Most recent ecological surveys of specific areas have been vegetation studies, for example, surveys of Dartmoor (Ward, Jones & Manton 1972) and mid-Wales (Edgell 1969). The area involved, although extensive, is usually fairly uniform and in these cases consisted of upland habitats only. It is becoming increasingly necessary, for planning the use of land for a variety of purposes, to undertake surveys of larger areas with a range of habitats; from those in the lowland urban and arable areas to those in the sheep-grazed and afforested areas of the uplands. One approach to ecological studies of this magnitude has been to evaluate the data according to the relative rarity and species diversity of the habitats present (Tubbs & Blackwood 1971). Another method has been used in producing a broad ecological description of the whole of Wales (Welsh Council 1971) by grading each kilometre square of the Ordnance Survey national grid according to its ecological features and joining squares of similar grading to produce a zoned map. An alternative approach has been for a number of ecologists to undertake detailed investigations into various aspects of a specific area, for example, Morecambe Bay (Corlett 1972; Anderson 1972; Prater 1972; Elliott & Corlett 1972; Gray 1972; Gray & Bunce 1972). With the increasing demand for large-scale survey, it became apparent that a simplified method of describing the ecological situation was often required, without the necessity for detailed species survey, the involvement of numbers of workers, or simplification by evaluation. The aim of such surveys should be to provide a quantitative rather than a qualitative ecological description. Habitats appeared to be useful basic units for simplified definition of ecological situations. The use of a system of clearly defined habitats to describe the environment in which animals were found has been described by Elton & Miller (1954) and Elton (1966). This system has been modified in the Biological Sites Recording Scheme (Society for the Promotion of Nature Reserves 1969) in an effort to standardize the description of sites considered to be of importance for conservation. The use of habitats as basic recording units has a number of advantages; the representation of both vegetation and fauna (if required, details of the species content can be added from the literature or by further study), precise definition and rapid identification. This type of approach has been used by Nicholson (1971) in producing an environmental record of an area by recording the relative dominance of its constituent habitats on a specifically designed chart, the 'geogram'. The present study also attempts to simplify an extremely complex situation, in this case by determining what habitats are present, how frequently they occur, the proportion of the area which each covers and their