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

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. Our 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.