Local management at low- to moderate-intensity benefits wild bees in European calcareous grasslands while landscape conservation effects vary
Abstract
Calcareous grasslands are important habitats for many pollinators including wild bees but have declined dramatically in habitat quantity and quality due to land use changes at local and landscape scale. Such developments might be mitigated by local management, such as low‐intensity land use and landscape measures, including the conservation of calcareous grasslands and the establishment of biodiversity‐friendly farming practices like agri‐environment schemes (AES). Yet, the effectiveness of these measures for conserving pollinator communities is still poorly explored and might depend, for example on the landscape context or the AES type (productive vs. non‐productive). Using transect walks, we investigated how local and landscape‐scale management affects bee communities in 96 calcareous grasslands in three European countries (Estonia, Germany, Spain), covering three biogeographic regions (boreal, continental, Mediterranean). Over a period of 2 years, we recorded 6716 individuals from 235 species across our study regions, underpinning the importance of calcareous grasslands for wild bee conservation. According to a local land use intensity index, we found that both long‐term abandonment and intensive management reduced wild bee species richness and abundance, either directly or indirectly through effects on floral resource availability. At the landscape scale, cover of calcareous grassland and AES in the surroundings benefited wild bee communities, though the effectiveness of AES often depended on the AES type and the landscape cover of calcareous grasslands. In Germany, for example productive AES increased wild bee abundance and richness only in landscapes with higher calcareous grassland cover, while non‐productive AES were most effective if landscape calcareous grassland cover was lower. However, landscape effects varied across study regions. Synthesis and applications. Conserving wild bee diversity in these grasslands requires avoiding long‐term abandonment and intensive management, while promoting local management at low to moderate intensity. Moreover, it is essential to conserve and restore calcareous grasslands in the surroundings. This may be complemented by implementing AES in the landscape, depending on the AES type, landscape and regional context. Our findings stress that future restoration and conservation planning should combine local and landscape management measures to successfully conserve wild bees in European calcareous grasslands.
What the paper shows and why it matters (AI-generated)
Calcareous (lime-rich) grasslands host many specialised and endangered wild bees. They have declined in area and quality in many European countries, attributed to abandonment, intensive use and habitat loss in the surrounding landscape. Many earlier studies compared simple categories, such as abandoned versus grazed sites. That ignores differences within each category, such as how far shrubs have taken over or how heavily animals graze. Evidence on landscape measures, such as nearby calcareous grassland cover or agri-environment schemes (public payments to farmers for biodiversity-friendly practices), was often limited to single regions and mixed, and a meta-analysis found no clear effect of abandonment on insects (Elliott et al. 2023). It remained unclear how bees respond along the local gradient from long-term abandonment to intensive management, and whether landscape measures work consistently across Europe.
The paper argues that local management at low to moderate intensity benefits wild bees in calcareous grasslands, which requires avoiding both long-term abandonment and intensive use, whereas the effect of landscape measures differs between regions and cannot be assumed to transfer. The study ranked 96 sites in Estonia, Germany and Spain on one index combining woody cover (abandonment) with active management, mainly grazing intensity. In Spain, bee abundance and richness fell towards both ends of the index (long-term abandonment, intensive use); in Estonia the support was weaker and partly linear, richness rising along the index. In Germany the index had no clear direct effect on abundance but acted indirectly, through flower cover and the number of flowering plant species. These flower measures raised bee numbers in all three regions. More calcareous grassland nearby increased bee abundance in Estonia and Germany but reduced it in Spain, and the effect of agri-environment schemes depended on scheme type and on grassland cover around the site.
For management, the paper concludes that grazing should stay at low to moderate intensity and that shrub removal can hinder the return of woody vegetation (succession) on abandoned sites. Conserving and restoring calcareous grassland in the surroundings matters as well, while agri-environment schemes can support bees but not fully replace lost semi-natural grassland. The paper holds that measures at both scales should be combined and adapted to each region, and it offers its findings as input for planning under the EU Nature Restoration Regulation.
References
- Elliott et al. (2023). Abandoning grassland management negatively influences plant but not bird or insect biodiversity in Europe. Conservation Science and Practice 5, e13008. doi:10.1111/csp2.13008