LED lighting increases the ecological impact of light pollution irrespective of color temperature

Blended-red lighting partially mitigates the cost of light pollution for arthropods

Light pollution disrupts the natural dark-light rhythmicity of the world and alters the spectral composition of the nocturnal sky, with far-reaching impacts on natural systems. While the costs of light pollution are now documented across scales and taxa, community-level mitigations for arthropods remain unclear. To test two light pollution mitigation strategies, we replaced all 32 streetlights in the largest visitor center in Grand Teton National Park (Wyoming, USA) to allow wireless control over each luminaries' color and brightness. We captured fewer arthropods, across most Orders, in the blended-red light compared to white (3000 K). Interestingly, we found an effect of light brightness and color, suggesting that, overall, more arthropods were attracted by brighter, and white color hues compared to blended-red. Our findings provide valuable insights into the mitigation of artificial light at night, likely one of the primary drivers of global arthropod declines.

Metal complex-based TADF: design, characterization, and lighting devices

The development of novel, efficient and cost-effective emitters for solid-state lighting devices (SSLDs) is ubiquitous to meet the increasingly demanding needs of advanced lighting technologies. In this context, the emergence of thermally activated delayed fluorescence (TADF) materials has stunned the photonics community. In particular, inorganic TADF material-based compounds can be ad hoc engineered by chemical modification of the coordinated ligands and the type of metal centre, allowing control of their ultimate photo-/electroluminescence properties, while providing a viable emitter platform for enhancing the efficiency of state-of-the-art organic light-emitting diodes (OLEDs) and light-emitting electrochemical cells (LECs). By presenting an overview of the state of the art of all metal complex-based TADF compounds, this review aims to provide a comprehensive, authoritative and critical reference for their design, characterization and device application, highlighting the advantages and drawbacks for the chemical, photonic and optoelectronic communities involved in this interdisciplinary research field.

Pulsed artificial light at night alters moth flight behaviour

Vehicle headlights create pulsed artificial light at night (pALAN) that is unpredictable, intense and extends into previously dark areas. Nocturnal insects often have remarkable low-light vision, but their slow pupillary light responses may leave them vulnerable to pALAN, which has important ecological consequences. To test this, we exposed nocturnal moths-important pollinators and prey-to four pALAN treatments. These comprised 'cool' and 'warm' lights, either emitted from phosphor-coated light-emitting diodes (LEDs) or RGB (red-green-blue) LEDs, matched in colour (CCT) and intensity to human vision. We assessed the initial behavioural response, likely crucial to the survival of an organism, of 428 wild-caught moths comprising 64 species. We found that exposure to a cool phosphor-coated LED light pulse increased instances of erratic flight and flight-to-light that are likely detrimental as they increase the risks of impact with a vehicle, predation or excess energy expenditure. Our findings suggest that pALAN can cause a wide range of behavioural responses in nocturnal moths, but that the most harmful effects could be minimized by reversing the current shift towards high CCT (cool) phosphor-coated LED car headlights. Lower CCT or RGB alternatives are likely to provide benefits for road safety while reducing ecological harm.

The Collapsible Light Trap: a portable Pennsylvania Light Trap for collecting aquatic insects

A Collapsible Light Trap (CLT) for collecting insects, particularly aquatic insects, is described here. CLT is a modified Pennsylvania Light Trap with the advantage of being collapsible and lightweight to be carried in a small backpack and very easy to set up in the field. CLT is equipped with LED light strip wrapped around a PVC tube and can be connected to a regular 12 V / 7 Ah battery, running for more than 48 uninterrupted hours. Complete CLT weighs 0.8-1.0 kg, depending on the metal used, and the battery weighs around 2 kg, being easily transportable to more remote collecting areas. Over the years, CLTs have been used for collecting and describing the diversity of aquatic insects from Brazil, particularly caddisflies. Depending on the locality, only one trap for one night can collect over a thousand insect specimens and more than 200 individuals of caddisflies.

Field comparison of broad-spectrum white LED-baited traps with narrow-spectrum green LED-baited traps in the capture of Anopheles mosquitoes (Diptera: Culicidae)

Light-Emitting Diodes (LEDs) have been effective light sources in attracting Anopheles mosquitoes, but the broad-spectrum white light, even with a wide-ranging application in lighting, have not been evaluated yet. In this study, the white light was field evaluated against the green one in the light trapping of anopheline mosquitoes by using two non-suction Silva traps and two CDC-type suction light traps. Anopheline mosquitoes were captured for two 21-night periods of collecting (2022 and 2023). In the first period, two LEDs were used per Silva trap, but three were used in the second one to increase the luminance/illuminance at traps. A CDC-type suction light trap equipped with an incandescent lamp was used in 2022 and a CDC-type suction light trap equipped with a 6 V-white light (higher luminance/illuminance) in 2023. A total of eight species and 3,289 specimens were captured in both periods. The most frequent species were Anopheles triannulatus s.l., An. goeldii, An. evansae and An. argyritarsis. In 2022, white LEDs were less attractive to anopheline mosquitoes than the other light sources, but without statistical difference among treatments (F = 2.703; P = 0.0752; df = 2). In 2023, even with an increased luminance/illuminance at traps, no statistical difference was found between the two LED-baited Silva traps (F = 6.690; P = 0.0024; df = 2), but rather between the 6 V-white-baited CDC-type suction light trap and green-baited Silva traps. Due to some drawbacks and the lower abundance of individuals caught by using white LEDs, the narrow-banded green LEDs is preferable to white ones for attracting anophelines.

