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Letters

Light pollution as a biodiversity threat

White light-emitting diode (LED) for night lighting disrupts photoperiod in plants, which affects the plant’s photosynthesis. Therefore, it is necessary to find a new type of white LED with little effect on plant photosynthesis. In this study, a series of phosphate phosphors Ca₉NaY_2/3(PO₄)₇:Dy³⁺ (CNYP:Dy³⁺) were synthesized. Cation Li⁺ substitute Na⁺ were used to improve the luminescence properties of CNYP:Dy³⁺ phosphor. The CNYP:Dy³⁺ phosphor exhibits visible white light emission with emission peaks at 480 nm (blue light) and 570 nm (yellow light) excited by the near ultraviolet light 350 nm. The optimal concentration of Dy³⁺ was 0.10 mol, and the mechanism of concentration quenching was evaluated as energy migration among the nearest or next-nearest Dy³⁺. The substitution of Na⁺ by Li⁺ of CNYP:0.10Dy³⁺ improves the internal quantum efficiency from 30.24 % to 59.05 %, and presents good near-zero thermal quenching performance at 423 K. To assess the suitability of this phosphor for urban ecological lighting, the spectrum resemblance (SR) index between the electroluminescence spectrum of the prepared pc-LED and the absorption spectra of chlorophyll a and b was evaluated as 6.63 % and 18.61 %, respectively. This work exhibits a feasible scheme for the development of urban ecological lighting.

Artificial light at night (ALAN) has been and is still spreading rapidly across the globe. Although many studies have demonstrated its adverse effects on the behavior and physiology of various organisms, little is known regarding its direct and indirect effects on soil animals. Therefore, the effects of ALAN and fauna exclusion and their interactions with Collembola were studied using field control experiments in the Hulunbuir Grassland, China's Erguna Forest Grassland Transition Zone Ecosystem Research Station. The Collembola were captured with pitfall traps, and their activity-density and species richness were calculated. The results showed that ALAN significantly increased the activity-density and species richness of Collembola. Fauna exclusion also increased the activity-density and richness of active Collembola at nighttime but not in the daytime. The effect of ALAN and fauna exclusion directly promoted Collembola but not through soil and plant properties. ALAN facilitated Collembola by extending their activity time, whereas fauna exclusion exerted a beneficial impact by reducing the number of predatory groups on Collembola. These two beneficial factors could collectively promote Collembola density and activity without contradicting each other.

Nighttime Light (NTL) is highly concentrated in China's coastal zone, leading to negative health impacts on both humans and wildlife. Particularly, in recent years, the widespread adoption of broad-spectrum Light-Emitting Diode (LED) light, a low-carbon technology providing substantial increases in luminosity, has led to certain ecological consequences. Thus, information regarding spatial distribution and composition of different NTL types is essential for formulating sustainable strategies that balance nighttime public security, energy consumption, and ecosystem conservation. However, the availability of such information remains limited. To address this challenge and meet the demand, we developed two new light indices, namely the Ratio Red Light Index (RRLI) and Ratio Blue Light Index (RBLI), based on SDGSAT-1 Glimmer Imager (GLI) multispectral NTL data. We then proposed a threshold method and applied it to the entire coastal zone of China to identify White LED (WLED), Red LED (RLED), and Other lights (Other). Results showed the following. (1) In the coastal zone of China, the total lighting area was 20,517 km², including 20,257 km² of terrestrial lights and 260 km² of offshore lights; (2) WLED light covered 67% (13,727 km²) of all lighting areas, while RLED lights accounted for only 1% (220 km²); (3) Guangdong had the largest lighting area (5221 km²), with the proportion of WLEDs being the highest among all coastal provinces (almost 90%); (4) The proportions of lighting areas were relatively low in Guangxi, Liaoning, and Hebei. This study represents the first attempt to identify NTL types over large regions at a finer spatial resolution. The approach proposed, including the light indices of RRLI and RBLI, as well as the defined thresholds, is universal and robust for use in NTL type classification. The developed lighting type map, containing comprehensive information on the spatial distribution and composition of NTL, could facilitate the sustainable management of China's coastal zones.

