Agri-environment scheme enhances small mammal diversity and abundance at the farm-scale

• Creation of 6 m field margins enhanced small mammal communities on arable farmland.
• Species richness and abundance of voles, mice and shrews increased substantially.
• A farm-scale effect of enhanced mammal populations was detected.
• Results suggest a spill-over effect from field margins onto conventional farmland.

The decline of farmland biodiversity over much of Europe has been largely attributed to agricultural intensification. Since the 1970s, governments have introduced agri-environment schemes (AES) aimed at mitigating this impact, but information on their success is limited. A five y, farm-scale experiment was conducted to test the efficacy of England's Environmental Stewardship AES in enhancing the species richness and abundance of small mammals (voles Cricetidae, mice Muridae, and shrews Soricidae) in an intensively-farmed arable landscape.Small mammal communities were sampled in spring and autumn on grassy field margins installed under the Entry Level Scheme (ELS) tier of Environmental Stewardship, where 1% of cropped land was converted to wildlife habitats. Results were compared with those from field margins on a second, experimental treatment (ELS Extra: ELSX) in which 5% of cropped land was taken out of production, and also field margins on a conventionally-farmed control treatment (‘cross compliance’: CC). Species richness and abundance of small mammals showed a significant increase on all treatments in spring and autumn. Many increases were greater on ELS and ELSX field margins compared to the CC controls, but there was little evidence that ELSX was more beneficial than ELS, and there were species-specific differences. Voles were not detected on any treatment in the initial sampling period but bank voles Myodes glareolus rapidly became abundant thereafter, particularly on ELS and ELSX field margins, and field voles Microtus agrestis also colonised. Wood mice Apodemus sylvaticus were present on all treatments in all sampling periods, but spring abundance declined as vole abundance increased.These results suggest that the Entry Level Scheme tier of the English agri-environment scheme is effective in enhancing small mammal communities on arable farmland, with potential benefits for higher trophic levels via their predators.