Declines in moth populations stress the need for conserving dark nights

Multi-year soundscape recordings and automated call detection reveals varied impact of moonlight on calling activity of neotropical forest katydids

Night-time light can have profound ecological effects, even when the source is natural moonlight. The impacts of light can, however, vary substantially by taxon, habitat and geographical region. We used a custom machine learning model built with the Python package Koogu to investigate the in situ effects of moonlight on the calling activity of neotropical forest katydids over multiple years. We prioritised species with calls that were commonly detected in human annotated data, enabling us to evaluate model performance. We focused on eight species of katydids that the model identified with high precision (generally greater than 0.90) and moderate-to-high recall (minimum 0.35), ensuring that detections were generally correct and that many calls were detected. These results suggest that moonlight has modest effects on the amount of calling, with the magnitude and direction of effect varying by species: half of the species showed positive effects of light and half showed negative. These findings emphasize the importance of understanding natural history for anticipating how biological communities respond to moonlight. The methods applied in this project highlight the emerging opportunities for evaluating large quantities of data with machine learning models to address ecological questions over space and time. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.

Reducing the fatal attraction of nocturnal insects using tailored and shielded road lights

The attraction of insects to artificial light is a global environmental problem with far-reaching implications for ecosystems. Since light pollution is rarely integrated into conservation approaches, effective mitigation strategies towards environmentally friendly lighting that drastically reduce insect attraction are urgently needed. Here, we tested novel luminaires in two experiments (i) at a controlled experimental field site and (ii) on streets within three municipalities. The luminaires are individually tailored to only emit light onto the target area and to reduce spill light. In addition, a customized shielding renders the light source nearly invisible beyond the lit area. We show that these novel luminaires significantly reduce the attraction effect on flying insects compared to different conventional luminaires with the same illuminance on the ground. This underlines the huge potential of spatially optimized lighting to help to bend the curve of global insect decline without compromising human safety aspects. A customized light distribution should therefore be part of sustainable future lighting concepts, most relevant in the vicinity of protected areas.

Behaviour and landscape contexts determine the effects of artificial light on two crepuscular bird species

Context

Artificial light at night (ALAN) is increasing worldwide, with many ecological effects. Aerial insectivores may benefit from foraging on insects congregating at light sources. However, ALAN could negatively impact them by increasing nest visibility and predation risk, especially for ground-nesting species like nightjars (Caprimulgidae).

Objectives

We tested predictions based on these two alternative hypotheses, potential foraging benefits vs potential predation costs of ALAN, for two nightjar species in British Columbia: Common Nighthawks (Chordeiles minor) and Common Poorwills (Phalaenoptilus nuttallii).

Methods

We modeled the relationship between ALAN and relative abundance using count data from the Canadian Nightjar Survey. We distinguished territorial from extra-territorial Common Nighthawks based on their wingboom behaviour.

Results

We found limited support for the foraging benefit hypothesis: there was an increase in relative abundance of extra-territorial Common Nighthawks in areas with higher ALAN but only in areas with little to no urban land cover. Common Nighthawks' association with ALAN became negative in areas with 18% or more urban land cover. We found support for the nest predation hypothesis: the were strong negative associations with ALAN for both Common Poorwills and territorial Common Nighthawks.

Conclusions

The positive effects of ALAN on foraging nightjars may be limited to species that can forage outside their nesting territory and to non-urban areas, while the negative effects of ALAN on nesting nightjars may persist across species and landscape contexts. Reducing light pollution in breeding habitat may be important for nightjars and other bird species that nest on the ground.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10980-024-01875-3.

Coping with light pollution in urban environments: Patterns and challenges

Artificial light at night is a growing environmental problem that is especially pronounced in urban environments. Yet, impacts on urban wildlife have received scant attention and patterns and consequences are largely unknown. Here, I present a conceptual framework outlining the challenges species encounter when exposed to urban light pollution and how they may respond through plastic adjustments and genetic adaptation. Light pollution interferes with biological rhythms, influences behaviors, fragments habitats, and alters predation risk and resource abundance, which changes the diversity and spatiotemporal distribution of species and, hence, the structure and function of urban ecosystems. Furthermore, light pollution interacts with other urban disturbances, which can exacerbate negative effects on species. Given the rapid growth of urban areas and light pollution and the importance of healthy urban ecosystems for human wellbeing, more research is needed on the impacts of light pollution on species and the consequences for urban ecosystems.

Light-specific wavelengths differentially affect the exploration rate, opercular beat, skin color change, opsin transcripts, and the oxi-redox system of the longsnout seahorse Hippocampus reidi

Light is a strong stimulus for the sensory and endocrine systems. The opsins constitute a large family of proteins that can respond to specific light wavelengths. Hippocampus reidi is a near-threatened seahorse that has a diverse color pattern and sexual dimorphism. Over the years, H. reidi's unique characteristics, coupled with its high demand and over-exploitation for the aquarium trade, have raised concerns about its conservation, primarily due to their significant impact on wild populations. Here, we characterized chromatophore types in juvenile and adult H. reidi in captivity, and the effects of specific light wavelengths with the same irradiance (1.20 mW/cm2) on color change, growth, and survival rate. The xanthophores and melanophores were the major components of H. reidi pigmentation with differences in density and distribution between life stages and sexes. In the eye and skin of juveniles, the yellow (585 nm) wavelength induced a substantial increase in melanin levels compared to the individuals kept under white light (WL), blue (442 nm), or red (650 nm) wavelengths. In addition, blue and yellow wavelengths led to a higher juvenile mortality rate in comparison to the other treatments. Adult seahorses showed a rhythmic color change over 24 h, the highest reflectance values were obtained in the light phase, representing a daytime skin lightening for individuals under WL, blue and yellow wavelength, with changes in the acrophase. The yellow wavelength was more effective on juvenile seahorse pigmentation, while the blue wavelength exerted a stronger effect on the regulation of adult physiological color change. Dramatic changes in the opsin mRNA levels were life stage-dependent, which may infer ontogenetic opsin functions throughout seahorses' development. Exposure to specific wavelengths differentially affected the opsins mRNA levels in the skin and eyes of juveniles. In the juveniles, skin transcripts of visual (rh1, rh2, and lws) and non-visual opsins (opn3 and opn4x) were higher in individuals under yellow light. While in the juvenile's eyes, only rh1 and rh2 had increased transcripts influenced by yellow light; the lws and opn3 mRNA levels were higher in juveniles' eyes under WL. Prolonged exposure to yellow wavelength stimulates a robust increase in the antioxidant enzymes sod1 and sod2 mRNA levels. Our findings indicate that changes in the visible light spectrum alter physiological processes at different stages of life in H. reidi and may serve as the basis for a broader discussion about the implications of artificial light for aquatic species in captivity.

