Summary: In many European agricultural landscapes, species richness is declining considerably. Studies performed at a very large spatial scale are helpful in understanding the reasons for this decline and as a basis for guiding policy. In a unique, large‐scale study of 25 agricultural landscapes in seven European countries, we investigated relationships between species richness in several taxa, and the links between biodiversity and landscape structure and management. We estimated the total species richness of vascular plants, birds and five arthropod groups in each 16‐km² landscape, and recorded various measures of both landscape structure and intensity of agricultural land use. We studied correlations between taxonomic groups and the effects of landscape and land‐use parameters on the number of species in different taxonomic groups. Our statistical approach also accounted for regional variation in species richness unrelated to landscape or land‐use factors. The results reveal strong geographical trends in species richness in all taxonomic groups. No single species group emerged as a good predictor of all other species groups. Species richness of all groups increased with the area of semi‐natural habitats in the landscape. Species richness of birds and vascular plants was negatively associated with fertilizer use. Synthesis and applications. We conclude that indicator taxa are unlikely to provide an effective means of predicting biodiversity at a large spatial scale, especially where there is large biogeographical variation in species richness. However, a small list of landscape and land‐use parameters can be used in agricultural landscapes to infer large‐scale patterns of species richness. Our results suggest that to halt the loss of biodiversity in these landscapes, it is important to preserve and, if possible, increase the area of semi‐natural habitat.

Summary: Agricultural intensification poses a serious threat to biodiversity as a consequence of increased land‐use intensity, decreased landscape heterogeneity and reduced habitat diversity. Although there is interest in the preservation of total species richness of an agricultural landscape (γ diversity), the effects of intensification have been assessed primarily by species richness at a local scale (α diversity). This ignores species richness between local communities (β diversity), which is an important component of total species richness. In this study, measures of land‐use intensity, landscape structure and habitat diversity were related to γ, α and β diversity of wild bees (Apoidea), carabid beetles (Carabidae), hoverflies (Syrphidae), true bugs (Heteroptera) and spiders (Araneae) within 16 local communities in 24 temperate European agricultural landscapes. The total landscape species richness of all groups was most strongly affected by increased proximity of semi‐natural habitat patches. Bees also decreased in landscapes with a high intensity of farmland management, demonstrating additive effects of both factors. Separating total species diversity into components, the decrease in total species richness could be attributed primarily to a decrease in species diversity between local communities. Species richness of the local communities of all investigated groups decreased with increasing land‐use intensity and, in the case of spiders, decreasing proximity of the semi‐natural habitat patches. The effect of increased habitat diversity appeared to be of secondary importance to total species richness but caused a shift in the relative contribution of α and β diversity towards the latter. Synthesis and applications. This study demonstrates that the effects of agricultural change operate at a landscape level and that examining species diversity at a local level fails to explain the total species richness of an agricultural landscape. The coincidence of patterns of β diversity with those of γ diversity emphasizes that such information is of crucial importance for the implementation and evaluation of restoration programmes aiming to restore sustainable countryside diversity. As local extinction processes in highly fragmented landscapes shape biodiversity, priority should be given to the conservation of diverse agricultural landscape remnants in Europe.

Summary: Arbuscular mycorrhizal (AM) fungi are obligate root symbionts that are present in most terrestrial ecosystems and have roles in plant mineral nutrition, carbon cycling and biotic interactions. In this work, 26 publications were surveyed that report on the occurrence of natural root‐colonizing AM fungi identified using rDNA region sequences. A total of 52 host plant species were investigated. Sixteen publications provided data enabling a comparison to be made of AM fungal taxon richness and community composition across 36 host plant species and 25 locations. Ninety‐five fungal taxa (small subunit rRNA gene sequence types) were involved, 49 of which were recorded from at least two study sites, and 65 from more than one host plant species. The number of AM fungal taxa per host plant species differed between habitat types: a significantly higher richness was found in tropical forests (18.2 fungal taxa per plant species), followed by grasslands (8.3), temperate forests (5.6) and habitats under anthropogenic influence (arable fields and polluted sites, 5.2). AM fungal communities exhibit differing compositions in broadly defined habitat types: tropical forests, temperate forests and habitats under anthropogenic influence. Grassland locations around the world host heterogeneous AM fungal communities. A number of AM fungi had a global distribution, including sequence types related to the Glomus intraradices/fasciculatum group, G. mosseae, G. sp. UY1225 and G. hoi, as well as the Glomus and Scutellospora types of unknown taxonomic affiliation. Widespread taxa occur in both natural and anthropogenic (disturbed) habitats, and may show high local abundance. However, about 50% of taxa have been recorded from only a single site. The current global analysis of AM fungal communities suggests that soil micro‐organisms may exhibit different distribution patterns, resulting in a high variability of taxon richness and composition between particular ecosystems.

Summary: In landscapes influenced by anthropogenic activities, such as intensive agriculture, knowledge of the relative importance and interaction of environmental factors on the composition and function of local communities across a range of spatial scales is important for maintaining biodiversity. We analysed five arthropod taxa covering a broad range of functional aspects (wild bees, true bugs, carabid beetles, hoverflies and spiders) in 24 landscapes (4 × 4 km) across seven European countries along gradients of both land‐use intensity and landscape structure. Species–environment relationships were examined in a hierarchical design of four main sets of environmental factors (country, land‐use intensity, landscape structure, local habitat properties) that covered three spatial scales (region, landscape, local) by means of hierarchical variability partitioning using partial canonical correspondence analyses. Local community composition and the distribution of body size classes and trophic guilds were most affected by regional processes, which highly confounded landscape and local factors. After correcting for regional effects, factors at the landscape scale dominated over local habitat factors. Land‐use intensity explained most of the variability in species data, whereas landscape characteristics (especially connectivity) accounted for most of the variability in body size and trophic guilds. Synthesis and applications.Our results suggest that management effort should be focused on land‐use intensity and habitat connectivity in order to enhance diversity in agricultural landscapes. Since these factors are largely independent, specific conservation programmes may be developed with regards to socio‐economic and agri‐environmental requirements. Changes in either of these factors will enhance diversity but will also result in specific effects on local communities related to dispersal ability and the resource use of species.