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'.

Artificial light at night disrupts male dominance relationships and reproductive success in a model fish species

Environmental light is perceived and anticipated by organisms to synchronize their biological cycles. Therefore, artificial light at night (ALAN) disrupts both diurnal and seasonal biological rhythms. Reproduction is a complex physiological process involving integration of environmental signals by the brain, and release of endocrine signals by the pituitary that regulate gametogenesis and spawning. In addition, males from many species form a dominance hierarchy that, through a combination of aggressive and protective behavior, influences their reproductive success. In this study, we investigated the effect of ALAN and continuous daylight on the behavior and fitness of male fish within a dominance hierarchy using a model fish, the Japanese medaka. In normal light/dark cycles, male medaka establish a hierarchy with the dominant males being more aggressive and remaining closer to the female thus limiting the access of subordinate males to females during spawning. However, determination of the paternity of the progeny revealed that even though subordinate males spend less time with the females, they are, in normal light conditions, equally successful at producing progeny due to an efficient sneaking behavior. Continuous daylight completely inhibited the establishment of male hierarchy, whereas ALAN did not affect it. Nonetheless, when exposed to ALAN, subordinate males fertilize far fewer eggs. Furthermore, we found that when exposed to ALAN, subordinate males produced lower quality sperm than dominant males. Surprisingly, we found no differences in circulating sex steroid levels, pituitary gonadotropin levels, or gonadosomatic index between dominant and subordinate males, neither in control nor ALAN condition. This study is the first to report an effect of ALAN on sperm quality leading to a modification of male fertilization success in any vertebrate. While this work was performed in a model fish species, our results suggest that in urban areas ALAN may impact the genetic diversity of species displaying dominance behavior.

Dose-effects in behavioural responses of moths to light in a controlled lab experiment

Insects play a critical role in providing numerous ecosystem services. However, insect diversity and biomass have been declining dramatically, with artificial light being suggested as a contributing factor. Despite the importance of understanding the dose-effect responses of insects to light emissions, these responses have been rarely studied. We examined the dose-effect responses of the greater wax moth (Galleria mellonella L.) to different light intensities (14 treatments and a dark control) by observing their behavioural responses in a light-tight box equipped with a LED light source (4070 K) and infrared cameras. Our findings reveal dose-effect responses to light, as the frequency of walking on the light source increased with higher light intensity. Additionally, moths exhibited jumps in front of the light source and jump frequency increased with light intensity. No direct flight-to-light behaviour or activity suppression in response to light was observed. Based on our analysis of the dose-effect responses, we identified a threshold value of 60 cd/m² for attraction (walking on the light source) and the frequency of jumps. The experimental design in this study offers a valuable tool for investigating dose-effect relationships and behavioural responses of various species to different light levels or specific light sources.

Endocrine effects of exposure to artificial light at night: A review and synthesis of knowledge gaps

Animals have evolved with natural patterns of light and darkness, such that light serves as an important zeitgeber, allowing adaptive synchronization of behavior and physiology to external conditions. Exposure to artificial light at night (ALAN) interferes with this process, resulting in dysregulation of endocrine systems. In this review, we evaluate the endocrine effects of ALAN exposure in birds and reptiles, identify major knowledge gaps, and highlight areas for future research. There is strong evidence for ecologically relevant levels of ALAN acting as an environmental endocrine disruptor. However, most studies focus on the pineal hormone melatonin, corticosterone release via the hypothalamus-pituitary-adrenal axis, or regulation of reproductive hormones via the hypothalamus-pituitary-gonadal axis, leaving effects on other endocrine systems largely unknown. We call for more research spanning a diversity of hormonal systems and levels of endocrine regulation (e.g. circulating hormone levels, receptor numbers, strength of negative feedback), and investigating involvement of molecular mechanisms, such as clock genes, in hormonal responses. In addition, longer-term studies are needed to elucidate potentially distinct effects arising from chronic exposure. Other important areas for future research effort include investigating intraspecific and interspecific variability in sensitivity to light exposure, further distinguishing between distinct effects of different types of light sources, and assessing impacts of ALAN exposure early in life, when endocrine systems remain sensitive to developmental programming. The effects of ALAN on endocrine systems are likely to have a plethora of downstream effects, with implications for individual fitness, population persistence, and community dynamics, especially within urban and suburban environments.

Introduction of artificial light at night increases the abundance of predators, scavengers, and parasites in arthropod communities

While recent studies explore the negative impacts of light pollution on arthropods, few studies investigated community-level responses to artificial light. Using an array of landscaping lights and pitfall traps, we track community composition over 15 consecutive days and nights, including a five-night pre-light period, a five-night during-light period, and a five-night post-light period. Our results highlight a trophic-level response to artificial nighttime lighting with shifts in the presence and abundance of predators, scavengers, parasites, and herbivores. We show that associated trophic shifts occurred immediately upon the introduction of artificial light at night and are limited to nocturnal communities. Lastly, trophic levels reverted to their pre-light state, suggesting many short-term changes in communities are likely the result of behavioral shifts. These trophic shifts may become common as light pollution increases, implicating artificial light as a cause of global arthropod community change and highlighting light pollution's role in global herbivorous arthropod decline.