Addition of nocturnal pollinators modifies the structure of pollination networks

Although the ecological network approach has substantially contributed to the study of plant-pollinator interactions, current understanding of their functional structure is biased towards diurnal pollinators. Nocturnal pollinators have been systematically ignored despite the publication of several studies that have tried to alleviate this diurnal bias. Here, we explored whether adding this neglected group of pollinators had a relevant effect on the overall architecture of three high mountain plant-pollinator networks. Including nocturnal moth pollinators modified network properties by decreasing total connectivity, connectance, nestedness and robustness to plant extinction; and increasing web asymmetry and modularity. Nocturnal moths were not preferentially connected to the most linked plants of the networks, and they were grouped into a specific "night" module in only one of the three networks. Our results indicate that ignoring the nocturnal component of plant-pollinator networks may cause changes in network properties different from those expected from random undersampling of diurnal pollinators. Consequently, the neglect of nocturnal interactions may provide a distorted view of the structure of plant-pollinator networks with relevant implications for conservation assessments.

Blue carbon sink capacity of mangroves determined by leaves and their associated microbiome

Mangroves play a globally significant role in carbon capture and storage, known as blue carbon ecosystems. Yet, there are fundamental biogeochemical processes of mangrove blue carbon formation that are inadequately understood, such as the mechanisms by which mangrove afforestation regulates the microbial-driven transfer of carbon from leaf to below-ground blue carbon pool. In this study, we addressed this knowledge gap by investigating: (1) the mangrove leaf characteristics using state-of-the-art FT-ICR-MS; (2) the microbial biomass and their transformation patterns of assimilated plant-carbon; and (3) the degradation potentials of plant-derived carbon in soils of an introduced (Sonneratia apetala) and a native mangrove (Kandelia obovata). We found that biogeochemical cycling took entirely different pathways for S. apetala and K. obovata. Blue carbon accumulation and the proportion of plant-carbon for native mangroves were high, with microbes (dominated by K-strategists) allocating the assimilated-carbon to starch and sucrose metabolism. Conversely, microbes with S. apetala adopted an r-strategy and increased protein- and nucleotide-biosynthetic potentials. These divergent biogeochemical pathways were related to leaf characteristics, with S. apetala leaves characterized by lower molecular-weight, C:N ratio, and lignin content than K. obovata. Moreover, anaerobic-degradation potentials for lignin were high in old-aged soils, but the overall degradation potentials of plant carbon were age-independent, explaining that S. apetala age had no significant influences on the contribution of plant-carbon to blue carbon. We propose that for introduced mangroves, newly fallen leaves release nutrient-rich organic matter that favors growth of r-strategists, which rapidly consume carbon to fuel growth, increasing the proportion of microbial-carbon to blue carbon. In contrast, lignin-rich native mangrove leaves shape K-strategist-dominated microbial communities, which grow slowly and store assimilated-carbon in cells, ultimately promoting the contribution of plant-carbon to the remarkable accumulation of blue carbon. Our study provides new insights into the molecular mechanisms of microbial community responses during reforestation in mangrove ecosystems.

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'.

Patterns of high-flying insect abundance are shaped by landscape type and abiotic conditions

Insects are of increasing conservation concern as a severe decline of both biomass and biodiversity have been reported. At the same time, data on where and when they occur in the airspace is still sparse, and we currently do not know whether their density is linked to the type of landscape above which they occur. Here, we combined data of high-flying insect abundance from six locations across Switzerland representing rural, urban and mountainous landscapes, which was recorded using vertical-looking radar devices. We analysed the abundance of high-flying insects in relation to meteorological factors, daytime, and type of landscape. Air pressure was positively related to insect abundance, wind speed showed an optimum, and temperature and wind direction did not show a clear relationship. Mountainous landscapes showed a higher insect abundance than the other two landscape types. Insect abundance increased in the morning, decreased in the afternoon, had a peak after sunset, and then declined again, though the extent of this general pattern slightly differed between landscape types. We conclude that the abundance of high-flying insects is not only related to abiotic parameters, but also to the type of landscapes and its characteristics, which, on a long-term, should be taken into account for when designing conservation measures for insects.

