Land classification for strategic ecological survey

Traditionally, ecological survey relies upon the intuitive interpretation of habitat patterns in the held. The statistical stratification developed for regional survey by the Institute of Terrestrial Ecology (ITE) is designed to minimise personal judgement in sample site location. The environmental strata within the classification are recognisable and give confidence to users from a variety of backgrounds. The methodology originated in the 1960s when multivariate statistics were developed and applied to ecological data. Initially, Great Britain (GB) was classified from environmental data recorded from 1200 out of the 240 000 km(2) of the National Grid. Logistic discrimination and discriminant functions were used to assign the remaining squares to original classes and to reassign the original squares. The final classes differed slightly from the initial divisions because the allocations use different data sets and different techniques. Field surveys of ecological parameters have been used to provide independent data for testing the classification, to characterise the classes and to provide national estimates of land coverage. The statistical rationale behind the methodology is described and the relevance of the experience gained during the development is discussed in relation to future work. Finally, applications of the classification are described demonstrating its use as a framework in a variety of ecological studies.