Flower Margins: Attractiveness over Time for Different Pollinator Groups

Supporting biodiversity in agricultural landscapes is key from both a conservation and ecosystem services perspective. Planting flower margins along crop field edges is one of the most established approaches to try and improve habitat and resources for insect pollinators on farms. Whilst there is growing evidence that these margins can result in increased pollinator abundance and diversity on farms in the short-term, there is little data looking at how these margins perform over longer periods. This study looked at the utilization of pollinator-friendly margins over time in an agricultural landscape in Hungary. ‘Operation Pollinator’ seed mixes with 12 species, were used at 96 farms in Hungary from 2010 to 2018. Insect pollinators were recorded on the sown flower margins and control margins (with naturally occurring vegetation) using walked transects. Repeated sampling of the margins was done over several years so that data was collected on margins from 0 (planted that season) to 7 years old. The abundance of pollinators in the Operation Pollinator flower margins was greater than in control margins for all groups recorded (honey bees, bumble bees, mining bees, trap-nesting bees, hoverflies and Lepidoptera). The biggest relative increase in abundance was in honey bees (768% increase in average abundance in the flower margin compared to the control across all observations), with mining (566%) and bumble bees (414%) showing the next largest increases. The abundance of bumble bees, trap-nesting bees and Lepidoptera in the margins did not vary with the age of the margin. Honey bees, mining bees and hoverflies all decreased in abundance with increasing margin age, as did flower abundance. The results suggest that for some pollinator groups, regardless of age, flower margins provide important resources in the agricultural landscape. However, this is not universally true and for certain pollinator groups, some re-sowing of the margins may be needed to sustain longer-term benefits.