Light Pollution Research Articles

Artificial light at night (ALAN) causes shifts in soil communities and functions.

Artificial light at night (ALAN) is increasing worldwide, but its effects on the soil system have not yet been investigated. We tested the influence of experimental manipulation of ALAN on two taxa of soil communities (microorganisms and soil nematodes) and three aspects of soil functioning (soil basal respiration, soil microbial biomass and carbon use efficiency) over four and a half months in a highly controlled Ecotron facility. We show that during peak plant biomass, increasing ALAN reduced plant biomass and was also associated with decreased soil water content. This further reduced soil respiration under high ALAN at peak plant biomass, but microbial communities maintained stable biomass across different levels of ALAN and times, demonstrating higher microbial carbon use efficiency under high ALAN. While ALAN did not affect microbial community structure, the abundance of plant-feeding nematodes increased and there was homogenization of nematode communities under higher levels of ALAN, indicating that soil communities may be more vulnerable to additional disturbances at high ALAN. In summary, the effects of ALAN reach into the soil system by altering soil communities and ecosystem functions, and these effects are mediated by changes in plant productivity and soil water content at peak plant biomass. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Spectral composition of light-emitting diodes impacts aquatic and terrestrial invertebrate communities with potential implications for cross-ecosystem subsidies.

Resource exchanges in the form of invertebrate fluxes are a key component of aquatic-terrestrial habitat coupling, but this interface is susceptible to human activities, including the imposition of artificial light at night. To better understand the effects of spectral composition of light-emitting diodes (LEDs)-a technology that is rapidly supplanting other lighting types-on emergent aquatic insects and terrestrial insects, we experimentally added LED fixtures that emit different light spectra to the littoral zone and adjacent riparian habitat of a pond. We installed four replicate LED treatments of different wavelengths (410, 530 and 630 nm), neutral white (4000 k) and a dark control, and sampled invertebrates in both terrestrial and over-water littoral traps. Invertebrate communities differed among light treatments and between habitats, as did total insect biomass and mean individual insect size. Proportional allochthonous biomass was greater in the riparian habitat and among some light treatments, demonstrating an asymmetrical effect of differently coloured LEDs on aquatic-terrestrial resource exchanges. Overall, our findings demonstrate that variation in wavelength from LEDs may impact the flux of resources between systems, as well as the communities of insects that are attracted to particular spectra of LED lighting, with probable implications for consumers. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Scaling artificial light at night and disease vector interactions into socio-ecological systems: a conceptual appraisal.

There is burgeoning interest in how artificial light at night (ALAN) interacts with disease vectors, particularly mosquitoes. ALAN can alter mosquito behaviour and biting propensity, and so must alter disease transfer rates. However, most studies to date have been laboratory-based, and it remains unclear how ALAN modulates disease vector risk. Here, we identify five priorities to assess how artificial light can influence disease vectors in socio-ecological systems. These are to (i) clarify the mechanistic role of artificial light on mosquitoes, (ii) determine how ALAN interacts with other drivers of global change to influence vector disease dynamics across species, (iii) determine how ALAN interacts with other vector suppression strategies, (iv) measure and quantify the impact of ALAN at scales relevant for vectors, and (v) overcome the political and social barriers in implementing it as a novel vector suppression strategy. These priorities must be addressed to evaluate the costs and benefits of employing appropriate ALAN regimes in complex socio-ecological systems if it is to reduce disease burdens, especially in the developing world. This article is part of the theme issue 'Light pollution in complex ecological systems'.

A framework for untangling the consequences of artificial light at night on species interactions.

Although much evidence exists showing organismal consequences from artificial light at night (ALAN), large knowledge gaps remain regarding ALAN affecting species interactions. Species interactions occur via shared spatio-temporal niches among species, which may be determined by natural light levels. We review how ALAN is altering these spatio-temporal niches through expanding twilight or full Moon conditions and constricting nocturnal conditions as well as creating patches of bright and dark. We review literature from a database to determine if ALAN is affecting species interactions via spatio-temporal dynamics. The literature indicates a growing interest in ALAN and species interactions: 58% of the studies we analysed have been published since 2020. Seventy-five of 79 studies found ALAN altered species interactions. Enhancements and reductions of species interactions were equally documented. Many studies revealed ALAN affecting species interactions spatially, but few revealed temporal alterations. There are biases regarding species interactions and ALAN-most studies investigated predator-prey interactions with vertebrates as predators and invertebrates as prey. Following this literature review, we suggest avenues, such as remote sensing and animal tracking, that can guide future research on the consequences of ALAN on species interactions across spatial and temporal axes. This article is part of the theme issue 'Light pollution in complex ecological systems'.

