A sustainable neighborhood in the Dutch town of Nieuwkoop is leaving on the welcome light for bats. And if all goes well, they'll never even notice it.

The groundbreaking initiative, a culmination of more than five years of research on the impact of artificial light on nocturnal species, uses street lighting that features a specialized bat-friendly recipe of LEDs. Unlike the LED lighting many of us are familiar with, this particular network of lights glows with a somewhat eerie red hue. To light-sensitive bats and other nocturnal creatures, however, this specialized spectrum preserves the night conditions critical to their well-being.

"Bats don't see red light as particularly bright, if they see it at all," Maurice Donners, a senior scientist and innovation specialist at Signify, which designed the new streetlights, told Fast Company. "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."

The motivating factor behind embracing the new streetlights came after Nieuwkoop decided to create a new neighborhood of 89 homes near a nature reserve for rare and threatened species. Besides committing the development to the highest sustainability standards possible, officials also discovered that the neighboring reserve was home to a large population of light-sensitive bats.

The species Myotis nattereri, one of several bat species whose feeding habits are adversely impacted by artificial light. (Photo: Kamiel Spoelstra/Signify)

To reduce the impact the new community would have on the bats' nocturnal feeding habits without compromising the safety of residents, developers reached out to Signify to investigate the use of its bat-friendly lights. The company, formerly known as Philips Lighting, had been working with researchers at the Netherlands Institute of Ecology and Wageningen University to understand how bat species interact with artificial lighting.

In a paper published in the Royal Society journal Proceedings B in 2017, they describe how their experiments with different flavors of LEDs led them to discover that light-shy bats are impacted by white and green light, but not red.

"Plecotus and Myotis species avoided white and green light, but were equally abundant in red light and darkness," the researchers wrote in the study. "The agile, opportunistically feeding Pipistrellus species were significantly more abundant around white and green light, most likely because of accumulation of insects, but equally abundant in red illuminated transects compared to dark control."

Borrowing a good idea

Fast-forward to 2019, when Worcestershire County Council in the United Kingdom picked up on this concept and ran with it. They are using the red LED streetlights to install what they're calling the U.K.'s first bat-friendly highway. As Melissa over on TreeHugger explains, it's a smart way to keep notoriously light-shy bats connected to their food sources.

Though not yet complete, the project started when the community recognized the need to light a previously unlit area for a pedestrian crossing. But adding traditional white lighting would have changed the bat's range — with devastating consequences. Just as wildlife corridors and turtle tunnels give animals a way to get what they need — food, water, safety — without interacting with dangerous humans, the bat-friendly highway will accomplish the same goal.

The first of two lights have been installed along a roughly 60-meter stretch of road by Warndon Woodlands Local Nature Reserve near Worcester, which is southwest of Birmingham, England.

Why red light works

Thought it features mostly red LEDs, the bat-friendly lights also contain a small amount of blue and yellow to help distinguish colors on the ground. (Photo: Signify)

Despite its initial appearance as something that might look more at home on the set of a horror film, Donners says the red hue of the lights quickly loses its ominous appearance.

"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 added to FastCo. "So it will adapt your perception. After a couple of minutes, you won't notice anymore that it's really red."

Similar to other smart lighting projects throughout the Netherlands, the bat-friendly lights in Nieuwkoop are networked and fully capable of such energy-saving features like dynamic dimming and scheduling. In addition, residents can also request changes in brightness to individual lights outside their homes. In the event of an emergency, the entire system can be raised to a higher light level to aid first responders.

As an added bonus, the red lights also don't attract bugs as much as their traditional counterparts.

"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," Guus Elkhuizen, city council member for Nieuwkoop municipality, said in a release. "We've managed to do this and kept our carbon footprint and energy consumption to a minimum."

You can see more of the lights installed within the new community in the promotional video below.

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