Between perfect habitat and ecological trap: even wildflower strips mulched annually increase pollinating insect numbers in intensively used agricultural landscapes

Abstract

Abstract: The loss of biodiversity and biomass of insects has a detrimental effect on eco-systems and associated ecosystem services, e.g. pollination. For this reason, various nature conservation measures for the promotion of insects are being created in agricultural landscapes. One of those measures is the so-called flower strip at the edge of fields. However, it is repeatedly propagated in the nature conservation community that by means of annually mulched flower strips, species richness and abundance of pollinators in intensively used agricultural areas cannot be increased. Furthermore, these measures might represent ecological traps. To check this criticism, we surveyed one to three meter wide perennial wild flower strips in intensively used agricultural areas, which have been mulched annually for three years, upon abundance, species numbers and biomass of bees and butterflies. By means of transect surveys, species richness and abundance were recorded and biomass was calculated. We compared the findings with those of reference field margins. Our results show an increase in species richness and abundance as well as a general increase in biomass of wild bees and butterflies in wild flower strips compared to findings in the reference field margins. Implications for insect conservation: Our study shows that small, annually mulched wild flower strips are able to promote biodiversity of wild bees and butterflies in the intensively used agricultural landscape. Further, our results obtained that this measure does not inevitably represent an ecological trap or sink habitat for most species.