Dark skies benefit people and wildlife

You may or may not have caught this news, but something really cool happened for the Middle Fork River Forest Preserve in northeast Champaign County late in 2018. Thanks to a collaborative effort by the Forest Preserve District and the Champaign-Urbana Astronomical Society it was designated an “International Dark Sky Park,” the very first in the state of Illinois. That’s a win for people who want access to a clear view of the stars and planets, and it’s 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 year, researchers in Manhattan found that the impacts on migrating birds of the annual tribute in lights to the victims of 9/11 abated almost instantly when the lights were turned off. 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 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 ecosystems without waiting to tease out exactly what all of them are. I say that because a certain amount of darkness constitutes one of the defining conditions under which we and the life around us have evolved.