Archives in the sands: using cultural and environmental records to manage future climate change in the Western Isles

Projections of future climate change include increases in sea-level, storminess, and coastal erosion. One area at risk (identified by the Scottish Environment Protection Agency - SEPA) is the Western Isles, Scotland. This highly dynamic environment, including the fertile and rare grassland known as ’machair’, is subject to both erosion and deposition resulting in significant change, including up to 50m of erosion recorded along certain portions of the coast in a single storm. This trend of large coastal change is expected to continue and assets within the study area likely to be affected include roads, farmland and farm infrastructure. Change will also cause damage and destruction to some known archaeological sites and will result in the exposure of other significant, currently buried, sites.

The overall aim of the PhD is to identify methods to help predict and mitigate the effects of future climate change on the fragile machair landscapes of the Western Isles using the cultural and environmental records of past coastal environments. This will involve identifying the main drivers that, when combined, can cause catastrophic coastal change, utilising archaeological data available from three study sites to provide a ‘long view’, in order to prioritise action plans for the conservation of vulnerable areas.

The Hambrecht et al. (2018) concept of Distributed Observing Networks of the Past (DONOP) will be adopted. A DONOP is a spatially distributed group of archaeological sites that together provide archives of human-environment interactions over long time-scales. The archaeological sites on the Western Isles form just such an archive, where it is possible to relate human behaviours and environmental changes within the relatively high temporal resolutions of dynamic environments.

The student will collate and analyse the environmental and archaeological studies completed by SCAPE and others in the Western Isles. Three locations adjacent to the low-lying machair landscapes of Uist and Benebecula (Baile Sear, Paible and Lioncleat) have already partially investigated by SCAPE and will be further studied in the field. The landscapes are characterised by the presence of intertidal peats and extensive eroding archaeological structures and deposits exposed at the coast edge. For example, Baile Sear is a tidal island with a sand dune and machair coast edge that has experienced significant coastal erosion with evidence of Bronze Age to Norse occupation, including Iron Age wheelhouses and associated middens. SCAPE’s work within the intertidal zone has led to C14 and OSL chronologies being developed and key layers containing environmental evidence identified. Deposits remain in the coastal sections and intertidal zone, and the previous work will can act as a springboard to assist the student develop their own targeted research.

At each of the three sites, the student will sample the sediments within and near to the surviving archaeological deposits. They will mould the project around their skills and interests by developing and applying a variety of methods - such as particle size analysis to understand changing sediment dynamics, pollen and charcoal to establish vegetation changes and human land use, and radiocarbon and optically stimulated luminescence dating to establish chronologies.

The student will develop a record of the changing coastal environment and human land use based on the data from the case studies. The integration of the archaeological and environmental datasets will elucidate drivers of coastal changes that could be applied widely to coastal environments and contribute to the DONOP approach. Finally, the student will integrate the DONOP data with relevant climate change projections to produce predictive maps of how the study areas might be affected by and respond to future climate change impacts.

The project aligns with increasing recognition that archaeological sites are archives that contain evidence of past change and adaptation. The sites in the Western Isles are ideal to test and expand this approach. The methodology and outcomes will be of relevance to other coastal areas across the globe facing similar issues. The project will also involve creating 3D models of the coast edge (either from pole-mounted cameras or drones), and these will be of use both to heritage managers (such as the Local Authority archaeologist) and to coastal geomorphologists working on the Dynamic Coast Project for the Scottish Government.