Effects of Artificial Light at Night on Organisms: From Mechanisms to Function

Since electric light was first commercially produced in the second half of the 19th century, the exposition of artificial light at night (ALAN) has been increasing worldwide; it is estimated that more than 80% of the human population experience nights contaminated with artificial light. Although this form of pollution has provided many benefits to humans, it also bears costs. ALAN can disrupt circadian rhythms, inducing a cascade of effects at several levels of biological organization, from influencing gene expression to changing fitness and interactions at the community and ecosystem levels. We are just beginning to understand the possible effects of ALAN exposure on organisms, from the proximate explanations of these effects (e.g. physiology) to the potential ecological and evolutionary consequences for populations and communities.

In order to better understand the possible consequences of ALAN exposure and its mechanisms, we urgently need more studies addressing all levels of biological organization, from proximate and ultimate perspectives. This is a complex problem that surely will benefit from both observational and experimental research. The results of these studies will likely allow decision-makers to make informed public policies to tackle light contamination. For instance, these studies can provide important information on whether, and how, ALAN affects the bacterial composition of soils (on which many living organisms depend), gene expression and physiology, developmental biology and reproductive success of plants and animals, species interactions (e.g. animal-plant interactions), animal behavior and communication, and overall ecological and evolutionary outcomes. One key component is to determine whether different light wavelengths differentially affect organisms, and whether or not there is an overall more benign light color that spares most organisms from negative consequences, or whether this is dependent on factors like life-history traits.

The goal of this Research Topic is to have a diverse array of papers addressing the effects of ALAN, including both proximate and functional causes, and thus to address the issue through the lens of Tinbergen’s four questions (ontogeny, mechanisms, function, and evolution). We welcome the submission of manuscripts addressing the effects of ALAN on all types of living organisms, from unicellular to multicellular, including bacteria (e.g. soil bacteria, gut bacteria, skin bacteria), fungi, plants, and animals. Specific themes include but are not limited to:
• Epigenetic effects of ALAN. This includes tackling questions on how ALAN may influence gene expression and its possible consequences (e.g. physiological, behavioral).
• Animal behavior including, among others, animal communication and sexual selection. This point addresses what changes in animal behavior are related to, or are a consequence of, ALAN exposure. We welcome studies addressing whether ALAN can influence animal signals (e.g. acoustic, visual, chemical, tactile, electrical) and the possible consequences of these changes (e.g. in sexual selection and reproduction), as well as any other types of behavioral changes (e.g. migration, cognitive processes, parental care).
• Population, community, and ecosystem-level structure, composition, function, and interactions. This point addresses, among other ideas, whether populations differing in ALAN levels are diverging (genetically or phenotypically), whether and how ALAN changes species interactions (e.g. prey-predator interactions, plant-animal interactions), whether and how ALAN affects interactions on a wider scale: e.g. nutrient cycles and interactions of species with non-living components (nutrients, humidity, temperature) in different ecosystems, and possible interactions between ALAN and other pollutants (e.g. urban noise) influencing biological outcomes.