Field margins are uncultivated strips of land bordering cultivated fields. They support a range of ecological functions and provide environmental benefits that extend to the wider agricultural ecosystem.
Defining Field Margins
These uncultivated strips of land are situated between a crop and the field boundary, commonly found alongside hedgerows, roads, or watercourses. Margins can take various forms, including naturally regenerated grass strips, deliberately sown wildflower mixes, or specific areas managed for particular plant communities. The width of these margins can vary, with recommendations often suggesting a minimum of 2 meters from the base of a hedgerow, although some can extend up to 12 meters or more into the field. This diversity in form and size allows field margins to serve different purposes within the agricultural setting.
Ecological Benefits
Field margins function as habitats and resource providers for a wide array of biodiversity. They are particularly beneficial for pollinators, such as various bee species and butterflies, by offering both nesting sites and a consistent supply of nectar and pollen, especially when adjacent crops are not in bloom. Research indicates that increasing the width of these wild strips can enhance the availability of forage for pollinators nesting within the landscape. Field margins also support beneficial insects, including natural predators and parasitoids that help control agricultural pests, thereby potentially reducing the need for chemical interventions.
Beyond insects, these margins provide food, shelter, and breeding grounds for birds like the yellowhammer and willow warbler, which nest in thick vegetation. Small mammals, such as field mice, voles, rats, and shrews, also find suitable habitat in these areas, in turn providing hunting grounds for predators like barn owls and kestrels. Field margins additionally act as ecological corridors, facilitating the movement of wildlife between fragmented habitats across the agricultural landscape. This connectivity helps to mitigate the negative effects of habitat loss and isolation on biodiversity.
Environmental Contributions
Field margins offer broader environmental advantages beyond direct support for living organisms. Their established vegetation plays a role in preventing soil erosion by stabilizing the soil, which is particularly important on sloped land or in areas prone to runoff. They also contribute to improved water quality by acting as buffer strips, filtering runoff from agricultural fields. This filtration reduces the leaching of nutrients and pesticides into nearby watercourses, protecting aquatic ecosystems.
Field margins also have a role in carbon sequestration. By allowing vegetation to grow and accumulate organic matter in the soil, these areas can store significant amounts of carbon. Scenarios involving different margin widths and vegetation types, such as grass strips or tree strips, have shown varying potentials for carbon accumulation, with tree strips offering greater capacity due to above-ground biomass. This contribution to carbon storage helps to mitigate greenhouse gas emissions.
Creating and Managing Field Margins
Field margins can be created by allowing existing grassland to regenerate naturally or by sowing specific mixtures of grasses and native wildflowers. Including a diversity of flowering plants, such as yarrow, black knapweed, and oxeye daisy, can significantly increase their value for wildlife by providing varied food sources and host plants for invertebrates. Wider margins are generally more beneficial for wildlife, and linking them to existing habitats, such as hedgerows or woodlands, enhances their effectiveness as movement corridors.
Appropriate mowing regimes are important to maximize the benefits of field margins; for instance, cutting in autumn after plants have flowered helps prevent vegetation from becoming too dense or turning into scrub, while avoiding summer mowing protects nesting wildlife and pollen/nectar sources. It is also important to prevent pesticide and fertilizer drift from adjacent cultivated fields, as these can negatively impact the biodiversity within the margins. In grazing situations, fencing off field margins to exclude livestock can further enhance their structural diversity, allowing vegetation to flower and set seed.