Artificial light at night is profoundly altering natural light cycles, particularly as perceived by many organisms, over extensive areas of the globe. This alteration comprises the introduction of light at night at places and times at which it has not previously occurred, and with different spectral signatures. Given the long geological periods for which light cycles have previously been consistent, this constitutes a novel environmental pressure, and one for which there is evidence for biological effects that span from molecular to community level. Here we provide a synthesis of understanding of the form and extent of this alteration, some of the key consequences for terrestrial and aquatic ecosystems, interactions and synergies with other anthropogenic pressures on the environment, major uncertainties, and future prospects and management options. This constitutes a compelling example of the need for a thoroughly interdisciplinary approach to understanding and managing the impact of one particular anthropogenic pressure. The former requires insights that span molecular biology to ecosystem ecology, and the latter contributions of biologists, policy makers and engineers.

Artificial lighting has transformed the outdoor nighttime environment over large areas, modifying natural cycles of light in terms of timing, wavelength, and distribution. This has had widespread benefits and costs to humankind, impacting on health and wellbeing, vehicle accidents, crime, energy consumption and carbon emissions, aesthetics, and wildlife and ecosystems. Here, we review these effects, particularly in the context of ongoing developments in the extent of artificial lighting and in the prevalent technologies being employed. The key issue that emerges is how best to maximize the benefits of artificial nighttime lighting whilst limiting the costs. To do so, three main strategies are required. First, important knowledge gaps need to be filled. Second, there is an urgent need to connect the research being conducted in different disciplines, which to date has been very disjointed. Third, it is imperative that much firmer and well-developed links are made between research, policy, and practice.Key words: accidents, aesthetics, crime, ecosystems, health, light pollution, lighting, night, sky glow, wellbeing.Résumé : L'éclairage artificiel a transformé l'environnement nocturne extérieur sur de grandes superficies, modifiant les cycles naturels de la lumière en terme de temps, de longueurs d'ondes et de distribution. Ceci s'est traduit par des coûts et bénéfices largement étendus pour l'humanité, affectant la santé et le bien-être, les accidents d'automobile, le crime, la consommation d'énergie et les émissions de carbones, l'esthétique ainsi que la faune et les écosystèmes. Les auteurs passent en revue ces effets, particulièrement dans le contexte de développement continu dans l'extension de l'éclairage artificiel et dans les technologies dominantes mises en oeuvre. La problématique clé qui en émerge consiste à savoir comment maximiser le mieux possible les bénéfices de l'éclairage nocturne artificiel tout en limitant les coûts. Pour atteindre cet objectif, trois stratégies principales s'imposent. Il faut d'abord combler des déficiences de connaissances. Deuxièmement, il existe un urgent besoin d'intégrer les travaux de recherche conduits dans diverses disciplines, lesquels ont été conduits de façon disparate jusqu'ici. Et troisièmement, il est impératif que des liens beaucoup plus solides et mieux développés se développent entre la recherche, les politiques et la pratique. [Traduit par la Redaction]

The field of ecology has focused on understanding characteristics of natural systems in a manner as free as possible from biases of human observers. However, demand is growing for knowledge of human–nature interactions at the level of individual people. This is particularly driven by concerns around human health consequences due to changes in positive and negative interactions. This requires attention to the biased ways in which people encounter and experience other organisms. Here we define such a ‘personalised ecology’, and discuss its connections to other aspects of the field. We propose a framework of focal research topics, shaped by whether the unit of analysis is a single person, a single population, or multiple populations, and whether a human or nature perspective is foremost.

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