Environmental Almanac

Dark skies benefit people and wildlife

Recent research shows how light pollution affects wildlife.

You may or may not know it, but there’s an effort underway to have the Middle Fork River Forest Preserve in northeast Champaign County certified as the first “Dark Sky Park” in Illinois. That would be great for people who want access to a clear view of the stars and planets, and it would be great for wildlife as well.

Most people understand that various products of human activity have the potential to harm wildlife when they’re released into the world, and we routinely call these products “pollutants.” Fewer people are accustomed to thinking of carelessly spread artificial light that way, but a growing body of evidence makes it clear we should.

To date, the poster creatures for the campaign to change the way people think about careless lighting are sea turtle hatchlings. As they emerge from nests on the beach they can become disoriented by lights on beachfront structures and wander toward them rather than sprinting directly toward the surf. This increases their risk of being eaten by predators or being caught on the beach and overheating when daytime comes around.

Of course, in central Illinois we have no sea turtle hatchlings to concern ourselves with as we manage our exterior lighting. But we do have other wild creatures, and light pollution affects them, too.

Take birds, for example. Many of them migrate at night, relying as they do on cues that can be obscured by artificial light. We’ve seen their bodies litter the sidewalks beside tall buildings where lights are left to shine out of windows at night, and we’ve seen as well that simple changes in our practices can alleviate the problem. Turn out the lights or block the windows, and far fewer birds run into tall buildings.

In a study published last fall, researchers found that the impacts on migrating birds of the annual tribute in lights to the victims of the 9/11 attack in Manhattan abated almost instantly when the lights were turned off. The tribute is created by training powerful searchlights into the sky to create columns of light resembling the towers of the World Trade Center. Researchers had observed that migrating birds in the vicinity were drawn to the lights and then became disoriented, slowing down, flying in circles, and calling frequently. By monitoring bird densities in the area and, when those get too high, simply turning off the lights for 20 minutes, researchers and organizers of the tribute have been able to protect the birds and conduct the memorial at the same time.

The effect of artificial light on night-flying insects has also been the subject of an important recent study. Scientists in Switzerland found that nocturnal pollinators visited a certain type of flower in lighted plots less than half as often as plots as dark ones. As a result, the flowers in the lighted plots produced less seed than the others, raising the possibility of cascading negative effects, since those flowers are also a source of food for other pollinators. 

Two things are worth keeping in mind as we move beyond our laissez-faire approach to light pollution. One is that it’s reasonable to proceed on the assumption that artificial light has negative effects on wildlife and ecosystems without waiting to tease out precisely what all of them are. I say that simply because a certain amount of darkness constitutes one of the defining conditions under which we and the life around us have evolved. 

The other thing worth remembering in this context is that there is no upside to light pollution, no constituency that benefits from it. Lights that shine up into the sky or across the landscape waste electricity and serve no good purpose—who needs that?