.
Traditionally wetlands were viewed as peripheral places that were inhospitable and therefore saw settlement of marginal people only. More recently this view has been challenged suggesting that wetlands were highly productive ecosystems that has attracted human activity from the very distant past right up until today. Indeed the foundations of many of the ancient world's great civilisations were built on wetlands - the Nile River and Lake Texcoco are two good examples.
This is not to say that certain wetlands through history were not viewed as marginal or indeed otherworldly places. There is substantial archaeological evidence to suggest that this was the case, especially from northern Europe where there appears to be a very long lived and widespread tradition of depositing artefacts (including people) into watery places.
Wetland archaeology offers insight into very intimate aspects of the past because of the exceptional preservation encountered. These detailed glimpses offer opportunities to develop an understanding of how things worked in the past in human time scales (ie. decades or generations rather than centuries or millennia) which in terrestrial archaeological contexts is often impossible.
Archaeology is inherently multi-disciplinary using a wide range of methods, and wetland archaeology is no different.
Wetlands often preserve a record of the past environment in their underlying sediments, so paleoecological methods are frequently employed alongside archaeological investigation in wetlands to understand the environment in the past. For example, if you are interested in what plant resources were available through time, doing pollen analysis of sediment cores can tell you what species of plant were present at different times.
Hydrology is very important in wetland archaeology and is often used to understand the threats posed to wetland sites. Measuring and modelling how water moves through the landscape has been a very important part of strategies for protecting and mitigating against damage to wetland archaeological sites.
The range of scientific analyses that can be performed in wetland contexts is wide, and again adds to the intimate level of detail that can gleaned from wetland sites that is frequently not possible in dry contexts.
Preservation is the theme which binds wetland archaeology into a coherent sub-discipline. This makes understanding the conditions of preservation that much more important.
Water preserves organic material by limiting the amount of oxygen available to organisms that would otherwise use that material as a source of energy. It does not, however, restrict all biological activity, and there are organisms that can digest organic material even in very low or zero oxygen environments. But, the organisms that are able to function in these environments do no like acidic conditions, so wherever waterlogged deposits are also somewhat acidic, remarkable preservation occurs.
This makes the presence of sphagnum moss an indicator of good preservation. Sphagnum moss is common throughout the northern hemisphere in wet or boggy ground conditions. It produces a slight acidic waste product through its normal biological functions and as a result the surrounding soil and ground has a lowered pH. In these areas, and the water bodies whose catchments run through them, have exceptional preservation.
As a general rule, wherever waterlogged or submerged conditions have low oxygen, low light and low energy there will be good preservation of organic remains.
28 June - 2 July 2016 WARP 30 Wetland Archaeological Research Programme
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