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Caithness Field Club Bulletin
DUNNET BAY S. S. S. I
- HISTORICAL AND PRESENT DAY ECOLOGY
This extract is taken from a report compiled for and funded by the Nature Conservancy Council. The report considers geomorphological factors within Dunnet Bay and the land immediately behind the dunes, and also the historical land use and current agricultural practises in relation to the present day ecology
Out to sea, the bottom of the bay is sand covered and slopes up gently (5o) to the shore. This gentle slope continues behind the dunes up to the Links. The ground profile across the Links from north-east to south-west is slightly concave with a main drainage channel, the Burn of Midsands, running from the centre, cutting through the dunes, and into the sea.
The topography of the Links undulates between sandy hummocks of variable size and damp hollows. The area of sandy soil reaches Loch Heilen, 3.25km inland. Much of the surrounding land has an acid peaty soil, so by contrast the Links, which are relatively high in calcium and have an alkaline pH, provide a foothold for a quite different type of vegetation.
Most of the Links are uncultivated and used as permanent pasture for sheep and cattle, apart from a small section of forestry. The dune ridge, which rises above 20m at the highest point, is separated from the links by the county road and no cultivation or grazing occurs on this area.
Most soils have developed over a long period of time, since the last glaciation, from the parent rock and organic materials. In contrast, the soils at the back of the dunes are young and have developed in the last few hundred years on top of blown sand.
The soils at Dunnet fall into two main categories, (a) brown calcareous soil which is found on the freely draining areas and sandy hummocks and (b) calcareous ground-water gley found in the damp hollows where drainage is impeded by submerged peat or the underlying rock profile. Part of the Links behind the forest and south of Couperhill (G.R. 235700), has a vegetation dominated by Calluna vulgaris and is undergoing podzolisation (Futty and Dry 1977). The profile is considered to be that of a ground-water gley, a modification of the calcareous ground-water gley found elsewhere.
Other soils found are rudimentary, (a) the skeletal soil of the dunes, consisting of unmodified sand with development of some organic "A" horizon where conditions are stable enough and (b) fossil soil layers - bands of "A" horizon which have formed during successive periods of stability and then been buried under a fresh input of blown sand. Up to three bands of fossil soil can be seen along the Sandy Burn.
Great variation in the depth of overlying sand is found, ranging from 2Om or more in the dune area to just a thin covering in some parts of the links. It seems probable that the site is more stable at present than it has been in the past. There are four active erosion points along the dune ridge, but judging by the slow rate of infill of the roadside ditches, not a great deal of sand is being carried inland. However, the landward side of the dunes has large tussocks of healthy growing marram grass (Ammophila arenaria) which requires a fresh input of sand for vigorous growth (Hope-Simpson and Jefferies 1966) and it is possible that these tussocks are capturing most of the blown sand at present.
Generally there appears to be a decrease in calcium carbonate content with increasing distance from the shore and an increase down the soil profile. These differences are attributed to surface leaching (Futty 1977) and tend to confirm that at present the input of fresh sand and calcium carbonate from the shore is insufficient to balance the leaching effect and that the imbalance becomes greater with increased distance from the shore.
The soils of the links have a basic pH ranging from pH 7.5 - 8.7. In the forest where ploughing has brought peat to the surface, a more acid soil is found of the order of pH 5 .5 (Pizzey 1974).
Forestry Commission analysis showed no abnormal concentration of soluble salts in the soil, although an input from the sea had been expected. It was concluded that rainfall was insufficient to leach these out.
Impeded drainage in the calcareous ground-water gley has been attributed to buried deposits of peat. In the forest it was felt that Calluna growth had been promoted by the exposure of peat deposits during ploughing. Experimental boreholes made by Chicago Bridge surveyors (1972) at the southern end of the dune ridge, cut through a layer of peat under the sand. Peat containing tree branches is exposed on the lower beach between tides and on the northern end of the dune front, a band of peat and wood, approx. 30cm has been revealed by recent erosion,. From this evidence it seems that, in at least some areas of the bay and Links, the pattern of peat growth was similar to surrounding areas prior to being covered with blown sand.