Drivers and pressures behind insect decline in Central and Western Europe based on long-term monitoring data

Insect declines have been discussed intensively among experts, policymakers, and the public. Albeit, decreasing trends have been reported for a long time for various regions in Europe and North America, but the controversial discussion over the role of specific drivers and pressures still remains. A reason for these uncertainties lies within the complex networks of inter-dependent biotic and abiotic factors as well as anthropogenic activities that influence habitats, communities, populations, and individual organisms. Many recent publications aim to identify both the extent of the observed declines and potential drivers. With this literature analysis, we provide an overview of the drivers and pressures and their inter-relationships, which were concluded in the scientific literature, using some of the best-studied insect groups as examples. We conducted a detailed literature evaluation of publications on Carabidae (Coleoptera) and Lepidoptera trends with data for at least 6 years in countries of Central and Western Europe, with a focus on agricultural landscapes. From the 82 publications identified as relevant, we extracted all reported trends and classified the respective factors described according to the DPSIR model. Further, we analysed the level of scientific verification (presumed vs correlated vs examined) within these papers for these cited stressors. The extracted trends for both species groups underline the reported overall declining trend. Whether negative or positive trends were reported in the papers, our semi-quantitative analysis shows that changes in insect populations are primarily anthropogenically driven by agriculture, climate change, nature conservation activities, urbanisation, and other anthropogenic activities. Most of the identified pressures were found to act on habitat level, only a fraction attributed to direct effects to the insects. While our analysis gives an overview of existing research concerning abundance and biodiversity trends of carabids and lepidopterans, it also shows gaps in scientific data in this area, in particular in monitoring the pressures along with the monitoring of abundance trends. The scientific basis for assessing biodiversity changes in the landscape is essential to help all stakeholders involved to shape, e.g. agriculture and other human activities, in a more sustainable way, balancing human needs such as food production with conservation of nature.

Anthropogenic Influence on Moth Populations: A Comparative Study in Southern Sweden

As moths are vital components of ecosystems and serve as important bioindicators, understanding the dynamics of their communities and the factors influencing these dynamics, such as anthropogenic impacts, is crucial to understand the ecological processes. Our study focuses on two provinces in southern Sweden, Västergötland and Småland, where we used province records from 1974 to 2019 in combination with light traps (in 2020) to record the presence and abundance of moth species, subsequently assessing species traits to determine potential associations with their presence in anthropogenically modified landscapes. This study design provides a unique opportunity to assess temporal changes in moth communities and their responses to shifts in environmental conditions, including anthropogenic impacts. Across the Västergötland and Småland provinces in Sweden, we recorded 776 moth taxa belonging to fourteen different taxonomic families of mainly Macroheterocera. We captured 44% and 28% of the total moth species known from these provinces in our traps in Borås (Västergötland) and Kalmar (Småland), respectively. In 2020, the species richness and abundance were higher in Borås than in Kalmar, while the Shannon and Simpson diversity indices revealed a higher species diversity in Kalmar. Between 1974 and 2019, the colonisation rates of the provinces increased faster in Småland. Ninety-three species were found to have colonised these provinces since 1974, showing that species richness increased over the study period. We reveal significant associations between the probability of a species being present in the traps and distinct traits compared to a provincial species pool. Traits over-represented in the traps included species with a high variation in colour patterns, generalist habitat preferences, extended flight periods, lower host plant specificity, and overwintering primarily as eggs. Our findings underscore the ongoing ecological filtering that favours certain species-specific traits. This study sheds light on the roles of climate change and anthropogenic impacts in shaping moth biodiversity, offers key insights into the ecological processes involved, and can guide future conservation efforts.

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.

Effects of anthropogenic light on species and ecosystems

Anthropogenic light is ubiquitous in areas where humans are present and is showing a progressive increase worldwide. This has far-reaching consequences for most species and their ecosystems. The effects of anthropogenic light on natural ecosystems are highly variable and complex. Many species suffer from adverse effects and often respond in a highly specific manner. Ostensibly surveyable effects such as attraction and deterrence become complicated because these can depend on the type of behavior and specific locations. Here, we considered how solutions and new technologies could reduce the adverse effects of anthropogenic light. A simple solution to reducing and mitigating the ecological effects of anthropogenic light seems unattainable, because frugal lighting practices and turning off lights may be necessary to eliminate them.

Field experimental evidence of sandy beach community changes in response to artificial light at night (ALAN)

Artificial light at night (ALAN) is a pervasive but still under-recognized driver of global change. In coastal settings, a large majority of the studies assessing ALAN impacts has focused on individual species, even though it is unclear whether results gathered from single species can be used to predict community-wide responses. Similarly, these studies often treat species as single life-stage entities, ignoring the variation associated with distinct life stages. This study addresses both limitations by focusing on the effects of ALAN on a sandy beach community consisting of species with distinct early- and late-life stages. Our hypothesis was that ALAN alters community structure and these changes are mediated by individual species and also by their ontogenetic stages. A field experiment was conducted in a sandy beach of north-central Chile using an artificial LED system. Samples were collected at different night hours (8-levels in total) across the intertidal (9-levels) over several days in November and January (austral spring and summer seasons). The abundance of adults of all species was significantly lower in ALAN treatments. Early stages of isopods showed the same pattern, but the opposite was observed for the early stages of the other two species. Clear differences were detected in the zonation of these species during natural darkness versus those exposed to ALAN, with some adult-juvenile differences in this response. These results support our hypothesis and document a series of changes affecting differentially both early and late life stages of these species, and ultimately, the structure of the entire community. Although the effects described correspond to short-term responses, more persistent effects are likely to occur if ALAN sources become established as permanent features in sandy beaches. The worldwide growth of ALAN suggests that the scope of its effect will continue to grow and represents a concern for sandy beach systems.

The Contribution of Singletons and Doubletons Captured Using Weak Light Heath Traps for the Analysis of the Macroheteroceran Assemblages in Forest Biotopes

In nearly every ecological community, most species are represented by a few individuals, and most individuals come from a few of the most common species. Singletons (one individual sampled) and doubletons (two individuals sampled) are very common in moth community studies. In some reports, these specimens are excluded from the analysis once they are considered a consequence of under-sampling or of contamination with tourist species that are just passing through. Throughout 12 nights in 2018 and 12 nights in 2019, two Heath traps, one with an 8 W ultraviolet lamp and the other with a 15 W actinic lamp, were positioned approximately 50 m apart at nine sites of four different biotopes in a mosaic forest ecosystem in the Narew National Park (NE Poland). We were able to differentiate moth assemblages according to the forest biotopes under study and by the year of research. With our results, it becomes more evident that singletons and doubletons sampled using weak light Heath traps should be included in the ecological analysis of Macroheteroceran moth assemblages, and our research strongly suggests that they are an important and consistent element of such a sampling method. We also demonstrate that weak light Heath traps are suitable for building an inventory scheme of moth assemblages in small forest areas and that singletons and doubletons can be crucial elements in long-term monitoring systems.

