National‐scale conservation assessments at an appropriate resolution

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Abstract
Most national‐scale conservation assessments are carried out at a resolution that is different from the actual size of protected areas in the study region. Coincidence between nature reserves and both hotspots (areas of high species richness) and complementary areas (sets of sites within which all species are represented) have been reported. However, the resolution (size of grid cells) of the species’ distribution data upon which many of these studies are based is often close to an order of magnitude larger than the size of the reserves. Presumably, only a proportion of the species recorded in the coarse grid cells will actually be present on reserves. We use fine (2 × 2‐km square grid cells) and coarse (10 × 10‐km square grid cells) resolution data of national distributions for breeding birds throughout Great Britain, and presence data for avian species on Royal Society for the Protection of Birds (RSPB) nature reserves, to investigate the proportion of species in the local area (100 km2) that are actually present on reserves. RSPB reserves contain between 50% and 70% of species from the local area. These proportions are significantly higher than for randomly selected, non‐reserve areas, indicating that RSPB reserves contain higher concentrations of bird species than the wider countryside. Furthermore, on RSPB reserves these proportions of threatened and non‐threatened species are equal, whereas in non‐reserve areas the proportions of non‐threatened species are significantly higher than threatened species. Thus, reserves hold a higher proportion of threatened species than occurs in the wider countryside.