Neolithic Land-Use and Environmental Degradation: A Study from the Western Isles of Scotland

Article excerpt

Introduction

The remarkable survival of partially waterlogged remains of a Neolithic settlement on an islet (Eilean Domhnuill) in Loch Olabhat, North Uist, Scotland, has allowed an integrated study of the inhabitants' exploitation of their environment. This paper highlights important evidence for potentially damaging subsistence strategies in the Hebridean Neolithic. The investigation included a programme of excavation on the islet itself and an environmental core taken from the sediments in the lake. On-site, environmental evidence was extracted from samples taken through a series of well-stratified sediments, including floor and hearth deposits. Micromorphology was applied to targeted samples taken through these occupation layers to inform questions of sediment formation processes.

The local environment

Eilean Domhnuill lies in freshwater Loch Olabhat (OS NGR: NF 7468 7532), in the northwest corner of North Uist, an island situated off the north-west coast of Scotland (Figure 2). Pollen from a core from Loch Olabhat indicates that in the later Mesolithic local woodland consisted predominantly of hazel and birch (Mulder 1999; Mulder & Edwards forthcoming). The estimated period 5150-4660 uncal. BP (c. 4000 to 3300 cal BC) begins with a reduction in arboreal pollen values. The range of the radiocarbon determinations could easily place the start of this event close to the beginning of the conventional Neolithic at around 5000 uncal. BP. However, during the period between about 4000 and 3300 cal. BC, arboreal pollen values, while reduced, still indicate some local woodland. These values decrease in stages with intermittent regeneration and, after a break in the record, have fallen substantially by the first millennium AD. Heather and Sphagnum increase at about 5150 uncal BP (c. 40003800 cal BC), which may indicate the spread of blanket peat. Cereal-type pollen in the Neolithic levels indicates probable cultivation in the area (cf. Table 1, Levels 9-5).

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Acceleration of mineral substrate erosion is evident in the core at c. 4830 uncal BP (c. 3700-3500 cal BC), when the curves for organic content and total arboreal pollen decline sharply. Above this, a change in sediment, from gyttja to silty clay, occurs from c. 4740 uncal BP (c. 3600-3400 cal BC). Such changes are inferred to represent the removal of woodland and the sheet-wash or rill erosion of sub-surface mineral soil strata. The latter are no longer being protected by a sufficiently cohesive vegetational cover as land utilisation, in terms of areal extent or intensity, continues to have an impact (Mulder & Edwards forthcoming).

Above this, from around 4660 uncal BP (c. 3500-3300 cal BC), the silty clay deposits become largely sterile. These deposits probably accumulated over some 2900 [sup.14]C years (c. 4660-1760 uncal BP, c. 3600 cal BC to 400 cal AD). This would mean that for about four millennia calendar years, there is no off-site palaeoenvironmental record beyond that indicative of prolonged erosion within the catchment. If this was a continuous event (the possibility of one or more hiatuses in the record cannot be precluded), then it may be that land use had intensified and/or catchment soils had been pushed beyond a threshold of erosional sensitivity (c.f. Edwards & Whittington 2001). There is insufficient evidence to indicate changes in sediment fluxes to the loch, or accumulation rates within it, during this period.

The settlement

Neolithic activity on the site generally focused on a single building, although multiple episodes of demolition and rebuilding created an almost tell-like accumulation of superimposed floors and hearth mounds (Armit 1992 & in prep). The buildings were small and generally rectilinear with rounded ends (Figure 4). They were usually defined by boulder foundations which would have supported turf or earthen superstructures. Preservation of individual structures was poor, but a composite picture has been developed from the numerous house fragments excavated. …