Effects of organic farming on flies in Danish field boundaries

Summary

The primary objective of this study was to see if organic farming increases the diversity and abundance of fly families in field boundaries when compared to similar conventional biotopes. Secondly, it was investigated whether an increasing organic farming period would increase diversity and abundance of flies. Furthermore, the results from the sampling programme were interpreted ecologically in terms of general community patterns by subjecting data to multivariate analysis.
The study revealed that biodiversity of flies was significantly higher within the organic field boundaries, but no difference was observed in terms of the organic farming period. Overall abundance of flies was similar in the groups and therefore affected by neither agricultural practise nor the organic farming period. Opomyzidae and Chloropidae contributed most to the dissimilarities between organic and conventional farming. Community pattern analyses indicated that families associated with grasses in general could be indicators of conventional farming, whereas flower-visiting flies were found in higher numbers within the organic farming system. The community pattern of field boundary vegetation could only account for a fraction of the total variation seen in fly community patterns, but a high level of flower coverage promoted the diversity of fly families. This study supports hitherto hypothesis of organic farming as a method of enhancing the integrity of nature within the agricultural landscape.