Nocturnal city lighting elicits a macroscale response from an insect outbreak population

Abstract

Anthropogenic environmental change affects organisms by exposing them to enhanced sensory stimuli that can elicit novel behavioural responses. A pervasive feature of the built environment is artificial nocturnal lighting, and brightly lit urban areas can influence organism abundance, distribution and community structure within proximate landscapes. In some cases, the attractive or disorienting effect of artificial light at night can draw animals into highly unfavourable habitats, acting as a macroscale attractive ecological sink. Despite their significance for animal ecology, identifying cases of these phenomena and determining their effective scales and the number of organisms impacted remains challenging. Using an integrated set of remote-sensing observations, we quantify the effect of a large-scale attractive sink on nocturnal flights of an outbreak insect population in Las Vegas, USA. At the peak of the outbreak, over 45 million grasshoppers took flight across the region, with the greatest numbers concentrating over high-intensity city lighting. Patterns of dusk ascent from vegetated habitat toward urban areas suggest a daily pull toward a time-varying nocturnal attractive sink. The strength of this attractor varies with grasshopper density. These observations provide the first macroscale characterization of the effects of nocturnal urban lighting on the behaviour of regional insect populations and demonstrate the link between insect perception of the built environment and resulting changes in spatial and movement ecology. As human-induced environmental change continues to affect insect populations, understanding the impacts of nocturnal light on insect behaviour and fitness will be vital to developing robust large-scale management and conservation strategies.

Impacts of Artificial Light at Night on Nocturnal and Diurnal Insect Biology and Diversity

“…ALAN also affected a diurnal endoparasitoid Venturia canescens (Hymenoptera: Ichneumonidae) that parasitises the larvae of the Pyralidae, by extending its activity level into the night (Gomes et al, 2021); females of V. canascens exposed to low level ALAN also demonstrated a transgenerational effect with increased development time and increased latency for feeding in their offspring. In a massive collective phototactic response, 45 million individuals of Trimerotropis pallidipennis (Orthoptera: Acrididae), that are usually diurnal, were attracted to city lights in Las Vegas, USA (Tielens et al, 2021) during one of the perennial population outbreaks. Consequently, phototaxis can have devastating effects on even diurnal insect populations by triggering inappropriate behavioural activity.…”

Recent advances in the remote sensing of insects

“…Using a combination of ALAN data from VIIRS and radar‐derived measurements of aerial insect abundance, Tielens et al . (2021) quantified the nocturnal movements of grasshopper swarms into urban areas as a result of attraction to light. Satellite data has also been used to investigate the phenological effects of light pollution on tree budburst (ffrench‐Constant et al ., 2016), suggesting potential for similar applications with insect phenology.…”

“…Weather radar data is already providing new insights into bird migration (Farnsworth et al ., 2016; Dokter et al ., 2018; Nilsson et al ., 2019), and early investigations suggest good potential for its application within entomology. In North America, for example, weather radar has been used successfully to determine the abundance, displacement speed and direction of migrating corn earworm moths ( Helicoverpa zea ) (Westbrook, Eyster & Wolf, 2014) around the Texas–Mexico border, and to investigate the movement of grasshopper swarms in response to urban light pollution (Tielens et al ., 2021). In Europe, the BioDAR project is currently developing a library of weather radar signatures for different insect functional groups and has a citizen science project using weather radar to investigate the nuptial flights of alate ants [see https://biodarproject.org/].…”

The development of an unsupervised hierarchical clustering analysis of dual‐polarization weather surveillance radar observations to assess nocturnal insect abundance and diversity

“…Numerous proof‐of‐concept and observational studies have shown that Doppler WSRs, with and without dual‐polarization, can be used to observe birds and insects and have argued for the potential of WSRs to provide insights into ecology (e.g. Bachmann & Zrnić, 2007 ; Chapman et al., 2011 ; Chilson, Bridge, et al., 2012 ; Chilson, Frick, et al., 2012 ; Dokter et al., 2011 ; Drake, 1990 ; Gauthreaux et al., 2008 ; Gauthreaux & Belser, 1998 ; Gourley et al., 2007 ; Melnikov et al., 2014 ; Melnikov et al., 2015 ; Rennie et al., 2010 ; Russell & Wilson, 1997 ; Russell & Wilson, 2001 ; Stepanian et al., 2020 ; Tielens et al., 2021 ; Westbrook et al., 2014 ; Westbrook & Eyster, 2017 ; Wilson et al., 1994 ; Zrnic & Ryzhkov, 1998 ; among many others). However, despite over 70 years passing since the first description of animals on radar (Crawford, 1949 ; Lack & Varley, 1945 ), the widespread application of WSRs for routine monitoring of volant animals is still hampered by two key problems: (i) the useful identification or categorization of taxa (the ‘classification problem’), and (ii) the quantification of biomass and biodiversity (the ‘quantification problem’).…”