Assessing national conservation priorities: An improved red list of British butterflies

An objective method of determining national conservation priorities is vital to use scarce resources effectively, but no method is yet widely accepted. The ‘Conservation Cube’ method of Avery et al. (1995: Ibis 137, 232–239), which includes three biological axes (National Status; International Importance; and European/global status), is tested for a highly threatened group of animals, British butterflies. The results are compared with Red Lists constructed using old and new IUCN criteria. A new feature of both procedures is the evaluation of threat due to rate of decline, and new thresholds are suggested to assess the decline of butterflies from published 10-km grid square distribution maps. The analysis shows that almost half (49%) of the 59 resident British butterflies are extinct or threatened: 8% are extinct; 12% are a high priority largely owing to their rapid rate of decline; whereas 29% are a medium priority owing to their moderate rates of decline. Most high priority species qualify as Vulnerable under the new IUCN criteria using UK guidelines, but many medium priority species fail to qualify. We suggest that all globally threatened species are classified at least as Vulnerable at national level and that two new Lower Risk categories are created: Internationally Significant and Moderate Decline. The two procedures would then form a comparable, rational procedure for identifying conservation priorities that is applicable to all animal groups for which distributional data are available.