The impacts of artificial light at night on the ecology of temperate and tropical reefs.

Despite 22% of the world's coastal regions experiencing some degree of light pollution, and biologically important artificial light at night (ALAN) reaching large portions of the seafloor (greater than 75%) near coastal developments, the impacts of ALAN on temperate and tropical reefs are still relatively unknown. Because many reef species have evolved in response to low-light nocturnal environments, consistent daily, lunar, and seasonal light cycles, and distinct light spectra, these impacts are likely to be profound. Recent studies have found ALAN can decrease reproductive success of fishes, alter predation rates of invertebrates and fishes, and impact the physiology and biochemistry of reef-building corals. In this paper, we integrate knowledge of the role of natural light in temperate and tropical reefs with a synthesis of the current literature on the impacts of ALAN on reef organisms to explore potential changes at the system level in reef communities exposed to ALAN. Specifically, we identify the direct impacts of ALAN on individual organisms and flow on effects for reef communities, and present potential scenarios where ALAN could significantly alter system-level dynamics, possibly even creating novel ecosystems. Lastly, we highlight large knowledge gaps in our understanding of the overall impact of ALAN on reef systems. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Does artificial light at night alter moth community composition?

Ecological studies investigating the effects of artificial light at night (ALAN) have primarily focused on single or a few species, and seldom on community-level dynamics. As ALAN is a potential cause of insect and biodiversity declines, community-level perspectives are essential. We empirically tested the hypothesis that moth species differentially respond to ALAN and that these responses can cause shifts in community composition. We sampled moths from prairie fragments in Colorado, USA. We tested whether local light sources, sky glow, site area and/or vegetation affected moth community diversity. We found that increased sky glow decreased moth abundance and species richness and shifted community composition. Increased sky glow shifted moth community composition when light and bait traps were combined; notably this result appears to be driven entirely by moths sampled at bait traps, which is an unbiased sampling technique. Our results show that ALAN has significant effects on moth communities and that local light sources have contrasting effects on moth community composition compared to sky glow. It is imperative that we better understand the contrasting effects of types of ALAN to comprehend the overall impacts of light pollution on biodiversity declines. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Insect communities under skyglow: diffuse night-time illuminance induces spatio-temporal shifts in movement and predation.

Artificial light at night (ALAN) is predicted to have far-reaching consequences for natural ecosystems given its influence on organismal physiology and behaviour, species interactions and community composition. Movement and predation are fundamental ecological processes that are of critical importance to ecosystem functioning. The natural movements and foraging behaviours of nocturnal invertebrates may be particularly sensitive to the presence of ALAN. However, we still lack evidence of how these processes respond to ALAN within a community context. We assembled insect communities to quantify their movement activity and predation rates during simulated Moon cycles across a gradient of diffuse night-time illuminance including the full range of observed skyglow intensities. Using radio frequency identification, we tracked the movements of insects within a fragmented grassland Ecotron experiment. We additionally quantified predation rates using prey dummies. Our results reveal that even low-intensity skyglow causes a temporal shift in movement activity from day to night, and a spatial shift towards open habitats at night. Changes in movement activity are associated with indirect shifts in predation rates. Spatio-temporal shifts in movement and predation have important implications for ecological networks and ecosystem functioning, highlighting the disruptive potential of ALAN for global biodiversity and the provision of ecosystem services. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Artificial light at night decreases plant diversity and performance in experimental grassland communities.

