11 Pressing Research Questions on How Light Pollution Affects Biodiversity

Artificial light at night (ALAN) is closely associated with modern societies and is rapidly increasing worldwide. A dynamically growing body of literature shows that ALAN poses a serious threat to all levels of biodiversity—from genes to ecosystems. Many “unknowns” remain to be addressed however, before we fully understand the impact of ALAN on biodiversity and can design effective mitigation measures. Here, we distilled the findings of a workshop on the effects of ALAN on biodiversity at the first World Biodiversity Forum in Davos attended by several major research groups in the field from across the globe. We argue that 11 pressing research questions have to be answered to find ways to reduce the impact of ALAN on biodiversity. The questions address fundamental knowledge gaps, ranging from basic challenges on how to standardize light measurements, through the multi-level impacts on biodiversity, to opportunities and challenges for more sustainable use.

MEASURES FOR REDUCING THE ADVERSE EFFECTS OF ARTIFICIAL LIGHT AT NIGHT: INTER-DISCIPLINARY DEVELOPMENT AND PROGRESS

The use of artificial light at night in the outdoor environment may introduce negative and unwanted side-effects such as light pollution and unwanted impacts on humans, ecosystems and biodiversity. Therefore, appropriate measures for reducing the adverse effects of artificial light at night are important to establish a sustainable use of outdoor lighting. This paper presents an updated overview and a state-of-the-art of available and effective measures for reducing artificial light at night, which range from strategical and high-level recommendations to more practical and applicable lighting design recommendations and principles. Another aim is to identify prioritized future research questions and areas that will enhance progress within the area. We present the current recommendations into three groups: (I) recommendations for legislation at the national or international levels, (II) recommendations for technical and practical adaptations of the lighting design and (III) recommendations for sensitive species, taxa, areas or ecosystems.

LIGHT EXPOSURE OF WORKERS IN DIFFERENT OCCUPATIONS

Twenty-four hours light exposure of employees in three different occupations was assessed for a working week during both summer and winter. Occupations being exposed to light at night and those exposed to low daytime light levels were represented by night shift working geriatric nurses and daytime working hotel staff, respectively. Their light exposure was compared to the light exposure of outdoor workers represented by refuse collectors. In winter, luminous exposure of night shift working geriatric nurses and daytime working hotel staff amounts to only 2 % and 12 % of the luminous exposure of outdoor workers, respectively. In summer, the respective values are 6 % and 21 %. This could lead to a desynchronization of circadian physiological processes in the human body.

A Systematic Review of Research Investigating the Combined Ecological Impact of Anthropogenic Noise and Artificial Light at Night

Levels of anthropogenic noise and artificial light at night (ALAN) are rapidly rising on a global scale. Both sensory pollutants are well known to affect animal behavior and physiology, which can lead to substantial ecological impacts. Most studies on noise or light pollution to date have focused on single stressor impacts, studying both pollutants in isolation despite their high spatial and temporal co-occurrence. However, few studies have addressed their combined impact, known as multisensory pollution, with the specific aim to assess whether the interaction between noise and light pollution leads to predictable, additive effects, or less predictable, synergistic or antagonistic effects. We carried out a systematic review of research investigating multisensory pollution and found 28 studies that simultaneously assessed the impact of anthropogenic noise and ALAN on animal function (e.g., behavior, morphology or life-history), physiology (e.g., stress, oxidative, or immune status), or population demography (e.g., abundance or species richness). Only fifteen of these studies specifically tested for possible interactive effects when both sensory pollutants were combined. Four out of eight experimental studies revealed a significant interaction effect, in contrast to only three out seven observational studies. We discuss the benefits and limitations of experimental vs. observational studies addressing multisensory pollution and call for more specific testing of the diverse ways in which noise and light pollution can interact to affect wildlife.

Changes in nocturnal insect communities in forest-dominated landscape relevant to artificial light intensity

Background Artificial light at night has recently been identified as a major factor adversely affecting global insect diversity. Here, we compared the insect diversity in Gwangneung Forest Biosphere Reserve, specifically in the Korea National Arboretum (with no artificial light at night), with that of three nearby urban sites with a gradient of artificial light at night (five locations at each site). We analyzed the effects of the artificial night lighting index, mean annual temperature, and field light intensity (lux) at night on the insect community structure. Results The urban sites generally exhibited higher species richness and abundance as well as clear indicator species compared with the control site. The size distribution of the collected insects markedly differed between the control and the three urban sites. The abundance of herbivorous and omnivorous insects increased and decreased, respectively, with the increase in light intensity. Species richness of herbivorous and omnivorous insects was likely correlated with the field light intensity at night and artificial night lighting index, respectively. Conclusions This study demonstrates the association between nighttime environment and marked changes in insect community structure and revealed consequent transition of ecosystem services by changes in trophic group composition.