The introduction of artificial lighting brings many benefits to urban environments. It improves visibility, increases the sense of comfort and safety, and can even be used as a powerful tool to create experiences and change perception of spaces.

All these benefits can only be achieved using the right light source with the right quality. Poor quality lighting, both traditional and LED, can have various negative consequences on the well-being and comfort of both nature and people. Among these drawbacks are increased light pollution and sky glow, discomfort of residents in cities caused by glare, harsh and uncontrolled lighting, and the negative impact on biodiversity.

This article explores the latter topic: the consequences of artificial lighting on biodiversity; in particular on birds and bats. It describes measures that need to be put in place to ensure that these animals are not disturbed by artificial lighting during feeding, migration and general behaviour.

The impact of artificial light on birds

In recent years, ecologists have conducted extensive research to show that bright lights attract and disorient birds, disrupting their flight paths. One aspect they have been able to show is that bird migration is disturbed near to high-intensity urban light installations and offshore sites, among other places. As a result, birds spend extra time flying around the light source, using up valuable energy resources instead of making progress on their migration routes. Consequently, many birds may not survive their arduous journey, or have less chance of breeding successfully at their destination.

To gather more knowledge about the phenomenon and potentially find a solution, Philips Lighting conducted their own research. To study the autumnal bird migration, a 9-month field study on coastal areas was followed up by research on an offshore platform in the North Sea. As part of this research, light sources on an offshore gas production platform were replaced by a specially developed light spectrum.

During the study, different species of birds were observed under different weather conditions. Birds were also counted at the ringing stations on nearby islands. The results, compared with historical data, clearly showed that when the conventional lamp source was replaced with a dedicated light spectrum, the number of birds circulating around the light source reduced significantly. Click here to download the white paper to read more about the methodology used and the primary results obtained.

Based on the outcome of this research, Philips Lighting designed a new light spectrum which does not distract birds during migration. It is designed to be placed on large lighted objects in dark surroundings, such as offshore installations, remote harbour or port installations, and certain city skyscrapers. While significantly reducing the nocturnal activities of birds, the light still provides sufficient light for people’s safety and comfort.

Putting a light recipe into practice on Ameland

Ameland is an island off the north coast of the Netherlands. It is located in the Wadden Sea, which is a UNESCO World Heritage site. Ameland is the breeding ground and wintering area for 10-12 million birds per year. The island has a clear vision towards sustainability and intends to become CO­2 neutral in the near future. This vision includes creating a liveable space for citizens and wildlife. Realizing the importance of minimizing the effect of artificial lighting on nature, the municipality requested Philips Lighting to find the most sustainable lighting solution for the island. This proved to be a special light recipe to reduce the negative impact of lighting on birds and ensure smooth bird migration. Click here to read the case study.

Bats are also affected by artificial light

Another major concern is the effect of artificial light on different bat species. Bats are extremely important to a balanced ecosystem. They control numbers of potentially irritating or harmful insects, and are highly effective in controlling agricultural pests, which can lead to a reduced need for pesticide sprays. They are also robust natural indicators of environmental health, as changes in bat populations indicate changes in aspects of biodiversity. The Habitats Directive published by the European Commission covers all bat species living within the European Union. The Directive requires all Member States to undertake positive measures to ensure that their bat populations are afforded a favourable conservation status.

Investigations carried out by a number of associations, such as the Bat Conservation Trust, have found that artificial light affects night-time movement and feeding of bats. Furthermore, it was found that different species react differently to artificial light, which can result in a significant disturbance of the overall ecosystem by giving unfair advantages to species that are less afraid of artificial light.

In short, light can have an impact on bats’ commuting routes. For example, lit roads can act as a barrier that bats either cannot or dare not cross. Light can also have direct or indirect effects on breeding colonies, hibernation sites and roosts. During research conducted in 2017 by the Bat Conservation Trust, it was found that white light LEDs dissuade slower flying species from drinking at cattle troughs, and even the drinking behaviour of faster flying species was impeded.

A seven-year study at eight different sites

To examine these impacts more closely, Philips Lighting initiated a study that tested the response of three species of bat to three different experimental light spectra in an otherwise dark and undisturbed natural habitat. Over seven years, research was conducted at eight sites in the Netherlands. Light posts were set up that emitted either white light or two different light recipes. The results of the research showed that certain species are very much afraid of artificial light and try to avoid it at all costs, but when applying the dedicated recipe with a selected spectrum, their behaviour was the same as during full darkness. Click here to download the white paper which explains the methodology used and the primary results obtained.

A light recipe to provide an optimal ecosystem for bats

In line with research findings, a new light spectrum was designed for animals that are distracted by short wavelength light. It displays minimal attraction for insects. Bats behave the same way as if it was full darkness, which therefore helps maintain the balance of the ecosystem by providing equal opportunities for all species. Lit roads don’t act as borders or obstacles to be crossed at night. At the same time, people have sufficient light to operate or drive safely.

Rare bats in Nieuwkoop get the benefit

Thanks to its rare and special flora and fauna, Zuidhoek in the municipality of Nieuwkoop in the Netherlands is part of the Natura 2000 network. The municipality decided to turn an old camp site into a residential area, but prior to construction work starting, they were obliged to assess the area’s flora and fauna. They discovered that it is an important feeding area for some rare bat species. Before proceeding with the housing program, they therefore had to put some conservation measures in place, including lighting that would not disturb the nocturnal feeding activity of the bats. The municipality selected the dedicated light recipe developed for bats by Philips Lighting. It does not impact the behaviour of the bats, but ensures sufficient illumination for the area’s human residents. Click here to read the case study.

The environmental benefits of LED lighting

The extensive field research carried out by Philips Lighting led to the development of the dedicated light recipes described in this article. The light recipes help ensure undisturbed bird migration, and prevent disturbance to the natural behaviour of bats. This innovative initiative shows that while future-proof lighting has a clear goal to improve energy efficiency, it can also contribute to the conservation of nature.