Artificial light at night (ALAN) affects many areas of the world and is increasing globally. To date, there has been limited and inconsistent evidence regarding the consequences of ALAN for plant communities, as well as for the fitness of their constituent species. ALAN could be beneficial for plants as they need light as energy source, but they also need darkness for regeneration and growth. We created model communities composed of 16 plant species sown, exposed to a gradient of ALAN ranging from 'moonlight only' to conditions like situations typically found directly underneath a streetlamp. We measured plant community composition and its production (biomass), as well as functional traits of three plant species from different functional groups (grasses, herbs, legumes) in two separate harvests. We found that biomass was reduced by 33% in the highest ALAN treatment compared to the control, Shannon diversity decreased by 43% and evenness by 34% in the first harvest. Some species failed to establish in the second harvest. Specific leaf area, leaf dry matter content and leaf hairiness responded to ALAN. These responses suggest that plant communities will be sensitive to increasing ALAN, and they flag a need for plant conservation activities that consider impending ALAN scenarios. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Nearby night lighting, rather than sky glow, is associated with habitat selection by a top predator in human-dominated landscapes.

Artificial light at night (ALAN) is increasing in extent and intensity across the globe. It has been shown to interfere with animal sensory systems, orientation and distribution, with the potential to cause significant ecological impacts. We analysed the locations of 102 mountain lions (Puma concolor) in a light-polluted region in California. We modelled their distribution relative to environmental and human-disturbance variables, including upward radiance (nearby lights), zenith brightness (sky glow) and natural illumination from moonlight. We found that mountain lion probability of presence was highly related to upward radiance, that is, related to lights within approximately 500 m. Despite a general pattern of avoidance of locations with high upward radiance, there were large differences in degree of avoidance among individuals. The amount of light from artificial sky glow was not influential when included together with upward radiance in the models, and illumination from moonlight was not influential at all. Our results suggest that changes in visibility associated with lunar cycles and sky glow are less important for mountain lions in their selection of light landscapes than avoiding potential interactions with humans represented by the presence of nearby lights on the ground. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Mitigating the impacts of street lighting on biodiversity and ecosystem functioning.

Street lights are not only a major source of direct light pollution emissions, but stock has been transitioning to light-emitting diode (LED) technology in many parts of the world, resulting in increases in the blue part of the visible spectrum that is more harmful to biodiversity and human health. But LEDs can be modified more easily than conventional sodium lamps by adjusting their intensity, spectral output and other features of street light systems. In this Opinion piece, I provide an updated overview of street light mitigation strategies and contend that research in this area has been slow. I show how experimental lighting rigs that mimic real street lights can be used for mitigation testing, since invertebrate behaviour, abundances and interactions can respond quickly and measurably. I demonstrate how advances in network ecology that use species interaction data can provide much-needed assessments of the impacts of street lights on biodiversity and ecosystem functioning, and ultimately provide new tools and metrics for biomonitoring. I acknowledge the limitations of measuring local, short-term responses of biodiversity and identify promising avenues for collaborating with industry and government agencies in new or existing road lighting schemes, to minimize the negative long-term impacts at marginal cost. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Impacts of artificial light at night on the early life history of two ecosystem engineers.

Sessile marine invertebrates play a vital role as ecosystem engineers and in benthic-pelagic coupling. Most benthic fauna develop through larval stages and the importance of natural light cycles for larval biology and ecology is long-established. Natural light-dark cycles regulate two of the largest ocean-scale processes that are fundamental to larvae's life cycle: the timing of broadcast spawning for successful fertilization and diel vertical migration for foraging and predator avoidance. Given the reliance on light and the ecological role of larvae, surprisingly little is known about the impacts of artificial light at night (ALAN) on the early life history of habitat-forming species. We quantified ALAN impacts on larval performance (survival, growth, development) of two cosmopolitan ecosystem engineers in temperate marine ecosystems, the mussel Mytilus edulis and the barnacle Austrominius modestus. Higher ALAN irradiance reduced survival in both species (57% and 13%, respectively). ALAN effects on development and growth were small overall, and different between species, time-points and parentage. Our results show that ALAN adversely affects larval survival and reiterates the importance of paternal influence on offspring performance. ALAN impacts on the early life stages of ecosystem engineering species have implications not only for population viability but also the ecological communities that these species support. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Long-term exposure to experimental light affects the ground-dwelling invertebrate community, independent of light spectra.