Artificial light at night increases top-down pressure on caterpillars: experimental evidence from a light-naive forest

Artificial light at night (ALAN) is a globally widespread and expanding form of anthropogenic change that impacts arthropod biodiversity. ALAN alters interspecific interactions between arthropods, including predation and parasitism. Despite their ecological importance as prey and hosts, the impact of ALAN on larval arthropod stages, such as caterpillars, is poorly understood. We examined the hypothesis that ALAN increases top-down pressure on caterpillars from arthropod predators and parasitoids. We experimentally illuminated study plots with moderate levels (10-15 lux) of LED lighting at light-naive Hubbard Brook Experimental Forest, New Hampshire. We measured and compared between experimental and control plots: (i) predation on clay caterpillars, and (ii) abundance of arthropod predators and parasitoids. We found that predation rates on clay caterpillars and abundance of arthropod predators and parasitoids were significantly higher on ALAN treatment plots relative to control plots. These results suggest that moderate levels of ALAN increase top-down pressure on caterpillars. We did not test mechanisms, but sampling data indicates that increased abundance of predators near lights may play a role. This study highlights the importance of examining the effects of ALAN on both adult and larval life stages and suggests potential consequences of ALAN on arthropod populations and communities.

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.

The rising moon promotes mate finding in moths

To counteract insect decline, it is essential to understand the underlying causes, especially for key pollinators such as nocturnal moths whose ability to orientate can easily be influenced by ambient light conditions. These comprise natural light sources as well as artificial light, but their specific relevance for moth orientation is still unknown. We investigated the influence of moonlight on the reproductive behavior of privet hawkmoths (Sphinx ligustri) at a relatively dark site where the Milky Way was visible while the horizon was illuminated by distant light sources and skyglow. We show that male moths use the moon for orientation and reach females significantly faster with increasing moon elevation. Furthermore, the choice of flight direction depended on the cardinal position of the moon but not on the illumination of the horizon caused by artificial light, indicating that the moon plays a key role in the orientation of male moths.

The experimental release of male moths show that moon presence, location, and elevation affect their finding of mates.

A nearly complete database on the records and ecology of the rarest boreal tiger moth from 1840s to 2020

Global environmental changes may cause dramatic insect declines but over century-long time series of certain species’ records are rarely available for scientific research. The Menetries’ Tiger Moth (Arctia menetriesii) appears to be the most enigmatic example among boreal insects. Although it occurs throughout the entire Eurasian taiga biome, it is so rare that less than 100 specimens were recorded since its original description in 1846. Here, we present the database, which contains nearly all available information on the species’ records collected from 1840s to 2020. The data on A. menetriesii records (N = 78) through geographic regions, environments, and different timeframes are compiled and unified. The database may serve as the basis for a wide array of future research such as the distribution modeling and predictions of range shifts under climate changes. It represents a unique example of a more than century-long dataset of distributional, ecological, and phenological data designed for an exceptionally rare but widespread boreal insect, which primarily occurs in hard-to-reach, uninhabited areas of Eurasia.

Measurement(s)	specimen record • biological parameters of specimen • environmental characteristics • sampling date • habitat image • specimen image
Technology Type(s)	digital curation
Factor Type(s)	year • month • ten-day period • day • geographic location • altitude • habitat • landscape type • presence of waterbody • ecoregion • developmental stage • sex • individual condition
Sample Characteristic - Organism	Menetries’ Tiger Moth Arctia menetriesii (Insecta: Lepidoptera: Erebidae)
Sample Characteristic - Environment	taiga biome • high-altitude environment
Sample Characteristic - Location	Northern Eurasia

Light Attraction in Carabid Beetles: Comparison Among Animals From the Inner City and a Dark Sky Reserve

Artificial light at night (ALAN) is altering the behaviour of nocturnal animals in a manifold of ways. Nocturnal invertebrates are particularly affected, due to their fatal attraction to ALAN. This selective pressure has the potential to reduce the strength of the flight-to-light response in insects, as shown recently in a moth species. Here we investigated light attraction of ground beetles (Coleoptera: Carabidae). We compared among animals (three genera) from a highly light polluted (HLP) grassland in the centre of Berlin and animals collected at a low-polluted area in a Dark Sky Reserve (DSR), captured using odour bait. In an arena setting tested at night time, HLP beetles (n = 75 across all genera) showed a reduced attraction towards ALAN. Tested during daytime, HLP beetles were less active in an open field test (measured as latency to start moving), compared to DSR (n = 143). However, we did not observe a reduced attraction towards ALAN within the species most common at both sides, Calathus fuscipes (HLP = 37, DSR = 118 individuals) indicating that not all species may be equally affected by ALAN. Reduced attraction to ALAN in urban beetles may either be a result of phenotypic selection in each generation removing HLP individuals that are attracted to light, or an indication for ongoing evolutionary differentiation among city and rural populations in their light response. Reduced attraction to light sources may directly enhance survival and reproductive success of urban individuals. However, decrease in mobility may negatively influence dispersal, reproduction and foraging success, highlighting the selective pressure that light pollution may have on fitness, by shaping and modifying the behaviour of insects.

