Effects of artificial light on multi-trophic population dynamics

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.

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.