Our planet endures a progressive increase in artificial light at night (ALAN), which affects virtually all species, and thereby biodiversity. Mitigation strategies include reducing its intensity and duration, and the adjustment of light spectrum using modern light emitting diode (LED) light sources. Here, we studied ground-dwelling invertebrate (predominantly insects, arachnids, molluscs, millipedes, woodlice and worms) diversity and community composition after 3 or 4 years of continued nightly exposure (every night from sunset to sunrise) to experimental ALAN with three different spectra (white-, and green- and red-dominated light), as well as for a dark control, in natural forest-edge habitat. Diversity of pitfall-trapped ground-dwelling invertebrates, and the local contribution to beta diversity, did not differ between the dark control and illuminated sites, or between the different spectra. The invertebrate community composition, however, was significantly affected by the presence of light. Keeping lights off during single nights did show an immediate effect on the composition of trapped invertebrates compared to illuminated nights. These effects of light on species composition may impact ecosystems by cascading effects across the food web. This article is part of the theme issue 'Light pollution in complex ecological systems'.

Part-night exposure to artificial light at night has more detrimental effects on aphid colonies than fully lit nights.

Artificial light at night (ALAN) threatens natural ecosystems globally. While ALAN research is increasing, little is known about how ALAN affects plants and interactions with other organisms. We explored the effects of ALAN on plant defence and plant-insect interactions using barley (Hordeum vulgare) and the English grain aphid (Sitobion avenae). Plants were exposed to 'full' or 'part' nights of 15-20 lux ALAN, or no ALAN 'control' nights, to test the effects of ALAN on plant growth and defence. Although plant growth was only minimally affected by ALAN, aphid colony growth and aphid maturation were reduced significantly by ALAN treatments. Importantly, we found strong differences between full-night and part-night ALAN treatments. Contrary to our expectations, part ALAN had stronger negative effects on aphid colony growth than full ALAN. Defence-associated gene expression was affected in some cases by ALAN, but also positively correlated with aphid colony size, suggesting that the effects of ALAN on plant defences are indirect, and regulated via direct disruption of aphid colonies rather than via ALAN-induced upregulation of defences. Mitigating ecological side effects of ALAN is a complex problem, as reducing exposure to ALAN increased its negative impact on insect herbivores. This article is part of the theme issue 'Light pollution in complex ecological systems'.

County-level artificial light at night (ALAN) in the contiguous US (2012-2019): spatial variations, temporal trends, and environmental justice analyses.

Artificial light at night (ALAN) is a growing environmental hazard with economic, ecological, and public health implications. Previous studies suggested a higher burden of light pollution and related adverse effects in disadvantaged communities. It is critical to characterize the geographic distribution and temporal trend of ALAN and identify associated demographic and socioeconomic factors at the population level to lay the foundation for environmental and public health monitoring and policy-making. We used satellite data from the Black Marble suite to characterize ALAN in all counties in contiguous US and reported considerable variations in ALAN spatiotemporal patterns between 2012 and 2019. As expected, ALAN levels were generally higher in metropolitan and coastal areas; however, several rural counties in Texas experienced remarkable increase in ALAN since 2012, while population-level ALAN burden also increased substantially in many metropolitan areas. Importantly, we found that during this period, although the overall ALAN levels in the USA declined modestly, the temporal trend of ALAN varied across areas with different racial/ethnic compositions: counties with a higher percentage of racial/ethnic minority groups, particularly Hispanic populations, exhibited significantly less decline. As a result, the differences in ALAN levels, as measured by the Black Marble product, across racial/ethnic groups became larger between 2012 and 2019. In conclusion, our study documented variations in ALAN spatiotemporal patterns across America and identified multiple population correlates of ALAN patterns that warrant further investigations. Future studies should identify underlying factors (e.g., economic development and decline, urban planning, and transition to newer lighting technologies such as light emitting diodes) that may have contributed to ALAN disparities in the USA.

