Abstract
Habitat loss and fragmentation are considered the foremost threats in pollinator decline, and in England and Wales, 97% of wildflower meadows were lost by 1984. The value of creating flower-rich margins in agricultural environments is established, yet there is growing potential to support pollinator populations in urban landscapes. We used citizen science to investigate the effectiveness of small 4m2 sown wildflower ‘mini-meadows’ in UK gardens and allotments in recruiting beneficial insects. Participants were allocated one of three treatment groups: Mix 1 (commercially available ‘meadow mix’); Mix 2 (formulated based on existing literature on pollinator foraging preferences); or Control (no additional wildflowers). All participants conducted insect sampling over two years using standardised pan and sticky trap methods May–August. Samples were returned for identification by trained specialists. Mini-meadows provided resource-rich habitats, increasing wild bee richness and supporting on average 111% more bumblebees, 87% more solitary bees and 85% more solitary wasps in the year following seed-sowing, compared to Control plots. The wildflower mixes were also taxon-specific in their attractiveness. Mix 1 attracted more solitary bees and bumblebees, whereas Mix 2 attracted more solitary wasps. There was no significant difference in the abundance of hoverflies between treatments. Higher abundance of solitary wasps and bees caught amongst the mini-meadow was perhaps due to shorter foraging ranges.Implications for insect conservationDomestic gardens and allotments provide huge potential habitat for pollinators, and small-scale floral enhancements can attract more beneficial insects in fragmented urban landscapes, supporting urban biodiversity, pollination services and biological control.
Highlights
Expanding urbanisation is a significant driver of habitat loss and fragmentation, with 55% of the global human population living in urban environments (Vié et al 2009; UN 2019)
The ‘Sow Wild!’ project focused on the effectiveness of sown mini-meadows in UK domestic gardens and allotments, addressing the following questions: i) Does the creation of a mini-meadow increase the abundance of ‘beneficial insects’ and richness of bee species. ii) Do wildflower mixes differ in their success in recruiting different groups of beneficial insects. iii) Does a mini-meadow have a positive ‘spillover’ effect on pollinator abundance throughout the garden or allotment
Sown wildflower species richness increased annually from Year 1 to Year 2, when considering all the floral data collected across the four sampling months and both mixes (Mean ± SE: 1 ± 0.11, to 2.43 ± 0.11 respectively) as was expected with the establishment and flowering of more biennial and perennial species in the second year
Summary
Expanding urbanisation is a significant driver of habitat loss and fragmentation, with 55% of the global human population living in urban environments (Vié et al 2009; UN 2019). Fewer studies have been conducted in gardens on the link between additional floral resources and pollinator abundance, yet they contribute considerable green space to urban areas. In a study of flowering species grown in discrete patches, 18 out of 40 bee-friendly wildflowers provided forage for 100% of observed bee species (Nichols et al 2019), and garden flowers can vary approximately 100-fold in their attractiveness to insects (Garbuzov and Ratnieks 2014), suggesting selectivity over plant species is key to increasing pollinator abundance (Nichols et al 2019). Ready-to-sow wildflower mixes targeting pollinators are readily available, to the best of our knowledge, there are no previous published studies on how successful these mixes are at increasing the abundance of insects and richness of bee species in domestic gardens or allotments. The ‘Sow Wild!’ project focused on the effectiveness of sown mini-meadows in UK domestic gardens and allotments, addressing the following questions: i) Does the creation of a mini-meadow increase the abundance of ‘beneficial insects’ (pollinators and natural enemies of pests) and richness of bee species. ii) Do wildflower mixes differ in their success in recruiting different groups of beneficial insects. iii) Does a mini-meadow have a positive ‘spillover’ effect on pollinator abundance throughout the garden or allotment
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