Conservation value of semi-natural pastures in Sweden:: Contrasting botanical and avian measures

Conservation of biodiversity in semi-natural pastures of Sweden is based mainly on management prescriptions to increase botanical values (i.e., species richness of vascular plants confined to pastures), assuming plants to be good indicators of overall biodiversity We compared species richness and abundance of 29 species of farmland birds breeding in 88 semi-natural pastures of different conservation value as evalutated by a nation-wide inventory of semi-natural pastures in Sweden. We tested whether there was an association Between existing measures of conservation value based mainly on the species richness and rarity of vascular plants, and three species richness subsets of farmland birds. Species richness of all farmland birds decreasing farmland birds, and dry pasture birds were not associated with the botanical conservation value of pastures. Pastures surrounded by open farmland contained significantly more farmland bird species and more decreasing farmland species than pastures located at forest-field edges within the same landscape. In addition, richness of all farmland bird species, decreasing farmland species, and decreasing dry pasture species increased significantly with increasing pasture area and increasing proportion of a short field layer (reflecting grazing intensity). The species richness of decreasing dry-pasture species of birds was also weakly positively correlated with the proportion of the field layer being artificially fertilized. Our results suggest that there are only weak relationships if any between species richness in birds and vascular plants at the local scale (2-15 ha), so using vascular plants as indicators of overall biodiversity may be unreliable. The present management prescription of intensive grazing to increase overall biodiversity is not supported by the literature on invertebrates, birds, and plants. We suggest that future management of semi-natural pastures should be revised to include a relaxed grazing intensity, which may increase heterogeneity of field layer height, allowing larger areas to be grazed with a given stock size, and may increase meat and milk production due to a higher quality of grazing.