Disentangling how urbanisation influences moth diversity in grasslands

Abstract

Urban areas have profound impacts on local species diversity and composition through a set of intertwined changes in the environment. As the world is rapidly urbanising while simultaneously facing a biodiversity crisis, a better understanding of how urbanisation influences biodiversity is necessary. To test if and how urbanisation influences moth diversity and whether urbanisation is acting directly or indirectly via urbanisation‐induced increased habitat isolation, smaller habitat area, higher light pollution and increased mowing intensity, we sampled moths with light trapping in 20 grasslands in the urban core of the city of Darmstadt (southwestern Germany) and 20 grasslands in the surrounding area. Moth abundance and diversity decreased with increasing urbanisation. Smaller habitat area and high mowing intensity reduced moth abundance, while other environmental variables including isolation and light pollution had only indirect effects. High levels of urbanisation were associated with reduced moth abundance, which in turn drove declines in diversity. Urbanised sites favoured generalist species and differed in species composition compared to sites in the surrounding. The results show that urbanisation is directly reducing moth abundance and diversity in cities. The negative effect of urbanisation is further attenuated by habitat fragmentation and high mowing intensity, which are both known drivers of biodiversity decline in urban areas and beyond. While urbanisation itself is often irreversible, reducing mowing intensity and preserving larger grassland areas could facilitate moths and other taxa in and around cities.

Insect ecology and conservation in urban areas: An overview of knowledge and needs

“…Patch quality matters, although is taxon-subjective, and those with greater heterogeneity can support greater insect activity, diversity and abundance (Azhar et al, 2024;Helden & Leather, 2004). These fragmented urban habitats can also experience varying and under-recorded degrees of management and disturbance; for example, mowing or unregulated use of pesticides in residential areas mediate the environmental and ecological factors that influence insect diversity in urban areas (Helden & Leather, 2004;Lowe et al, 2019;Sanetra et al, 2024).…”

“…Many works indicate a homogenisation and decrease in functional type, species diversity and/or insect abundance as urban density increases (in this SI see: Barao et al, 2024;Casanelles-Abella et al, 2024;Federico et al, 2024;Rivest & Kharouba, 2024;Sanetra et al, 2024;Svenningsen et al, 2024). This picture is, however, nuanced (e.g., Ancillotto & Rocco, 2024;Federico et al, 2024;Ombugadu et al, 2024) and although urban areas can detrimentally impact some insect taxa through the predominance of artificial environments, constrained habitats and disturbances, other taxa can adapt and thrive in the mosaic of semi-natural and novel environments, management variation and abundant resources (Curry et al, 2024;Hill et al, 2024;Nunes et al, 2024;Plummer et al, 2024;Xu et al, 2024).…”