Small mammals on ELS field margins: how do they respond to agri-environment schemes?

Broughton, Richard K.. 2013 Small mammals on ELS field margins: how do they respond to agri-environment schemes? Mammal News, 166. 3.

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Since 2005 NERC’s Centre for Ecology & Hydrology (CEH) has been evaluating how farmland biodiversity may be enhanced by habitat management options available under Environmental Stewardship, the English agri-environmental scheme. Under the Common Agricultural Policy UK farmers adopt basic ‘cross compliance’ environmental standards, including leaving 1-2 metre wide uncropped margins around arable fields. Under the Entry Level Scheme (ELS) tier of Environmental Stewardship, farmers can gain additional subsidy for installing 6-m-wide field margins of rough grasses to provide habitat for e.g. small mammals. However, few studies have examined how small mammals respond to agri-environment schemes in Britain (reviewed in Macdonald et al. 2007, Mammal Review 37), and the potential large-scale benefits of ELS margins remain untested. Between 2005 and 2011 CEH compared small mammal communities on field margins across the 1,000 ha Hillesden estate, a typical lowland arable farm in Buckinghamshire. A randomised block experiment was established, with five replicate blocks of farmland each containing three areas of management (43-70 ha): (1) standard ‘cross compliance’ with conventional 1-2 m field margins; (2) a typical ELS regime where 1% of farmland was taken out of production and 6-m-wide grassy field margins were installed; (3) a trial ‘ELS-Extra’ treatment that took 5% of land out of production and installed 6-m-wide grassy field margins and flower-rich plots. Using Longworth live-trapping, we compared small mammal communities on conventional and grassy field margins between these treatments. Trapping was carried out on five morning and evening sessions over three days in autumn and spring, in four years of the six year period. We used two trap-lines totalling 22 traps on each treatment replicate, to see how the small mammal communities developed after margin installation. In total 13,200 traps were checked during the study. The results were very encouraging (Broughton et al., in prep.). Over the study duration the number of species detected on the estate increased from one, wood mouse (Apodemus sylvaticus), to include bank vole (Myodes glareolus), field vole (microtus agrestris), harvest mouse (Micromys minutus), common shrew (Sorex araneus), pygmy shrew (S. minutus) and water shrew (Neomys fodiens), with occasional house mouse (Mus musculus), brown rat (Rattus norvegicu) and weasel (Mustela nivalis). In autumn, generalised linear modelling indicated that average species richness was 44% greater on ELS and ELS-Extra field margins than on conventional cross compliance margins, with significantly greater abundance of bank and field voles. The average number of animals of all species in autumn was generally greater on the ELS/ELS-Extra margins, but this was not statistically significant and overall abundance also increased on cross compliance margins. Across the estate, the overall number of animals detected in autumn quadrupled within 3 years before stabilising at this higher level. The modelling indicated a more complicated pattern in spring, with an increase in species richness across all treatments over time, and an increase in overall abundance on ELS/ELS-Extra margins but no change on cross compliance. This pattern was driven by declining numbers of wood mice that were largely replaced by bank and field voles, perhaps hinting at inter-specific competition. In summary, these results indicated that installation of 6-m-wide grassy field margins led to substantial increases in the diversity and abundance of small mammals not only on those margins created under ELS, but also on surrounding conventional farmland. This implied a possible ‘spill over’ effect of ELS margins creating a reservoir of animals that dispersed into other areas. However, we found no additional benefit of the ELS-Extra treatment over standard ELS, suggesting that the 1% of farmland given over to ELS management was sufficient to achieve positive benefits at the farm-scale.

Item Type: Publication - Article
Programmes: CEH Topics & Objectives 2009 - 2012 > Biodiversity
UKCEH and CEH Sections/Science Areas: Pywell
Additional Keywords: small mammals, Hillesden, ELS, agri-environment scheme, AES
NORA Subject Terms: Ecology and Environment
Agriculture and Soil Science
Related URLs:
Date made live: 16 Jul 2013 10:49 +0 (UTC)

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