Summary
Modern organisms evolved under predictable natural light cycles, using subtle changes in daylight and darkness to regulate essential behaviors such as foraging, migration, reproduction, and seasonal timing. However, the rapid expansion of artificial lighting has profoundly altered these natural lighting regimes, with well-documented consequences for wildlife phenology, behavior, and reproductive success that cascade into changes in community structure and ecosystem function. While most ecological research has focused on how the brightness, timing, and color spectrum of artificial light affect organisms, this study draws attention to an overlooked but widespread characteristic of many lighting technologies: flicker. Many artificial light sources—such as LEDs, fluorescents, and some high-pressure lamps—emit light in rapid pulses rather than as a continuous stream. Whether an organism perceives this flicker depends on its critical fusion frequency (CFF), the threshold at which pulsed light is seen as steady. By compiling the largest cross-taxa dataset of CFF values to date, the authors demonstrate that a substantial portion of species possess visual systems capable of detecting flicker produced by commonly used lamps. Because flickering light is known to induce stress, impair vision, and alter behavior in humans and other animals, the study suggests that flicker may be an unrecognized but significant ecological stressor with the potential to disrupt species interactions, sensory ecology, and ecosystem functioning. The authors argue that the ecological impacts of light flicker deserve far greater attention in both research and environmental management.
PMID: 24874801
PMCID: PMC4038456
DOI: 10.1016/s0304-3940(01)02549-3
Abstract
Organisms have evolved under stable natural lighting regimes, employing cues from these to govern key ecological processes. However, the extent and density of artificial lighting within the environment has increased recently, causing widespread alteration of these regimes. Indeed, night-time electric lighting is known significantly to disrupt phenology, behaviour, and reproductive success, and thence community composition and ecosystem functioning. Until now, most attention has focussed on effects of the occurrence, timing, and spectral composition of artificial lighting. Little considered is that many types of lamp do not produce a constant stream of light but a series of pulses. This flickering light has been shown to have detrimental effects in humans and other species. Whether a species is likely to be affected will largely be determined by its visual temporal resolution, measured as the critical fusion frequency. That is the frequency at which a series of light pulses are perceived as a constant stream. Here we use the largest collation to date of critical fusion frequencies, across a broad range of taxa, to demonstrate that a significant proportion of species can detect such flicker in widely used lamps. Flickering artificial light thus has marked potential to produce ecological effects that have not previously been considered.
Inger R, Bennie J, Davies TW, Gaston KJ. Potential biological and ecological effects of flickering artificial light. PLoS One. 2014 May 29;9(5):e98631. doi: 10.1371/journal.pone.0098631. PMID: 24874801; PMCID: PMC4038456.