Abstract
Urbanisation is an important global driver of biodiversity change, negatively impacting some species groups whilst providing opportunities for others. Yet its impact on ecosystem services is poorly investigated. Here, using a replicated experimental design, we test how Central European cities impact flying insects and the ecosystem service of pollination. City sites have lower insect species richness, particularly of Diptera and Lepidoptera, than neighbouring rural sites. In contrast, Hymenoptera, especially bees, show higher species richness and flower visitation rates in cities, where our experimentally derived measure of pollination is correspondingly higher. As well as revealing facets of biodiversity (e.g. phylogenetic diversity) that correlate well with pollination, we also find that ecotones in insect-friendly green cover surrounding both urban and rural sites boost pollination. Appropriately managed cities could enhance the conservation of Hymenoptera and thereby act as hotspots for pollination services that bees provide to wild flowers and crops grown in urban settings.
Highlights
Urbanisation is an important global driver of biodiversity change, negatively impacting some species groups whilst providing opportunities for others
Our rural sites supported a higher overall Insecta species richness and biomass compared to urban sites (Fig. 2a, b), differences which remained significant when controlling for local and landscape variables (GLMM, Z = 4.301, P < 0.001, Fig. 2a; linear mixed model (LMM), t = 2.387, P = 0.048, Fig. 2b)
This difference was likely driven by increased visitation rates, largely of bumble bees, within urban habitats and was associated with increasing Hymenopteran phylogenetic diversity and Hymenopteran species richness, which were enhanced by increasing habitat edge density but suppressed by agriculture in the surrounding landscape
Summary
Urbanisation is an important global driver of biodiversity change, negatively impacting some species groups whilst providing opportunities for others. Insects are a vital component of terrestrial biodiversity, underpinning important ecosystem services such as pollination, soil formation and control of herbivorous pest species[1]. They are of considerable conservation concern, highlighted by a >75% decline in flying insect biomass over the past 27 years in German nature reserves[2], a 78% decline in arthropod abundance and 34% decline in arthropod species richness between 2008 and 2017 in German grasslands[3] and by a 33% range decline of bee and hover fly species between 1980 and 2013 in Britain[4].
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