Biodiversity in the city: Sown meadows as urban refuges for pollinators

By Dr. Chinta SidharthanReviewed by Lexie CornerDec 2 2024

Urban development and intensive agriculture have significantly reduced natural habitats, impacting pollinators like bees, butterflies, and hoverflies. As cities expand, green spaces are increasingly designed to support biodiversity and ecosystem services. Sown wildflower meadows have gained attention as an urban greening strategy, but their ecological effectiveness compared to natural meadows remains uncertain.

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In a recent study published in Ecological Entomology, researchers from the University of Life Sciences in Poland investigated the potential of sown wildflower meadows to support pollinator diversity and abundance. Conducted in Warsaw, Poland, the research compared pollinator communities in sown and natural meadows, offering insights into their capacity to mitigate habitat loss and sustain urban pollinator populations.

Background

Pollinator populations are declining globally due to habitat destruction, urbanization, and agricultural intensification. The expansion of urban areas and agricultural fields reduces the availability of floral resources and nesting habitats essential for pollinators such as bees, butterflies, and hoverflies. Urban green spaces offer potential refuges for these species, but their ecological value largely depends on effective management practices.

Natural meadows offer diverse floral resources, but such habitats are often absent in urban areas due to limited space and landscaping practices. Sown wildflower meadows have emerged as a potential solution, offering floral diversity and aesthetic appeal while requiring minimal maintenance. However, the ecological effectiveness of these artificial meadows remains uncertain.

Previous studies have reported a positive correlation between pollinator abundance and floral richness, but very few studies have examined how these findings apply to sown meadows. Differences in patch size, plant composition, and urban fragmentation may further complicate evaluations of their ecological value.

Study design

The study, conducted over two years (2017–2018) in Warsaw, focused on 11 meadow sites, including sown wildflower meadows and natural meadows. Sown meadows were created with seed mixtures containing grasses, native species, and perennials, while natural meadows were unmanaged wastelands or minimally mowed grasslands.

Pollinator surveys were conducted during peak activity (June–August) on sunny, windless days. Researchers sampled pollinators using aerial nets during standardized 20-minute observation periods, ensuring consistent comparisons across meadow types. Insects were identified at the species level, with protected species recorded and released.

Key metrics included pollinator abundance, species richness, and community composition across bees, butterflies, and hoverflies. Patch size and flowering plant species were also recorded. Diversity within samples (α-diversity) was measured using the Shannon-Wiener index, while differences between samples (β-diversity) were analyzed using Jaccard distance. The impact of meadow size on pollinator diversity and abundance was also evaluated.

Key findings

The study showed that sown wildflower meadows can support pollinator communities at levels comparable to natural meadows in urban environments. The abundance and species richness of bees and hoverflies were similar across both meadow types, while butterfly abundance was higher in natural meadows, though species richness did not differ significantly. Larger patch sizes were associated with increased butterfly diversity but showed no significant effect on bees or hoverflies.

The taxonomic α-diversity of bees, butterflies, and hoverflies was consistent across meadow types. β-diversity analyses indicated similar species turnover between natural and sown meadows for bees and hoverflies, while butterflies exhibited higher taxonomic β-diversity in sown meadows. The presence of certain rare or protected butterfly species in sown meadows highlighted their value for urban biodiversity.

Despite being smaller in size, sown meadows had similar floral compositions to natural meadows, providing critical resources for pollinators. These findings suggest that sown meadows, with appropriate management, can serve as effective substitutes for natural habitats in fragmented urban landscapes, particularly for generalist pollinators like hoverflies and some bee species.

However, the study highlighted the limitations of sown meadows in supporting specialized pollinators, emphasizing the need to preserve larger, intact natural habitats while incorporating artificial meadows into urban planning.

Conclusions

The study showed that sown wildflower meadows can function as valuable habitats for pollinators in urban areas. While both sown and natural meadows supported bees and hoverflies effectively, natural meadows were found to better sustain butterfly populations, underscoring their ongoing importance.

The findings suggest that sown meadows, with proper management, offer a practical and low-maintenance approach to enhancing urban biodiversity, particularly in fragmented landscapes. Integrating natural habitat conservation with sown meadow initiatives can create supportive environments for pollinators in urban settings.

Journal reference

Zajdel, B., Dylewski, Ł., Jojczyk, A., BanaszakCibicka, W., Kucharska, K., Borański, M., Gąbka, J. (2024). Sown wildflower meadows: Can they replace natural meadows in urban spaces for bees, butterflies and hoverflies? Ecological Entomology. DOI:10.1111/een.13396 https://resjournals.onlinelibrary.wiley.com/doi/10.1111/een.13396