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Biodiversity conservation requires efficient methods for choosing priority areas for in situ conservation management. We compared three quantitative methods for choosing 5% (an arbitrary figure) of all the 10 × 10 km grid cells in Britain to represent the diversity of breeding birds: (1) hotspots of richness, which selects the areas richest in species; (2) hotspots of range‐size rarity (narrow endemism), which selects areas richest in those species with the most restricted ranges; and (3) sets of complementary areas, which selects areas with the greatest combined species richness. Our results show that richness hotspots contained the highest number of species‐in‐grid‐cell records (with many representations of the more widespread species), whereas the method of complementary areas obtained the lowest number. However, whereas richness hotspots included representation of 89% of British species of breeding birds, and rarity hotspots included 98%, the areas chosen using complementarity represented all the species, where possible, at least six times over. The method of complementary areas was also well suited to supplementing the existing conservation network. For example, starting with grid cells with over 50% area cover by existing “Sites of Special Scientific Interest,” we searched for a set of areas that could complete the representation of all the most threatened birds in Britain, the Red Data species. The method of complementary areas distinguishes between irreplaceable and flexible areas, which helps planners by providing alternatives for negotiation. This method can also show which particular species justify the choice of each area. Yet the complementary areas method will not be fully able to select the best areas for conservation management until we achieve integration of some of the more important factors affecting viability, threat, and cost.

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Sir-Myers et al. 1 , in their new analysis of global biodiversity hotspots, recommend areas where conservation actions should be focused to minimize losses in the imminent extinction crisis. We strongly support initiatives to produce clear, efficient and practical goals for conservation to guide biodiversity planners and decision-makers in governments, agencies, conventions and non-governmental organizations (NGOs). However, as things stand there is only limited consensus on global conservation priorities at international level. We believe that the time is now right for scientists and practitioners to work together to develop a commonly adopted blueprint for action. A key first step would be a structured debate to identify common goals; to pool data sets; and to agree on the contributions that non-equivalent measures of priority, such as diversity, endemism, threat, viability and ecological function should make. All this should lead to a powerful and cost-effective product. Most important, however, is correspondence

A definition of biodiversity is adopted that takes account not only of numbers of species, but also of the degrees of difference among them. The most appropriate measure of species differences is likely to be made in terms of genealogical relationships, as embodied in taxonomic classifications. Five new measures of taxonomic diversity are compared with existing measures of species richness and taxonomic root weighting for prioritising areas for the conservation of biodiversity, using as an example some data for 43 bumble bee species of the sibiricus-group. Although certain of the new measures can be shown to perform better than any existing methods, more extensive trials are needed, and further refinements can be anticipated. We conclude that combining species richness with taxonomic diversity to give a single measure inevitably involves compromise, as either component could be maximised in its own right. Nonetheless, the new prioritisation methods are already capable of giving practical results.

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