Organic Farming: Biodiversity Impacts Can Depend on Dispersal Characteristics and Landscape Context

Feber, R, Johnson, P, Bell, J, Manley, Will, Mathews, F, Norton, L, Townsend, M and Macdonald, D (2015) Organic Farming: Biodiversity Impacts Can Depend on Dispersal Characteristics and Landscape Context. PLOS One. ISSN 1932-6203

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Organic farming, a low intensity system, may offer benefits for a range of taxa, but what affects the extent of those benefits is imperfectly understood. We explored the effects of organic farming and landscape on the activity density and species density of spiders and carabid beetles, using a large sample of paired organic and conventional farms in the UK. Spider activity density and species density were influenced by both farming system and surrounding landscape. Hunting spiders, which tend to have lower dispersal capabilities, had higher activity density, and more species were captured, on organic compared to conventional farms. There was also evidence for an interaction, as the farming system effect was particularly marked in the cropped area before harvest and was more pronounced in complex landscapes (those with little arable land). There was no evidence for any effect of farming system or landscape on web-building spiders (which include the linyphiids, many of which have high dispersal capabilities). For carabid beetles, the farming system effects were inconsistent. Before harvest, higher activity densities were observed in the crops on organic farms compared with conventional farms. After harvest, no difference was detected in the cropped area, but more carabids were captured on conventional compared to organic boundaries. Carabids were more species-dense in complex landscapes, and farming system did not affect this. There was little evidence that non-cropped habitat differences explained the farming system effects for either spiders or carabid beetles. For spiders, the farming system effects in the cropped area were probably largely attributable to differences in crop management; reduced inputs of pesticides (herbicides and insecticides) and fertilisers are possible influences, and there was some evidence for an effect of non-crop plant species richness on hunting spider activity density. The benefits of organic farming may be greatest for taxa with lower dispersal abilities generally. The evidence for interactions among landscape and farming system in their effects on spiders highlights the importance of developing strategies for managing farmland at the landscape-scale for most effective conservation of biodiversity.

Item Type: Article
Keywords: Organic farming, Farms, Species diversity, Agriculture, Plants, Agricultural production, Biodiversity, Beetles
Divisions: Agriculture, Food and Environment
Depositing User: Marieke Guy
Date Deposited: 19 Dec 2018 16:44
Last Modified: 20 Oct 2022 14:41

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