Artificial field defects: A low-cost measure to support arthropod diversity in arable fields

Abstract

Biodiversity is rapidly declining worldwide, with agricultural intensification being among the main drivers of this process. Effective conservation measures in agricultural landscapes are therefore urgently needed. Here we introduce a novel low-cost conservation measure called artificial field defects, i.e., areas where crop is not sown and spontaneous vegetation grows. To evaluate their biodiversity potential, we compared abundance and species richness of various arthropod taxa between artificially created field defects and control plots within oilseed rape (OSR) fields. The effectiveness of field defects to support biodiversity was examined using an experiment with a factorial design comparing OSR flowering and ripening phases, location of field defects (field edge vs interior) and field defect type (sown with a nectar-rich plant vs no sowing). Arthropod sampling was conducted by employing several complementary methods: pitfall trapping, pan trapping, sweep netting and individual counting. Butterflies, true bugs, bees and wasps were more abundant and species-rich in both types of defects than in OSR controls. In contrast, ground-dwelling taxa had more individuals and species in controls. Overall, arthropod abundance and species richness increased, and field defects became relatively more attractive, during OSR ripening compared to OSR flowering. Location of defects had little effect, with only butterfly and spider assemblages being more abundant and species-rich at field edges compared to interiors. Our data indicate that artificial field defects can provide a simple agri-environmental measure to support various arthropod groups. However, further studies are needed to assess their biodiversity value at the landscape scale, and evaluate the balance between costs and benefits for farmers.