The spectral composition of a white light influences its attractiveness to Culex pipiens mosquitoes

Insect attraction to artificial light can potentially facilitate disease transmission by increasing contact between humans and vectors. Previous research has identified specific wavelength bands, such as yellow and red, that are unattractive to biting flies. However, narrow-band, non-white lights are unsuitable for home lighting use as their very poor color rendering is often considered aesthetically undesirable. The creation of a white light that is unattractive to insects has so far remained elusive. White light can be created by combining a number of narrow-band light-emitting diodes (LEDs). Through choice chamber experiments on Culex pipiens (Cx. pipiens) mosquitoes, we examine whether combining specific wavelength bands has an additive, subtractive or synergistic effect on insect attraction. We show that a white light created by combining narrow-band red, green and blue (RGB) LEDs is less attractive to Cx. pipiens than a broad-spectrum white light; and that a white light created by combining narrow-band blue and yellow LEDs is more attractive than a broad-spectrum white light. White light produced by RGB combinations could therefore serve as a safer and cheaper light in countries where phototactic vectors and vector-borne disease are endemic.

A review of the effects of artificial light at night in urban areas on the ecosystem level and the remedial measures

This paper attempts to realize the balance between humans and ecology in designing the nighttime light environment of urban parks by clarifying the influence of nighttime artificial light on the ecosystem of urban parks. Firstly, we reviewed the effects of nighttime artificial light on individual predation and reproduction of animals and personal growth and reproduction of plants. Secondly, we discuss the impact of individual changes caused by artificial lighting on ecosystem function at the ecosystem and analyze its advantages and disadvantages. The results showed that nighttime artificial light had a double-sided impact on the ecosystem, which would hurt the ecosystem function, but had a positive effect on the green space, which lacked natural light and had high plant density. This paper focuses on the areas with increased application of artificial lighting and rich species of animals and plants in night cities, such as urban forest parks and urban green spaces. It discusses how to reduce the intrusion of artificial lighting on ecosystems and how to make better use of the positive effect of artificial light.

Environmental risks from artificial nighttime lighting widespread and increasing across Europe

The nighttime environment of much of Earth is being changed rapidly by the introduction of artificial lighting. While data on spatial and temporal variation in the intensity of artificial lighting have been available at a regional and global scale, data on variation in its spectral composition have only been collected for a few locations, preventing variation in associated environmental and human health risks from being mapped. Here, we use imagery obtained using digital cameras by astronauts on the International Space Station to map variation in the spectral composition of lighting across Europe for 2012-2013 and 2014-2020. These show a regionally widespread spectral shift, from that associated principally with high-pressure sodium lighting to that associated with broad white light-emitting diodes and with greater blue emissions. Reexpressing the color maps in terms of spectral indicators of environmental pressures, we find that this trend is widely increasing the risk of harmful effects to ecosystems.

Light pollution spatial impact assessment in Hong Kong: Measurement and numerical modelling on commercial lights at street level

With rapid urbanization, the use of external lighting to illuminate cities for night-time activity is on the rise worldwide. Many studies have suggested the excessive use of external lighting causes light pollution, which harms human health and leads to energy wastage. Although more awareness has been raised, there are not many regulations and guidelines available. As one of the cities most affected by light pollution in the world, Hong Kong has started exploring this issue within the general and business communities. However, studies that quantitatively evaluate the problem of light pollution in this city are lacking. This study aimed to assess light pollution quantitatively through measurement and numerical modelling. To achieve this, measurement protocols were developed, and site measurements were carried out in one of the known problem areas, Sai Yeung Choi Street in Mong Kok district. Through this exercise, both vertical and horizontal illuminances on the street level and the light distribution along the street were determined. An average level of 250 lx for the vertical illuminance was found, which was 3-4 times higher than the recommended brightness for normal activity. The light environment of the measured area was also modelled with the simulation program DIALux. This effort complemented the measurements by providing a means to increase the resolution on the light variation and to visualize light pollution in a 3D environment. The simulation results were verified by correlating the numerical model with measurements. The correlated model was exercised in a subsequent sensitivity study to predict possible outcomes with changing lighting pattern and lighting lumen level. This study serves to quantify this issue, which helps with the further development of effective solutions.

Costs and benefits of "insect friendly" artificial lights are taxon specific

The expansion of human activity into natural habitats often results in the introduction of artificial light at night, which can disrupt local ecosystems. Recent advances in LED technology have enabled spectral tuning of artificial light sources, which could in theory limit their impact on vulnerable taxa. To date, however, experimental comparisons of ecologically friendly candidate colors have often considered only one type of behavioral impact, sometimes on only single species. Resulting recommendations cannot be broadly implemented if their consequences for other local taxa are unknown. Working at a popular firefly ecotourism site, we exposed the insect community to artificial illumination of three colors (blue, broad-spectrum amber, red) and measured flight-to-light behavior as well as the courtship flash behavior of male Photinus carolinus fireflies. Firefly courtship activity was greatest under blue and red lights, while the most flying insects were attracted to blue and broad-spectrum amber lights. Thus, while impacts of spectrally tuned artificial light varied across taxa, our results suggest that red light, rather than amber light, is least disruptive to insects overall, and therefore more generally insect friendly.