Wind direction is predominantly from the south-east but winds from the north-west are almost co-dominant. Dunnet Bay lies along the north-west to south-east axis and is exposed to winds from both these directions. Ritchie and Mather (1970) conclude that this is one of the reasons for a single dune ridge with a steep landward slope i.e. a proportion of the winds are acting to push the sand backwards to the sea, leaving a ridge in a state of equilibrium between these two opposing forces.
The water-table on the Links is high, coming to the surface in places between the drier hummocks. Water drains freely through the dunes onto the beach keeping most of the sand damp between the tides, apart from a narrow band immediately in front of the dunes. The dampness will play a part in preventing sand blow from the beach onto the dunes, since wet sand will require a higher wind speed to lift it off the ground. (A wind speed of 10m/sec will start to lift small, dry particles of sand.)
Historical lnvolvement of Man with the Dunnet Site
Aerial photographs of the dunes and Links reveal many marks left by man, sites of old buildings, tracks and a road, areas of abandoned cultivation, ditches, stone walls and, more recently, the planting of Dunnet Forest.
The earliest discernible remains of man's activity are the hut circles, cairns and other remnants of prehistoric habitation. The biggest group - the Greenland links complex - lies on the south west border of the forest. None of the sites has undergone a complete archaeological investigation nor has any accurate dating been attempted, so the information available is purely a description of surface features.
The site at Dunnet is complex and may have been inhabited over a long period of time, from the Neolithic farmers through to early Iron-age i.e. 3, 000 BC - 600 BC, but until more archaeological work is done any dating has to be speculative.
Long term effects caused by early farming methods are difficult to assess and on an unstable site such as Dunnet, these areas may have been covered with sand. Locally, the remains of the hut circles do contribute a change to the area by modifying drainage and providing extra shelter for animals.
The Vikings were farming in Caithness between AD 875 - 1230. During this time the weather was markedly warmer and drier and grain was exported to Scandinavia, but apart from place names in the Dunnet area these early settlers have left no mark. Possibly, like the Viking site at Freswick, their homes and land have been covered by sand. As the dunes at Dunnet are currently being eroded, it is possible that in the future habitation layers and middens may be uncovered.
Chronologically, the next obvious sign of man's activity is that of "run-rig" farming (runnel and ridge). This was a farming system which divided arable land into strips, the ridge, with a depression or runnel in between. Each ridge was farmed by a different tenant and although a tenant might have more than one ridge in a field these would not be in adjacent strips.
Fields in Scotland were rarely square and, as further land was taken into cultivation, an irregular network of fields built up, each enclosed by a turf wall. The runnels were usually in a direction to facilitate drainage. One account of the origins of run-rig farming (MacDonald 1875) states that it started . . . . . " in times of incessant feuds as a preservative against one neighbour setting fire to another's field." It also encouraged mutual interest within a community to help fight off any invading enemies. Accounts give the size of a rig as 6 paces wide and 240 paces long.
After the Viking period in Caithness, the weather generally become worse with years of crop failure which continued until the late 16th century. Clan warfare was also rife, so that a system of mutual help and defence brought about by the run-rig system might well have been a necessity.
Latterly run-rig farming became a hindrance to forming development. As there was no guarantee that a tenant would be farming the some strip of land each year there was no incentive to improve the ground.
There are two areas of patterning on the links, visible on both the earliest (1946) and more recent (1975) aerial photographs that could be attributed to run-rig, these are on the Links of Old Tain and by the quarries on Greenland Links. The site on the links of Old Tain is particularly interesting as this area is referred to in the literature as a site where good farmland was spoiled by blowing sand (N.S.A. 1840). The patterning does seem to confirm that the land was once cultivated. It is not clear whether there were any buildings associated with the land, but the fact that the run-rig pattern is still visible suggests only a thin covering of sand and a relatively late date for this particular sand movement. It is possible that the sand input, although not large, was enough to make further cultivation of already marginal land impracticable.
