Early-season mass-flowering crop cover dilutes wild bee abundance and species richness in temperate regions : A quantitative synthesis

Summary, in English

Pollinators benefit from increasing floral resources in agricultural landscapes, which could be an underexplored co-benefit of mass-flowering crop cultivation. However, the impacts of mass-flowering crops on pollinator communities are complex and appear to be context-dependent, mediated by factors such as crop flowering time and the availability of other flower resources in the landscape. A synthesis of research is needed to develop management recommendations for effective pollinator conservation in agroecosystems. By combining 22 datasets from 13 publications conducted in nine temperate countries (20 European, 2 North American), we investigated if mass-flowering crop flowering time (early or late season), bloom state (during or after crop flowering) and extent of non-crop habitat cover in the landscape moderated the effect of mass-flowering crop cover on wild pollinator abundance and species richness in mass-flowering crop and non-crop habitats. During bloom, wild bee abundance and richness are negatively related to mass-flowering crop cover. Dilution effects were predominant in crop habitats and early in the season, except for bumblebees, which declined with mass-flowering crop cover irrespective of habitat or season. Late in the season and in non-crop habitats, several of these negative relationships were either absent or reversed. Late-season mass-flowering crop cover is positively related to honeybee abundance in crop habitats and to other bee abundance in non-crop habitats. These results indicate that crop-adapted species, like honeybees, move to forage and concentrate on late-season mass-flowering crops at a time when flower availability in the landscape is limited, potentially alleviating competition for flower resources in non-crop habitats. We found no evidence of pollinators moving from mass-flowering crop to non-crop habitats after crop bloom. Synthesis and applications: Our results confirm that increasing early-season mass-flowering crop cover dilutes wild pollinators in crop habitats during bloom. We find that dilution effects were absent late in the season. While mass-flowering crop cultivation alone is unlikely to be sufficient for maintaining pollinators, as part of carefully designed diverse crop rotations or mixtures combined with the preservation of permanent non-crop habitats, it might provide valuable supplementary food resources for pollinators in temperate agroecosystems, particularly later in the season when alternative flower resources are scarce.

• Author: L. G.A. Riggi; C. A. Raderschall; T. P.M. Fijen; J. Scheper; H. G. Smith; D. Kleijn; A. Holzschuh; G. Aguilera; I. Badenhausser; S. Bänsch; N. Beyer; E. J. Blitzer; R. Bommarco; B. Danforth; J. P. González-Varo; H. Grab; G. Le Provost; K. Poveda; S. G. Potts; M. Rundlöf; I. Steffan-Dewenter; T. Tscharntke; M. Vilà; C. Westphal; Berggren; O. Lundin
• Department/s: LU Profile Area: Nature-based future solutions; Centre for Environmental and Climate Science (CEC); BECC: Biodiversity and Ecosystem services in a Changing Climate; Lund university sustainability forum; Biodiversity and Conservation Science
• Publishing year: 2023-12-20
• Language: English
• Publication/Series: Journal of Applied Ecology
• Links: http://dx.doi.org/10.1111/1365-2664.14566
• Document type: Journal article
• Publisher: John Wiley & Sons Inc.
• Topic: Ecology
• Keywords: dilution effects; floral resource; landscape composition; mass-flowering crops; pollinator abundance; pollinator richness; seasonal effects
• Status: Epub
• Research group: Biodiversity and Conservation Science
• ISBN/ISSN/Other: ISSN: 0021-8901