A Systematic Review for Establishing Relevant Environmental Parameters for Urban Lighting: Translating Research into Practice

The application of lighting technologies developed in the 20th century has increased the brightness and changed the spectral composition of nocturnal night-time habitats and night skies across urban, peri-urban, rural, and pristine landscapes, and subsequently, researchers have observed the disturbance of biological rhythms of flora and fauna. To reduce these impacts, it is essential to translate relevant knowledge about the potential adverse effects of artificial light at night (ALAN) from research into applicable urban lighting practice. Therefore, the aim of this paper is to identify and report, via a systematic review, the effects of exposure to different physical properties of artificial light sources on various organism groups, including plants, arthropods, insects, spiders, fish, amphibians, reptiles, birds, and non-human mammals (including bats, rodents, and primates). PRISMA 2020 guidelines were used to identify a total of 1417 studies from Web of Science and PubMed. In 216 studies, diverse behavioral and physiological responses were observed across taxa when organisms were exposed to ALAN. The studies showed that the responses were dependent on high illuminance levels, duration of light exposure, and unnatural color spectra at night and also highlighted where research gaps remain in the domains of ALAN research and urban lighting practice. To avoid misinterpretation, and to define a common language, key terminologies and definitions connected to natural and artificial light have been provided. Furthermore, the adverse impacts of ALAN urgently need to be better researched, understood, and managed for the development of future lighting guidelines and standards to optimize sustainable design applications that preserve night-time environment(s) and their inhabiting flora and fauna.

Disruptive effect of artificial light at night on leaf litter consumption, growth and activity of freshwater shredders

Artificial light at night (ALAN) is a globally widespread phenomenon potentially affecting ecosystem processes, such as leaf litter breakdown, which is a source of organic matter in fresh waters. Here, we conducted a long-term experiment to test the effects of ALAN (2 lx) differing in spectral composition: white LEDs and high pressure sodium lamps (HPS) on leaf consumption, growth and activity of two macroinvertebrate species of shredders: Gammarus jazdzewskii and Dikerogammarus villosus (Crustacea, Amphipoda), compared to the undisturbed light-dark cycle. We also tested if the nocturnal illumination would influence the algal community colonising leaves, which is an important component of the leaf-shredder diet. We found that LED light increased the consumption of leaves by both species, which was nearly twice as high as in other treatments, and supressed the growth rate of G. jazdzewskii, whereas the growth of D. villosus was not affected by either light type. Moreover, D. villosus reduced its activity when exposed to ALAN of both types. As ALAN-induced changes in shredder growth and consumption were not associated with their increased activity or decreased food quality, we suggest that LED light may be a source of physiological stress for shredders, raising their energy expenditure, which was compensated by increased food intake. We have shown that LED illumination induces greater effects on wildlife than alternative, narrow wavelength spectrum light sources, such as HPS lamps, and may potentially alter the litter breakdown in aquatic ecosystems. It may accelerate the turnover of leaves by shredders, but on the other hand, it may negatively affect the fitness of macroinvertebrates and thus disturb the leaf processing over a longer term.

Rethinking the campus transportation network in the scope of ecological design principles: case study of Izmir Katip Çelebi University Çiğli Campus

The concept of sustainability, which has become increasingly important in every aspect of life, has become a topic that is often emphasized for university campuses, which can be considered a small urban model. Many universities in Turkey and abroad are working on sustainable campuses. They set many environmental, social, and economic targets such as reducing the carbon footprint, using green technologies, designing by human and environment oriented principles, using green transportation systems, reducing costs, and eliminating social injustice. In this study, the transportation network of İzmir Katip Çelebi University, Çiğli Campus, which was established on an area of 70 ha in 2010, was examined within the scope of sustainability and ecological design criteria, and a transportation network focused on pedestrian and bicycle was also suggested. This study consists of two stages. In the first stage, the current situation analysis of the campus transportation was presented, and in the second stage, recommendations were made for a sustainable transportation system within the campus, taking into account the ecological design criteria.

Street lighting has detrimental impacts on local insect populations

Reported declines in insect populations have sparked global concern, with artificial light at night (ALAN) identified as a potential contributing factor. Despite strong evidence that lighting disrupts a range of insect behaviors, the empirical evidence that ALAN diminishes wild insect abundance is limited. Using a matched-pairs design, we found that street lighting strongly reduced moth caterpillar abundance compared with unlit sites (47% reduction in hedgerows and 33% reduction in grass margins) and affected caterpillar development. A separate experiment in habitats with no history of lighting revealed that ALAN disrupted the feeding behavior of nocturnal caterpillars. Negative impacts were more pronounced under white light-emitting diode (LED) street lights compared to conventional yellow sodium lamps. This indicates that ALAN and the ongoing shift toward white LEDs (i.e., narrow- to broad-spectrum lighting) will have substantial consequences for insect populations and ecosystem processes.

Impact of different wavelengths of artificial light at night on phototaxis in aquatic insects

The use of artificial light at night (ALAN) is increasing exponentially worldwide and there is growing evidence that ALAN contributes to the decline of insect populations. One of the most conspicuous ecological effects is the strong attraction of ALAN to flying insects. In several studies, light sources with strong short wavelength emissions have been shown to attract the highest numbers of flying insects. Furthermore, flying stages of aquatic insects are reported to be more vulnerable to ALAN than flying stages of terrestrial insects. This is concerning because freshwater habitats are likely affected by ALAN that originates from human activity centers, which are typically close to sources of freshwater. However, the effects of ALAN on aquatic insects, that spend their larval phase (amphibiotic insects) or their whole life cycle (fully aquatic insects) in freshwaters, are entirely understudied. Here, we investigated phototaxis of aquatic insects to ALAN at different wavelengths and intensities. We used floating light traps and compared four, near monochromatic, lights (blue, green, red and yellow) at two different photopic light intensities in a ditch system, which was not exposed to ALAN previously. Similar to flying stages of (aquatic and terrestrial) insects we found a strong positive phototaxis of aquatic life stages. However, in contrast to the flying stages there is no clear preference for short-wavelength light. Overall, responsivity to wavelengths in the center of the visible range (green, yellow; 500-600nm) was significant for all orders of aquatic insects studied and the nymphs of Ephemeroptera didn't respond to blue light at all. This is likely an adaption to how light is attenuated in freshwater systems, where not only the water itself but also a variety of optical constituents act as a color filter, often like in in our case filtering out short-wavelength light. Therefore, insects living in freshwater bodies often live in longer wavelength-dominated environments and might therefore be especially sensitive to green/yellow light. In conclusion, the different spectral sensitivities of both aquatic and flying insects should be taken into account when planning lighting near fresh water.