Integrated molecular and behavioural data reveal deep circadian disruption in response to artificial light at night in male Great tits (Parus major)

Globally increasing levels of artificial light at night (ALAN) are associated with shifting rhythms of behaviour in many wild species. However, it is unclear whether changes in behavioural timing are paralleled by consistent shifts in the molecular clock and its associated physiological pathways. Inconsistent shifts between behavioural and molecular rhythms, and between different tissues and physiological systems, disrupt the circadian system, which coordinates all major body functions. We therefore compared behavioural, transcriptional and metabolomic responses of captive great tits (Parus major) to three ALAN intensities or to dark nights, recording activity and sampling brain, liver, spleen and blood at mid-day and midnight. ALAN advanced wake-up time, and this shift was paralleled by advanced expression of the clock gene BMAL1 in all tissues, suggesting close links between behaviour and clock gene expression across tissues. However, further analysis of gene expression and metabolites revealed that clock shifts were inconsistent across physiological systems. Untargeted metabolomic profiling showed that only 9.7% of the 755 analysed metabolites followed the behavioural shift. This high level of desynchronization indicates that ALAN disrupted the circadian system on a deep, easily overlooked level. Thus, circadian disruption could be a key mediator of health impacts of ALAN on wild animals.

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.

Towards Insect-Friendly Road Lighting-A Transdisciplinary Multi-Stakeholder Approach Involving Citizen Scientists

Simple Summary

Road lighting is a service provided at night, mainly to ensure the secure and safe passage of humans. However, lighting at night can have adverse effects on insects or ecosystems, which are not yet considered in planning. Here, we introduce a comprehensive approach for the design and implementation of a novel insect-friendly road luminaire. The lighting design provides an optimized radiation geometry that avoids emissions at the trajectory height of insects, reduces the attraction of insects and the fragmentation of their habitats, and at the same time provides adequate night-time illumination in residential areas. The effects of the new design on insect behavior and night sky brightness will be evaluated two years before and two years after the change of the road luminaires and additionally in a direct comparison, as some luminaires of the old design will remain as controls. Citizen scientists are involved in the identification of insects and the measurement of night sky brightness. A broad public engagement program also highlights discussions about the competing interests of different stakeholders in lighting design, explicitly including the effects of illumination on insect fauna and biodiversity.

Abstract

(1) The project “Tatort Streetlight” implements an insect-friendly road light design in a four year before–after, control–impact (BACI) approach involving citizen scientists. It will broaden the stakeholder interests from solely anthropogenic perspectives to include the welfare of insects and ecosystems. Motivated by the detrimental impacts of road lighting systems on insects, the project aims to find solutions to reduce the insect attraction and habitat fragmentation resulting from roadway illumination. (2) The citizen science approach invites stakeholders to take part and join forces for the development of a sustainable and environmentally friendly road lighting solution. Here, we describe the project strategy, stakeholder participation and motivation, and how the effects of the alternative road luminaire and lighting design can be evaluated. (3) The study compares the changes in (a) insect behavior, (b) night sky brightness, and (c) stakeholder participation and awareness. For this purpose, different experimental areas and stakeholders in four communities in Germany are identified. (4) The project transfers knowledge of adverse effects of improperly managed road illumination and interacts with various stakeholders to develop a new road lighting system that will consider the well-being of street users, local residents, and insects.

Artificial light reduces foraging opportunities in wild least horseshoe bats

Artificial light at night has been proposed as a global threat to biodiversity. Insectivorous bats are strictly nocturnal animals that are vulnerable to disruption from artificial light. Given that many light-sensitive bats tend to avoid night light during roost departure, it is often assumed that nighttime light pollution reduces their foraging opportunities, albeit empirical evidence in support of this hypothesis remains elusive. Here, we used least horseshoe bats, Rhinolophus pusillus, to assess whether white artificial light is detrimental for the opportunities of foraging. We manipulated the levels of ambient illumination and perceived predation risk inside the bat roost. We monitored bats' emergence activity using high-speed video and audio recording systems. DNA-based faecal dietary analysis and insect survey were applied to determine activity time of prey in foraging areas. Following experimentally manipulation of white light-emitting diode (LED) lighting 0-15 min after sunset, bat pass, flight duration, and echolocation pulse emission decreased. The mean emergence time of bats flying out was delayed by 14 min under lit treatment compared with the dark control. Only 10% of bats left for foraging during 40 min of light exposure. Aversive effects of LED light on bat emergence were robust regardless of the presence of a potential predator. Insect prey reached a peak of abundance between 30 and 60 min after sunset. These results demonstrate that white artificial light hinders evening emergence behavior in least horseshoe bats, leading to a mismatch between foraging onset and peak food availability. Our findings highlight that light pollution overrides foraging onset, suggesting the importance of improving artificial lighting scheme near the roosts of light-sensitive bats.

Artificial light at night disrupts species interactions and changes insect communities

Artificial light at night (ALAN) is globally increasing, posing a threat to biodiversity. The impact of nocturnal illumination on individual insects has been relatively well documented. Recent studies show that ALAN also impacts species interactions, including intra-specific communication, trophic interactions and plant-pollinator interactions, with cascading effects in the ecosystem and impacts on ecosystem functioning that extend beyond nocturnal communities and illuminated areas. Reduced population sizes and changes in community composition because of exposure to ALAN have been reported but the understanding of the impacts of ALAN on insect communities is currently limited to few groups and ecosystems. The theoretical framework on how ALAN impacts insect communities and populations is poorly developed, limiting our understanding and the formulation of relevant hypotheses.

Learning to feed in the dark: how light level influences feeding in the hawkmoth Manduca sexta

Nocturnal insects like moths are essential for pollination, providing resilience to the diurnal pollination networks. Moths use both vision and mechanosensation to locate the nectary opening in the flowers with their proboscis. However, increased light levels due to artificial light at night (ALAN) pose a serious threat to nocturnal insects. Here, we examined how light levels influence the efficacy by which the crepuscular hawkmoth Manduca sexta locates the nectary. We used three-dimensional-printed artificial flowers fitted with motion sensors in the nectary and machine vision to track the motion of hovering moths under two light levels: 0.1 lux (moonlight) and 50 lux (dawn/dusk). We found that moths in higher light conditions took significantly longer to find the nectary, even with repeated visits to the same flower. In addition to taking longer, moths in higher light conditions hovered further from the flower during feeding. Increased light levels adversely affect learning and motor control in these animals.

