Separating climatic and possible human impacts in the early Holocene: biotic response around the time of the 8200 cal. yr BP event

Abstract

H. 2006. Separating climatic and possible human impacts in the early Holocene: biotic response around the time of the 8200 cal. yr BP event.ABSTRACT: The early Holocene is characterised by rapid climate change events, which in the North Atlantic region are often associated with changes in thermohaline circulation. Superimposed on this in northwest Europe is localised evidence for human impact on the landscape, although separating climatic and anthropogenic mechanisms for environmental change is often difficult. Biotic and sedimentological evidence from a lacustrine sequence from the Inner Hebrides, Scotland, shows a considerable reduction in inferred local woodland centred upon 8250 cal. yr BP. These data correlate precisely with a distinctive rise in the charcoal:pollen ratio and hence suggest a possible Mesolithic human impact upon the vegetation around this time. A quantitative temperature reconstruction from chironomid analyses from the same sequence, supported by sedimentological data, indicates that the fall in arboreal pollen taxa occurred as climate warmed significantly during the early Holocene. This warming was followed by a significant cold event, with mean July temperatures reduced by 2 C, that lasted for at least 320 years ca. 7790-7470 cal. yr BP. Woodland recovered during this phase suggesting that the vegetation during the 8250 cal. yr BP interval was likely to have been responding to human activity, and not climate, and hence it is possible at specific sites to separate the influence of these key drivers of environmental change.

Early-Holocene temperature variability inferred from chironomid assemblages at Hawes Water, northwest England

“…Similar temperatures for the EHWP are recorded in the sediments of Little Hawes Water (Lang et al, 2010), a carbonate lake in the same catchment as Hawes Water, and at Urswick Tarn (Lang et al, 2009), another coastal carbonate lake within northwest England. C-IT from the Inner Hebrides, Scotland (Edwards et al, 2007) is substantially lower for this period (~12.5°C). Cooler temperatures would be expected because of the more northerly position of the Inner Hebrides in relation to Hawes Water, however as there is only one data point for the Inner Hebrides site during this period it is not possible to compare trends or identify an EHWP.…”

The Chironomidae of Gróthúsvatn, Sandoy, Faroe Islands: climatic and lake-phosphorus reconstructions, and the impact of human settlement

“…Changes in trophic status can also be evaluated using a chironomid-inferred total phosphorus (TP) model . It has also been shown that subfossil chironomid assemblages can be useful indicators of the extent of historical and prehistoric human impacts on lakes (Sayer et al, 1999;Little et al, 2000;Brooks et al, 2001;Heiri and Lötter, 2003), though not always unequivocally (Edwards et al, 2006).…”

Bronze Age upland settlement decline in southwest England: testing the climate change hypothesis

“…Berglund, 2003;Caseldine et al, 2005;Edwards et al, 2007;Finsinger and Tinner, 2006;Magny, 2004;Tinner et al, 2003;Turney et al, 2006;van Geel et al, 1996), including changes in subsistence patterns (Taylor et al, 2000; and catastrophic collapse of society (Haug et al, 2003). Conversely, it has also been argued that the evidence for such changes, in particular the abandonment of upland settlement, is questionable and that past societies would have adapted to changes in the prevailing climate (e.g.…”