The organic farms in this region do

The organic farms in this region do have significantly larger areas of semi-natural vegetation than their conventional counterparts, as well as differences in the proportions of grass fields and arable fields (Table 1). However, our study revealed no difference in farm size and structure (in terms of field sizes) or any aspect of landscape element diversity between organic and conventional farms in the south-west of England. Organic farms supported higher levels of plant abundance, species richness and diversity in arable fields but not in semi-natural areas of vegetation where there were no differences between organic and conventional farms.

Organic farms had significantly greater total area of semi-natural (woodlands) and boundary vegetation (field margins and hedges) and this may have an impact on biodiversity at higher trophic levels. There was no difference in hedgerow ground area between organic and conventional farms but analysis of summer measurements of hedge cross-sectional area showed a significant difference when height was taken into account. Hedgerows on organic farms were higher (also found by Fuller et al. 2005) suggesting they are trimmed less often, or that hedgerows on conventional farms are cut to shorter heights than those on organic farms. Higher hedgerows, with larger surface area, have been correlated with increased bat foraging activity (Wickramasinghe et al. 2003) and higher butterfly diversity (Ouin & Burel 2002). Bird species richness has been found to increase with the amount of hedgerow on farms, but only up to a certain landscape density, beyond which greater amounts do not result in greater species richness