Investigating the impact of street lighting changes on garden moth communities

Night time illumination of cities is undergoing radical change through the adoption of new street lighting technologies, but the impacts of these large-scale changes on biodiversity have not been explored. Moths are of particular concern because of their nocturnal ‘flight-to-light’ responses. Here we examine in situ effects of (1) street lamp replacement and (2) the spatial distribution of local street lighting on garden moth communities in Birmingham, UK, to determine whether current shifts in street lighting infrastructure are leading to an increased attraction of moths into suburban areas. Using a unique before-after-control-impact survey, we show that switching from narrow (low-pressure sodium) to broad spectrum (high-pressure sodium) lamps significantly increases the diversity of macro-moths in suburban gardens. Furthermore, we demonstrate the complex ways in which the moth community differentially responds to variation in street lighting characteristics. In particular we found that macro-moth attraction was greatest at high lamp densities, whilst micro-moth families responded more strongly to street lamp proximity and the density of UV-emitting lamps specifically. Our findings indicate that moths are attracted to suburban gardens with closer, more dense and more spectrally diverse local street lighting, and suggest that suburban areas could represent ecological traps for moth communities if they have insufficient resources to support moth survival and reproduction. Further research is now needed to determine whether street lighting is progressively damaging moth communities, and to understand whether these impacts could be mitigated through changes to street lighting regimes or through the provision of ecologically important habitats in urban landscapes.