Mitigating the impact of LED streetlighting on insects
Many moths have been undergoing dramatic declines in Great Britain over the past couple of decades1. This is important because adult moths are important pollinators2 and they are a crucial part of the food chain for other vertebrate and invertebrate predators. Some of the drivers of moth declines, including habitat loss, agricultural intensification and climate change, are large-scale drivers which need to be addressed at national and international scales. However, artificial lighting at night is another potential driver of moth declines3: previous PhDs in our labs have demonstrated the negative impacts of streetlighting on adult moths4 and on their larvae5, and our preliminary work (unpublished) suggests impacts on the development of nocturnal butterfly larvae.
LED lighting (which emit more light in the blue spectrum than the traditional sodium streetlights) has been shown to be particularly problematic5. This is concerning because of the large-scale, widespread shift towards LEDs for public lighting over the past decade6. However, LEDs are beneficial because they are more energy efficient and reliable than alternative light sources and, crucially, can be individually and remotely controlled. This provides options to fine-tune the lighting regime (e.g. reducing the brightness of the lights, part-night lighting or part-night dimming, dimming linked to movement sensors, or changing the colour temperature from bluer to yellower lighting) to reduce impacts on nocturnal nature and on humans. Furthermore, lighting has been proposed to indirectly affect moth populations via parasitism, although this remains untested3. Parasitoids are primarily diurnal, so artificial lighting potentially releases them from their day-time niche.
Field work will primarily be conducted on the Isle of Wight. The whole island is a UNESCO Biosphere reserve (recently awarded in 2019, with the aim of bringing the community together in pursuit of a culturally and ecologically sustainable future) and the island’s council is applying for the south-west of the island to be an International Dark Skies Park. The Isle of Wight was one of the early adopters of LED street lighting, with the switch to LEDs complete in 2015. The LED streetlights can be individually controlled remotely in terms of brightness and timing by our end-user collaborator (Ringway Island Roads Ltd). Our other end-user collaborator (ARC Consulting) has a strong track record in public engagement, so can support assessment on the public acceptability of potential changes (considering the trade-off between biodiversity benefits and public safety).
This project will have the following objectives:
OBJ. 1: To test the real-world impact of changing the regimes of LED streetlighting (brightness, timing and/or colour hue) on moths (adults and larvae, and their parasitoids);
OBJ. 2: To experimentally test the impact of changing regimes of LED lighting on growth rates of lepidopteran larvae (nocturnal-feeding moth and butterfly larvae);
OBJ. 3: To predictively model the impact of changing lighting regimes on regional moth populations, including constraints such as public acceptability, best practice of lighting professionals and costs.
Impact summary: This work is combines fundamental ecological research with solutions-focussed impact, specifically exploring how impacts of LED lighting on biodiversity can be mitigated, thus aligning strongly with NERC and UKRI’s strategies. Recent research by the team5 received international press coverage and was cited as evidence in statements from local councils about the importance of reducing the impacts of light pollution. The current research will address the gap in evidence about societally-acceptable ways of mitigating the impacts of artificial lighting. At the regional level, within our Isle of Wight case study region, we have already established good links with the Isle of Wight council through Island Roads (the contractors responsible for delivering streetlighting on the island). Our findings will therefore directly link to the delivery of future lighting on the Isle of Wight and more widely, through their contacts with the Institute of Lighting Professionals. ARC Consultancy (end-user collaborators) were instrumental in the Biosphere Reserve designation and so will facilitate wider impact amongst the public in the Isle of Wight, including the application for a Dark Skies Park on the island.
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The impact of streetlighting can be locally severe. What can be done to mitigate these effects on biodiversity? (Photo credit: Douglas Boyes)