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 conservationOur 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.
Highlights
During the last decades, several studies revealed a notable decline of insect species richness and biodiversity (Kosior et al 2007; Goulson et al 2008; Scheper et al 2014)
Flower strips which are close to other flower strips or similar nature conservation measures, as well as strips which are close to roads or railroad tracks, with obvious soil compaction or shading were excluded for data acquisition
Between the one-year and threeyear old flower strips a significant increase could be found in both groups
Summary
Several studies revealed a notable decline of insect species richness and biodiversity (Kosior et al 2007; Goulson et al 2008; Scheper et al 2014). In Germany a decrease of about 75% of biomass of flying insects was recorded during 1989–2016 in nature conservation areas (Hallmann et al 2017). Main reasons for the decrease are the loss of habitat structures, climate change and the intensification of agriculture (Steffan-Dewenter 2003; Le Féon et al 2010; Ewald et al 2015; Seibold et al 2019), which causes, amongst others, losses in food plant abundance for flower-visiting insects (Abrahamczyk et al 2020). In Germany about 50% of the land surface is used for agriculture (including grassland) (Umweltbundesamt 2019). This extensive proportion shows that it is necessary to collaborate with local farmers, for establishing large-scale effective nature conservation measures and by that means support insect habitats (Gonthier et al 2014).
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