New lighting tech with potential to limit impact on bats from street lighting

A new residential development Nieuwkoop (Netherlands) has been constructed with red street lights. The development is next to the Nieuwkoopse Plassen nature reserve, which is part of the Holland-Utrecht low fenland region (called the Groene Hart (transl. Green Heart)) of the Netherlands. This nature area of 2,000 hectares is among the most important wetland regions in the Netherlands.

The reserve is important for a range of species, but one key issue with the proposed development was the potential impact of artificial light on bats.

The development proposal looked at a range of ecological issues, but the interesting thing to draw on for us is a novel approach to lighting. So as not to disturb the nocturnal feeding and night time activity of the bats, a special light recipe was developed by Signify (formerly Phillips Lights), the University of Wageningen and ecology NGOs. Normal street lights can affect a bat’s flight and overall night time behaviour as well as their insect prey which tend to congregate around the lights.

Bats don’t see red light as particularly bright, if they see it at all,” says Maurice Donners, a senior scientist and innovation specialist at Signify, which designed the new street lights. “So if you have certain bat species that are really avoiding light, we thought the obvious thing to do was take a portion of red light which is visible to us, but is much less visible, or perhaps even invisible, to bats.”

For humans, Donners says the lights perform as well as typical LEDs–the brightness meets the same requirements for rural neighbourhoods, and human eyes quickly adapt to the colour. “We have a mechanism in our visual system which is much like the automatic white balance in a modern camera, which will tell our brains actually the lighting which you see, is white,” he says. “So it will adapt your perception. After a couple of minutes, you won’t notice anymore that it’s really red.” A mix of a few other colours in the light, including a little blue and yellow, makes it possible to distinguish colours–for example, when you’re trying to find a car in a parking lot.

The lights can be set to dim late at night, and brighten when an ambulance or fire truck drives by. The system can also automatically brighten lights when pedestrians or cyclists approach, though that function isn’t used in this neighbourhood.

The company is also working on lights that can benefit other wildlife. Migrating birds, Donners says, typically aren’t disturbed by ordinary residential streetlights. But if an area is particularly bright and surrounded by darkness–for example, an oil platform in the middle of the ocean–that can make birds swerve off-course. Another light recipe, a blue-green colour, in this case, can help birds. Signify plans to use those lights on an island off the Dutch coast in the North Sea, replacing the island’s entire public lighting system to help migrating birds. (The bird-friendly lights, notably, aren’t any better for bats than ordinary streetlights–there’s no solution for all species, yet, other than darkness.)

The new lights for bats likely only make sense in certain locations. “In a really big city centre with lots of noise and traffic and all kinds of other irritating factors for bats, it might not be that useful to do something like this,” he says. “In areas where lighting is a predominant disturbing factor, and there is actually a reason to focus on bats and not on some particular other species, then this might be a good solution.”

Nieuwkoop is the first town in the world to use smart LED street lights that are designed to be friendly to bats. When developing our unique housing program our goal was to make the project as sustainable as possible, while preserving our local bat species with minimal impact to their habitat. We’ve managed to do this and kept our carbon footprint and energy consumption to a minimum.

Guus Elkhuizen, City Council Member, Nieuwkoop municipality

Prime Environment will be drawing on this new technology in our recommendations for projects where there are significant potential impacts on bats from lighting.

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