Partial mowing of urban lawns supports higher abundances and diversities of insects

Jennifer Wintergerst,Christian Schmidt,Manuela Bartel,Matthias Nuss,Tommy Kästner

doi:10.1007/s10841-021-00331-w

Jennifer Wintergerst, Christian Schmidt + Show 3 more

Open Access

https://doi.org/10.1007/s10841-021-00331-w

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Abstract

Within the citizen science project “Flowering meadows for Saxonian butterflies”, more than 640 meadows are partially and at maximum three times annually mowed in order to change urban lawns into habitats for insects. In 2019, insect diversity was evaluated using the 100 sweep net technique during five visits at nine butterfly meadows (BM) and nine intensively mowed lawns (IML). The mean arthropod biomass of these five visits per site is significantly higher on BM compared to IML. All adult individuals of Apidae, Coleoptera, Heteroptera, Orthoptera, Papilionoidea as well as Asilidae and Syrphidae have been identified morphologically, revealing 260 species from all study sites. The mean number of species per visit is significantly higher on BM compared to IML. 90 species are recorded as larva and the mean number of species per visit is significantly higher on BM compared to IML. 42 species are recorded as larva as well as adult. The records of larvae provide evidence for reproduction on the meadows.Implications for insect conservationOur results clearly demonstrate that a reduced mowing frequency together with an always partial mowing of the area support higher biomass, abundances and diversities of insects as well as reproduction of insects on urban lawns. Therefore, reduced mowing frequency together with partial mowing is recommended for urban lawns as well as meadows in the countryside and conservation areas to foster insect diversity.

Highlights

Urban lawns fulfil different functions for human recreation (White et al 2013; Tsurumi and Managi 2015), but a large part of these areas is not used at all despite intensive mowing
Thanks to the observations recorded by the participants on the project website, we learned that insects are coming back already during the first season during which the mowing regime is adapted
The outliers are based on a high abundance of orthopterans on butterfly meadows (BM) 1708 and a high abundance of honeybees on intensively mowed lawns (IML) 1708

Summary

Introduction

Urban lawns fulfil different functions for human recreation (White et al 2013; Tsurumi and Managi 2015), but a large part of these areas is not used at all despite intensive mowing. Garbuzov et al (2014) applied four different mowing regimes in a suburban public park in Saltdean, UK They found 50 times greater insect abundance in that area of the park which has been not mowed for a year, while significantly lowest abundance was found where regular mowing took place every two weeks during spring and summer. A mowing management comprising only one or two mowing events per year and the removal of the mown grass from the surface is applied in the city of Tübingen, Germany since 2010 It significantly increases the diversity indices of orthopterans, butterflies, hemipterans and bees (Hiller and Betz 2014; Kricke et al 2014; Unterweger et al 2017; Wastian et al 2016). This confirms results from the city of Rennes in France where plant diversity increased by 15% to 62% after 25 years of reduced mowing frequency

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