Effects of artificial light on multi-trophic population dynamics

Lead Research Organisation: University of Exeter
Department Name: Biosciences

Abstract

Daily, lunar and seasonal cycles of natural light have been key forms of environmental variation across the Earth's surface since the first emergence of life, and have driven the development of biological phenomena from the molecule to the ecosystem. These natural patterns have, however, over the last 100 years come to be greatly disrupted through the introduction of artificial light into the nighttime environment. This derives from a diversity of sources, including street lighting, advertising lighting, architectural lighting, security lighting, domestic lighting and vehicle lighting. Indeed, artificial nighttime lighting is already estimated to be experienced directly and indirectly (through skyglow - scattering by molecules or aerosols in the atmosphere of artificial nighttime light that is emitted or reflected upwards) by nearly 20% of the global land area, and to be growing at about 6% per year. The extent of the problem is evidenced by frequently reproduced satellite and astronaut acquired nighttime images of the Earth.

The introduction of artificial light into the nighttime environment has doubtless provided significant and substantial benefits to humankind. But, given that biological systems are fundamentally shaped by light, there have inevitably been a wide array of environmental impacts. Studies have particularly focussed on the effects on individual organisms, and have highlighted consequences of artificial nighttime light for physiology, foraging, daily movements, migratory behaviour, reproductive behaviour, and mortality. Whilst population level effects are predicted to follow, these remain poorly understood. Moreover, it is unknown how these change with the intensity and the spectrum of artificial nighttime light. This means that it is difficult to make the best possible recommendations as to how artificial nighttime lighting (e.g. street lighting) might be modified to optimise the trade-off between human benefits and environmental costs. This is particularly significant at a time of large scale and rapid introduction of new lighting technology and use of 'smart illumination'; many street and other lighting systems are moving to 'whiter' lights, commonly using light-emitting diodes (LEDs), and central management systems are increasingly enabling more flexible approaches to the implementation of public lighting.

In this project we will determine the impact of artificial light at night of different intensity and spectrum on population dynamics, using an established aphid-parasitoid-hyperparasitoid experimental study system.

Planned Impact

Much contention surrounds the most appropriate levels of artificial lighting of the nighttime environment, and how best to deliver these. On the one hand, there is much evidence of negative environmental impacts, including on human health and wellbeing, and on wildlife. On the other hand, such lighting brings substantial human benefit, and even though effects on levels of crime and vehicular accidents are complex, there is widespread perception that such effects are strongly beneficial. Indeed, proposals and attempts to cut levels of street lighting have often met with great public opposition. 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 (government, lighting contractors & environmental NGOs).

(i) General public - the project provides an opportunity to use the case of artificial nighttime lighting to improve public understanding of the trade-offs that lie at the heart of many policy decisions, 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 population responses of organisms, and we will take advantage of these data to develop teaching materials on the nature of science and policy, relating to environmental change impacts on biological systems, directed to secondary school students, and to work with cohorts of such students through a Teacher Affiliate program.

(ii) Government, lighting contractors & environmental NGOs - a number of governmental and non-governmental groups have a significant interest in improved understanding of the likely organismal responses to 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. Against this background, rather limited use has been made by these stakeholders of 'model' organisms to help direct their thinking and understanding. We will use our research project as a case study to explore, through workshops, the potential benefits of such an approach.

Publications

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Sanders D (2021) A meta-analysis of biological impacts of artificial light at night. in Nature ecology & evolution

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Sanders D (2018) How ecological communities respond to artificial light at night. in Journal of experimental zoology. Part A, Ecological and integrative physiology

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Gaston K (2017) Impacts of Artificial Light at Night on Biological Timings in Annual Review of Ecology, Evolution, and Systematics

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Garrett J (2019) Skyglow extends into the world's Key Biodiversity Areas in Animal Conservation

 
Description This research has determined the impact of artificial nighttime lighting (as produced by street lighting and other such sources) on the structure and dynamics of multi-species communities, which has thus far been a significant knowledge gap. Key findings have been that (i) responses may often be non-linear, such that for some species these are more acute at lower rather than higher intensities of lighting; (ii) responses may often be influenced by the spectrum of lighting, with organisms at different trophic levels being impacted in different ways; and (iii) responses can have a strong top-down component, resulting from the influence of artificial lighting on predators, especially when these are able to extend their activity into the night as a consequence of the lighting.
Exploitation Route The findings contribute important insight into the environmental impacts of artificial nighttime lighting, particularly establishing that influences extend beyond the behaviour of individual organisms to the structure and dynamics of whole communities. They highlight that these impacts cannot simply be solved by reducing the intensity of nighttime lighting, but make clear the importance of limiting lighting to those places and times when it is genuinely required.
Sectors Environment

 
Title A meta-analysis of biological impacts of artificial light at night 
Description This is a database of published studies, that measuered how the exposure to artificial light at night impacts the physiology, daily activity patterns and life-history traits. The data were collected using a systematic review with searches in Web of Science and Scopus. We also provide the R-code that was used to analyse the dataset with meta-analytic models in MCMCglmm. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
URL http://datadryad.org/stash/dataset/doi:10.5061/dryad.wpzgmsbjn
 
Title Effects of different intensities of artificial light at night on multi-trophic population dynamics 
Description The datasets contain insect numbers, plant biomass, successful attacks of parasitoids, and behavioural response of parasitoids. The data have been sampled as part of the NERC project NE/N001672/1 "Effects of artificial light on multi-trophic population dynamics". The data are based on direct observations of insects and plants in field and laboratory experiments testing for the impact of different intensities of artificial light at night on an experimental insect food web with control (no light), and white LED light with 0.1,1,5,10,20,50,100 lux. Data collection was done in a field site, and controlled temperature room at Penryn Campus of University of Exeter, Penryn, UK. The field experiment was set up on 29th July 2016 and ran for nine weeks, while the additional experiments were conducted between summer 2016 and spring 2018. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
 
Description Conference presentation 
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 a broad audience, which sparked questions and discussion.
Year(s) Of Engagement Activity 2016
 
Description Conference presentation 
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 a broad audience, which sparked questions and discussion.
Year(s) Of Engagement Activity 2018
 
Description Podcast for biology site 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Extended podcast interview recorded for a popular biology site
Year(s) Of Engagement Activity 2020
 
Description Public lecture 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact c.100 people attended an open presentation, which sparked debate and discussion.
Year(s) Of Engagement Activity 2018
 
Description Seminar. 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact Presentation to a broad audience, which sparked questions and discussion.
Year(s) Of Engagement Activity 2018
 
Description Training workshop for teachers 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Schools
Results and Impact Teachers attended a dedicated workshop run at the ESI, which included developing materials for use in classes.
Year(s) Of Engagement Activity 2017
 
Description Web pages developed 
Form Of Engagement Activity Engagement focused website, blog or social media channel
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Web pages developed to provide information on ecological impacts of artificial nighttime lighting.
Year(s) Of Engagement Activity 2017
 
Description Workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Policymakers/politicians
Results and Impact Workshop on impacts of artificial nighttime lighting, with attendance from broad array of sectors.
Year(s) Of Engagement Activity 2018
 
Description Workshop run for teachers 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact A day long workshop organised to help teachers use light pollution as a topic in their lessons
Year(s) Of Engagement Activity 2019