Exposure to Artificial Light at Night and the Consequences for Flora, Fauna, and Ecosystems

Abstract

The present review draws together wide-ranging studies performed over the last decades that catalogue the effects of artificial-light-at-night (ALAN) upon living species and their environment. We provide an overview of the tremendous variety of light-detection strategies which have evolved in living organisms - unicellular, plants and animals, covering chloroplasts (plants), and the plethora of ocular and extra-ocular organs (animals). We describe the visual pigments which permit photo-detection, paying attention to their spectral characteristics, which extend from the ultraviolet into infrared. We discuss how organisms use light information in a way crucial for their development, growth and survival: phototropism, phototaxis, photoperiodism, and synchronization of circadian clocks. These aspects are treated in depth, as their perturbation underlies much of the disruptive effects of ALAN. The review goes into detail on circadian networks in living organisms, since these fundamental features are of critical importance in regulating the interface between environment and body. Especially, hormonal synthesis and secretion are often under circadian and circannual control, hence perturbation of the clock will lead to hormonal imbalance. The review addresses how the ubiquitous introduction of light-emitting diode technology may exacerbate, or in some cases reduce, the generalized ever-increasing light pollution. Numerous examples are given of how widespread exposure to ALAN is perturbing many aspects of plant and animal behaviour and survival: foraging, orientation, migration, seasonal reproduction, colonization and more. We examine the potential problems at the level of individual species and populations and extend the debate to the consequences for ecosystems. We stress, through a few examples, the synergistic harmful effects resulting from the impacts of ALAN combined with other anthropogenic pressures, which often impact the neuroendocrine loops in vertebrates. The article concludes by debating how these anthropogenic changes could be mitigated by more reasonable use of available technology – for example by restricting illumination to more essential areas and hours, directing lighting to avoid wasteful radiation and selecting spectral emissions, to reduce impact on circadian clocks. We end by discussing how society should take into account the potentially major consequences that ALAN has on the natural world and the repercussions for ongoing human health and welfare.

Artificial light at night leads to circadian disruption in a songbird: integrated evidence from behavioural, genomic and metabolomic data

“…Addressing effects of ALAN is therefore urgent [10,59]. Our data contribute to the rising evidence for dose-dependent responses of behavior and physiology [22,30,60], which might allow mitigating against ALAN impacts on wildlife by reducing light intensity [61].…”

“…For wild animals, our study adds to emerging evidence of detrimental effects of ALAN on physiological pathways [9,10,21]. For example, under ALAN molecular markers for sleep deprivation were elevated, hypothalamic expression of genes such as TLR4 was altered [16], neuronal features in the brain were changed, and cognitive processes and mental health-like states were impaired [16,20,56,57].…”

“…The orchestration of these processes involves complex interactions between sensory input, central and peripheral clocks, and effector systems [2]. There is increasing evidence that ALAN disrupts these processes, with possible consequences ranging from compromised human health to loss of ecosystem functions [8–10]. In free-living and captive organisms, altered daily and annual activity has been widely reported, and experimental illumination has confirmed causal effects of ALAN [11,12].…”

Grasping darkness: the dark ecological network as a social-ecological framework to limit the impacts of light pollution on biodiversity

“…These authors have even shown that, for these taxa, ALAN poses a threat equivalent to others such as soil artificialization and the proportion of intensive agriculture on a large scale (Azam et al 2016). Such spatial and temporal perturbation of habitats and species is suspected in turn to profoundly affect the functioning dynamics of populations, communities, and ecosystems (Falcón et al 2020).…”

Wavelength-dependent effects of artificial light at night on phytoplankton growth and community structure

“…To test for the effect of ALAN wavelengths on single species growth and assemblage biomass and diversity we run two concurrent experiments from 23/11/2021 and for a period of 18 days: Since algae use light as a source of both information and energy (Bennie, Davies, Cruse, & Gaston, 2016;Falcón et al, 2020), light treatments were standardised to irradiance levels rather than illuminance levels. Daytime light irradiance was 6.5 Watt m -2 and was provided by a 10W flood light (Prolite, Ritelite Systems Ltd, UK) equipped with two arrays of high-power LEDs (6,000K).…”