Darkness at night: What a concept! The case against dusk-to-dawn outdoor lighting

I remember the first time I really appreciated the stars above a Northwoods lake, about 40 years ago. It was around midnight. The lake was remote enough not to receive light from any city or village. It was sparsely developed so that there was no light from houses or cabins. And the moon was just a sliver. The sky absolutely blazed.

These days it’s harder to experience the night sky in true darkness. Light pollution, from cities, from homes, from pier lights, interferes with quality sky gazing. A long-time friend, Dan Heim, is an avid sky watcher (I highly recommend his blog at https://sky-lights.org/). He lives near Phoenix, Arizona, but his observations about light pollution contain lessons fully relevant to those of us here in the northern lake country. Here is Dan’s message:

“In 1995 when we built our home in Arizona, most of the lights you see in the accompanying photo weren’t there. The light dome above Phoenix was visible, especially on cloudy nights, but it was tolerable. Since that time, the dome has steadily grown in size and brightness. This is my view to the south and, as you can see, some of my new neighbors have very bright yard lights. Those are unshielded 150-watt bulbs, and they’re on all night. Local zoning only requires fixtures above 150 watts to be shielded, so I have no legal remedy.

“I’ve been a skygazer all my life, and a vocal advocate for dark skies. The misconception people seem to have is that yard lights provide security. I understand their concern — in this unincorporated rural area north of Phoenix, emergency response times can be 30 minutes. But unshielded dusk-to-dawn yard lights have little impact on security. They cast harsh shadows that can help a prowler hide behind the glare. Lighting activated by a motion sensor is far more effective. The sudden illumination does deter prowlers, especially when combined with an audible alarm.

“Running a yard light all night causes other problems. It degrades the night sky for neighbors. It also attracts insects, which in turn attract predators like rodents, arachnids, and bats. That buffet then attracts larger predators like snakes and coyotes. Do you really want that happening around your property? Plus, a 150-watt bulb burning 12 hours every day will add about $85 annually to your electric bill.

“Research has also shown how outside lighting can disrupt circadian rhythms (waking/sleeping cycles) in aquatic, terrestrial, arboreal, and aerial ecosystems. Millions of years of evolution have programmed the DNA of many species to rely on a seasonal day/night cycle to trigger feeding, mating, predation, and migration.  “And it doesn’t have to be a 150 watt yard light. The same issues arise with any type of outdoor lighting. For example, path lights on docks or in gardens, and dedicated fixtures for boathouses, corrals, decks, and gazebos. So turn off all those outdoor lights, set up your recliner, and enjoy the wonders revealed by a dark night sky.”