Ecological impacts of the LED-streetlight retrofit on insectivorous bats in Singapore

Cities around the world are transitioning to more efficient lighting schemes, especially retrofitting traditional, high-pressure sodium (HPS) streetlights with light-emitting diode (LED) lights. Although these initiatives aim to address the problems of urban sustainability and save money, the ecological impacts of these retrofits remain poorly understood, especially in brightly lit cities and in the tropics, where urbanisation is most rapid. We performed an experimental study of the retrofit in Singapore-focusing on insectivorous bats, whose activity we monitored acoustically along paired control (HPS-lit) and treatment (LED-lit) streets. We recorded seven species along these streets, but only obtained enough recordings to measure the effect of light type for three of them-all of which can reasonably be described as urban adapters. The strongest predictor of bat activity (an index of habitat use) was rainfall-it has a positive effect. Light type did not influence bat activity or species composition of the bat assemblage along these streets, though it did interact with the effects of rainfall and traffic noise for one bat species. Ultimately, the retrofit may be ecologically meaningless to urban-adapted, tropical insectivores that already experience high levels of light pollution as they do in Singapore. However, while our findings may appear reassuring to those concerned with such retrofits in other tropical and/or brightly-lit cities, they also highlight the contextual nature of ecological impacts. We point out that they should not be prematurely generalised to other locales and systems. In particular, they do not imply no impact on species that are less urban-adapted, and there is a clear need for further studies, for example, on responses of other foraging guilds and of bats (and insects) throughout the tropics.

Artificial light and biting flies: the parallel development of attractive light traps and unattractive domestic lights

Light trapping is an important tool for monitoring insect populations. This is especially true for biting Diptera, where light traps play a crucial role in disease surveillance by tracking the presence and abundance of vector species. Physiological and behavioural data have been instrumental in identifying factors that influence dipteran phototaxis and have spurred the development of more effective light traps. However, the development of less attractive domestic lights has received comparatively little interest but could be important for reducing interactions between humans and vector insects, with consequences for reducing disease transmission. Here, we discuss how dipteran eyes respond to light and the factors influencing positive phototaxis, and conclude by identifying key areas for further research. In addition, we include a synthesis of attractive and unattractive wavelengths for a number of vector species. A more comprehensive understanding of how Diptera perceive and respond to light would allow for more efficient vector sampling as well as potentially limiting the risk posed by domestic lighting.

Management of flying insects on expressways through an academic-industrial collaboration: evaluation of the effect of light wavelengths and meteorological factors on insect attraction

Insect outbreaks often occur in the absence of natural enemies and in the presence of excess suitable host materials. Outbreaks of gypsy moths are especially problematic in remote areas located in high-latitude regions in Japan because the majority of adults emerge during the short summer season and initiate synchronous mass flight toward artificial lights. The aggregation of moths in public facilities not only is an annoyance to visitors but also permits the establishment of new populations the following year. The aim of this study was to establish a method to reduce the numbers of large moths that are attracted to lights in the rest areas of expressways in Hokkaido based on the results of research on their behavioral ecology and physiology. First, we conducted extensive insect surveys using light traps that emit light at different wavelengths; the traps were set along the expressways in the summers of 2014-2018. The insects attracted to the light were roughly classified into those showing a preference for broadband light wavelengths (from UV-A to green) and short light wavelengths (from UV-A to blue). The former included aquatic insects and winged ants, and the latter included moths and beetles. Next, we analyzed correlations between moth emergence and daily meteorological data. When gypsy moths were abundant during an outbreak, the daily catch of gypsy moths was positively correlated with the highest ambient temperature on the catch day but not with the visibility range, wind speed, or moon phase. In contrast, the daily catch of oak silkmoths did not correlate with any of these parameters. Our results provide guidance for the management of forest insects inhabiting cool-temperate to subarctic regions based on light wavelengths with reference to weather variables.

Exposure to Artificial Light at Night and the Consequences for Flora, Fauna, and Ecosystems

