Artificial light as a driver of nighttime landscape ecology

Lead Research Organisation: UNIVERSITY OF EXETER
Department Name: Biosciences

Abstract

Artificial light, from streetlights and other sources, is eroding natural light cycles over large areas of the globe; more than 80% of people now live under light polluted skies. Artificial light is thus giving rise to an environmental pressure on organisms that they have not previously encountered in their evolutionary histories. Documented impacts include effects on the physiology and behaviour of individual organisms, the abundance and distribution of species, and the structure and functioning of ecological communities. However, the exposure of organisms to artificial light in real landscapes, and thus the spatial extent and temporal dynamics of these effects, remain poorly understood. In major part this is because there is a substantial mismatch between the relatively coarse spatial and temporal scales at which artificial light has to date typically been mapped (often using satellites) and the relatively fine spatial and temporal scales at which organisms will often experience artificial nighttime lighting. This lack of detail constrains understanding of how animals move within, and respond to, dynamic lightscapes. In this project we will address this important limitation. We will measure the spatial and temporal distributions of artificial nighttime lighting across urban and suburban sites, and use these data to build generalisable models of their light dynamics. We will then produce high resolution maps that more accurately represent the ecological barriers, fragmentation and patch structure of light in urban and suburban areas and test these with new ecological data on the movements of hedgehogs, bats and moths. Only once ecological risks of artificial light at night have been understood at relevant spatial and temporal scales can better mitigation strategies be implemented to alleviate pressure from this pernicious driver of global change.

Planned Impact

There has been increasing public and policy debate around the negative impacts of artificial lighting of the nighttime environment (including on views of the natural nighttime sky, on the natural environment, and on human health), and how best to limit these whilst delivering the substantial (actual and perceived) human benefits that such lighting can provide. However, discussion of these issues has often been framed in quite a generalised way, with little reference to the complexity of the nighttime lightscapes that are being created and the challenges that these pose for the movements of many organisms. This project is therefore clearly of value to two groups of non-academic stakeholders, the general public, and those more directly concerned with the provision of artificial nighttime lighting and with its environmental impacts (government, environmental and conservation agencies, environmental consultancies, & lighting contractors).
(i) General public - the project provides an opportunity to improve public understanding of the form and dynamics, and the ecological impacts, of artificial nighttime lighting, and to encourage a scientifically literate citizenry that understands the profound and rapid effects that arise from anthropogenic environmental changes. The research project will provide a tangible link between the environmental change created by artificial nighttime lighting and the responses of organisms, and we will take advantage of these data to use visual imagery to convey what artificial nighttime lighting is, and the environmental pressure this constitutes and its consequences. In our experience presenting our previous research on the ecological effects of artificial light, we have found that the subject is easily relatable and captures the imagination of a wide audience and has been an effective way to engage the public through participation in events such as Dark Sky Festivals, public talks and through local, national and international media coverage of our research.
(ii) Government, environmental and conservation agencies, environmental consultancies, & lighting contractors - a number of governmental and non-governmental groups have a significant interest in improved understanding of the likely environmental consequences of artificial nighttime lighting, for purposes ranging from shaping their own public engagement programs to making better public lighting policy and on-the-ground management decisions. One of the challenges faced lies in the undoubted complexity of the issues and the associated uncertainties. In particular, while there is a growing consensus among scientists and understanding among policymakers that artificial light has profound ecological effects on many species, the significance of artificial nighttime lighting is not well understood outside of a few local case studies on single species, and as a consequence opportunities for mitigating negative impacts through changes in lighting policies may be missed. We will use the work of the research project to improve understanding of the environmental impacts of artificial nighttime lighting, to explore together what this means for environmental policy and planning, and how best practice can most effectively be promulgated. Mitigating the negative impacts of artificial light on ecosystems often presents a potential win-win situation for policymakers, where environmental, financial, health and social costs could be minimised through low-cost solutions; however identifying and implementing such solutions is often hampered by major knowledge gaps in understanding of the full effects of artificial light in spatially and temporally complex ecological systems. This project will directly seek to address these gaps in existing knowledge.

Publications

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Bullough K (2023) Artificial light at night causes conflicting behavioural and morphological defence responses in a marine isopod in Proceedings of the Royal Society B: Biological Sciences

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Cox D (2023) Cathemerality: a key temporal niche in Biological Reviews

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Cox Daniel T. C. (2024) Ecosystem functioning across the diel cycle in the Anthropocene in TRENDS IN ECOLOGY & EVOLUTION

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Cox DTC (2024) Ecosystem functioning across the diel cycle in the Anthropocene. in Trends in ecology & evolution

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Cox DTC (2023) Global erosion of terrestrial environmental space by artificial light at night. in The Science of the total environment

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Morrell S (2024) Changing streetlighting schemes and the ecological availability of darkness in Journal of The Royal Society Interface

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Sanders D (2023) How artificial light at night may rewire ecological networks: concepts and models. in Philosophical transactions of the Royal Society of London. Series B, Biological sciences

 
Description This work has developed a new model for predicting how light is emitted from multiple outdoor artificial light sources, and that can be used to evaluate potential ecological impacts at landscape relevant scales.
Analyses using the model have shown that, given the manner in which they are retrofitted, there are clear trade-offs between the ecological impacts of different lighting types.
Exploitation Route They will help in the evaluation of the potential environmental/ecological impacts of different artificial lighting regimes.
Sectors Environment