Blinded by the Light: Artificial Light Lowers Mate Attraction Success in Female Glow-Worms (Lampyris noctiluca L.)

Nocturnal light pollution from anthropogenic origin is increasing worldwide and is recognised as a major threat for nocturnal biodiversity. We studied the impact of artificial light on the mate attraction success of female common glow-worms (Lampyris noctiluca L.) by daily monitoring their glowing status in the field, acting as a proxy for mating status throughout the mating season. We found that females in dark surroundings typically stopped glowing after one night, indicating that they had mated, while females in illuminated areas glowed for significantly more nights, in some cases up to 15 nights. Our study confirms previous findings and hypotheses that females exposed to artificial light suffer from a reduced mate attraction success with a negative impact on populations.

Experimental light at night has a negative long-term impact on macro-moth populations

Van Grunsven et al. experimentally test the long-term effects of artificial light on natural moth populations. In the initial two years there was no effect on populations, but in the latter three years population sizes were reduced compared with the dark controls. This shows that artificial light negatively affects moth populations.

Light pollution impairs urban nocturnal pollinators but less so in areas with high tree cover

The increase in artificial light at night (ALAN) is widely considered as a major driver for the worldwide decline of nocturnal pollinators such as moths. However, the relationship between light and trees as 'islands of shade' within urban areas has not yet been fully understood. Here, we studied (1) the effects of three landscape variables, i.e. sources of ALAN (mercury vapour/LED street lamps; overall light pollution), impervious surfaces (e.g. roads, parking lots and buildings), and tree cover on species richness and abundance of two major macro-moth families (Noctuidae and Geometridae) and (2) the potential mitigating effect of trees on macro-moths attracted to ALAN. We undertook a landscape-scale study on 22 open green areas along an urban-rural gradient within Berlin, Germany, using light traps to collect moths. Macro-moths were identified to species level and GLMMs applied with the three landscape variables at different scales (100 m, 500 m and 1000 m). We found a significant negative effect of mercury vapour street lamps on macro-moth species richness, while impervious surfaces showed significant negative effects on abundance (total and Geometridae). We further found significant positive effects of tree cover density on species richness and abundance (total and Geometridae). Effects of tree cover, however, were mostly driven by one site. LED lamps showed no predictive effects. A negative effect of ALAN (MV lamps and overall light) on macro-moths was most prominent in areas with low tree coverage, indicating a mitigating effect of trees on ALAN. We conclude that mercury vapour street lamps should be replaced by ecologically more neutral ALAN, and that in lit and open areas trees could be planted to mitigate the negative effect of ALAN on nocturnal pollinators. In addition, sources of ALAN should be carefully managed, using movement detection technology and other means to ensure that light is only produced when necessary.

Wavelength-dependent effects of artificial light at night on phytoplankton growth and community structure

Artificial light at night (ALAN) is a disruptive form of pollution, impacting physiological and behavioural processes that may scale up to population and community levels. Evidence from terrestrial habitats show that the severity and type of impact depend on the wavelength and intensity of ALAN; however, research on marine organisms is still limited. Here, we experimentally investigated the effect of different ALAN colours on marine primary producers. We tested the effect of green (525 nm), red (624 nm) and broad-spectrum white LED ALAN, compared to a dark control, on the green microalgae Tetraselmis suesica and a diatom assemblage. We show that green ALAN boosted chlorophyll production and abundance in T. suesica. All ALAN wavelengths affected assemblage biomass and diversity, with red and green ALAN having the strongest effects, leading to higher overall abundance and selective dominance of specific diatom species, some known to cause harmful algal blooms. Our findings show that green and red ALAN should be used with caution as alternative LED colours in coastal areas, where there might be a need to strike a balance between the effects of green and red light on marine primary producers with the benefit they appear to bring to other organisms.

A transdisciplinary research agenda for understanding insect responses to ecological light pollution informed by evolutionary trap theory

Evolutionary traps are phenomena in which rapid environmental change causes environmental cues that historically guided adaptive behavioral or life-history decisions to become poor predictors of the consequences of such decisions for an organism's fitness. Evolutionary trap theory offers an ideal framework for understanding and mitigating the effects of ecological light pollution (ELP) on insects. We emphasize the utility of an evolutionary trap perspective in demonstrating the importance of an integrated understanding of the sensory, behavioral, evolutionary, and demographic mechanisms underlying insect responses to ELP. We also highlight neglected areas of research where greater focus can help enhance understanding of how ELP affects the persistence, evolutionary trajectory, and population dynamics of insects across space and time.

A window to the world of global insect declines: Moth biodiversity trends are complex and heterogeneous

Moths are the most taxonomically and ecologically diverse insect taxon for which there exist considerable time-series abundance data. There is an alarming record of decreases in moth abundance and diversity from across Europe, with rates varying markedly among and within regions. Recent reports from Costa Rica reveal steep cross-lineage declines of caterpillars, while other sites (Ecuador and Arizona, reported here) show no or only modest long-term decreases over the past two decades. Rates of decline for dietary and ecological specialists are steeper than those for ecologically generalized taxa. Additional traits commonly associated with elevated risks include large wingspans, small geographic ranges, low dispersal ability, and univoltinism; taxa associated with grasslands, aridlands, and nutrient-poor habitats also appear to be at higher risk. In temperate areas, many moth taxa limited historically by abiotic factors are increasing in abundance and range. We regard the most important continental-scale stressors to include reductions in habitat quality and quantity resulting from land-use change and climate change and, to a lesser extent, atmospheric nitrification and introduced species. Site-specific stressors include pesticide use and light pollution. Our assessment of global macrolepidopteran population trends includes numerous cases of both region-wide and local losses and studies that report no declines. Spatial variation of reported losses suggests that multiple stressors are in play. With the exception of recent reports from Costa Rica, the most severe examples of moth declines are from Northern Hemisphere regions of high human-population density and intensive agriculture.

