The value of woody hedgerows for moth diversity on organic and conventional farms

Habitat destruction and degradation are important drivers of biodiversity loss within agro-ecosystems. However, little is known about the effect of farming practices and the value of woody hedgerows on Lepidoptera in North America. The purpose of this work was to study moth diversity in woody hedgerows and croplands of organic and conventional farms. In addition, the influence of vegetation composition and abiotic variables on species richness, abundance, and composition was examined. Moths were sampled with light traps during six weeks in the summer of 2001. Vegetation data and abiotic variables were obtained for all sites. In total, 26,020 individuals from 12 families and 408 species were captured. Most species were uncommon. Only 35 species included >100 individuals while for 71% of species <10 individuals were found. The Noctuidae represented 221 species and 85% of all individuals captured. Woody hedgerows harbored more species and in greater number than croplands. There was no significant difference in moth diversity between organic and conventional farms, except that the Notodontidae were significantly more species rich in organic than in conventional sites. Results show that species richness, abundance, and composition were greatly influenced by habitat types (hedgerow versus crop field) and abiotic variables (minimum temperature which was correlated to moon illumination, rainfall, and cloud cover). Moth species composition was significantly correlated to vegetation composition. This study broadens our understanding of the factors driving moth diversity and expands our knowledge of their geographic range. The maintenance of noncrop habitats such as woody hedgerows within agro-ecosystems seems paramount to preserving the biodiversity and abundance of many organisms, including moths.