A Palaeoecological approach to understanding the impact of coastal changes in Late Holocene societies using the Isles of Scilly as a case study
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The overall aim of this thesis was to explore the impact of environmental changes (relative sea level increase and climate) on coastal communities and to investigate how these environmental factors controlled subsistence economies through the Holocene. The hypothesis tested was that relative sea level rise is a key factor influencing location and subsistence strategies of coastal communities throughout the Holocene and that, due to environmental conditions, these changes will be more evident in islands. The Isles of Scilly, located 27 miles off the south west coast of England, provide a good case study for the response of communities to marine inundations and environmental changes. This project aimed also to obtain a high resolution record of vegetation and storminess during the last 3000 years in Scilly, with a robust chronological setting, and also to offer an accurate shape of the coastline of Scilly since the early Holocene. Three terrestrial pollen stratigraphic sequences from the Isles of Scilly were obtained, covering the past 3000 years, from the two main wetland areas of Scilly (one in Higher Moors and two in Lower Moors) with the potential to reveal changing patterns of vegetation reflecting intensity and type of land use. Detailed palaeoenvironmental interpretation has been provided by high resolution pollen analysis. These pollen diagrams suggest that the landscape of Scilly has been an open landscape, heavily managed for both pastoral and arable agriculture since the Bronze Age. There is evidence that the climate during the Holocene period was highly varied. The occurrence of blown sand in the sample cores has been used as an indicator of past storm intensity, by high resolution particle size analysis and Loss-On-Ignition. The three cores show dissimilarities in the storminess indicator during the same periods. It is argued that this reflects that sand deposition and transport is highly site specific and controlled by topography, sediment availability, wind directions and vegetation cover. An important part of this thesis was to determine the impact of relative sea level rise in Scilly and the extent of the islands over time. A new sea level curve for Scilly has been generated through GIA (Glacial Isostatic Adjustments) using the Bradley et al (2011) method. Palaeogeography maps were produced applying the sea level curve to a new combined bathymetric and topographic model for Scilly. Scilly separated from the mainland around 11500 cal BP, and the islands obtained their modern configuration around 4000 cal BP. The palaeogeography, palaeoecological and the archaeological records of Scilly show that changes in the coastal configuration and storminess had little apparent influence on society from the 1st millennium AD into medieval times. Both, the archaeological and palaeoenvironmental record, have demonstrated that Scillonian societies had a strong resilience and were able to adapt to environmental changes by diversifying their economic strategies and taking advantage of the new conditions, such as new coastal margins. This adaptability was strong until the development of more complex societies and major land reduction conditions that probably led to a tipping point in resilience. There is no apparent discontinuity in land-use on Scilly during the last 3,000 years, although there have been important social and environmental changes.
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