The Nature Conservation Review is presented in two parts. The first begins with a synoptic account of the field of ecological variation found in Britain, to provide a general background for the more detailed and separate treatment of the seven major formations of Coastlands; Woodlands; Lowland Grasslands, Heaths and Scrub; Open Waters; Peatlands; Upland Grasslands and Heaths; and Artificial Ecosystems. Treatment of each formation has varied according to the special features and problems associated with each. The formation sections begin with accounts of habitat and vegetation, broadly following the lines of what seemed to be the most appropriate classification for each, with discussion of ecological and geographical relationships; where possible, vegetation types are named. The ensuing accounts of flora and fauna are again ecological and bio- geographical, but deal also with abundance of species; much of this information is presented in tabular form. The purpose of this presentation of scientific information is to provide a framework of reference against which the selection of key sites can be viewed.

There is then a discussion of criteria for comparative site assessment which to some extent repeats what has already been said on this topic, but deals with the particular and varying emphasis required according to the particular formation. The special and general features of each formation needing representation in the national series are then enumerated.

Next in each formation section is a short review of the key sites chosen, following a somewhat elastic general plan and consisting of a resume, in geographical order from south to north, of the sites and their position in the field of variation. There is often some discussion of the reasons for gradings given and indications of relative value of related sites, including alternative choices. Bonus habitats represented on sites chosen mainly to represent other formations are also mentioned. Each key site has a reference number, so that details of its scientific interest may be quickly obtained by consulting vol. 2. Under Upland Grasslands and Heaths and Coastlands, no subdivision of the formation has been made in the reviews of sites chosen, as the amount of diversity within many sites would lead to the same site being described under two or more categories. In the other formations, the geographical scan of key sites is made under several different subdivisions of the main type, e.g. in Peatlands, under the six different classes of mire. Cross-references are made when the same site is mentioned both under different major formations and under different subdivisions of these. Each formation section ends with an index of sites, giving grading, region, name of site, county and, in some cases, tabulated ecological information. The formation sections are followed by two separate sections which discuss the conservation of flora and fauna in relation to the series of sites.

In vol. 2 of the Review, key sites are listed in a standard geographical order under their formation (as in the Index of Sites for each formation in the first part) and for each there are details of relevant environmental factors, and notable ecological features, vegetation types, and selected species of plants and animal, including some rarities. The representation of features belonging to other formations is mentioned, and there are cross- references. Where relevant, relationships to other sites of similar character may be discussed. These accounts of key sites are, in fact, intended to provide a summary of their intrinsic scientific features and therefore of the case for their selection and grading.

Areas of sites are measured only approximately, unless they are already established as NNRs, in which case exact figures are given: the area quoted for coastal sites is confined to that part which lies above Mean Low Water. Grid references are of 4 or 6 figures, as is considered most appropriate to indicate the location of a site.

Scientific nomenclature is according to the standard systematic works listed in the Bibliography. English names for trees, shrubs, vertebrates, butterflies and moths have been generally used, though the scientific equivalents are all given somewhere in the text. Scientific names for other plants and animals are normally used throughout; for many lower organisms there is no accepted English name.

To save space, some common plant species which are the only representatives of their genus in Britain are referred to by their generic name only, after their full scientific name has been mentioned at least once. For the same reason the term Britain is used to denote Great Britain (England, Scotland and Wales).

All altitudes relate to height above Ordnance Datum (OD) unless otherwise stated. References to Nature Conservancy regions and to counties reflect the position in 1972. It is hoped that factual information is correct up to 1972, but environmental change is so rapid in many situations that some statements will inevitably become out of date in the period between final draft and publication.