A multitaxa assessment of the effectiveness of agri-environmental schemes for biodiversity management

Abstract

Agri-environmental schemes (AES) aim to restore biodiversity and biodiversity-mediated ecosystem services in landscapes impoverished by modern agriculture. However, a systematic, empirical evaluation of different AES types across multiple taxa and functional groups is missing. Within one orthogonal design, we studied sown flowering AES types with different temporal continuity, size, and landscape context and used calcareous grasslands as seminatural reference habitat. We measured species richness of 12 taxonomic groups (vascular plants, cicadas, orthopterans, bees, butterflies, moths, hoverflies, flower visiting beetles, parasitoid wasps, carabid beetles, staphylinid beetles, and birds) representing 5 trophic levels. A total of 54,955 specimens were identified using traditional taxonomic methods, and bulk arthropod samples were identified through DNA metabarcoding, resulting in a total of 1,077 and 2,110 taxa, respectively. Species richness of most taxonomic groups, as well as multidiversity and richness of pollinators, increased with temporal continuity of AES types. Some groups responded to size and landscape context, but multidiversity and richness of pollinators and natural enemies were not affected. AES flowering fields supported different species assemblages than calcareous grasslands, but assemblages became more similar to those in seminatural grasslands with increasing temporal continuity. Our results indicate that AES flowering fields and seminatural grasslands function synergistically. Flowering fields support biodiversity even when they are relatively small and in landscapes with few remaining seminatural habitats. We therefore recommend a network of smaller, temporally continuous AES flowering fields of different ages, combined with permanent seminatural grasslands, to maximize benefits for biodiversity conservation and ecosystem service delivery in agricultural landscapes.

Relationship of insect biomass and richness with land use along a climate gradient

“…Yet, despite evidence of the negative effects of pesticides 7 , habitat loss 11 , and low habitat quality 12 on insect communities, whether agricultural intensification is indeed the main culprit in the widespread insect decline is unclear, as losses have occurred not only in agricultural but also in forested environments 6,13 . Moreover, land-use intensity studies have been largely restricted to forests and grasslands 13 or have focused on specific land-use effects, such as those within agricultural or urban areas 14,15 . An additional consideration is the impact of other potential drivers of insect decline, such as climate change, that act simultaneously with land-use intensification 16,17 .…”

Interactive effects of climate and land use on pollinator diversity differ among taxa and scales

“…Identifying some insect groups morphologically rather than with DNA metabarcoding would possibly have yielded more accurate results, but metabarcoding is extremely suitable for large sample sizes and taxa like Diptera with limited taxonomic expertise ( 61 ). To reduce common metabarcoding issues such as species richness inflation and an unbalanced identification of different taxonomic groups, we used barcode index numbers (BINs) instead of operational taxonomic units (OTUs) as a surrogate of species richness ( 62 ).…”

“…Together with forest habitats (or low-intensity land use), the diversity of flowering plants can increase the diversity of all pollinator taxa across spatial scales. Thus, measures to enhance the richness, abundance, and temporal continuity of flowering-plant resources in different habitat types are imperative to promote pollinators and thus to increase the adaptive capacity of ecosystems to a changing climate ( 61 ).…”

Biodiversity in agricultural landscapes: different non-crop habitats increase diversity of ground-dwelling beetles (Coleoptera) but support different communities

“…Nevertheless, our data clearly show that both field margins and sown wildflower fields promote biodiversity in an agricultural landscape, and are thus valuable for restoring biodiversity and ecosystem services. A combination of approaches will likely yield highest benefits, evidenced by variation among the assemblages of different habitat types (see also Boetzl et al 2021). Nevertheless, permanent fallows are indispensable for conservation, as they comprise refuge areas for different specialists or particularly large species (e.g.…”

“…While some agri-environmental schemes are considered successful (Perkins et al 2011), the benefits of others have been widely discussed (Kleijn et al 2011). So called greening measures were introduced with the last CAP reform to reduce the negative impact of agriculture on the environment and to counteract the loss of biological diversity (Birkhofer et al 2018;Boetzl et al 2021). There is broad agreement that remnants of (semi-)natural vegetation and long-term fallows comprise important conservation areas for arthropods in agricultural landscapes (Geiger et al 2009;Holland et al 2017), but the effectiveness of grassy field margins versus shortterm set-aside, wild-flower-sown fields is rather unclear.…”