Fairy circles and peat bogs: reconstructing ecosystems of the past: Palaeoecology in Environmental Archaeology

By Tim Mighall

Presenting palaeoecological evidence of past human activities from across the globe has been a regular feature of many papers published in Environmental Archaeology. Evidence for human-environment interactions, utilising both on-site records (e.g. from settlements) and off site records (such as peat bogs, lake sediments and dryland soils) has been published throughout the journal’s history. The majority of studies are multi proxy, using a variety of microfossil and macrofossils including pollen, non-pollen palynomorphs, beetles and mollusca. Whilst the palaeoecological contributions in EA are temporally diverse, stretching from the Mesolithic to the medieval period, there has been numerous papers which have focused on the Norse. As a result, publications with a strong palaeoecological emphasis are slightly skewed towards the North Atlantic region but there are many other interesting contributions from elsewhere in Europe, including the UK, Spain, Scandinavia, The Netherlands, as well as the occasional contribution from the Southern Hemisphere.

ENV006FairyCirclesProxies such as pollen have been used to reconstruct environmental changes associated with specific archaeological sites or features on a local spatial scale. For example, in EA 6 a palaeoecological evaluation of fairy circles was successfully completed by Prøsch-Danielsen (2001). Fairy circles are a group of mysterious earthworks restricted to the coastal heathlands of SW Norway (Figure A, left). They are believed to be the result of a specialised farming practice. Their form comprises an enclosure defined by a bank with an oval or rectangular ditch in loose deposits.  A palynological-based study revealed that the fairy circles were probably used as bases for haystacks. Fairy circles may date back to the Late Iron Age and been in use up until c. AD 1835. As well as helping to establish the function of an archaeological feature, microfossil analysis can also refine our biogeographical history of plants. Gelorini and Bourgeois (2005) report the first find of black mulberry (Morus nigra L.) pollen in a Late Bronze Age at Sint-Gillis-Waas/Kluizemolen in Belgium (Figure B, below right). Although no macrofossils have been discovered as yet, the results of this study may imply the tree was grown locally and much earlier than previously thought. In neighbouring countries, macrobotanical remains are only known as Roman introductions. Now largely an ornamental tree, the Romans used the berries of black mulberry to make sweet wine, called Moretum.

ENV010pollenRecords reconstructed from other archives such as peat bogs offer insights to environmental changes at the regional scale, particularly when more traditional forms of archaeological evidence are used in combination with palaeoecological reconstructions. Examples include a spatial study of upland vegetation change in the Aber valley, Snowdonia. Here Woodbridge et al. (2012) reconstructed vegetation changes from five sites across an altitudinal gradient. They showed that pastoral land use varied with altitude and highlighted the value of developing fine spatial sampling strategies to reconstruct small-scale vegetation changes which is not possible to observe when presenting pollen data from a single core.  On a much larger scale, Blanco-Gonzalez & López Sáez (2013) present a regional synthesis of the history of human activities in the Duero Basin in central Iberia. Their examination of both archaeological and palynological evidence (both non-pollen palynomorph and pollen data), enabled them to piece together a story of occupation in this mountainous area. A lake-basin approach was used by Prøsch-Danielsen and Sandgren (2003) to reconstruct human impact associated with a series of archaeological features/sites ranging from the Mesolithic to the medieval age. The power of palynology and complementary proxies to detect weak signals of agrarian activity is demonstrated in this study and these traces predate the known archaeological record. While most of the palynological studies focus on wider landscape changes associated with agriculture and deforestation, Mighall et al. (2004) used pollen and geochemical records to reconstruct evidence of past pollution associated with metal mining in the northern Pennine Orefield and reconstruct the impact of mining/metallurgy on vegetation. In one of the first papers to combine biological and geochemical proxies, they showed that metal mining had little impact on woodland until medieval times as lead pollution recorded in the peat bogs correlates with the growth of lead mining from the eleventh century AD onwards. The absence of a well defined Roman lead pollution signal is intriguing.

EA also has been an outlet for more methodological-based research. For example, in EA 4 Davies (1999) analysed the total molluscan assemblages across a woodland-grassland boundary, noting the respond of species to such an important boundary change is not always consistent with the vegetation structure. The results clearly have implications for how we interpret our fossil records. Julie Jones and colleagues developed a methodology to assess the state of preservation of pollen and plant macrofossil remains in peat deposits at risk from extraction and wastage. This approach may be useful for assessing the potential of a deposit to provide a representative palaeoenvironmental reconstruction before undertaking full analyses (Jones et al. 2007). Similarly, Horrocks et al. (2002) evaluated the presence of wetland microfossils, including pollen and diatoms, in dryland agricultural soils in Polynesian stone mounds at a site in northern New Zealand. They suggest that the presence of the microfossils can be used in an archaeological context to infer land use although understanding the depositional history of microfossils in such soils is problematic. Sageidet (2005) also demonstrated the use of such deposits to infer landscape change. In this study, soil pollen analysis was used to reconstruct land occupation phases and land use changes between 4500 and 2300 uncalibrated 14C years BP through a clearance cairn field at Orstad, Jæren in SW Norway.

ENV015norsesettlementOf course it is increasingly rare for a palaeoecological study to be undertaken using a single proxy. Multi proxy studies are now ‘the norm’ as new and novel methods have been developed and combine with more traditional proxies to increase our understanding of the relationship between humans and their landscape.  One notable region that demonstrates the contribution of palaeoecological studies to understand past human-environment interactions has been the North Atlantic region, in particular focussing on the Norse settlers of Orkney, Shetland, Iceland, and Greenland. These contributions to EA include thematic, site-specific and regional landscape studies. Indeed, a co-authored paper, lead by Tom Amorosi, was published in volume 1 of Environmental Archaeology back in 1998. This contribution discusses the politics and palaeoecology of animal fodder based on evidence accrued from animal bones, plant macrofossils, invertebrate fauna as well as pollen. Additional dimensions to this research include the use of tephrochronology by Andrew Dugmore et al. (2000) to date more firmly the timing of the first human impacts on the Icelandic environment with the Norse colonisation (known as Landnám) during the ninth century AD.  New studies published in the journal continue to provide new insights about the nature of farming on the North Atlantic islands: Sveinbjarnardóttir et al. (2007) used multiple proxies (pollen, plant macrofossils, soil micromorphology and insects) to place a high status Icelandic farm into its environmental context.  One feature of the high status farm is the cultivation of barley which was found in the pollen record. Interestingly, there was no apparent link between the growing of barley and climate, suggesting that other factors such as soil fertility, imports and labour availability were more influential. Other settlement types have also been investigated. Vickers & Sveinbjarnardóttir (2013) presented new evidence from a subfossil insect assemblage from a shieling site on Iceland. Their results suggest that synanthropic insects, previously assumed to be absent from such sites, may be preserved in shieling deposits.  Their presence has important implications for the use of insect remains to identify seasonal activities at such sites. The aftermath of the Norse period seems to have had little long term impact on the beetle fauna. Post Norse deposits at Sandhavn, a farm located within the Eastern settlement (Figure C, top left), revealed an assemblage more typical of the natural fauna (Vickers & Panagiokopulu, 2011). Such a targeted set of multi proxy investigations demonstrate the value of palaeoecological research. Research of this kind continues to reveal new insights about human-environmental interactions and to place the archaeology into its environmental context.

Figure A: Photo of a fairy circle (Volume 6, 2001)
Figure B: Fossil pollen grain of Morus nigra L. – black mulberry. (Volume 10, 2005)
Figure C: Norse farm at Sandhavn, Eastern Settlement, Greenland. Photo: J.E. Schofield (Volume 15, 2011)