Connecting spectral radiometry of anthropogenic light sources to the visual ecology of organisms

Abstract

AbstractHumans have drastically altered nocturnal environments with electric lighting. Animals depend on natural night light conditions and are now being inundated with artificial lighting. There are numerous artificial light sources that differ in spectral composition that should affect the perception of these light sources and due to differences in animal visual systems, the differences in color perception of these anthropogenic light sources should vary significantly. The ecological and evolutionary ramifications of these perceptual differences of light sources remain understudied. Here, we quantify the radiance of nine different street lights comprised of four different light sources: Metal Halide, Mercury Vapor, Light Emitting Diodes, and High‐Pressure Sodium and model how five animal visual systems will be stimulated by these light sources. We calculated the number of photons that photoreceptors in different visual systems would detect. We selected five visual systems: avian UV/VIS, avian V/VIS, human, wolf and hawk moth. We included non‐visual photoreceptors of vertebrates known for controlling circadian rhythms and other physiological traits. The nine light types stimulated visual systems and the photoreceptors within the visual systems differently. Furthermore, we modelled the chromatic contrast (Just Noticeable Differences [JNDs]) and color space overlap for each light type comparison for each visual system to see if organisms would perceive the lights as different colors. The JNDs of most light type comparisons were very high, indicating most visual systems would detect all light types as different colors, however mammalian visual systems would perceive many lights as the same color. We discuss the importance of understanding not only the brightness of artificial light types, but also the spectral composition of light types, as most organisms have different visual systems from humans. Thus, for researchers to understand how artificial light sources affect the visual environment of specific organisms and thus mitigate the effects, spectral information is crucial.