3.2.1 Climate Change

The indicators of climatic change include pollen, insects, plant microfossils such as sphagnum and fungal spores, and evidence of precipitation; however, interpretation of the evidence is not straightforward, and is often debated (Tipping et al 2012). The general picture in the Highlands is much as elsewhere (ScARF Bronze Age section 3.2), with major deterioration in the Bronze Age and medieval periods, but this gross generalisation blurs regional and other chronological differences, where it seems that episodic and sudden changes often occurred. The evidence for Scotland was reviewed in Tipping et al (2012), with largescale key climatic events summarised. However, it is also clear that even during climatic deterioration settlement continued in many areas despite more difficult conditions, with different adaptations to changing conditions being testament to the resilience of inhabitants (Tipping 1994; Tipping et al 2008b; Dodgshon 2004; Oram forthcoming a).

A number of palaeoclimate studies have been undertaken in the Highlands; for example the flow country of Caithness and Sutherland (Blackford et al 1992); Strath of Kildonan (Charman et al 1995); Abernethy, Strathspey (Birks 2003); West Glen Affric (Davies et al 2004; Tipping et al 2006); Loch Sionascaig, Wester Ross (Birks 1993); Ben Gorm Moss on Skye (Langdon and Barber 2005); northwest Sutherland (Charman et al 2001) and Kentra Moss and Loch Sunart in Lochaber (Ellis and Tallis 2000; Cage and Austin 2010). There were clearly differences in climate impact in different areas in Scotland (Langdon and Barber 2005; Charman et al 2006, 346), again showing the need for local studies. Birks (2003) noted the importance of looking at macrofossil remains alongside pollen data when assessing climate change in northern Scotland amongst other places. The potential of using sphagnum moss to investigate climate variability and its human impacts at Highland sites was highlighted by Ellis and Tallis (2000) and Langdon and Barber (2005). Potential study areas exist throughout the Highlands that would build up local and regional studies.

Coastal heritage sites provide evidence for changes in the position of coastlines and coastal environments though time which may be driven by climate change such as periods of enhanced storminess in the past, and recent sea level rise. They also have great potential as indicators of current and future climate-driven coastal changes. The University of St Andrew’s SCAPE Trust has done research in this area including supporting a network of volunteers to monitor the condition of sites at risk and collecting empirical data about changing coastlines, all of which will aid understanding of how climate change affects coastal processes and the impact upon different coastal environments (https://scapetrust.org/scharp/).

Sand dune accumulation is seen as a product of abrupt climate change rather than sea level fluctuations (RARFA 4.4.2). Studies of sand dune formation have been undertaken in Wester Ross (Wilson 2002) but few other areas in the Highlands.

The impact of volcanic eruptions was considered a factor in climate change, and a number of studies have been undertaken including in the Highlands. Sites in the Highands where tephra was considered as part of the study are spread throughout the region (see Kelly et al 2017, Tipping et al 2008a, Blundell and Barber 2005, Langdon & Barber 2005; Gillie 2003; Charman et al 1995, Blackford et al 1992). Analysis of cores from Altnabreac and Loch Leir, both in the Flow Country between Caithness and Sutherland, revealed tephra layers that appear at about the same times as the decline of pine, with the authors arguing a possible causal link (Blackford et al 1992). Studies at Loch Farlary, also in Sutherland, however showed the decline several hundred years later (Tipping et al 2008a; Case Study Environmental Investigations at Garbh Catchment). Even if linked to the eruption, some authors question how much of a lasting impact occurred as a result of eruptions, for example at Lairg (McCullagh and Tipping 1998, 208–9). Tephra deposits are also not uniform over the region; this is a variability which needs further investigation. Regardless of whether they are a factor in climatic change leading to vegetation differences, when combined with radiocarbon dating, they help provide comparability of environmental cores in different areas (Langdon and Barber 2005; Kelly et al 2017).

While studies can reveal local challenging climatic conditions, the impact on human settlement is not always clear cut. Tipping et al (2012) noted the difficulties linking archaeological evidence of change to environmental evidence, but only in a few places has this been attempted for the Highlands; undoubtedly more work could be done. Examination at sites in Glen Affric showed clear evidence of peat formation before human settlement and climatic deterioration with short-lived but abrupt episodes, but, in general human settlement continued throughout (Davies et al 2004). The landscape investigations at Lairg showed similar resilience (McCullagh and Tipping 1998).

Peat Formation

Peat formation relates to climatic change. The formation of peat had a number of consequences. In some cases, it buried settlement history, reduced tree cover and resources, and affected agricultural and subsistence potential. In many parts of the Highlands it was and still is also a source of fuel for millennia, with peat cutting scars visible in the landscape, and trackways deliberately formed for access to this important source.

Two main types of peat formed in the Highlands: ombrotrophic or raised bogs generally on lowland sites, plains, valleys or basins, fed by precipitation, and blanket peat over large areas (Langdon and Barber 2005). As well as the date peat started forming, it is also important to try and assess rate and spatial development in areas, as has been done at Oliclett, Caithness (Tipping 2008).

The information for the Highlands has not been gathered in one place, but the studies clearly show peat formation occurred across different periods in the region, even on a local level (Langdon and Barber 2005; Tipping 2008; Ratcliffe et al 2018); Tipping (1994, 15) noted that in the Highlands it was essential that chronologies for the spread of blanket peat be generated from individual sites, and not from nearby areas. This variety hinders regional generalisations, especially given the gaps in our records, and emphasises the importance of environmental studies being undertaken near settlements.

Tipping cited Oliclett in Caithness as the site that provides the most detailed understanding of blanket peat development in Scotland; this was a study designed to provide a context for a Mesolithic lithic site which was buried by the peat. A number of paleoenvironmental techniques were employed, providing details from the Mesolithic onwards and showing complete peat cover by the mid Iron Age (Tipping 2008, 2105–17).

These studies have shown the need for numerous radiocarbon dates at sites and the importance of covering different landscape areas within the target site. The long timeframe of peat development cautions against dating a site based on a single radiocarbon date (Tipping 2008, 2019). More data needs to be obtained before researchers can fully consider regional differences and comparisons.

While earlier studies suggested that peat development caused site abandonment, this has been shown not to be the case at a number of Highland situations (Davies et al 2004) and the role of farming communities in promoting or hindering encroaching peat is important to document. For example, at the intensively studied landscape at Lairg, peat formation was relatively late and gradual, and this does not seem to have contributed to the settlement demise (McCullagh and Tipping 1998, 210). Similarly at the Allt Garbh catchment area near Rogart, an upland and lowland site were investigated. While agricultural activity at the upland site of Loch Farlary declined during the climatic deterioration of the Late Bronze Age, human activity is still evidenced (Tipping et al 2008b; Case Study Environmental Investigations at Garbh Catchment).