In general, the evidence suggests that by about 2500 BC, most sites show some sign of human activity that affected woodland cover, but its nature, duration and impact vary within the Highlands. By about 2000 BC, the reduced extent of woodland is seemingly correlated with an intensification of agriculture. While this is a general pattern through much of Scotland (Tipping 1994), we do not know whether it applies equally throughout the Highland Region.
For instance, archaeologists know that between 3000 BC and 2000 BC, Scots Pine extended in range out from a mostly eastern and southern territory to the north and west before disappearing almost entirely north of the Great Glen over the course of c 2000-1800 BC (Tipping 1994, 25). Does this pattern repeat in each firth and glen, and what did such an apparent major environmental change signify for the local human population?
The excavations at Lairg (McCullagh and Tipping 1998) provided a detailed long chronology for the Chalcolithic and Bronze Age sequence. This showed that, against a regional backdrop of wetter conditions, increasing soil acidity and the loss of pine woodland during the earlier Bronze Age, the scrub woodlands were held in check by increased grazing. Locally there is also physical evidence for tillage from the 2nd millennium BC, though it is less clear whether the tilling was episodic, occurred in short bursts or continuous over a millennium. The pollen record does not detect the apparent abandonment of dwellings and fields around 1000 BC that has been suggested by archaeology. Instead, pollen records show a landscape strongly influenced by agriculture and probably focussed on animal husbandry but with an element of woodland management; there is no decline in this system of land use until about 200 BC (Smith 1998, 199).
Elsewhere in the Highland Region, a Bronze Age regeneration of woodland has been identified at Suisgill in Helmsdale, Sutherland (Andrews et al 1985), and the Garbh catchment area near Golspie in Sutherland (Tipping et al 2008a; Case Study Environmental Investigations at Garbh Allt catchment). At Suisgill there was decline in woodland during the late Neolithic, which has been interpreted as small-scale clearance, but this was followed by a period of woodland regeneration after about 1650 BC, which continued into the Iron Age with a brief set back in c 650 BC (Tipping 1994, 25).
The multi-disciplinary study at Loch Farlary is a good example of how a series of short-lived events can be teased out using cores with good dating. Two phases of pine decline were identified, the first in the late Mesolithic. After recolonisation in the Middle to late Neolithic, there was another gradual decline of pine in the Middle Bronze Age. It became extinct in the Late Bronze Age, probably due to grazing pressures (Tipping et al 2008a; 2008b; Case Study Environmental Investigations at Garbh Allt catchment). The story may be different for some other places in the Highlands. For example, at Loch Sionascaig in Wester Ross, a sharp decline was interpreted at around 2550 BC (Birks 1993), though sampling intervals and limited dating may mask the picture.
Recent excavations near Inverness are gradually improving the understanding of woodland cover in the Bronze Age. At the Bronze Age cemetery at Seafield West (MHG3944; Case Study Bronze Age Cemetery at Seafield West), the charcoal analysis showed a wide range of species nearby. Hazel and birch dominated, but oak, cherry, alder, pine and apple were also evident. There were two wooden coffins, one plank-built and the other a hollowed-out tree trunk, but the wooden remains were too poorly preserved to identify the species (Cressey and Sheridan 2003, 72–3). Charcoal from burnt mounds offer great potential for analysis of woodland use and possible management. Nearby pollen and charcoal at Beechwood, showed a similar picture; this burnt mound had a wooden trough, made from oak planks (Cressey and Strachan 2003). More detailed, dated multiperiod sampling is needed.
The situation to the south of the Great Glen shows a different and complex pattern. Wood pollen has been investigated at Loch a’Chnuic, Loch Garten, Loch Pityoulish and Loch Einich, all of which have revealed slightly different pictures of woodland clearance and recolonisation (Tipping 1994, 26).
At Loch Cleat, Trotternish, on Skye, sustained clearance occurred in the Early Bronze Age around 2200 BC, perhaps due to more intensive cultivation on the more fertile soils, and by the end of the Bronze Age, the area was virtually treeless (Tipping 1994, 27–8). At the Middle to Late Bronze Age settlement at Home Farm (Kiltaraglen), Portree, Skye, charcoal finds from all periods were dominated by alder, birch and hazel, similar to other sites on Skye such as High Pasture Cave (MHG32043; Case Study High Pasture Cave). The regular size of the roundwood at Home Farm (MHG51648) suggests that some coppicing techniques were used and therefore that there was some form of woodland management (Hastie 2013, 50–1).
On Rum early agricultural activity during the late Neolithic from around 2950 BC was followed by continuing woodland decline in the Early Bronze Age. Near Mallaig, survey suggested small scale periods of woodland decline between 2600 and 1600 BC and sustained clearance in the Late Bronze Age (Tipping 1994, 28).
Unlike with pine, there was no obvious sharp decline in the birch/hazel/oak woodlands of northern and western Scotland during the Bronze Age. While there was a gradual decline, it appears that much of the woodland survived in this period. The reasons have been debated, with human activity, grazing pressure, exposure, blanket peat spread, and soil deterioration all being proposed. (ScARF Chalcolithic and Bronze Age section 3.2).
Most modern excavations of domestic contexts, burnt mounds and some funerary sites, produce charcoal which represents how woodlands were exploited as the source for fuel and, possibly, building material. At Lairg, as at many other sites, it was the alder, birch and hazel portion of the local woodland that bore the brunt of Bronze Age exploitation. This is perhaps no surprise as these species grow quickly, produce long poles and are relatively easily cut down compared to oak or pine.
These same three species occurred in the charcoal-rich sediments of the circular House 4 at Lairg, in what was interpreted as a conflagration deposit (McCullagh and Tipping 1998). House 4 measured over 10m in diameter, and it would have required the use of long poles to reach from the wall to the apex of the conical roof. Even if this span was achieved by lashing shorter poles together, this ubiquitous style of building required a ready supply of load-bearing poles and fibrous material to bind them together. These materials would have been gathered in a single felling, and the relationship between these events and their reiterations through the lifespan of the buildings are not detected by pollen analysis. This is an overlooked element of the Bronze Age environmental record.
Other insights come from the Clava Cairns (MHG3013; MHG3002; MHG4366) outside Inverness (Case Study Clava Type Cairns). Here the soil profiles below the cairns show evidence for burnt hazel. This suggests that hazel was used in the funeral pyres and pollen suggests that the trees were probably felled when the hazel was in bloom in early spring. A well-preserved sequence under the central ring cairn suggested that some time before the cairn was built, the area was scrub or woodland made up of primarily hazel and also some birch. Periodic clearances are indicated by analysis, perhaps for small scale cultivation, as the soils became nutrient poor and heathland developed. Before the central cairn was built, the vegetation was burnt off, but the ground was allowed to become grassy before building. This evidence for burning before construction also appears at the northeast cairn. Pine, lime and elm are also present in very low quantities, suggesting they may have been transported to the site (Hoaen 2000).
Taken together, the evidence shows a complex picture with regional and local variations. As noted in Chapter 3, this is also a picture with gaps, and additional well-dated sites and sampling, together with the integration of evidence from recent excavations, are needed to fill in the gaps. The problem remains that amid the evidence for seemingly contemporary events, discriminating between cause, effect and coincidence, continues to be highly challenging.