 
Title Collection of studies included in the review from How artificial light at night may rewire ecological networks: concepts and models 
Description Artificial light at night (ALAN) is eroding natural light cycles thereby changing species distributions and activity patterns. Yet, little is known about how ecological interaction networks respond to this global change driver. Here, we assess the scientific basis of the current understanding of community-wide ALAN impacts. Based on current knowledge, we conceptualize and review four major pathways by which ALAN may affect ecological interaction networks by (i) impacting primary production, (ii) acting as an environmental filter affecting species survival, (iii) driving the movement and distribution of species, and (iv) changing functional roles and niches by affecting activity patterns. Using an allometric-trophic network model, we then test how a shift in temporal activity patterns for diurnal, nocturnal, and crepuscular species impacts food web stability. The results indicate that diel niche shifts can severely impact community persistence by altering the temporal overlap between species, which leads to changes in interaction strengths and rewiring of networks. ALAN can thereby lead to biodiversity loss through the homogenization of temporal niches. This integrative framework aims to advance a predictive understanding of community-level and ecological-network consequences of ALAN and their cascading effects on ecosystem functioning.This article is part of the theme issue 'Light pollution in complex ecological systems'. 
Type Of Material Database/Collection of data 
Year Produced 2023 
Provided To Others? Yes  
URL https://rs.figshare.com/articles/dataset/Collection_of_studies_included_in_the_review_from_How_artif...
 
Title Collection of studies included in the review from How artificial light at night may rewire ecological networks: concepts and models 
Description Artificial light at night (ALAN) is eroding natural light cycles thereby changing species distributions and activity patterns. Yet, little is known about how ecological interaction networks respond to this global change driver. Here, we assess the scientific basis of the current understanding of community-wide ALAN impacts. Based on current knowledge, we conceptualize and review four major pathways by which ALAN may affect ecological interaction networks by (i) impacting primary production, (ii) acting as an environmental filter affecting species survival, (iii) driving the movement and distribution of species, and (iv) changing functional roles and niches by affecting activity patterns. Using an allometric-trophic network model, we then test how a shift in temporal activity patterns for diurnal, nocturnal, and crepuscular species impacts food web stability. The results indicate that diel niche shifts can severely impact community persistence by altering the temporal overlap between species, which leads to changes in interaction strengths and rewiring of networks. ALAN can thereby lead to biodiversity loss through the homogenization of temporal niches. This integrative framework aims to advance a predictive understanding of community-level and ecological-network consequences of ALAN and their cascading effects on ecosystem functioning.This article is part of the theme issue 'Light pollution in complex ecological systems'. 
Type Of Material Database/Collection of data 
Year Produced 2023 
Provided To Others? Yes  
URL https://rs.figshare.com/articles/dataset/Collection_of_studies_included_in_the_review_from_How_artif...
 
Title Colour_Results.csv;Isopods_R.pfd;Path_Results.csv;Path_Shadow.csv;path_Speed.csv from Artificial light at night causes conflicting behavioural and morphological defence responses in a marine isopod 
Description Sea-slater calibrated photography measurements, taken before and after each trial, converted to bluetit cone catch quanta;R markdown script showing the full statistical analysis;Measurements of the sea-slaters' movement;Data showing the proportion of time sea-slaters spent in each zone;Data of the sea-slaters' speed and intermittent movement 
Type Of Material Database/Collection of data 
Year Produced 2023 
Provided To Others? Yes  
URL https://rs.figshare.com/articles/dataset/Colour_Results_csv_Isopods_R_pfd_Path_Results_csv_Path_Shad...
 
Title Colour_Results.csv;Isopods_R.pfd;Path_Results.csv;Path_Shadow.csv;path_Speed.csv from Artificial light at night causes conflicting behavioural and morphological defence responses in a marine isopod 
Description Sea-slater calibrated photography measurements, taken before and after each trial, converted to bluetit cone catch quanta;R markdown script showing the full statistical analysis;Measurements of the sea-slaters' movement;Data showing the proportion of time sea-slaters spent in each zone;Data of the sea-slaters' speed and intermittent movement 
Type Of Material Database/Collection of data 
Year Produced 2023 
Provided To Others? Yes  
URL https://rs.figshare.com/articles/dataset/Colour_Results_csv_Isopods_R_pfd_Path_Results_csv_Path_Shad...
 
Title Model code to simulate animal behaviour in response to light 
Description This dataset contains the material required to reproduce 3D volumetric data describing the energy density of photons within a simulated environment and heatmaps and journey lengths for ensembles of weighted walkers experiencing specific simulated environments. The dataset includes source code for snapshots of the Monte Carlo Radiative Transfer (MCRT) code used to run simulations, the weighted random walking code used to emulate the behaviour of animals experiencing the simulated environment, as well as inputs and configuration files for both codes. The MCRT software outputs 3D volumetric data describing the energy density of photons within the simulated environment. Then, the weighted random walk code takes 2D planes from this data and produces heatmaps and journey lengths for ensembles of weighted walkers experiencing these simulated environments. 
Type Of Material Computer model/algorithm 
Year Produced 2024 
Provided To Others? Yes  
Impact Insights into how different artificial lighting types impact ecology. 
 
Description ALAN 2023 Conference (Calgary) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presentation to an international conference audience, sparked questions and discussion.
Year(s) Of Engagement Activity 2023
 
Description Biodiversity festival presentation 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Public/other audiences
Results and Impact Presentation to general public that sparked questions and discussion.
Year(s) Of Engagement Activity 2023
 
Description Presentation (Mayo) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Presentation at dark sky festival, followed by questions and discussion about impacts of artificial light.
Year(s) Of Engagement Activity 2022
 
Description Webinar presentation (NE) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Webinar presentation to government agency staff, followed by extensive questions and debate.
Year(s) Of Engagement Activity 2023