Читать книгу Natural History in the Highlands and Islands - F. Darling Fraser - Страница 13

The northern end of Drum Albyn and its coasts becomes definitely a harder country north of Loch Carron than the West Highland Atlantic zone. The large island of Skye, set athwart the Minch, has an undoubted effect of checking the flow of warm water of the North Atlantic Drift. The coasts of the North-West have several long sea lochs, but the coast as a whole is tighter-knit than the islands and coasts of the Atlantic zone which fans out from the Firth of Lorne into the Atlantic Ocean.

The rocks of the northern zone on the western side are mostly very hard, and poor in such minerals as make good soil; they are Lewisian gneiss, Torridonian sandstone and quartzite; these three have little either of calcium or of fine particles which will become clay and contribute to the soil picture. Furthermore, where the bed rock itself is not showing through (and often it is over 50 per cent of the landscape) the ground is covered with peat which has no bottom of shell sand or clay which, on disintegration or removal of the peat, might become productive soil. Sand dunes occur on the coast at only a few places such as Gairloch, Gruinard Bay, Achnahaird on the north coast of the Coigach peninsula, across Rhu Stoer and at Achmelvich, and at Sandwood Bay a few miles south of Cape Wrath. None of these are of shell sand.

It is a hard, rocky coast to which a multitude of short, rapid rivers run from Drum Albyn—the Laxford from Loch Stack and Loch Mor into Loch Laxford; the Inver from Loch Assynt into Enard Bay; the Kirkaig out of the lochs below Suilven; the Polly, the Kannaird, the Broom and the Dundonnell Rivers; the superb Gruinard River which is only six miles long on its run from Loch na Sheallag; the Little Gruinard, even shorter, coming from the Fionn Loch which is one of the most famous trout lochs in the North; and the River Ewe, only two miles long after it leaves Loch Maree, but very broad; the Kerry River running into Gairloch, famed for its pearls; and the Applecross River which drains much of the peninsula of that name. Most of these rivers are noted for salmon and sea trout, though some are curiously poor. As things stand at the moment the rivers of this region, so variable in their flow from day to day, make up in economic value for the poverty of the land for agricultural and pastoral purposes and for general lack of timber.

The boreal or sub-arctic affinities of the northern zone are most marked on the two geological formations already named, the gneiss and the sandstone. Each rock has its very distinctive form and each contributes to what is probably the wildest scenery in Scotland except for the small area of the Cuillin Hills of Skye (Plate IIIa). But here in the interplay of gneiss, sandstone and quartzite the naturalist may walk for a week or more and see no human habitation other than an occasional stalker’s cottage. So rough and wild is the country that habitations unconnected with sport are difficult to find away from the sea’s edge. The outcrop of limestone in the Assynt district allows the exception of the crofting townships of Elphin and Cnockan to which allusion was made in the first chapter.

The Lewisian gneiss of the mainland rises to greater heights in the general run of the country than it does in the Hebrides, except in Harris and at one place in South Uist. Also, it is not hidden under such a blanket of peat as in Lewis. The gneiss country of Sutherland and Ross is one of a myriad little hills of great steepness, with little glens running hither and thither among them. The lochans are seemingly countless and most of them have a floor of peat. The gneiss hills themselves are like rock buns, looking as if they had risen in some giant oven and set into their rough shapes. This ground holds up the water in pockets in the rock and allows the formation of cotton sedge bogs and such very shallow lochans as grow water lobelia and water lilies. When these lochans are near the sea and grow reeds the bird life is rich. Greenshanks (Plate XIIb) are common in the gneiss country—say one pair to 3,000 acres, which is quite twice as many as may be found on the adjoining Torridonian sandstone. Heather (Calluna) is not common on the gneiss; the complex is one of dwarf willow, sedge and poor grasses. Also, this type of vegetation does not appreciably alter in the altitudinal range of the gneiss. For example, I could find no major difference in sample patches in the Gruinard Forest at the foot of Carn nam Buailtean at 600 feet, and at the top of Creag Mheall Mor in the Fisherfield Forest at over 2,000 feet. The hills maintain over all their mottled pattern of green and grey, and when the snow is on the tops there is never the distinctive line at about 1,750 feet which is commonly seen on the Torridonian formation.