Urban soils host diverse bacteria crucial for ecosystem functions and urban health. As urbanization rises, artificial light at night (ALAN) imposes disturbances on soil ecosystems, yet how ALAN affects the structure and stability of soil bacterial community remains unclear. Here we coupled a short-term incubation experiment, community profiling, network analysis, and in situ field survey to assess the ecological impacts of ALAN. We showed that ALAN influenced bacterial compositions and shifted the bacterial network to a less stable phase, altering denitrification potential. Such transition in community stability probably resulted from an ALAN-induced decrease in competition and/or an increase in facilitation, in line with the Stress Gradient Hypothesis. Similar destabilizing effects were also detected in bacterial networks in multiple urban soils subjected to different levels of ALAN stress, supporting the action of ALAN on naturally-occurring soil bacterial communities. Overall, our findings highlight ALAN as a new form of anthropogenic stress that jeopardizes the stability of soil bacterial community, which would facilitate ecological projection of expanding ALAN exposure.

Background: Outdoor artificial light at night (ALAN) has been linked to an elevated risk of diabetes, but the available literature on the relationships between ALAN and glucose homeostasis in pregnancy is limited.

Methods: A prospective cohort study of 6730 pregnant women was conducted in Hefei, China. Outdoor ALAN exposure was estimated using satellite data with individual addresses at a spatial resolution of approximately 1 km, and the average ALAN intensity was calculated. Gestational diabetes mellitus (GDM) was diagnosed based on a standard 75-g oral glucose tolerance test. Multivariable linear regression and logistic regression were used to estimate the relationships between ALAN and glucose homeostasis.

Results: Outdoor ALAN was associated with elevated glucose homeostasis markers in the first trimester, but not GDM risk. An increase in the interquartile range of outdoor ALAN values was related to a 0.02 (95% confidence interval [CI]: 0.00, 0.03) mmol/L higher fasting plasma glucose, a 0.42 (95% CI: 0.30, 0.54) μU/mL increase in insulin and a 0.09 (95% CI: 0.07, 0.12) increase in homeostatic model assessment of insulin resistance (HOMA-IR) during the first trimester. Subgroup analyses showed that the associations between outdoor ALAN exposure and fasting plasma glucose, insulin, and HOMA-IR were more pronounced among pregnant women who conceived in summer and autumn.

Conclusions: The results provided evidence that brighter outdoor ALAN in the first trimester was related to elevated glucose intolerance in pregnancy, especially in pregnant women conceived in summer and autumn, and effective strategies are needed to prevent and manage light pollution.

Artificial light at night has become an emerging environmental pollutant, posing a serious threat to biodiversity. Cave-roosting animals are vulnerable to light pollution due to long-term adaptation to nocturnal niches, and the problem is especially severe in the context of cave tourism and limestone mining. Mitigating the adverse impacts of artificial light on cave-dwelling animals presents a challenge. This study aimed to assess the relative contributions of spectral parameters and light intensity to the emergence behavior of nine cave-roosting bat species: Rhinolophus macrotis, Rhinolophus pearsonii, Rhinolophus rex, Rhinolophus pusillus, Rhinolophus siamensis, Rhinolophus sinicus, Hipposideros armiger, Myotis davidii, and Miniopterus fuliginosus. We manipulated light spectra and intensities through light-emitting diode (LED) lighting and gel filters at the entrance of bat roost. We monitored nightly passes per species to quantify bat emergence under the dark control and ten lighting conditions (blue, green, yellow, red, and white light at high and low intensities) using ultrasonic recording. Our analyses showed that the number of bat passes tended to be reduced in the presence of white, green, and yellow light, independent of light intensity. In contrast, the number of bat passes showed no pronounced differences under the dark control, blue light, and red light. The number of bat passes was primarily affected by LED light's blue component, red component, peak wavelength, and half-width instead of light intensity. These results demonstrate that spectral parameters of LED light can significantly affect emergence behavior of cave-dwelling bats. Our findings highlight the importance of manipulating light colors to reduce the negative impacts of light pollution on cave-roosting bats as a function of their spectral sensitivity. We recommend the use of gel filters to manage existing artificial lighting systems at the entrance of bat-inhabited caves.