Ashby, Mark and Stevens, Carly and Wilby, Andy and Potts, Simon (2018) Enhancing the benefits to biodiversity and ecosystem services within arable field margins. PhD thesis, Lancaster University.
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Abstract
We need to move towards more sustainable farming methods that maximise yields whilst protecting the environment. One approach that would achieve this goal is ecological intensification, which seeks to manage the biodiversity and ecological processes underpinning agricultural production so that damaging farming practices can be replaced or reduced. Forb-rich arable field margins have been shown to benefit flower-visiting insects such as wild bees, and recent evidence suggests that they can also enhance the levels of pollination and pest control in adjacent crop fields. They may also promote a suite of additional ecosystem services of societal and agronomic importance, but this has yet to be established. Furthermore, the ability of forb-rich field margins to deliver multiple benefits (i.e. ecosystem multifunctionality), including pest control and pollination, is likely to be contingent on a range of local and landscape factors. Using a range of pre-existing field margin plots (n = 98) distributed across 16 arable farms in central eastern England, this study first sought to examine whether high quality forb-rich field margins promote ecosystem multifunctionality more effectively than low quality forb-poor field margins. This involved measuring a range ecosystem services within and adjacent to field margin plots, including pest control, pollination, soil carbon storage, flood alleviation, the abundance of invertebrate ecosystem service providers and the amount of invertebrate biodiversity. Secondly, it established whether arable field margins provide adequate foraging resources for flower-visiting insects. And thirdly, it determined the local and landscape factors (including margin quality) that best promote ecosystem service provision and invertebrate biodiversity within agro-ecosystems. The findings indicated that quality was the most important determinant of ecosystem multifunctionality within arable field margins, as high quality margins supported significantly greater levels of pest control, pollination, flood alleviation and invertebrate biodiversity. However, a range of additional local and landscape management prescriptions further enhanced the multifunctionality of arable field margins, such as the level of vehicle traffic margins receive, vegetation height, landscape complexity and the amount of floral resources provided by the adjacent hedgerow. Despite the multiple benefits of high quality field margins, they were also found to enhance invertebrate crop pests. This may reduce the willingness of farmers to adopt forb-rich habitats on their land. Finally, the present study highlights that more consideration should be given to the forb species included within field margin seed mixes, as certain species were found to promote agronomically damaging crop pests, whereas other species not currently included in field margin seed mixes were extremely attractive to several important flower-visiting taxa or flowered during spring; a period in which field margins are floristically poor. This thesis clearly demonstrates that forb-rich field margins provide multiple agronomic, societal and biodiversity benefits, and outlines the important drivers of ecosystem multifunctionality. As such, it provides farmers and landowners with a clear set of management guidelines for promoting biodiversity and ecosystem services within arable field margins.