Lighting for Wildlife
by Tom Velat, Natural Resources
DuPage forest preserves close one hour after sunset, but that doesn’t mean the animals that call them home call it a night. Many species only become active when the stars come out. But if you step outside your home at night, you may notice there aren’t as many stars as there were when some of us were kids. The culprit? Light pollution, the overabundance of artificial light in the environment, especially excessive or misdirected light, that not only affects the number of stars we see but can also affect how we — and wildlife — function at night.
People are familiar with air pollution such as smog. It’s visible during the day, and we definitely notice it when we take a breath. Light pollution is nothing we can smell or easily see, but like smog it can have a negative effect on our well-being. Like other animals, humans have a “circadian rhythm,” the natural wake-sleep cycle that takes place every 24 hours. According to research cited by the Illinois Coalition for Responsible Outdoor Lighting, overly bright nighttime ambient light can disrupt this rhythm, increasing levels of stress and incidents of disease. Relatively recent studies show that wildlife can experience similarly negative reactions.
Moths are a good example. We know they’re attracted to lights at night, but most people don’t realize moths often stay at artificial light sources well after the sun comes up and the lights go off. This disrupts the insects’ reproductive successes and larval development and makes them easy pickings for predators that learn to frequent these spots.
There aren’t many studies on large wild mammals, but a few on small nocturnal ones suggest that light pollution affects them as well. In one study, mice exposed to the same type of light present on a typical Chicago night showed notable decreases in activity. How this relates to larger mammals in the wild has yet to be studied.
Birds, unfortunately, are perhaps our area’s most noticeable examples of the hazards of light pollution. According to the Chicago Audubon Society, over 250 species of migrating birds move through the area each spring and fall, about 5 million individual birds each season. One study from 2017 showed that artificial light, usually from skyscrapers, has a dramatic effect on some of them. Many birds are attracted to the lights and tend to gather around the source in large groups, wearing themselves out. As they do so, they either collide with the buildings, succumb to exhaustion, or become weakened, vulnerable prey for hungry predators.
This effect was noted as well in New York City near the nighttime memorial for victims of the Sept. 11 attacks. At the site, two beams of light, each with 44 xenon bulbs, rise into the sky to mark where the World Trade Center towers once stood. Now, however, the lights are turned off periodically for about 20 minutes, creating intervals of darkness that allow birds to disperse within minutes and continue their migration journeys.