The hypothesis that sown 6m grass margin strips at the edges of arable fields have a positive impact on farmland biodiversity was tested using a paired field approach on 42 fields in southern England during 2003. Half the sites had margin strips created under the UK Countryside Stewardship Scheme. The sites were grouped into small, intermediate or open landscapes on the basis of average field size and sampled in the field centre and the pre-existing field boundary. Orthoptera, important bird food items which were only found in field boundaries, were more abundant where strips were sited, reflecting added habitat resources. Predatory Lycosid spiders were consistently more abundant in boundaries of small fields with 6m margins. Linyphiidae were more abundant in the centre of smaller fields. There are benefits to farmland biodiversity from introducing new margin strips at the edges of arable fields, but scheme administrators may need to address landscape structure and mean field size to achieve significant enhancement of populations of some declining farmland species.
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