Relative importance of pasture size and grazing continuity for the long-term conservation of European dung beetles

Habitat area and continuity are both key issues in conservation biology, for example in the choice and design of areas used as nature reserves. We analyzed how grazing continuity and pasture area affect species richness, functional groups and red-listed species of dung beetles, functionally important but often highly threatened organisms found in pasture areas. We used literature and our own field data to study a chronosequence of 22 pastures ranging from recently established sites up to 1000 years of grazing history in five European countries. Our results show a strong positive effect of grazing continuity on total species richness, especially within the first hundred years of permanent grazing. Species richness showed a stronger increase with grazing continuity in habitat specialists than in habitat generalists. However, the number of red-listed dung beetle species increased strongly with the size of a pasture, leading to higher proportions of red-listed species on large than on small pastures. Due to the length of time needed for specialist species to become established, priority should be given to the conservation of existing pasture areas, and new areas should ideally be connected to these habitats to facilitate colonization. Relatively large pastures (>130 ha) or a coherent network of small pastures are required to ensure long-term survival of red-listed dung beetles.