Early descriptions of the dunes and Links all mention blown sand and create a picture of instability. Even at this early date the importance of marram grass for stabilisation was recognised and active planting recommended. The pulling of bent (marram) was prohibited by an act during the reign of George 11 (Pennant 1780), nevertheless marram may have been used as an alternative to rushes for thatching corn-screws and so increasing dune instability.
Apart from human activity and damage, rabbits were probably a much greater destructive force. Rabbits arrived in Scotland in Medieval times and although they may not have reached Caithness until later, they were well established by the time the Rev. Jolly was writing his account of the Parish of Dunnet (O.S.A.S. 1791).. .. "and the sandy ground in the neighbourhood of Dunnet Bay, would make a good warren, if they were preserved. But as they expose the sand to driving, by breaking the ground, the proprietor allows every person to shoot them without restriction".... This pattern of unlimited hunting seems to have continued up until the advent of myxomatosis in 1954. Apart from breaking the surface, the rabbits grazed the vegetation so thoroughly that only at the height of summer was there excess grass for farm animals. Thus from an agricultural point of view the ground was very poor.
The first aerial photographs(1946) of Dunnet Bay show large areas of bare sand in the dunes, locally thought to be due to rabbit damage A set of later photographs (1975) after myxomatosis, show that most of these areas have 'healed' over and marram grass is flourishing.
The flagstone Industry in Castletown started in 1825, and although sand was used to polish the stone, this came from sources other than Dunnet beach. Nevertheless the man behind the flagstone industry - James Traill (1758-1843) did have an effect on the local landscape as owner of the estates of Rattar and Greenland. The farm manager was a Mr. Purves previously employed on the Langwell estate of Sir John Sinclair, the agricultural innovator.
From 1832-1844 work was done on drainage, reclamation, squaring and fencing of fields under the guidance of Mr. Purves. The sheep drains and stone walls which are still in existence on the Links today probably date from this time. It was possibly as sheep grazings, for the newly introduced Cheviot sheep, that the Links could yield the best financial return. One area of slightly better land at West Greenland was walled off separately and may have been utilised differently.
Robert Dick, 19th century amateur botanist, walked the length of Dunnet Bay during his expeditions. Unfortunately the plants in his herbarium tend to be simply labelled "Caithness". Of the few which are specifically given as from the Dunnet area, all are still found today, which tends to imply some vegetational similarity between then and now. Descriptions of a slightly later date confirm this (Crampton 1911, Horne 1907).
In 1879 the county road between Dunnet and Castletown was built. Prior to this the beach was used by traffic, between the two villages. Storms and high tides must have made this route impossible at times. In fact the siting of the road is unfortunate because of the instability of dune systems generally, but also because it spoils the integrity of the dunes and links. The road necessitates dune stabilisation by various means and in the past sand clearance has been needed. Both of these activities will modify the natural development of the site.
During World War II tank traps were placed on the seaward side of the dunes where access might have been possible and it was thought that these reduced erosion of the dune fronts. The tank traps are now gone, but a more permanent reminder of wartime activities exists at the Castletown end of the dune ridge. This was removed to provide sand for building the aerodrome at Thurdistoft. Fresh sand does not seem to have accumulated in this area since the war which suggests a reduced input from the beach in the recent past. There could be a number of factors involved in the change: (a) reduced sand input from the sea on to the beach, (b) reduced exposure of dry sand between tides and (c) changing wind patterns and strength.
The most recent change on the Links has been the planting of Dunnet Forest. This was begun in 1954 and although it was intended to plant 366 hectares only 127 hectares were eventually planted, including 18 hectares of dune. The area planted was reduced because of the high failure rate among the young trees. The forest was regarded as experimental by the Forestry Commission and a large number of different tree species were planted. Failure was attributed to wind damage, the calcareous soil and a high water table. Latterly replanting was stopped because of doubts about the commercial future of the venture. Recently (1985) the forest has been acquired by the Nature Conservancy Council, who intend managing it for the indigenous plant and animal populations. The open areas created by tree failure and the greater diversity of tree species than are normally found In a conifer plantation, help to make this area particularly attractive.