K. Birkhofer, J. Ekroos, E.B. Corlett, H.G. Smith

Department of Biology, Lund University, Sölvegatan 37, 22362 Lund, Sweden.

Abstract

Organic farming is promoted as a sustainable alternative to conventional farming, with positive effects on the diversity of plants and selected animal taxa. Here, we used a literature survey to collect presence/absence data on the composition of farmland bird, ground beetle, spider as well as butterfly and moth communities from 28 independent studies to identify genera and (sub-)families that had either higher (winners) or lower (losers) species richness under organic farming. We further tested if the taxonomic breadth of communities and the number of species of conservation concern differed between farming systems and if climate or fertilization intensity altered responses of animal communities to organic farming. Our results suggest that there are both winners and losers of organic farming and that this effect depends on whether taxa are predaceous (losers) or exclusively feed on plant material (winners). Organic farming did not lead to a higher number of exclusive species, but significantly more species of conservation concern were observed under organic farming. Organic farming consistently led to a slightly higher taxonomic breadth of bird communities. Finally, we did not find support that local long-term climatic conditions or differences in fertilization rates between farming systems altered the effect of organic farming. Overall, we did not find strong support for general positive effects of organic farming on animal diversity in the analysed groups across Central and Northern Europe.

Keywords: Agri-environment schemes; Biodiversity conservation; Climate; Land-use intensity; Rare species; Taxonomic distinctness.