Projection of Light Pollution and Environmental Impact Estimation Based on Population and GDP: The Case of Türkiye

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'.

This study investigates the impact of artificial light at night (ALAN) along the Sicilian coasts, using satellite data from 2016 to 2023, focusing on three distinct spatial domains: terrestrial areas within 1 km from the coastline, marine areas extending up to 1 km offshore, and marine areas up to 1 nautical mile from the coast. In coastal zones, ALAN is a significant anthropogenic pressure with potentially detrimental effects on ecosystems. By integrating satellite data with geographic datasets such as Corine Land Cover (CLC), Natura 2000 protected areas, and Posidonia oceanica meadows, this study aims to characterize and analyse the temporal and spatial variations in ALAN across these domains. The findings reveal substantial differences in light pollution between domains and over time, with coastal terrestrial areas exhibiting the highest levels of ALAN. In contrast, marine areas further offshore experience reduced light pollution, particularly within the 1-nautical-mile domain. This study also indicates that protected areas, especially those within the Natura 2000 network, show significantly lower ALAN levels than non-protected areas, highlighting the effectiveness of conservation efforts. Statistical analyses, including ANOVAs, demonstrate that factors such as geographic domain, year, province, and CLC classes significantly influence ALAN distribution. This study advocates for considering ALAN as a critical factor in environmental impact assessments, such as those under the Maritime Spatial Planning Directive (MSP) and Marine Strategy Framework Directive (MSFD), providing valuable insights to support policies aimed at mitigating the environmental impact of light pollution on coastal and marine ecosystems.

Artificial light at night disrupts immune rhythms in wild rodents under semi-natural conditions.

Dear Editor, Artificial light at night (ALAN) has become an inseparable feature of modern life, driving 24-hour productivity by supporting economic growth, continuous healthcare, transportation, and global connectivity. However, this advancement carries hidden costs, particularly to human health. Emerging evidence underscores that long-term nocturnal light exposure is not merely a nuisance but a serious public health issue, with profound consequences for metabolic health [1]. Metabolic syndrome (MetS): a cluster of risk factors including hypertension, central obesity, insulin resistance, glucose intolerance, and dyslipidemia, is a growing global epidemic, affecting an estimated 20-25% of adults worldwide [2]. While traditionally attributed to lifestyle factors such as diet and physical inactivity, ALAN has now emerged as a modifiable risk factor. MetS dramatically increases the risk of type 2 diabetes and cardiovascular disease. Populations most at risk from ALAN include urban dwellers exposed to pervasive light pollution, shift workers, and individuals using smartphones or computers late into the night. ALAN contributes to MetS by activating the autonomic system and disrupting the circadian rhythm, which depends on the natural light–dark cycle to synchronize vital processes such as hormone secretion, thermoregulation, and metabolism [3]. ALAN, particularly short-wavelength blue light, suppresses melatonin, the "hormone of darkness", thereby impairing glucose metabolism, reducing insulin sensitivity, and promoting weight gain [4]. Epidemiological data strengthen this connection. For instance, an extensive study including over 1.6 million individuals demonstrated that higher ALAN exposure correlated with obesity, hypertension, insulin resistance, type 2 diabetes, and cardiovascular disease [5]. Another cohort analysis reported associations between ALAN and hypertension, obesity, and incident hypercholesterolemia [6]. Additionally, Wang et al. (2023) found that ALAN exposure accounted for 26.80% of metabolic disease cases in Ningxia, China, with risk exceptionally high in men. [7] Together, these findings suggest that chronic nighttime light exposure acts as an obesogenic factor, reinforcing the pathogenesis of MetS. The implications of ALAN with MetS extend beyond individual behaviour into the realm of public health and policy. Widespread light pollution requires systemic solutions: urban planning reforms such as shielded street lighting, stricter regulations on outdoor lighting, and workplace strategies such as circadian-friendly lighting, scheduled rest breaks, and education on sleep hygiene to mitigate circadian disruption for night-shift workers. For clinicians, counselling of MetS should move beyond the usual modifiable risk parameters (diet and exercise) to also include ‘light hygiene’ such as avoiding bright light exposure before bedtime, using blackout curtains or masks, and adopting warmer, dimmer lighting in the evening. Ultimately, the link between ALAN and metabolic dysfunction is no longer speculative but supported by growing clinical and epidemiological evidence. Yet research remains limited in nationwide epidemiological and retrospective cohort studies, especially in diverse and high-risk populations. Future studies should prioritize these populations to clarify causal pathways and guide effective public health interventions. In conclusion, ALAN is a pervasive and modifiable contributor to metabolic syndrome. Addressing this requires a multipronged approach: patient education on light hygiene, incorporating circadian health into lifestyle counselling, and public health policies to reduce light pollution. Recognizing light at night as an environmental risk factor is essential to curb the growing burden of metabolic disease

