Low impact of two LED colors on nocturnal insect abundance and bat activity in a peri-urban environment

Janine Bolliger,Stephan Blum,Beat Wermelinger,Martin K Obrist,Tom Hennet,Jörg Haller

doi:10.1007/s10841-020-00235-1

Abstract

Artificial light at night (ALAN) is an important driver of change in ecological environments of the 21th century. We investigated the impact on nocturnal insect abundance and bat activity of two LED light colors (warm-white 2700 K, cold-white 6500 K) in a peri-urban environment. Bat activity (predominantly Pipistrellus pipistrellus) was largely driven by prey availability (insects), while insect abundance was responsive to nightly weather conditions (precipitation, temperature). Thus, both insects and bats were not differentially responsive to cold-white or warm-white LEDs. These findings are largely in contrast with literature, particularly for insects. However, as most published experiments on ALAN were conducted in areas that were lit solely for the purpose of the experiment, we would like to bring forward that (1) adaptation to environmental constraints may play a role in peri-urban environments that have been exposed to ALAN for many decades; or (2) impacts of cold-white LEDs on nocturnal insects may be lower than expected, because nocturnal insects adapted to low-light conditions may be put off by cold white light sources (6500 K).

Highlights

Artificial light at night (ALAN) is identified as an important driver of environmental change in the 21st century (Davies et al 2012; Davies and Smyth, 2018; Hölker et al 2010)
Recent reviews point out that artificial light at night impacts practically all aspects in the life cycle of nocturnal insects: orientation, movement, foraging pattern, mate choice, predator availability, larval development, physiological processes and, last, but not least, adaptive and behavioral traits (Desouhant et al 2019; Owens et al 2019; Owens and Lewis 2018)
New developments in LED technology provide long-lived and energy efficient lighting infrastructure (Djuretic and Kostic 2018), they have been the focus of many critical assessments claiming that LED might be detrimental because their spectral composition peaks in the blue range to which many nocturnal insects appear sensitive ((Donners et al 2018; Eccard et al 2018; Grubisic et al 2018; Longcore et al 2015; Pawson and Bader 2014, but see Macgregor et al (2019))

Summary

Introduction

Artificial light at night (ALAN) is identified as an important driver of environmental change in the 21st century (Davies et al 2012; Davies and Smyth, 2018; Hölker et al 2010). New developments in LED technology provide long-lived and energy efficient lighting infrastructure (Djuretic and Kostic 2018), they have been the focus of many critical assessments claiming that LED might be detrimental because their spectral composition peaks in the blue range to which many nocturnal insects appear sensitive ((Donners et al 2018; Eccard et al 2018; Grubisic et al 2018; Longcore et al 2015; Pawson and Bader 2014, but see Macgregor et al (2019)). Replacing the older street lights with energy saving LEDs can lead to brighter illumination. LED technology allows for selective adjustment of spectral composition of light emission (Pimputkar et al 2009), potentially leading to a LED colour spectrum less attractive for insects (Longcore et al 2015)

Methods

Results

Conclusion