If you can’t see the stars, blame light pollution

Wind Cave National Park at night (Photo: Bill Gabbert)

Wind Cave National Park at night (Photo: Bill Gabbert)

During her time as a park ranger at Wind Cave National Park in western South Dakota, Diane Knutson saw a lot of stars — and a lot of dark. But when she would return to her Rapid City home, the scene was quite different, she says at TEDxRapidCity. Light pollution blocked out the stars, and outside of the city, one could hear songbirds singing mating calls in the middle of the night, their internal clocks offset due to artificial light.

Light pollution is the cause of many disruptions in the ecosystem and our lives, Knutson says, from the mistimed cries of birds to distracted insects to the purchase of blackout curtains. “We need to protect nocturnal habitats, stargazing opportunities and our nocturnal plants and animals,” she says.

80% of people in the U.S. cannot see the Milky Way from where they live due to light pollution, Knutson says. “To get to a naturally dark sky [from Rapid City], you would have to drive two hours to the corner of northwest South Dakota to an area called Slim Buttes, which has a Class 1 dark sky,” she says. A Class 1 night sky is completely naturally lit, the darkest on the Bortle scale, which is used by stargazers to classify the brightness of skies. “Rapid City is a Class 9 sky — where light pollution is 100-200 times brighter than natural darkness,” Knutson says. “But the thing is — Rapid City is not alone.”

An illustration of the Bortle scale, a means of classifying the amount of visibility in an area’s night skies (Illustration:  Stellarium)

An illustration of the Bortle scale, a means of classifying the amount of visibility in an area’s night skies (Illustration: Stellarium)

So how do Class 9 areas start to see the stars again? By being careful and thoughtful about light use, Knutson says.

She advocates for the outdoor lighting plans designed by the International Dark-Sky Association (IDA), which recommend using shielded lights to minimize glare and surplus lighting, as well as bulbs with a color temperature of no more than 3,000 Kelvins, to decrease the ill effects that come of blue light, which disrupts the behavior of sea turtle hatchlings, migratory birds, and other creatures.

The International Dark-Sky Association's recommended light fixtures, those they suggest to avoid and their Kelvin chart

The International Dark-Sky Association’s recommended light fixtures, those they suggest to avoid and their Kelvin chart

When outdoor lights go upward and outward, and stay on all night, they waste a lot of energy, Knutson says. In fact, the IDA estimates that “at least 30 percent of all outdoor lighting in the U.S. alone is wasted … [which leads to] release of 21 million tons of carbon dioxide per year.”

Knutson suggests we take another look at light — for the sake of wildlife, the environment, our sleep and our stargazing.

To learn more, watch her whole talk below:

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