Influence of bioenergy crops on pollinator activity varies with crop type and distance

• Published in: Global change biology. Bioenergy Vol. 10; no. 12; pp. 960 - 971
• Main Authors: Berkley, Nicholas A. J., Hanley, Mick E., Boden, Rich, Owen, Robyn S., Holmes, Jordan H., Critchley, Russell D., Carroll, Kathryn, Sawyer, Daniel G. M., Parmesan, Camille
• Format: Journal Article
• Language: English
• Published: Oxford John Wiley & Sons, Inc 01.12.2018
• Subjects: Agricultural land; agriculture; Anthropogenic factors; Arable land; Biodiversity; bioenergy; biofuel; Bombus; Bumblebees; Butterflies & moths; Cereals; Climate change; conservation; Crops; Cultivation; Ecosystem services; Ecosystems; Energy crops; Food availability; Food plants; Human influences; Land use; Landscape; Miscanthus; Perennial crops; Plant reproduction; Pollination; Pollinators; Renewable energy; Resource management; Willow; willow short‐rotation coppice
• ISSN: 1757-1693; 1757-1707
• DOI: 10.1111/gcbb.12565

Compared to traditional arable crops, second‐generation perennial energy crops (PECs) are generally associated with increased biodiversity and ecosystem services, but robust experimental studies on this subject are few. Consequently, the potential for PEC cultivation to contribute to enhanced pollination processes in adjacent farmland remains unclear. In a 4‐year field study across multiple sites and two PECs (Miscanthus x giganteus and willow short‐rotation coppice), we examine whether pollinator visits to crop margin wildflowers were augmented by PEC cultivation. Each field was paired with two cereal fields, one adjacent to the PEC and one distant, and we recorded wildflower visits to crop margins by three pollinator groups: hoverflies, bumblebees and butterflies/moths. We also quantified floral resources, since crop‐specific management seemed a likely means of influencing margin wildflowers and thus pollinator activity. Our results add quantitative support to the suggestion that PECs should enhance ecosystem processes in agri‐landscapes. However, benefits were highly context‐dependent. Consistent enhancement of pollinator activity in margins of PEC fields was only apparent for willow where the relative frequency of flower visitation was higher for all three pollinator groups compared to adjacent or distant cereals. This distribution was most likely positively associated with the increased availability of preferred food plants in willow margins. In Miscanthus, by contrast, opposing trends arose for different pollinator taxa: Lepidoptera were the only pollinator group more frequently associated with PEC margins; bumblebees showed no variation while hoverflies were comparatively more abundant in distant cereal margins than in other crop types. Future land‐use practices should consider how PEC identity affects both target species and ecosystem processes. Tackling anthropogenic climate change through cultivation of willow, in particular, may yield local conservation benefits for both wildflowers and pollinators, although strategic cultivation of PECs to enhance pollination processes in the wider agri‐environment may not be achievable. Using observational transects, the visitation frequency to margin wildflowers was established for three pollinator taxa (hoverflies, bumblebees and butterflies/moths) in two perennial energy crops (PECs), Miscanthus and willow short‐rotation coppice, and compared to adjacent and distant cereal controls. In willow, trends showed significantly greater cumulative, and taxa‐specific, flower visitation compared to cereals. Miscanthus showed neutral effects upon cumulative visitation with the direction of response varying between taxa. In neither case was there a significant enhancement of visitation to the margins of adjacent cereal crops when compared to those of distant cereal crops. We conclude that neither PEC influenced pollinator activity around adjacent cereals but there was a clear positive effect of willow on biodiversity and pollinator activity along willow margins.