Denmark trials red streetlights to protect wildlife « Euro Weekly News

In a suburb north of Copenhagen, Danish planners are trialling an unconventional approach to street lighting that could reshape how cities worldwide think about illumination at night. Along a stretch of road in Gladsaxe Municipality, conventional white streetlights have been replaced with red LED lights in an effort to reduce the disruptive effects of artificial illumination on nocturnal wildlife, particularly bats, while maintaining safe visibility for people.

The project marks a shift in urban planning away from the longstanding assumption that brighter, whiter light automatically equates to safer streets. Authorities are seeking a balance between public safety, biodiversity protection and broader environmental goals, a dilemma familiar to modern cities that border natural habitats.

Red Lights Near Wildlife Habitat

The pilot installation focuses on a section of road near local woodland where several bat species forage and navigate at night. Research and ecological surveys have shown that shorter wavelength light, including white and blue LEDs, can disrupt the behaviour of bats and other light-sensitive animals, altering feeding patterns and fragmenting habitats.

Bats rely on darkness and their acute hearing and echolocation to hunt insects. Studies indicate that red light, which lies at the longer wavelength end of the visible spectrum, is significantly less disruptive to bats and allows their activity levels to remain comparable with those in natural darkness.

In areas used by bats, the new red lighting aims to minimise ecological disruption without eliminating public lighting entirely. Municipal planners say complete darkness would be ideal for wildlife but is not practical on public roads for safety and accessibility reasons. Instead, red LEDs are used selectively in ecologically sensitive sections, while conventional warm white lighting remains at busy junctions and pedestrian crossings.

Balancing Safety and Biodiversity

The Gladsaxe project has been developed through collaboration between engineers, environmental experts and urban designers. The solution was carefully designed to reconcile the needs of humans and wildlife. Red light was chosen because it permits sufficient visual guidance for drivers and cyclists while reducing interference with nocturnal animal behaviour.

Planners also note that the red streetlights serve a dual purpose: meeting technical requirements for public infrastructure while signalling that the area is a special natural environment that warrants protection. Early public response in the Gladsaxe area has been neutral to positive, with no significant complaints about visibility or safety since the red lights were installed. Monitoring of traffic safety indicators has not revealed an increase in incidents, although long-term ecological data are still being collected and analysed before the concept can be evaluated fully.

Part of Broader Environmental Goals

The initiative aligns with Gladsaxe Municipality’s broader commitment to environmental sustainability and the promotion of urban planning practices that integrate ecological considerations. By incorporating biodiversity protection into routine infrastructure upgrades, in this case, streetlight replacements, local authorities aim to demonstrate how small changes in urban design can support wildlife without compromising human needs.

Although the current trial is limited to one stretch of road, the implications extend beyond Denmark. Urban centres across Europe and beyond face similar challenges as cities expand into natural landscapes. Light pollution has been increasingly recognised as a form of environmental pressure alongside air and noise pollution, affecting nocturnal creatures including bats, birds and insects.

If long-term monitoring confirms that red-spectrum lighting successfully mitigates harm to wildlife without reducing public safety, city planners may begin to consider its application more widely, particularly near parks, forests and designated wildlife corridors. The trial thus adds to a growing conversation about how artificial lighting can be adapted to support both ecological resilience and human activity.

Global Interest in Responsible Lighting

Denmark’s experiment resonates with international efforts to rethink urban lighting. Other cities have implemented similar strategies, such as dimming lights seasonally to support bat populations or following “dark sky” principles to preserve night skies.

The pilot red lights in Gladsaxe accentuates a pragmatic pathway for modern cities: rather than simply turning lights off or continuously increasing brightness, altering the colour spectrum offers a middle ground. By using red light to reduce ecological disruption while preserving visibility, the project points to an innovative method for addressing a challenge that many urban areas face, how to light the night responsibly in an era of heightened environmental awareness.