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

Flight areas of British butterflies: assessing species status and decline

“…Thus, nationally widespread species have declined just as much within the North Wales region as more restricted species, even though previous analyses based on the national 10 km grid have indicated that localized species have su¡ered higher percentage declines (Heath et al 1984;Thomas 1994;Thomas & Abery 1995). Coarse-grained maps grossly underestimate population-level rates of decline, particularly for common species that initially have many populations per grid square (Thomas & Abery 1995;Warren et al 1997). Decline rates per unit area may be comparable for widespread and localized species, but localized species initially occupy much smaller total areas (table 1 and ¢gure 1).…”

“…Thirteen out of 23 conservation priority (Warren et al 1997) butter£y species in Britain have been subject to partial (regional) or complete (national) population-level mapping (table 1). For these species, every known population within the sample area has been visited, the approximate colony boundaries mapped and the extent of their £ight areas calculated.…”

“…In addition to a simple measurement of area, the IUCN (1994) criteria also require species to meet two out of the following three criteria: severe fragmentation, continuing decline and extreme £uctuations (Mace & Lande 1991). These species generally ful¢l the ¢rst and third of the criteria and most of them also ful¢l the second (Warren et al 1997). Using 10 km 2 occupancy, only zero, zero and three of these species would fall into these three categories, respectively: coarse-grained data grossly overestimate current status (Thomas & Abery 1995).…”

“…For practical reasons, species ranges are commonly plotted as presence^absence in 10 km Â10 km grid squares in northern Europe, in 50 km or coarser grids in less heavily researched parts of the world and as relatively crude range maps in ¢eld guides. It is widely accepted that species may populate only a small proportion of occupied' areas, but the need for rapid conservation policies and actions has already driven widespread use of these data (Vane-Wright et al 1991;Groombridge 1992;Prendergast et al 1993;Gaston 1994;Quinn et al 1997;Warren et al 1997;Kunin 1998). Therefore, the consequences of measuring range areas in di¡erent ways should be quanti¢ed (Gaston 1994;Thomas & Abery 1995;Warren et al 1997;Kunin 1998).…”

Accounting for habitat when considering climate: has the niche of the Adonis blue butterfly changed in the UK?

“…bellargus is bivoltine in the UK and its sole larval host plant is Hippocrepis comosa, with the offspring of the second adult generation overwintering as larvae. Between 1950 and the 1980s, 70 % of P. bellargus colonies in the UK had gone extinct and its range had retracted by 42 % (Thomas 1983;Warren et al 1997). Since receiving Priority Species status in the UK Biodiversity Action Plan in the 1990s, the number of UK colonies of P.…”