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'.

Biodiversity is negatively affected by light pollution, caused by artificial light at night (ALAN). Light-emitting diodes facilitate new lighting technologies to mediate the negative effects of ALAN, such as dynamic ALAN where light intensity can be adjusted to traffic density. Organisms living in highly light-polluted areas may show adaptations to mitigate the negative effects of ALAN. In a split-brood rearing experiment, larvae of two moth species (Ochropleura plecta and Agrotis exclamationis) originating from low-medium and high-medium skyglow populations were grown under either continuous ALAN, dynamic ALAN or control-dark conditions. We tested for ALAN effects on larval mortality, feeding behaviour, development and body mass, and whether effects depended on skyglow levels in the population of origin. Contrary to previous studies, we found either no or positive effects of ALAN on larval development, with similar or stronger effects of dynamic ALAN compared to continuous ALAN. For A. exclamationis, we showed evidence for faster development, increased growth rate and higher body mass under ALAN. This could reduce larval exposure to parasites and increase fecundity. We found no evidence for evolutionary responses in low-medium or high-medium skyglow larvae. Our results show that ALAN does not affect larval development the same way in all species.

BackgroundThe timing of behavior and habitat use of nocturnal animals can be influenced by the lunar cycle in nature. The prevalence of artificial light at night (ALAN) has been recognized as a source of environmental pollution. The interaction between ALAN and the lunar cycle on bat behavior is important for understanding anthropogenic effects on bats. We utilized a decade (2012–2022) of acoustic monitoring data collected in North Carolina, United States, to investigate the relationship between bat activity, lunar cycle, and light pollution. We examined whether the amount of lunar illumination affected species-specific nightly activity and whether hourly bat activity patterns varied between nights with different moon phases. We further investigated if the relationship between bat activity and the lunar cycle might be altered by light pollution.ResultsWe found that seven bat species showed activity variation across nights in relation to the amount of moon illumination when ALAN was absent. In general, bats were less active on full moon nights compared to new moon nights. Light pollution interacted with the bat–lunar relationship in five of the seven species, masking the effect of the lunar cycle. We identified delayed bat activity patterns on nights with a full or waxing moon in seven species, and light pollution altered that pattern in four species. Overall, ALAN was associated with decreased bat activity independent of lunar cycle effects.ConclusionsOur study demonstrated that at a broad spatial scale, ALAN negatively affected many North American temperate bat species and altered their lunar chronobiology. As light pollution is spreading to historically dark areas and habitats, ALAN might couple with other threats, such as the white-nose syndrome or climate change, to cause cascading damage in the environment that depends on ecosystem services such as pest control provided by bats. We argue that further research and conservation actions are needed to mitigate the impact of light pollution.