The present review draws together wide-ranging studies performed over the last decades that catalogue the effects of artificial-light-at-night (ALAN) upon living species and their environment. We provide an overview of the tremendous variety of light-detection strategies which have evolved in living organisms - unicellular, plants and animals, covering chloroplasts (plants), and the plethora of ocular and extra-ocular organs (animals). We describe the visual pigments which permit photo-detection, paying attention to their spectral characteristics, which extend from the ultraviolet into infrared. We discuss how organisms use light information in a way crucial for their development, growth and survival: phototropism, phototaxis, photoperiodism, and synchronization of circadian clocks. These aspects are treated in depth, as their perturbation underlies much of the disruptive effects of ALAN. The review goes into detail on circadian networks in living organisms, since these fundamental features are of critical importance in regulating the interface between environment and body. Especially, hormonal synthesis and secretion are often under circadian and circannual control, hence perturbation of the clock will lead to hormonal imbalance. The review addresses how the ubiquitous introduction of light-emitting diode technology may exacerbate, or in some cases reduce, the generalized ever-increasing light pollution. Numerous examples are given of how widespread exposure to ALAN is perturbing many aspects of plant and animal behaviour and survival: foraging, orientation, migration, seasonal reproduction, colonization and more. We examine the potential problems at the level of individual species and populations and extend the debate to the consequences for ecosystems. We stress, through a few examples, the synergistic harmful effects resulting from the impacts of ALAN combined with other anthropogenic pressures, which often impact the neuroendocrine loops in vertebrates. The article concludes by debating how these anthropogenic changes could be mitigated by more reasonable use of available technology - for example by restricting illumination to more essential areas and hours, directing lighting to avoid wasteful radiation and selecting spectral emissions, to reduce impact on circadian clocks. We end by discussing how society should take into account the potentially major consequences that ALAN has on the natural world and the repercussions for ongoing human health and welfare.

Light Emitting Diode (LED) Usage in Organizations: Impact on Environmental and Economic Performance

Environmental sustainability is receiving serious attention from organizations. Green practices and the use of green technologies such as Light Emitting Diode (LED) among organizations can reduce energy consumption, besides providing numerous benefits to the environment as well as organizations. Using the Belief–Action–Outcome framework, the stakeholder and social contract theory, this study aims to investigate the external and internal factors that influence LED usage, and the subsequent impact this may have on organizational outcomes. Data were collected from 300 Malaysian organizations that were LED users. Findings showed that social expectation had a significant positive influence on organizations’ environmental concern while stakeholder pressure and organizations’ environmental concern had a direct significant positive influence on LED usage. The findings further revealed that LED usage has a positive impact on organizations’ environmental and economic performance. This study contributes to the green and sustainability literature by identifying the relationship between specific macro level and micro level factors, and its link to organizations’ use of LED, and the subsequent impact on organizational outcomes. The identification of the antecedents and consequences of LED usage can help managers to formulate strategies that contribute to green climate within organizations, thereby supporting green technology usage and environmental sustainability.

Artificial lighting impairs mate attraction in a nocturnal capital breeder

Artificial lighting at night (ALAN) is increasingly recognised as having negative effects on many organisms, though the exact mechanisms remain unclear. Glow worms are likely susceptible to ALAN because females use bioluminescence to signal to attract males. We quantified the impact of ALAN by comparing the efficacy of traps that mimicked females to attract males in the presence or absence of a white artificial light source (ALS). Illuminated traps attracted fewer males than did traps in the dark. Illuminated traps closer to the ALS attracted fewer males than those further away, whereas traps in the dark attracted similar numbers of males up to 40 m from the ALS. Thus, ALAN impedes females' ability to attract males, the effect increasing with light intensity. Consequently, ALAN potentially affects glow worms' fecundity and long-term population survival. More broadly, this study emphasises the potentially severe deleterious effects of ALAN upon nocturnal insect populations.

Exposure to artificial light at night during the larval stage has delayed effects on juvenile corticosterone concentration in American toads, Anaxyrus americanus

Artificial Light At Night (ALAN) is an environmental stressor that can disrupt individual physiology and ecological interactions. Hormones such as corticosterone are often responsible for mediating an organism's response to environmental stressors. We investigated whether ALAN was associated with a corticosterone response and whether it exacerbated the effects of another common stressor, predation. We tested for consumptive, non-consumptive, and physiological effects of ALAN and predator presence (dragonfly larvae) on a widespread amphibian, the American toad (Anaxyrus americanus). We found predators had consumptive (decreased survival) and non-consumptive (decreased growth) effects on larval toads. ALAN did not affect larval toads nor did it interact with the predator treatment to increase larval toad predation. Despite the consumptive and non-consumptive effects of predators, neither predators nor ALAN affected corticosterone concentration in the larval and metamorph life-stages. In contrast to studies in other organisms, we did not find any evidence that suggested ALAN alters predator-prey interactions between dragonfly larvae and toads. However, there was an inverse relationship between corticosterone and survival that was exacerbated by exposure to ALAN when predators were absent. Additionally, larval-stage exposure to ALAN increased corticosterone concentration in juvenile toads. Our results suggest the physiological effects of ALAN may not be demonstrated until later life-stages.

Nano Wave Plates Structuring and Index Matching in Transparent Hydroxyapatite-YAG: Ce Composite Ceramics for High Luminous Efficiency White Light-Emitting Diodes

Replacing traditional luminous silicone or resins with phosphor in ceramics (PiCs) as color converters has been proposed as an efficient way to improve thermal stability of high-power white light-emitting diodes (WLEDs). However, excessive light scattering in existing PiCs results in enormous phosphor-converted light losses, which makes the luminosity of current PiCs color converters less efficient and means that they can only be used in devices working in reflective mode. By introducing nano wave plate structuring and Rayleigh scattering, luminous hydroxyapatite (HA)-YAG: Ce ceramics are prepared from mesoporous HA nanorods and YAG: Ce phosphors at 850 °C, enabling for the first time WLEDs equipped with PiC color converters in transmission mode. With low-temperature sintering and a highly transparent matrix, the quantum yield of HA-YAG: Ce retains ≈90% of the raw phosphor, and WLEDs with the color converters exhibit a record luminous efficiency of 170 lm W^-1 and a correlated color temperature below 4500 K. A facile and practical strategy of using nano structural modulation to eliminate birefringence-induced light scattering for fabricating high-performance ceramic converters suitable for multiple mode luminaires is demonstrated.