The gneiss is difficult country to walk through: by keeping to the little glens it is impossible to steer a straight course for any distance and no one would attempt to go in a straight line over the hills. On the upper gneiss country where many detours are necessary round rock faces and soft spots, a speed of one mile an hour is quite good going. It is also quite easy to lose one’s self, for these little round hills are all very much alike.

The crofting townships on the gneiss are strictly coastal. Their arable grounds (Plate 7b) are usually tiny patches of an acre or less in the hollows or in the less steep faces of the rocks. Loch Laxford, a sea loch, shows some typical low gneiss country with crofts at Foindlemore and Fanagmore.

The gneiss tends to get higher the farther it goes inland. A’ Mhaighdean (the maiden) reaches 2,850 feet above the Dubh Loch in Ross, 10–12 miles from the sea as the crow flies. It forms a high cliff face on this hill of exceptional grandeur, a rare thing for the formation on the mainland. Its sea cliffs are nowhere impressive here because they are never sheer or higher than a couple of hundred feet. Even the Torridonian, a formation which one might expect to make magnificent cliffs, does not provide these in any quantity at the sea’s edge. The island of Handa, near Scourie and opposite Fanagmore at the mouth of Loch Laxford, is a splendid exception. The Torridonian rock is stratified horizontally, so the vertical breaks make nesting ledges for sea birds such as guillemots, razorbills and kittiwakes. There are sheer cliffs of nearly 400 feet on Handa, and in the little screes of earth among these, now covered with fescue and scurvy grass, there are large colonies of puffins and fulmar petrels. The white-tailed sea eagle nested on Handa until the second half of the 19th century. Handa is one of the few places on the Torridonian sandstone which provide true sea-bird cliffs. No other place on the formation can compare with it for numbers of auks, except perhaps Clo Mor, about four miles east of Cape Wrath, where there is a cliff of over 800 feet.

The splendour of the Torridonian is in the peaks it makes inland. Some are fantastic and others superb. There is only one Suilven and it is undoubtedly the most fantastic hill in Scotland (Plate 3b). It rises to 2,309 feet out of a rough sea of low gneiss. Seen from north and south it has a distinctive shape of a very steep frontal cliff and rounded top called Casteal Liath (the grey castle), then a dip and a lesser knob before a more gentle slope down to the east. But when seen from west or east the extreme thinness of the hill is apparent. Probably the Dolomites would be the nearest place where such an extraordinary shape of a hill could be seen. Suilven means the pillar which is a good name for the hill seen from the west. It is often likened to a sugar loaf, also. There are greyish-white quartzite boulders sprinkled on the top, yet there is a little alp of grass up there and an occasional bed of Rhacomitrium moss. The great terraces of Caisteal Liath itself are but thinly marked by such grasses and sedges as Festuca ovina forma vivipara and Luzula spicata as can send their roots far into the cracks.

One of the striking things about the Torridonian peaks of the far north-west is their isolation, caused by the vast denudation which has taken place, leaving these few hard cores of sedimentary rock overlying the wilderness of gneiss hillocks and innumerable lochans. The term hard core is here being used metaphorically and not geologically. North of Suilven and Loch Assynt is the massif of Quinag, five conical peaks capped with quartzite, with a fine rampart of cliff and scree on the west side, which is nearly three miles long. The massif is no higher than 2,653 feet, but how much more impressive is it than half a hundred three-thousand-footers in the Central Highlands! South of Suilven there is Cul Mor, 2,786 feet, surrounded on three sides by great precipices; and Stac Polly, 2,009 feet (Plate 4b and Plate 10) the narrow ridge of which is like one of those fairy castles of childhood tales perched on the top of steep slopes. Ben More Coigach rises to over 2,000 feet in under a mile from the sea as the crow flies. The air of this countryside with its lower rainfall is generally much clearer than farther south in the Highlands and adds to that sub-arctic quality which characterizes the area.

