“I Got Rhythm”

George and Ira Gershwin wrote some spot-on lyrics in 1930, and Judy Garland made them famous. “I got rhythm,” she belted out as she danced across the stage. Now, you may not dance like Garland, beat the drums like Thetiktokdrummer, or keep time like Toscanini, but you’ve got rhythm, too. Our shared primal beat is called circadian rhythm.

Circadian rhythm is the cyclical, 24-hour period of biological activity.[1] For some 600 million years, all life forms on earth evolved with a regular cycle of light and dark. This daily change is circadian rhythm. It influences behavior, reproduction, and other essential life functions.

Light and dark cycles have been predictable and reliable over millions of years. Something new is throwing us off tempo, though. Artificial lights at night have changed the beat of the age-old rhythms of life. Flip a switch and the lights go on - you can stay up all night studying for an exam. Program the lights and your yard can be lit from dusk to dawn. Install bright streetlights and nearby residents get to stay awake all night – whether they want to or not!

“The circadian rhythm, which can be thought of as our internal food and sleep clock, has been with us since the beginning of time, following the day’s natural progression from darkness to light and back again.”

— Johan Eklöf, The Darkness Manifesto

The ubiquitous presence of artificial light in our lives means that we are increasingly out of sync with nature’s rhythm. This has health consequences for us humans, and far-reaching consequence for wildlife, plants, and natural ecosystems.

For humans, circadian rhythm determines our sleep time and our wakeful hours. “Artificial light can wreak havoc on natural body rhythms in both humans and animals,” according to the National Geographic.[2] “An increased amount of light at night lowers melatonin production, which results in sleep deprivation, fatigue, headaches, stress, anxiety, and other health problems.” The blue light from screens on phones, tablets, and computer monitors has a particularly negative effect on melatonin.

Circadian rhythm influences wildlife migration, courtship, and reproduction. Light pollution disrupts this rhythm in forests, fields, lakes, and streams. Darkness is the milieu in which nocturnal pollinators visit night-flowering plants. Porch and deck lights disrupt those interactions in gardens and yards. Streetlights attract pollinating insects by the thousands, drawing them from their essential duties as pollinators. Bats are lured to the swirling clouds of insects, removing them from their natural habitat. Lights near parks and forest preserves remove the cover of darkness for prey animals and alter the hunting patterns of predators. Migrating birds are distracted by artificial lights and waste precious time and energy during their journey to breeding or wintering grounds.

Plants need darkness, too. They take cues from the seasonal shift in natural light/dark cycles. The budding of leaves, the opening of flowers and changing leaf color are all influenced by circadian rhythm. Streetlights interrupt the darkness that plants need to calibrate their seasonal growth.

Here’s the good news: you can affect change to bring natural darkness back to your life. Take a look at the lights around your house. Are the lights useful? Consider how the light will affect the wildlife in your yard, the plants in the garden, and the neighbors. Are the light fixtures directed where the light is needed? Be sure the light isn’t pointed upward or towards anything that doesn’t need to be illuminated. Next, check the light level. Use the lowest light level possible. There’s no need to light the outdoors like an operating room! Lastly, use warm color bulbs. Bright whitish-blue light is harmful to wildlife, plants and people. Select lights on the warmer end of the light spectrum.