Cities worldwide have replaced orange high-pressure sodium (HPS) streetlights with white LEDs—promising energy savings. But this “upgrade” is worsening light pollution and harming ecosystems, because we optimized for lumens per watt, not system health.

The Sky Is Getting Brighter Despite lower power use, satellite data shows global skyglow is increasing by ~2% yearly (Science Advances, 2016). Why?

White LEDs (often 4000K–5000K) emit intense blue light, which scatters 3× more in the atmosphere than HPS’s amber glow. Poorly shielded fixtures leak upward—even “retrofit” kits in old housings often lack proper optics. Cheaper operating costs encourage over-lighting (Jevons paradox). Real Ecological Harm Peer-reviewed studies confirm:

Insects swarm blue-rich LEDs → local population collapse (Biol. Lett., 2018). Migratory birds collide with buildings due to disorientation from skyglow. Bats, frogs, and other nocturnal species show disrupted foraging and reproduction. The AMA even warned in 2016 that high-CCT streetlights suppress melatonin and increase glare—reducing nighttime safety.

A Better Path This isn’t anti-LED—it’s pro-systems thinking. Solutions exist:

Use ≤2700K LEDs (less blue, better visual comfort)

Mandate full-cutoff fixtures (zero uplight)

Dim lights after midnight via motion or scheduling

Cities like Tucson and Davis prove you can cut energy and protect the night.