Before leaving this far northern corner, the ranges of Foinaven, 2,980 feet, and of Ben More Assynt, 3,273 feet, must be mentioned. The group culminating in Foinaven is without doubt the barest range in Scotland, and composed of that unyielding white rock, the Cambrian quartzite. The northern part is like a giant E, the crossbars being ridges peppered heavily with boulders which form screes again below the shoulders: the hollows of the E are fine corries on the slopes of which the snow bunting has bred. The southern part is a horseshoeshaped ridge of which Ben Arkle, 2,580 feet, is the western rampart. This hill of Cambrian quartzite with its banding of white scree may be viewed to perfection from the highroad on the shores of Loch Stack; but for the greatest glory of this range a six-mile trek must be made to reach the vast horseshoe corrie and Loch an Easain Uaine, the loch of the green falls. It is well to rest here awhile and realize that the pine marten is probably commoner in this neighbourhood than anywhere else in Britain, to remember the snow bunting up in the tumble of boulders and possibly see him feeding on the buds of Saxifraga oppositifolia. The alpine species of plant creep far down these bare hillsides and one wonders what there is here to recompense the deer for the energy used in attempting to graze these slopes. The boreal affinity of this range was further emphasized by the occurrence of alpine butterwort (Pinguicula alpina), which was found nowhere else in Britain but on the high tops of Sutherland and Ross; unfortunately this species may now be quite extinct, as it has not been found since 1900, according to Druce’s Comital Flora. The same authority puts 1794 as the last date on which this plant was found in Skye.

Ben More Assynt itself is a solid quartzite cap with igneous intrusions set upon a mass of Lewisian gneiss. There has been a series of geological overthrusts in the region, in which tumults areas of limestone have come to the surface. This limestone has affected the natural history of the whole region, causing a wealth of crustacean and other aquatic life on the waters affected by the limestone, differences in the temperature of the water of some streams which suddenly rise from the rock, allowing the formation of water-worn caves in which have gathered soil and bones of animals of earlier times. Such organic remains are rare in the Northern Highlands.

The comparatively low ground of all this northern region of the gneiss, so difficult of access and so plentifully strewn with lochs, is also a place where sub-arctic birch scrub (Plate IV) is common and there is a certain amount of hazel. There are large stretches of birch in Inverpolly Forest (Plate 4b) in the vicinity of Loch Sionnascaig, which is one of the most beautiful lochs in the whole Highlands. There are pristine birch-wooded islands in the loch where the grey lag goose bred not so long ago and where the pintail duck has bred recently. There is more birch round Lochinver and below the north face of Quinag, and many a stretch may be found on the hill far from the roads, in places which are almost unknown to the naturalist. Some day we may find the redwing building in these woods, for this bird has been heard singing here from time to time in April, and the redwing is essentially a native of the sub-arctic birch wood.

The eastern side of the extreme Northern Highlands is given up to extensive sheep-farming. The hills are of no great height and are of easy slope. The herbage is sweet and good. The largest sheep farms in Great Britain are here, some having upwards of 10,000 ewes. The breed kept is the Cheviot of the distinctive lustrous-woolled Sutherland type. The lambs are sold annually at the great sales at Lairg. No man was more responsible for the development of Cheviot sheep-farming in the North than Sir John Sinclair of Ulbster, in the 1790’s. The influence of sheep-farming on the natural history has been profound and will be given special attention in a later chapter.

This far northern area has been treated at some length, because it is the most remote part of the Highlands and one of which detailed studies in natural history have been rare. It may be recommended as an exhilarating and fruitful field for exploration.

South of Loch Broom, the Torridonian hills are more thickly grouped and reach their highest peaks. Their spiry form and the high corries facing to the east are distinctive. The quality of herbage is generally poor and the terraces formed in the lower reaches of the Torridonian hold up the heavy rainfall so that it is often quite impossible to get about dryshod. How different is the nature of the ground from those smooth dry slopes of glacial sand and gravel which are such a marked feature of the Central Highlands! The differences brought about in the vegetational complex have not been sufficiently stressed by plant ecologists in the past. The ground has not been well walked through and explored as yet.

