Читать книгу Britain’s Structure and Scenery - L. Stamp Dudley - Страница 7

THE WEALTH of a country’s fauna and flora is not to be measured by numbers of species alone. Its wealth lies rather in variety, and to a naturalist in the British Isles the fascination of the native fauna and flora is in the great variety to be found in a small space. Gilbert White’s immortal Natural History of Selborne is, in essence, the natural history of a single parish of a few square miles. Yet like many another English parish Selborne, at the western end of the Weald in Hampshire near the borders of Surrey and Sussex, embraces within its limited area many distinctly different habitats or environments, each with its characteristic and often contrasted plants and animals. On the one side lie the open, wind-swept chalk downs with their calcareous soils and lime-loving plants, on the other the coarse sands of the Lower Greensand formation with sterile, acid, hungry soils—too “hungry” to attract the farmer and so given over to heathland and woodland of oak, birch and pine—whilst between the two are the Gault vale with its heavy clay soils and the magnificent “foxmould” developed on the Upper Greensand and accounted one of the finest agricultural soils in the whole of Britain. Such contrasts within a single parish or group of parishes are by no means unusual—indeed parish boundaries were often drawn originally so as to include as great a variety as possible of types of land—and they are reflected in the relief or form of the ground, in soils, in the natural vegetation cover and its associated animal life as well as in the way man, though kept within certain limits, has adapted the natural environment to his own ends. Small differences of elevation, slope, aspect and shelter cause purely local variations in the climate giving rise to different “microclimates” in the area, but they are variations sufficient to spell success or failure in many a farming enterprise, just as they permit or prevent the survival of a given species of the wild flora or fauna.

Those who are accustomed to larger spheres are apt to be obsessed with the discovery that it is by no means difficult to travel by road or rail from coast to coast of Britain, from east to west or even from north to south, in a single day. Yet in 25 miles of such a journey may be found a variety of scenery only to be equalled in a journey of ten times that distance in other lands. The kaleidoscopic rapidity with which the British scene changes is well illustrated from our coastline. It has recently been calculated that the coastline of England and Wales alone—the deeply indented and island-fringed coastline of Scotland is much longer in proportion—is some 2751 miles in length. Within that length may be found mud-flats, sand-dunes, shingle beaches, raised beaches and drowned valleys, sheltered bays and stormy headlands, together with cliffs of the most varied types. The cliffs alone range from the crumbling or slippery boulder clay slopes but a few feet high along parts of the east coast to giants rising almost sheer for a thousand feet from the sea below ; in colour and material they range from the dazzling white chalk of the south and east, or the brilliant red of the New Red Sandstone of Torbay, to the majestic greys and ochres of the granite coasts or the forbidding grey and black of some of the slate cliffs. Inland the story is the same. In the Scottish Highlands it is easy to find a dozen square miles not only without a human habitation or track, but also where the foot of man rarely treads and which even scarcely knows the foot of one of his domestic animals. Yet another dozen square miles of a part of the English lowland may be almost as densely peopled as any similar area on the earth’s surface and one where wild nature seems almost to have been eliminated.

England, Wales and Scotland are divided into 85 counties or shires (England 40, Wales 12, Scotland 33) most of which have persisted with few changes of boundary for more than a thousand years. These years have seen vast changes and some of the counties appear to-day anomalous in a modern world—small, sparsely populated, and poor—but, notwithstanding, intensely proud of their history and tradition and jealous of their ancient rights and privileges. Others have become, with vastly increased populations, too unwieldy and have been divided, so that there are now in England 50 Administrative Counties, making a total for Britain, without the Isle of Man, of 95 Administrative Counties, not including the large towns and cities which are County Boroughs having the status of counties. It would be interesting to know how many of the 45,000,000 people of Britain can lay claim to have set foot in each of the 95 counties. There are whole counties so far off the beaten track that not a man in a thousand has visited them or knows anything of the conditions of life in them, often so greatly different from his home area. How many, for example, know the Shetlands where the midwinter sun at noon does not rise more than six degrees above the horizon but where it is possible to read at midnight in summer without artificial light? If one liked to make the test more severe and ask how many of the 45,000,000 have visited every one of the inhabited islands which make up the British Isles it is most probable that the answer would be—none.

All this is intended to suggest the remoteness, the inaccessibility and the generally unknown character of so many parts of what, if one is content to think merely in terms of square miles and average density of population, is a small and very densely peopled country. So much of it is, indeed, a terra incognita even to the well-travelled minority. To the new naturalist there is much to be explored. It may be that to find a new species of plant or animal not yet described would be an event of unlikely occurrence, but there are many areas where the vegetation has never been mapped or described, where the changing balance of plant and animal life is waiting to be observed and recorded for the first time and where the explanation of observed changes is still a matter of guesswork. Some of the unexplained features are matters of the highest economic importance—the changing character of hill pastures, the new plant relationships created by afforestation and the introduction of foreign trees are some that spring to mind—and all are pregnant with possible scientific results.

Such are the opportunities awaiting the field observer. He has in his homeland what is in many respects a museum model illustrating the evolution of the world as a whole. For the great variety of environments is the outward and visible reflection of a long and complex geological history. Each of the great ages in the earth’s evolution has left its mark on these islands; rocks laid down in all the great periods of geological time are to be found represented in the British Isles.

It thus becomes the purpose of this book to trace the geological evolution of our homeland—to trace, step by step, the building of the British Isles. By this means we are able to understand the structure or the build of its contrasted regions. We are, in fact, attempting to understand the structure and the development of the stage upon which the drama of British natural history is played. In studying the broader aspects we need to consider the British Isles as a whole but, since so many of the books in this series consider primarily the island of Britain—that is England, Wales and Scotland—with its associated smaller islands, we shall consider in more detail and draw most of our examples from it. In tracing the evolution of the structure of the country and of its physical features we are, in fact, attempting to visualise the long history which lies behind the basal elements in its scenery—mountain and plain, hill and dale—recognising at the same time that the intimate details of that scenery are the work of man and lie outside the scope of this volume.