A national strategy for nature conservation was formally prescribed in 1947 with the publication of the Government White Papers Conservation of nature in England and Wales (Cmd 7122) and National Parks and the conservation of nature in Scotland (Cmd 7235). These documents presented the basic philosophy that the practice of nature conservation in Britain should centre around the safeguarding of a fairly large number of key areas adequately representing all major types of natural and semi-natural vegetation, with their characteristic assemblages of plants and animals, and habitat conditions, of climate, topography, rocks and soils, and biotic influences. Geological and physiographic features were to be represented for their own intrinsic interest. Since such areas were intended to be set aside for a range of human uses in posterity, their selection had to be related to the variety of interests involved. In implementing nature conservation strategy, this key area concept has been expressed most significantly in the statutory declaration of a series of 150 National Nature Reserves, which provide the means of safeguarding many important sites, and in the notification of some 3500 Sites of Special Scientific Interest (SSSI). The growth of the voluntary conservation bodies movement has also led to the setting up of many nature reserves without statutory protection.

During the last two decades up to 1976, human pressures on the land of Britain have caused a rate and scale of attrition of wildlife and habitat even greater than that foreseen in 1947. At the same time, growing interest in the biology and ecology of the natural environment has led to fuller survey and the identification of many more sites of high scientific value and importance to nature conservation. The Nature Conservancy therefore kept progress in the site conservation programme under periodic review, first in 1955, and then in 1965 when a still more comprehensive reappraisal of the situation was launched. This report presents the results of the last review, which has aimed at compiling a countrywide list of sites whose safeguarding is a matter of priority and urgency within the provisions for nature conservation in Britain.

This review has, however, been concerned essentially with biological features, and though these are considered in relation to the background of physical environment, the conservation of physical features other than soils (i.e. geological and physiographic features) has been left for separate, later assessment. Many important physical features are represented within biologically valuable key sites, but their inclusion is only incidental.

The key area concept itself is fairly straightforward, but the actual process of choosing sites and compiling a list to represent an adequate national sample of all major ecosystems¹ raises some extremely complex and difficult problems, both conceptual and practical. The earlier expositions of nature conservation requirements in Cmd 7122 did not dwell on these problems, but made recommendations intended to be taken as reasonable conclusions, having regard to the declared objectives, and the experience of those concerned with site selection.

It is now felt, however, that the case for safeguarding a national series of sites should explain why these key areas are important to nature conservation, and how the assessment of their quality is made. Considerable thought has therefore been given to the rationale behind the assessment and selection of key areas, and the next chapter spells out this thinking in some detail. This is a difficult field in which value judgements figure prominently and so a good deal of subjectivity of approach is inevitable. The valuation placed upon features of the ecosystem is to a large extent directly related to the fulfilment of some human purpose, be it scientific, educational, aesthetic or economic. There are profound philosophical problems in defining the ultimate purpose of nature conservation, and it is sufficient to say here that generally accepted criteria, relating to the range of human concern, have been defined and used in the evaluation of site features and therefore of overall site quality.

A four-point grading of quality has been devised for areas sufficiently important to be notified on SSSIs. Sites in the top two classes are regarded as of national importance to nature conservation; they exemplify the key area concept, and are termed 'key sites'. Each is described in vol. 2 of this report. Grade i sites are those of the highest importance; the safeguarding of these is regarded as essential to the success of nature conservation in Britain. Grade 2 sites are of almost equal importance, but either duplicate the features of related grade i sites or are of slightly lesser quality, or both. The conservation of grade 2 sites is a matter of less extreme urgency, but nevertheless requires considerable thought and effort.

The selection of key sites has required a systematic and comprehensive survey of areas of natural and semi-natural ecosystems over as much of Britain as could be covered in the time available. In general, the datum line is 1967, although revision to take account of subsequent developments has been made wherever possible. The Review thus provides an extensive body of scientific data about our national capital of habitat and wildlife, and an inventory of sites graded according to their nature conservation value. ' Nature conservation value' expresses the range of human interest in wildlife and its habitat, and physical features. Wildlife is defined here as the sum total of the animals and plants of Britain, excluding domesticated or captive animals and introduced plants grown for human purposes; it thus embraces not only the native flora and fauna, but also introduced plant species which are not deliberately managed as a crop.

Vol. i of this report contains a synopsis of the choice of key sites and the reasons for their selection. It has seemed essential to present this choice in relation to a statement of the whole range of nature conservation interest in Britain, in the form of a background account of the range of natural and semi-natural ecosystems, with their physical features, flora and fauna. This account gives a framework of reference for the sites chosen and therefore contains a justification for their conservation, when read in conjunction with the site descriptions and the criteria for their assessment and selection. Vol. i is therefore written for a mixed audience, including landowners, administrators, planners and developers; and some sections presume little or no technical knowledge, though the need for scientific adequacy necessitates use of a certain number of technical terms and concepts, and scientific names. The background information accordingly includes an exposition of certain ecological principles at a fairly basic level, but the first part is intended also to contain sufficient detail to be of use to nature con- servationists and others with technical knowledge. The difficulties of writing for an audience consisting of both laymen and experts have proved considerable, and there is a danger that the result will please neither, though it is hoped that both will find something of value. Vol. i can, if necessary, stand on its own as an exposition of the Nature Conservation Review. For those requiring fuller and more technical information about the character and interest of specific sites, vol. 2 provides the detailed descriptions. The document as a whole is intended to serve as a compendium of information and reference work on nature conservation interest in Britain, in which the sites of greatest importance are presented in relation to the wider background of wildlife and habitat over the country as a whole.

The present review is thus a presentation of material relating to the intrinsic scientific or nature conservation interest of these priority sites (including existing National Nature Reserves), but does not consider the methods by which they should be safeguarded. There have, moreover, been developments in the philosophy and practice of nature conservation in the last 20 years, notably in a reinforcement of the view that safeguarding key areas by no means satisfies the total requirement, and that there is a need to conserve the much greater part of the national capital of wildlife and habitat which lies outside this relatively small sample. There is a feeling too that arable farmland, derelict land and, to some extent, built-up areas, should be considered as well as less artificial habitats. The further requirements for nature conservation generated by this wider outlook are not specifically considered in the present review, but the background account of the whole field of interest gives some indication of what is involved, and some attempt is made to assess the contribution which the safeguarding of grade i and 2 sites would make to the conservation of Britain's flora and fauna.

This report is not intended to be a final, totally definitive statement on the subject, for field survey is still incomplete, and the methods of site assessment and selection are realistic rather than ideal. It is inevitable that, with further advances in basic knowledge and methods, and perhaps also through change of view and revision of needs, the present list of key sites will require amendment and/or addition. However, the list of sites now defined is presented as the best which can be achieved under the limitations of present circumstances, and as a recommended basis for early action in promoting conservation measures.

In the light of information received since preparation of the final draft, a few additions and a few regradings have been made to the list of key sites; details are given in the Appendix.