Field scale organic farming does not counteract landscape effects on butterfly trait composition

Abstract:
We tested how dispersal capacity, host plant specificity and reproductive rate influenced the effects of farming system and landscape composition on butterfly species richness and abundance. In no case did variation in these traits explain species responses to organic farming, indicating that all species benefit equally. In contrast, butterflies with high mobility and reproductive rate were disproportionally more abundant in landscapes dominated by arable land, and the species richness of butterflies with low mobility tended to decrease with increasing proportion of arable land whereas those of high mobility remained fairly constant. Hence, although organic farming increased biodiversity, it did not counteract landscape effects on butterfly trait composition. As a trait dependent loss of biodiversity may result in a larger decline of functional trait diversity compared to species diversity, these results imply that organic farming may not increase or restore functional agro-ecosystem diversity. Information provided by species traits, rather than biodiversity per se, may provide important information for successful revisions of future agri-environment schemes.