Light pollution and insufficient sleep: Evidence from the United States

OBJECTIVES

The objective of this study was to test whether light pollution is associated with lower or insufficient sleep. The American Medical Association recently issued a public notice cautioning against the effects of nighttime light on sleep quality and quantity. Light pollution, through the suprachiasmatic nucleus, disrupts circadian rhythm by reducing the secretion of melatonin, a sleep-inducing hormone.

METHODS

I used 282 403 individual self-reports of sleep hours and insufficient sleep from the 2014 and 2016 metropolitan and micropolitan statistical area (MMSA) Behavioral Risk Factor Surveillance System (BRFSS) and the prevalence of insufficient sleep during 2014 in 2823 US counties from the County Health Rankings. The nighttime artificial light data are from the cloud-free Visible Infrared Imaging Radiometer Suite available from the National Oceanic and Atmospheric Administration in the US.

RESULTS

At the MMSA level, for a 10-unit increase in nighttime light (nW/[cm² sr]) the estimated decline in sleep was about 5.59 minutes per day and the odds of reporting insufficient sleep (<7 hours) increased by 13.77%. At the county-level, for a 10-unit increase in nighttime light, the prevalence of insufficient sleep increased by 2.19%.

CONCLUSIONS

Although light pollution was negatively associated with sleep outcomes, the practical effect sizes were small. The small effects suggest that the effects at the population level are negligible, and the effect of nighttime light pollution is more idiosyncratic.

Color polarization vision mediates the strength of an evolutionary trap

Evolutionary traps are scenarios in which animals are fooled by rapidly changing conditions into preferring poor-quality resources over those that better improve survival and reproductive success. The maladaptive attraction of aquatic insects to artificial sources of horizontally polarized light (e.g., glass buildings, asphalt roads) has become a first model system by which scientists can investigate the behavioral mechanisms that cause traps to occur. We employ this field-based system to experimentally investigate (a) in which portion(s) of the spectrum are polarizationally water-imitating reflectors attractive to nocturnal terrestrial and aquatics insects, and (b) which modern lamp types result in greater attraction in this typical kind of nocturnal polarized light pollution. We found that most aquatic taxa exhibited preferences for lamps based upon their color spectra, most having lowest preference for lamps emitting blue and red light. Yet, despite previously established preference for higher degrees of polarization of reflected light, most aquatic insect families were attracted to traps based upon their unpolarized spectrum. Chironomid midges, alone, showed a preference for the color of lamplight in both the horizontally polarized and unpolarized spectra indicating only this family has evolved to use light in this color range as a source of information to guide its nocturnal habitat selection. These results demonstrate that the color of artificial lighting can exacerbate or reduce its attractiveness to aquatic insects, but that the strength of attractiveness of nocturnal evolutionary traps, and so their demographic consequences, is primarily driven by unpolarized light pollution. This focuses management attention on limiting broad-spectrum light pollution, as well as its intentional deployment to attract insects back to natural habitats.

The impact of artificial light at night on nocturnal insects: A review and synthesis

In recent decades, advances in lighting technology have precipitated exponential increases in night sky brightness worldwide, raising concerns in the scientific community about the impact of artificial light at night (ALAN) on crepuscular and nocturnal biodiversity. Long-term records show that insect abundance has declined significantly over this time, with worrying implications for terrestrial ecosystems. The majority of investigations into the vulnerability of nocturnal insects to artificial light have focused on the flight-to-light behavior exhibited by select insect families. However, ALAN can affect insects in other ways as well. This review proposes five categories of ALAN impact on nocturnal insects, highlighting past research and identifying key knowledge gaps. We conclude with a summary of relevant literature on bioluminescent fireflies, which emphasizes the unique vulnerability of terrestrial light-based communication systems to artificial illumination. Comprehensive understanding of the ecological impacts of ALAN on diverse nocturnal insect taxa will enable researchers to seek out methods whereby fireflies, moths, and other essential members of the nocturnal ecosystem can coexist with humans on an increasingly urbanized planet.

A transition to white LED increases ecological impacts of nocturnal illumination on aquatic primary producers in a lowland agricultural drainage ditch

The increasing use of artificial light at night (ALAN) has led to exposure of freshwater ecosystems to light pollution worldwide. Simultaneously, the spectral composition of nocturnal illumination is changing, following the current shift in outdoor lighting technologies from traditional light sources to light emitting diodes (LED). LEDs emit broad-spectrum white light, with a significant amount of photosynthetically active radiation, and typically a high content of blue light that regulates circadian rhythms in many organisms. While effects of the shift to LED have been investigated in nocturnal animals, its impact on primary producers is unknown. We performed three field experiments in a lowland agricultural drainage ditch to assess the impacts of a transition from high-pressure sodium (HPS) to white LED illumination (color temperature 4000 K) on primary producers in periphyton. In all experiments, we compared biomass and pigment composition of periphyton grown under a natural light regime to that of periphyton exposed to nocturnal HPS or, consecutively, LED light of intensities commonly found in urban waters (approximately 20 lux). Periphyton was collected in time series (1-13 weeks). We found no effect of HPS light on periphyton biomass; however, following a shift to LED the biomass decreased up to 62%. Neither light source had a substantial effect on pigment composition. The contrasting effects of the two light sources on biomass may be explained by differences in their spectral composition, and in particular the blue content. Our results suggest that spectral composition of the light source plays a role in determining the impacts of ALAN on periphyton and that the ongoing transition to LED may increase the ecological impacts of artificial lighting on aquatic primary producers. Reduced biomass in the base of the food web can impact ecosystem functions such as productivity and food supply for higher trophic levels in nocturnally-lit ecosystems.

