Denmark is quietly piloting a radical rethink of urban lighting: replacing standard white streetlights with red-spectrum LEDs to protect nocturnal wildlife without sacrificing safety. In Gladsaxe, a municipality outside Copenhagen, authorities installed red streetlights along Frederiksborgvej, a tree-lined bat corridor home to seven species, including the light-sensitive common pipistrelle and brown long-eared bat.
The shift is grounded in ecological photobiology. Short-wavelength white and blue-rich LED light disrupts bat foraging and navigation by altering insect behavior and interfering with natural darkness cues. Red-spectrum lighting, with its longer wavelengths, has been shown to significantly reduce behavioral disturbance while still providing usable roadway visibility. Municipal traffic engineer Jonas Jørgensen described it as the optimal compromise where total darkness wasn’t feasible.
The bat-friendly lighting forms part of the EU-backed Lighting Metropolis – Green Mobility program, which supports sustainable infrastructure across Denmark and Sweden. Working with lighting designers at Light Bureau, Gladsaxe limited red lighting to ecologically sensitive zones while retaining warm white illumination in high-traffic areas.
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This move also directly targets light pollution as a form of habitat fragmentation. Research prepared for the Danish Road Directorate has warned that conventional road lighting can sever feeding routes and stress bat populations even when habitat remains physically intact.
Beyond biodiversity, the transition advances climate and efficiency goals. Gladsaxe is upgrading roughly 5,000 luminaires to LED systems as part of a wider regional rollout exceeding 50,000 fixtures. LEDs reduce power draw, lower maintenance cycles, and enable smart dimming controls — aligning with SDGs 7, 11, 13, and 15. Gladsaxe has formally branded itself Denmark’s first “SDG Municipality,” embedding sustainability metrics into infrastructure decisions.
There’s also a subtle urban design function: the red glow signals protected ecological zones to drivers and pedestrians, acting as environmental signage without words. According to Light Bureau’s Philip Jelvard, the lighting itself becomes a behavioral cue that the area supports sensitive species.
Public acceptance so far has been smooth, with no reported safety complaints. Bat monitoring continues, and if the data confirms reduced disturbance, this Danish experiment could reshape how cities worldwide balance visibility with ecological preservation.