Direct and ambient light pollution alters recruitment for a diurnal plant-pollinator system

Artificial light at night (ALAN) functions as a novel environmental stimulus that has the potential to disrupt interactions among species. Despite recent efforts to explain nocturnal pollinators' responses to this stimulus, the likelihood and associated mechanisms of attraction towards artificial light and potential consequences on fitness for diurnal pollinators is still largely unclear. Here, we took advantage of the obligate mutualism between yucca moths (Tegeticula maculata maculata) and yucca plants (Hesperoyucca whipplei) to understand how direct light exposure and skyglow can influence a pairwise plant-pollinator interaction. To surmise whether adult moths exhibit positive phototaxis, we deployed a set of field-placed light towers during the peak of yucca flowering and compared the number of moths caught in traps between dark-controlled and light-treated trials. Adult moth abundance was much higher when light was present, which suggests that ALAN may alter this diurnal moth's activity patterns to expand their temporal niche into the night. To evaluate ALAN effects on yucca fruit set and moth larva recruitment, we measured skyglow exposure above yucca plants and direct light intensity from a second set of light towers. Both larva and fruit recruitment increased with skyglow, and fruit set also increased with direct lighting, but the relationship was weaker. Contrarily, larva recruitment did not change when exposed to a gradient of direct light, which may instead reflect effects of ALAN on moth physiology, such as disrupted female oviposition, or misdirecting behaviors essential to oviposition activity. Our results suggest that ALAN can positively influence the fitness of both plants and moths in this tightly co-evolved mutualism, but the benefits to each species may depend on whether night lighting is direct or indirect. Whether such effects and mechanisms could relate to susceptibility to the presence of ALAN on this or other plant-pollinator relationships will remain an important focus of future research.

DNA diet profiles with high-resolution animal tracking data reveal levels of prey selection relative to habitat choice in a crepuscular insectivorous bird

Given the global decline of many invertebrate food resources, it is fundamental to understand the dietary requirements of insectivores. We give new insights into the functional relationship between the spatial habitat use, food availability, and diet of a crepuscular aerial insectivore, the European Nightjar (Caprimulgus europaeus) by relating spatial use data with high-throughput sequencing (HTS) combined with DNA metabarcoding. Our study supports the predictions that nightjars collect a substantial part of their daily nourishment from foraging locations, sometimes at considerable distance from nesting sites. Lepidopterans comprise 65% of nightjars' food source. Nightjars tend to select larger species of Lepidoptera (>19 mm) which suggests that nightjars optimize the efficiency of foraging trips by selecting the most energetically favorable-larger-prey items. We anticipate that our findings may shed additional light on the interactions between invertebrate communities and higher trophic levels, which is required to understand the repercussions of changing food resources on individual- and population-level processes.

Very important dark sky areas in Europe and the Caucasus region

ALAN (artificial light at night) can give, if done adequately, a lot of benefits for human society, but it affects reproduction, navigation, foraging, habitat selection, communication, trophic and social interactions of the biota in the same time. Taking into account dramatic increase in light pollution of the night sky and night environment during the past decades, the creation of refugia where natural habitats are not influenced by ALAN is very important. We selected promising territories without, or with a low impact of, ALAN for the development of a VIDA (Very Important Dark Area) Network in Europe and the Caucasus region. 54 VIDAs within the borders of 30 countries were chosen, located in different biogeographic regions, at different altitudes, and in juxtaposition with protected areas. Special attention has been paid to sea and ocean islands, non-polluted by ALAN, as well as to large parts of European Russia and Kazakhstan where there is still a low level of light pollution. These places might be a basis for the protection of biodiversity from the consequences of ALAN, and they can also serve as key education centers for increasing the awareness of the problem of light pollution of the sky at night. Due to the fact that light propagates far away in the atmosphere, the protection of VIDAs can be obtained only if a strong anti-light pollution action is enforced also in the surrounding areas, at least 100 km from the borders of the VIDAs.

Unlocking the potential of historical abundance datasets to study biomass change in flying insects

Trends in insect abundance are well established in some datasets, but far less is known about how abundance measures translate into biomass trends. Moths (Lepidoptera) provide particularly good opportunities to study trends and drivers of biomass change at large spatial and temporal scales, given the existence of long-term abundance datasets. However, data on the body masses of moths are required for these analyses, but such data do not currently exist.To address this data gap, we collected empirical data in 2018 on the forewing length and dry mass of field-sampled moths, and used these to train and test a statistical model that predicts the body mass of moth species from their forewing lengths (with refined parameters for Crambidae, Erebidae, Geometridae and Noctuidae).Modeled biomass was positively correlated, with high explanatory power, with measured biomass of moth species (R 2 = 0.886 ± 0.0006, across 10,000 bootstrapped replicates) and of mixed-species samples of moths (R 2 = 0.873 ± 0.0003), showing that it is possible to predict biomass to an informative level of accuracy, and prediction error was smaller with larger sample sizes.Our model allows biomass to be estimated for historical moth abundance datasets, and so our approach will create opportunities to investigate trends and drivers of insect biomass change over long timescales and broad geographic regions.