There are two high hills of the Torridonian which have north-eastern corries quite the most magnificent of their kind and few who have seen them both can decide which is the better. This in itself should show how similar are such groups of hills and the forces which moulded them. I allude to An Teallach of Dundonnell (Plate IIIb and Plate 4a), 3,485 feet, and Beinn Eighe, 3,456 feet, between Kinlochewe and Loch Torridon. Each of these hills has three corries facing NNW. to NE. Coire Mhic Fearchair is the most westerly of the corries of Beinn Eighe, and the Toll Lochan corrie of An Teallach is the easterly one of the range. Some of the buttresses in Coire Mhic Fearchair are exceptionally fine and the corrie makes an almost perfect horseshoe, but for myself I think I prefer the Toll Lochan corrie, for the cliff face at the head of the lochan is of greater depth and of superb architecture, nearly 1,800 feet of it.

Between An Teallach and another corried Torridonian peak, Beinn Dearg Mor, 2,934 feet, is the broad amphitheatre known as Strath na Sheallag, at the head of Loch na Sheallag, from which the Gruinard River runs. This strath is beloved of the deer, and though so remote it draws cattle, sheep and ponies to it from far away. Just as An Teallach has Beinn Dearg Mor as an outlier, so has Beinn Eighe her Beinn Dearg, 2,995 feet, almost a replica of its cousin of Strath na Sheallag. Liathach, 3,456 feet, Beinn Alligin, 3,232 feet, and Slioch, 3,217 feet, these are just three more of these splendid Torridonian peaks—clear of peat from 1,750 feet upwards and often topped with a white cap of quartzite boulders. The sudden change from wet peat-laden terraces to the upper slopes of bare rock, or thin covering of brash and alpine vegetation, results in a sharp snow line in winter which gives these hills a special seasonal beauty. This sudden cessation of the peat immediately allows a different flora, one of plants which can withstand droughts and sudden changes of humidity, and which prefer sweeter conditions than are possible on peat. Here and there among the alpine poa grass and viviparous sheep’s fescue are straggling plants of dwarf juniper, clinging close to the rock. Sea pink and thyme are also to be found on the gravel. Eagle, peregrine falcon and wild cat abound in this country, and as it is all deer forest and not grouse moors of any consequence, the eagle is allowed more sanctuary than it has been given farther south and east.

The glens of the Torridonian area of the North are often well wooded. They have been owned by people with a fair (or perhaps unfair!) measure of worldly riches, who have been able to spend a good deal of money on planting for amenity. Take Dundonnell for example, at the head of Little Loch Broom: the loch side is bare of trees and is given up to crofting townships, but soon after the head of the loch is reached one is into a fine wooded glen. There are a few hundred acres of Scots pine of greatly varying density stretching up the southern side to an altitude of 1,000 feet. There are alders, oaks, rowans, and hazels along the river bank, and some hundreds of acres of birch at the head of the glen reaching up to 1,500 feet. But all round the cultivated strath and the house which was built in 1769 there are signs of planting for beauty: limes, many fine beeches, sycamores, ashes, elms, oaks, chestnuts and big old geans; and until a few years ago there were many acres of fine larches on the north side. The wild life of such a glen is obviously profuse and varied. We have these men of a past age to thank for planting that which we now enjoy, just as we may blame those of a century earlier who were denuding the Highlands of timber.

Loch Maree is another place where there are some very fine woods, but here the sub-arctic quality of the northern zone is being lost and replaced by the complex of sub-alpine vegetation. Near where the Ewe River from Loch Maree goes into the sea in Loch Ewe there is a famous garden which grows a great variety of rhododendrons and azaleas and many sub-tropical plants and plants from Oceania. This is just another facet of the Highland paradox, the garden at Inverewe lying between the stark precipices of Ben Airidh Charr and the bare windswept slabs of Greenstone Point where the sea is never still. And if I may add one more touch of paradox, I saw a kingfisher on the rocks at Greenstone Point at the edge of the tide, one September day.