Artificial light at night (ALAN) provides an array of important benefits but might also adversely affect humans and other living organisms. Yet, the existing reviews of accumulated knowledge about the multifaceted effects associated with exposure to ALAN focus on distinct ecosystem components. As a result, our understanding of potential system-wide impacts of ALAN exposure is insufficient.

This paper attempts to bridge this knowledge gap by reviewing a wide range of studies, with a particular focus on identifying the impacts of ALAN exposure that are common to different species.

The survey is conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and covers peer-reviewed articles published from 2000 to 2019.

Seventy-four eligible articles, out of 1223 initially identified, were selected and synthesized. 20% of them focus on humans, while the rest explore other living organisms, such as vertebrates, avian species, arthropods, aquatic organisms, and vegetation. The review demonstrates that similar adverse effects of ALAN exposure, ranging from sleep disturbance, depression, weight gain, eating and movement disorders, to elevated risk of cancer, are manifested across different components of the ecosystem, and therefore entail wider and more complex risks to its stability and integrity.

To reduce ecosystem risks, associated with constantly increasing ALAN levels, illumination policies should be based on directional and reduced nighttime lighting, which can help to avoid unnecessary exposures. The study highlights knowledge gaps that warrant further research attention.