Automated flight-interception traps for interval sampling of insects

Recent debates on insect decline require sound assessments on the relative drivers that may negatively impact insect populations. Often, baseline data rely on insect monitorings that integrate catches over long time periods. If, however, effects of time-critical environmental factors (e.g., light pollution) are of interest, higher temporal resolution of insect data is required during very specific time intervals (e.g., between dusk and dawn). Conventional time-critical insect trapping is labour-intensive (manual activation/deactivation) and temporally inaccurate as not all traps can be serviced synchronically at different sites. Also, temporal shifts of environmental conditions (e.g., sunset/sunrise) are not accounted for. We present a battery-driven automated insect flight-interception trap which samples insects during seven user-defined time intervals. A commercially available flight-interception trap is fitted to a turntable containing eight positions, seven of them holding cups and one consisting of a pass-through hole. While the cups sample insects during period of interest, the pass-through hole avoids unwanted sampling during time-intervals not of interest. Comparisons between two manual and two automated traps during 71 nights in 2018 showed no difference in caught insects. A study using 20 automated traps during 104 nights in 2019 proved that the automated flight-interception traps are reliable. The automated trap opens new research and application possibilities as arbitrary insect-sampling intervals can be defined. The trap proves efficient, saving manpower and associated costs as activation/deactivation is required only every seven sampling intervals. In addition, the timing of the traps is accurate, as all traps sample at exactly the same intervals and ensure comparability. The automated trap is low maintenance and robust due to straightforward technical design. It can be controlled manually or via smartphone through a Bluetooth connection. Full construction details are given in Appendices.

Impacts of artificial light on food intake in invasive toads

Artificial light at night (ALAN) is a major form of anthropogenic disturbance. ALAN attracts nocturnal invertebrates, which are a food source for nocturnal predators, including invasive species. Few studies quantify the effects of increased food availablity by ALAN on invasive vertebrate predators, and enhancement of food intake caused by ALAN may also be influenced by various environmental factors, such as proximitity to cities, moon phase, temperature, rainfall and wind speed. Revealing the potential impacts on invasive predators of ALAN-attracted invertebrates, and the influence of other factors on these effects, could provide important insights for the management of these predators. We constructed and supplied with artificial light field enclosures for invasive toads, and placed them at locations with different levels of ambient light pollution, in northeastern Australia. In addition, we determined the effect of rainfall, temperature, wind speed, and lunar phase on food intake in toads. We found that ALAN greatly increased the mass of gut contents of invasive toads compared to controls, but that the effect was increased in dark lunar phases, and when there were low ambient light pollution levels. Effects of rainfall, temperature and wind speed on food intake were comparatively weak. To avoid providing food resources to toads, management of ALAN in rural areas, and during dark lunar phases may be advisable. On the contrary, to effectively capture toads, trapping using lights as lures at such times and places should be more successful.

Working with Inadequate Tools: Legislative Shortcomings in Protection against Ecological Effects of Artificial Light at Night

The fundamental change in nocturnal landscapes due to the increasing use of artificial light at night (ALAN) is recognized as being detrimental to the environment and raises important regulatory questions as to whether and how it should be regulated based on the manifold risks to the environment. Here, we present the results of an analysis of the current legal obligations on ALAN in context with a systematic review of adverse effects. The legal analysis includes the relevant aspects of European and German environmental law, specifically nature conservation and immission control. The review represents the results of 303 studies indicating significant disturbances of organisms and landscapes. We discuss the conditions for prohibitions by environmental laws and whether protection gaps persist and, hence, whether specific legislation for light pollution is necessary. While protection is predominantly provided for species with special protection status that reveal avoidance behavior of artificially lit landscapes and associated habitat loss, adverse effects on species and landscapes without special protection status are often unaddressed by existing regulations. Legislative shortcomings are caused by difficulties in proving adverse effect on the population level, detecting lighting malpractice, and applying the law to ALAN-related situations. Measures to reduce ALAN-induced environmental impacts are highlighted. We discuss whether an obligation to implement such measures is favorable for environmental protection and how regulations can be implemented.

Why conservation biology can benefit from sensory ecology

Global expansion of human activities is associated with the introduction of novel stimuli, such as anthropogenic noise, artificial lights and chemical agents. Progress in documenting the ecological effects of sensory pollutants is weakened by sparse knowledge of the mechanisms underlying these effects. This severely limits our capacity to devise mitigation measures. Here, we integrate knowledge of animal sensory ecology, physiology and life history to articulate three perceptual mechanisms-masking, distracting and misleading-that clearly explain how and why anthropogenic sensory pollutants impact organisms. We then link these three mechanisms to ecological consequences and discuss their implications for conservation. We argue that this framework can reveal the presence of 'sensory danger zones', hotspots of conservation concern where sensory pollutants overlap in space and time with an organism's activity, and foster development of strategic interventions to mitigate the impact of sensory pollutants. Future research that applies this framework will provide critical insight to preserve the natural sensory world.

Insect Declines in the Anthropocene

Insect declines are being reported worldwide for flying, ground, and aquatic lineages. Most reports come from western and northern Europe, where the insect fauna is well-studied and there are considerable demographic data for many taxonomically disparate lineages. Additional cases of faunal losses have been noted from Asia, North America, the Arctic, the Neotropics, and elsewhere. While this review addresses both species loss and population declines, its emphasis is on the latter. Declines of abundant species can be especially worrisome, given that they anchor trophic interactions and shoulder many of the essential ecosystem services of their respective communities. A review of the factors believed to be responsible for observed collapses and those perceived to be especially threatening to insects form the core of this treatment. In addition to widely recognized threats to insect biodiversity, e.g., habitat destruction, agricultural intensification (including pesticide use), climate change, and invasive species, this assessment highlights a few less commonly considered factors such as atmospheric nitrification from the burning of fossil fuels and the effects of droughts and changing precipitation patterns. Because the geographic extent and magnitude of insect declines are largely unknown, there is an urgent need for monitoring efforts, especially across ecological gradients, which will help to identify important causal factors in declines. This review also considers the status of vertebrate insectivores, reporting bias, challenges inherent in collecting and interpreting insect demographic data, and cases of increasing insect abundance.