We examined the butterfly fauna at 62 sites in southeastern Sweden within a region exhibiting high variation in the landscape surrounding the studied grasslands. The landscape varied from an intensively-managed agricultural landscape with a large amount of open fields to a landscape with a high amount of deciduous forest/seminatural grassland. We made 12 179 observations of 57 species of butterflies. The amount of neighbouring deciduous forest/semi-natural grassland, with /25% tree and bush cover, was the most important environmental factor explaining the variation in the butterfly assemblages. Landscape analyses at three different spatial scales showed that the variation in butterfly assemblages could be explained only at the largest scale (radius 5000 m) and not at the smaller ones (radii 500 and 2000 m). Logistic regressions were used to predict presence/absence of butterfly species. Our study indicated that there may be critical thresholds for the amount of habitat at the landscape scale for several butterfly species as well as for species richness. For Melitaea athalia , there was a sharp increase in occupancy probability between 3 and 10% deciduous forests/semi-natural grasslands at the 5000-m scale. For 12 other species, the value for 50% probability of occurrence varied between 2 and 12% deciduous forest/ semi-natural grassland. Species which had high occupancy probabilities in landscapes with a low amount of surrounding deciduous forests/semi-natural grasslands were significantly more mobile than others. Our study highlights the importance of applying a landscape perspective in conservation management, and that single-patch management might fail in maintaining a diverse butterfly assemblage.

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Summary1. Like many butterflies, the woodland brown Lopinga achine has disappeared from many locations in western Europe due to habitat loss. The population dynamics and the effects of tree and bush cover on population size were studied experimentally south of Linköping, Sweden. 2. Most populations in the study area were small (< 500 individuals) and fluctuated synchronously between years. Long-term population dynamics and occurrence were closely correlated with tree and bush cover. Populations occurred only at sites with ≥ 60% canopy cover, but population density decreased sharply where cover exceeded 90%. Survival from egg to adult was highest at the edges of glades (2·3 adults per female) and lowest in the deepest shade (0·7 adults) or open sun (0·6 adults). The annual rate of canopy closure at unmanaged sites decreased linearly with tree and bush cover, approximately 1% closure at 60% cover and 0·3% at 85% cover, making it possible to predict the impact of habitat changes for L. achine . 3. In 1992-95, vegetation was cleared experimentally to create new glade edges at six unmanaged sites where the risk of extinction was high because few glades remained. On average, population size at five of the managed sites increased by > 90%. The population at the sixth site, managed in 1995, decreased by 30%. 4. Cover of the host-plant Carex montana increased significantly at edges of new glades and decreased in closed unaffected woods. Successful restoration probably requires the presence of C. montana along edges of new glades from the onset of management because this plant was slow to colonize plots where it was initially absent. 5. Currently, 86% of the sites in southern Sweden occupied by L. achine are unmanaged. If this situation continues, the metapopulation in this study will probably collapse within 20-40 years. Recovery programmes for L. achine should emphasize metapopulation dynamics, host-plant cover and vegetation dynamics over time. As with many butterflies, successful conservation requires a blend of detailed autoecology and active site management to produce the required successional conditions.