Artificial light at night (ALAN) is increasing exponentially worldwide, accelerated by the transition to new efficient lighting technologies. However, ALAN and resulting light pollution can cause unintended physiological consequences. In vertebrates, production of melatonin—the “hormone of darkness” and a key player in circadian regulation—can be suppressed by ALAN. In this paper, we provide an overview of research on melatonin and ALAN in vertebrates. We discuss how ALAN disrupts natural photic environments, its effect on melatonin and circadian rhythms, and different photoreceptor systems across vertebrate taxa. We then present the results of a systematic review in which we identified studies on melatonin under typical light-polluted conditions in fishes, amphibians, reptiles, birds, and mammals, including humans. Melatonin is suppressed by extremely low light intensities in many vertebrates, ranging from 0.01–0.03 lx for fishes and rodents to 6 lx for sensitive humans. Even lower, wavelength-dependent intensities are implied by some studies and require rigorous testing in ecological contexts. In many studies, melatonin suppression occurs at the minimum light levels tested, and, in better-studied groups, melatonin suppression is reported to occur at lower light levels. We identify major research gaps and conclude that, for most groups, crucial information is lacking. No studies were identified for amphibians and reptiles and long-term impacts of low-level ALAN exposure are unknown. Given the high sensitivity of vertebrate melatonin production to ALAN and the paucity of available information, it is crucial to research impacts of ALAN further in order to inform effective mitigation strategies for human health and the wellbeing and fitness of vertebrates in natural ecosystems.

Artificial light at night (ALAN) is a pervasive anthropogenic pollutant, increasing in intensity and scope. While its impacts on biological and ecological processes are well documented among terrestrial taxa, marine organisms have received less attention, though a quarter of the world's coastlines are affected by artificial light at night. Furthermore, the intergenerational effects of artificial light at night have never been documented in the wild. We conducted a field manipulation experiment in the lagoon of Mo'orea, French Polynesia, using LED (Light-Emitting Diode) lights to test artificial light at night's effects on adult life-history and offspring fitness of the coral reef anemonefish Amphiprion chrysopterus. Exposing adults and embryos to LEDs, we found artificial light at night enhanced adult growth but did not alter measured reproductive traits, including fecundity. We observed reduced parental reproductive hormone levels with downstream consequences for offspring. Hatching success was unchanged, but offspring showed reduced embryonic heart rate and yolk sac size, and drastically diminished larval escape responses and swimming performance. This comprehensive study is the first in a wild organism to demonstrate combined intergenerational and direct negative effects of artificial light at night, highlighting limited compensatory capacity. These impacts could impair larval recruitment and hinder population replenishment in reef fish. This research underscores urgent need for conservation and management to address artificial lighting impacts.

Even low light pollution levels affect the spatial distribution and timing of activity of a “light tolerant” bat species

Anthropogenic noise and light pollution additively affect sleep behaviour in free-living birds in sex- and season-dependent fashions

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'.

Artificial light at night (ALAN), also known as light pollution, is a growing environmental problem worldwide. However, only a few studies have examined whether soil organisms that search for food at the surface at night can be affected by ALAN. We investigated the effects of ALAN on the above-ground foraging activity of anecic earthworms (Lumbricus terrestris), on the soil water infiltration and on the germination and growth of a cover crop (Phacelia tanacetifolia). In a full-factorial greenhouse experiment, we tested four factors: ALAN (about 5 lx during the night vs. total darkness), earthworms (two specimens vs. none), plant species (Phacelia alone vs. mixed with ragweed Ambrosia artemisiifolia) and sowing depth (surface-sown vs. sown in 5 cm depth). Data were analysed using multifactorial ANOVAs. Earthworms removed 51% less surface litter under ALAN than under dark conditions. ALAN had no effect on Phacelia germination but resulted in increased height growth and biomass production when the seeds were buried. Earthworms reduced Phacelia germination and biomass production. ALAN reduced water leaching through the experimental units, probably due to interactions between the subsurface casts and plant roots. We conclude that ALAN, as emitted from streetlights, can lead to complex ecological effects in ecosystems that merit further investigation.

Effects of dim artificial light at night on locomotor activity, cardiovascular physiology, and circadian clock genes in a diurnal songbird

Impacts of Artificial Light at Night (ALAN) on coastal ecosystems: A study on the herbivore Ampithoe valida with focus on sex-dependent responses.