Dark Sky Parks: public policy that turns off the lights

Dark skies are culturally, ecologically, and economically valuable natural resources but little has been written on how dark sky conservation is being enacted through environmental policy and legislation. Using the Multiple Streams Framework and qualitative data from over 300 policy documents, we characterize the problems, policy solutions, and politics around protecting night sky resources. We find that the core public policy problem of diminishing night skies is perceived by stakeholders to be light pollution produced from surrounding urban development. To address this problem, decision-makers enact policy solutions of creating Dark Sky Parks on protected landscapes with rigorous and scientific processes. These technical ideas for creating Dark Sky Parks are transmitted to decision-makers at park and landscape scales. Dark sky conservation is a political process as well, which attracts bipartisan support from policy-makers from different political parties due to the economic potential of astrotourism. Our work has general applications for the role of managers and NGOs in creating science policy, engaging the public, and enacting policy change, as was seen in the context of the International Dark Sky Association providing resources, technical information, and support for managers and other stakeholders to encourage actions at various scales to protect rapidly-disappearing dark skies.

Adaptive Illumination: Designing a Smart Street Lighting System for Sustainable Urban Environments

In the age of rapid technological advancement and increasing urbanization, the need for sustainable and efficient infrastructure has never been more pronounced. As cities grow and evolve, so do the challenges related to managing their energy consumption, safety, and environmental footprint. One of the critical components of urban infrastructure that has a direct impact on all these areas is street lighting. Traditional street lighting systems, while essential for safety and visibility, often consume excessive amounts of energy, contribute to light pollution, and require significant maintenance. This is where the concept of adaptive illumination comes into play as shown in Figure 1.
 Adaptive illumination refers to the design and implementation of street lighting systems that can adjust their brightness and intensity based on real-time environmental conditions and human activity. Unlike conventional systems that remain uniformly lit throughout the night, adaptive systems use sensors, data analytics, and connectivity to dynamically modify their output. This not only results in significant energy savings but also reduces light pollution and enhances the overall safety and comfort of urban residents.[1]
 The sustainability aspect of adaptive illumination cannot be overstated. As the world grapples with climate change and the pressing need to reduce carbon emissions, every kilowatt-hour saved has a cascading positive effect on the environment. By ensuring that street lights are only as bright as they need to be, cities can dramatically decrease their energy consumption. This is particularly relevant in the context of urban areas, which are often the largest consumers of electricity within a region.

Energy Efficiency Analysis in the Case of Sustainable Lighting Design Butterfly Valley Park (Konya)

The concept of lighting is of great importance in providing the security that people need so that they can have a quality of life and in meeting their aesthetic needs. Lighting design is related to the physical structure and the environment, and thanks to the lighting design, the aesthetic and functional needs of people will be met and the quality of life will be increased. The need to reflect the historical, cultural and aesthetic values of the city has brought the issue of urban lighting to the agenda. Lighting systems, which are applied without paying attention to the necessary lighting standards and criteria, cause some problems in urban spaces. One of these problems is light pollution; It is generally defined as the use of light in the wrong place, in the wrong amount, in the wrong direction and at the wrong time. Light pollution adversely affects the natural life and daily lives of people, and it is necessary to take various measures to eliminate such negativities in human life, to detect and eliminate these problems. In this study; The standards for the lighting of the city parks obtained by the literature studies were determined, the current lighting situation of the Butterfly Valley Park and the recommended lighting design produced by the Relux software in accordance with the standards. According to the findings; In the current lighting project, the total power consumed as a result of the lighting of all the lamps of the area has been calculated as 96 005.0 W. In the proposed lighting project, the total power consumed as a result of the burning of all lamps was calculated as 27 630.0 W. The obtained energy gain was found to be 96 005.0 W – 36 700.0 W = 68 375.0 W. As a result of working in the light of this information, energy savings of 1 in 3 have been achieved.

