Night-time light pollution harms the environment but simple changes can reduce impact, report concludes

23 November 2023

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Illuminated bridge in darkness, with light reflected on a river
Aquatic habitats are particularly sensitive to light pollution, with no barriers to stop light spill

Science communicators at the University of the West of England (UWE Bristol) have produced a detailed report that highlights how to stop or lower environmental harm caused by light pollution at night. The report concludes that the impact of light pollution can be lowered through a variety of measures, including: national legislation, such as artificial light free zones; practical schemes in towns and villages, such as sensor triggered lights; technical adaptations to lighting design, for example, to limit light spill; and identifying sensitive taxa or habitats, then managing these areas to avoid the impact, i.e. removing lighting, or using red lights rather than white.

The growing world population coupled with industrialisation has led to an increase in use of artificial light at night globally, with light pollution a rapidly emerging threat. In Europe for example, the loss of truly dark spaces was five per cent in just six years from 2015 to 2021. The report, written by the Science for Environment Policy team, at the university’s Science Communication Unit for the European Commission, illustrates that despite human kind’s need for night-time lighting, light pollution is causing a severe problem for the environment and human kind, disrupting wildlife behaviour and migration patterns, and impacting human health.

Nicola Shale, an ecologist and the editor of the report, said: “It’s important to dispel the myth that an area with brighter light at night is always safer. We have all experienced the blindness caused by poorly designed glaring light at night, it temporarily blinds you and makes it difficult to see your surroundings easily. Dimmer lighting located on suburban paths and through parks can benefit biodiversity and our (human) health.”

Night time active species including migratory birds, the European glow worm and rare lesser horseshoe bat are just some of the array of light sensitive species that can be detrimentally affected by light pollution from electrical lighting at night. This light can come from outdoor lighting on streets, at ports, or light spilling out from buildings (such as stadiums or skyscrapers) and ships.

The report used European and global case studies of best practice to highlight the types of good practise that can be used in a variety of settings. One example is the National 9/11 Museum's ‘Tribute in Light’, which releases trapped migratory birds by the intermittent switching off of the light. Dimming lighting, part night lighting and sensor activated lighting is also recommended best practice to protect light sensitive species and save on energy consumption. Other measures suggested in the report include: adaptive street lighting, buffer zones around dark reserves, dark corridors – connecting dark infrastructure, buildings designed to reduce light spill and reflection on glass, and dense vegetation to hinder light spill.

Nicky Shale said: “The ideal solution is to remove or switch off artificial lights at night, keeping naturally dark areas dark and protecting species in these habitats. But when there is a human need and this isn’t feasible, the least amount of light should be used, with precise lighting only of the area needed and only for the time needed. Warmer coloured LED lights (amber and red) are less harmful to most species, than white or blue lights. These are another option to mitigate the impacts from light pollution.”

Associate Professor Mark Steer, a member of the Ecology and Conservation Research Lab at UWE Bristol, said: “This is an important piece of work that underscores the urgent measures needed to mitigate the growing environmental harm caused by light pollution. Turning off lights in natural areas, and removing them where possible, should always be the default, but reducing harm by using dimmable, sensor controlled and shielded lights is preferable where lighting is a necessity.

“Red lights do seem to have a lower impact on many species compared to white light, but this is not always the case. The lesser horseshoe bat is so light sensitive even red light affects their behaviour. The report helps to provide some of the solutions needed to mitigate the impacts of new development, as well as offering hope for restoring populations of light-sensitive species where they currently cannot survive.”

The full report can be found on the European Commission website.

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