The impact of artificial light at night on nocturnal insects: A review and synthesis

Abstract

In recent decades, advances in lighting technology have precipitated exponential increases in night sky brightness worldwide, raising concerns in the scientific community about the impact of artificial light at night (ALAN) on crepuscular and nocturnal biodiversity. Long-term records show that insect abundance has declined significantly over this time, with worrying implications for terrestrial ecosystems. The majority of investigations into the vulnerability of nocturnal insects to artificial light have focused on the flight-to-light behavior exhibited by select insect families. However, ALAN can affect insects in other ways as well. This review proposes five categories of ALAN impact on nocturnal insects, highlighting past research and identifying key knowledge gaps. We conclude with a summary of relevant literature on bioluminescent fireflies, which emphasizes the unique vulnerability of terrestrial light-based communication systems to artificial illumination. Comprehensive understanding of the ecological impacts of ALAN on diverse nocturnal insect taxa will enable researchers to seek out methods whereby fireflies, moths, and other essential members of the nocturnal ecosystem can coexist with humans on an increasingly urbanized planet.

Keywords: artificial light at night; bioluminescence; fireflies; light pollution; nocturnal insects; visual ecology.

Figure 1

Spectral emission of different ALAN types. ALAN sources, such as incandescent and halogen bulbs, and mercury vapor lamps emit large amounts of energy as infrared radiation (heat); mercury vapor and metal halide lamps also emit a non‐negligible amount of UV radiation. Low‐pressure sodium lamps and LEDs are comparatively efficient ALAN sources, both capable of emitting nearly monochromatic visible light (see text). Neutral (red) and cool (blue) temperature white LEDs have been plotted on the same graph for comparison. Modified from Elvidge, Keith, Tuttle, and Baugh (2010) with permission

Figure 2

Spectral sensitivity in humans and insects. (a) Spectral sensitivities of blue (S, short‐wavelength), green (M, mid‐wavelength), and red (L, long‐wavelength) sensitive photoreceptors in humans presented as 10° cone fundamentals, calculated from Stiles and Burch (1959) color matching functions (Stockman & Sharpe, 2000; www.cvrl.org/). Humans are insensitive to UV wavelengths (<390 nm), perceive visible light wavelengths (390–700 nm) as color, and perceive infrared wavelengths (>700 nm) as heat. (b) Human luminosity function, used to predict relative “brightness” as perceived by humans. (c) Spectral sensitivity of the photoreceptors of honeybee workers, thought to have retained the trichromatic color vision of ancestral insects (Briscoe & Chittka, 2001; modified from Peitsch et al., 1992). (d) Electroretinography of a male Big Dipper firefly Photinus pyralis suggests that this species may have lost its short‐wavelength sensitive opsin (modified from Lall, Chapman, Ovid Trouth, & Holloway, 1980)