Artificial light at night and breast cancer risk: The findings from CECILE study (France)

Abstract Background Environmental exposure to artificial light at night (LAN) has become ubiquitous in modern societies. Experimental and epidemiological studies suggested that LAN exposure disrupts circadian rhythm, inhibits melatonin production, and increases the risk of breast cancer. Objectives We aimed to assess the association of exposure to outdoor LAN with breast cancer risk, along with possible effect modifications of this association. Methods We used data from a population-based case-control study, including 1185 incident breast cancer cases and 1282 healthy controls enrolled in 2005-2007 from two French departments- Côte d’Or and Ille-et-Vilaine. Data for outdoor LAN exposure was obtained using radiance-calibrated images from Defense Meteorological Satellite Program (DMSP) for 1995-2006. Exposure was assessed for 10 years before inclusion in the study by cross-referencing the DMSP images and the geocoded locations of residences in ArcGIS. Logistic regression was used to obtain odds ratios (OR) and 95% confidence intervals (CI) for the association, adjusting for sociodemographic factors, urbanization, reproductive factors, lifestyle-related factors, night shift work, and air pollution. Results The overall OR for breast cancer per 1 interquartile range (IQR) increase in LAN exposure (159.9 nW/cm2/sr) was 0.98 (95% CI: 0.81-1.17). Subgroup analyses showed slightly higher ORs in post-menopausal women (OR: 1.15; 95% CI: 0.97-1.37) and a stronger association for HER2-positive breast tumors (OR: 1.55; 95% CI: 1.03-2.31). Conclusions We did not find any overall association between outdoor LAN and breast cancer; however, possible associations in certain subgroups were indicated. The strength of this study was the use of calibrated satellite images for exposure assessment and the consideration of a large set of potential confounders. Further large-scale studies using improved exposure assessment methods, including blue light and indoor exposure measurement, are required. Key messages • Light pollution is growing as the newest form of environmental pollution in modern society, potentially affecting health. • More studies are required to explore and ascertain its public health impact.

Environmental exposure assessment in the German National Cohort (NAKO)

Abstract Background The environment plays a major role in human health and wellbeing. Air pollution, non-optimal temperatures, noise and lack of greenspace have been identified as the main external drivers, but their interplay is not well understood. Moreover, negative impacts are expected to increase in the coming decades due to population growth and climate change, especially in urban areas. Therefore, we aimed to assess the exposure to multiple environmental indicators and compare the spatial variation across NAKO participants to lay the foundation for subsequent health analyses. Methods We collected German-wide data from different sources for the following environmental indicators: short- and long-term air pollution (particulate matter, nitrogen dioxide, ozone), short- and long-term meteorology (air temperature, relative humidity), noise and greenness. All exposures were assigned to the NAKO participants based on their baseline residential addresses. Results The NAKO study regions ranged from highly urbanized areas (Berlin, Hamburg) with up to 4,123 inhabitants/km2 to rural regions (Neubrandenburg) with 732 inhabitants/km2. This large variation is reflected in the individual environmental exposures. PM2.5 and NO2 levels ranged from 7.7-16.2 and 4.2-32.6 µg/m3, respectively. Annual mean temperature for 2017 ranged between 8.1-11.7 °C. Noise data were available only for 22% of participants, of which 42% fell into the lowest and 1.9% into the highest category of Lden 55-59 and Lden >75 dB(A), respectively. Greenness also showed considerable contrasts (Normalized Difference Vegetation Index between 0.09-0.82). Conclusions An extensive population-based data set with high-quality environmental indicators is available for the first time across Germany. Expanding the database by adding innovative indicators (e.g. light pollution, walkability) as well as socioeconomic factors (e.g. unemployment rate, deprivation) will further increase its impact on science and public health.

Multiparameter study for a new ground-based telescope in Egypt

ABSTRACT A multiparameter analysis was conducted to evaluate the impact of meteorological parameters, night sky brightness and seismic hazards on proposed sites for the new optical/infrared Egyptian astronomical telescope. The European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5) data set is used to obtain the following meteorological parameters: total cloud coverage fraction, precipitable water vapour, relative humidity, wind speed and direction, and air temperature. To estimate the aerosol optical depth, we used the Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA-2). Light pollution over the candidate sites was measured using the Visible Infrared Imaging Radiometer Suite (VIIRS) day/night band. In order to assess the seismic hazards for the candidate sites, the seismic input in terms of maximum acceleration and response spectra was computed using a physics-based ground motion approach to assess the seismic hazards and, consequently, the designation of a seismic-resistant structure for the proposed sites. Of the seven nominated sites, two sites are found to have the best measurements and might be considered as future sites for the new Egyptian astronomical telescope. The first site is located in the south of the Sinai peninsula, while the second site is located in the Red Sea mountains region.