Emerging threat of the 21st century lightscape to global biodiversity

Over the last century the temporal and spatial distribution of light on Earth has been drastically altered by human activity. Despite mounting evidence of detrimental effects of light pollution on organisms and their trophic interactions, the extent to which light pollution threatens biodiversity on a global scale remains unclear. We assessed the spatial extent and magnitude of light encroachment by measuring change in the extent of light using satellite imagery from 1992 to 2012 relative to species richness for terrestrial and freshwater mammals, birds, reptiles, and amphibians. The encroachment of light into previously dark areas was consistently high, often doubling, in areas of high species richness for all four groups. This pattern persisted for nocturnal groups (e.g., bats, owls, and geckos) and species considered vulnerable to extinction. Areas with high species richness and large increases in light extent were clustered within newly industrialized regions where expansion of light is likely to continue unabated unless we act to conserve remaining darkness. Implementing change at a global scale requires global public, and therefore scientific, support. Here, we offer substantial evidence that light extent is increasing where biodiversity is high, representing an emerging threat to global biodiversity requiring immediate attention.

The Value of Darkness: A Moral Framework for Urban Nighttime Lighting

The adverse effects of artificial nighttime lighting, known as light pollution, are emerging as an important environmental issue. To address these effects, current scientific research focuses mainly on identifying what is bad or undesirable about certain types and uses of lighting at night. This paper adopts a value-sensitive approach, focusing instead on what is good about darkness at night. In doing so, it offers a first comprehensive analysis of the environmental value of darkness at night from within applied ethics. A design for values orientation is utilized to conceptualize, define, and categorize the ways in which value is derived from darkness. Nine values are identified and categorized via their type of good, temporal outlook, and spatial characteristics. Furthermore, these nine values are translated into prima facie moral obligations that should be incorporated into future design choices, policy-making, and innovations to nighttime lighting. Thus, the value of darkness is analyzed with the practical goal of informing future decision-making about urban nighttime lighting.

Numerical research on the effects the skyglow could have in phytochromes and RQE photoreceptors of plants

The increase of artificial light at night has a terrible impact on organisms with nightlife patterns such as a migration, nutrition, reproduction and collective interaction. Plants are not free from this issue as they have life cycle events occurring not only yearly but also daily. Such events relate to daytime variations with seasons in which the flowers of deciduous trees bloom and the leaves of certain trees fall off and change color. A response of plants to artificial light at night still remains poorly quantified; but recent scientific research suggest that skyglow can disturb plants processes. For instance, low levels of light affect deciduous plants, which shed their leaves as days grow short in the fall. In this paper we model skyglow considering the features of artificial light that can affect natural processes of plants during the night. A case-study was conducted to mimic skyglow effects in real location for which experimental data exist. In our numerical simulations we found that some lighting systems can have an effect on plant photoreceptors and affect the phenology of plants. Specifically, the lamps that emit the electromagnetic energy in a wide spectral range can have greater effect on the photosensitivity of the plants. We believe the results obtained here will motivate botanists to make a targeted experiment to verify or challenge our findings. If the night light can change plant behavior under some conditions, it can have significant implications in botany, biology, or even agriculture.

Why artificial light at night should be a focus for global change research in the 21st century

The environmental impacts of artificial light at night have been a rapidly growing field of global change science in recent years. Yet, light pollution has not achieved parity with other global change phenomena in the level of concern and interest it receives from the scientific community, government and nongovernmental organizations. This is despite the globally widespread, expanding and changing nature of night-time lighting and the immediacy, severity and phylogenetic breath of its impacts. In this opinion piece, we evidence 10 reasons why artificial light at night should be a focus for global change research in the 21st century. Our reasons extend beyond those concerned principally with the environment, to also include impacts on human health, culture and biodiversity conservation more generally. We conclude that the growing use of night-time lighting will continue to raise numerous ecological, human health and cultural issues, but that opportunities exist to mitigate its impacts by combining novel technologies with sound scientific evidence. The potential gains from appropriate management extend far beyond those for the environment, indeed it may play a key role in transitioning towards a more sustainable society.

The Reality of Light Pollution: A Field Survey for the Determination of Lighting Environmental Management Zones in South Korea

Light pollution has been receiving increased attention worldwide. Scientific research has provided convincing evidence that ties artificial lighting to health-related issues. Consequently, the involved parties are now leaned towards the implementation of regulations to help limit the use of artificial lighting. Many countries, together with international organizations, have embarked on setting standards and regulations aimed at halting the excessive and improper usage of artificial lighting, there-by eradicating light pollution and its effects. In Korea, outdoor lighting at night is a common phenomenon. Moreover, as the economic development grows even further, the use of artificial lighting is expected to increase making Korea vulnerable to the adverse effects of artificial lighting. In this study, we discuss the issue of light pollution based on field measurements conducted in Seoul, South Korea. The measurements were undertaken to broaden the understanding and assessment of light pollution. During the investigation, we noted that the most severe forms of light pollution were found in developed urban and densely commercialized areas. Currently, there are ongoing light pollution measurement projects around the entire Korea. It would be informative to see how the rest of South Korea compares to the Capital, Seoul in terms of light pollution levels.