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The Hong Kong skyline lights up the night.
© Jim Richardson

With possible extinction looming, starry skies are now recognized by the National Park Service as American scenery entitled to the same protection as the leafy giants of the redwood forests, the Everglades’ wetlands and the wolves in Yellowstone. Stargazing has become one of the most popular attractions at national parks, and more than 65 rangers have been trained to use telescopes, teach basic astronomy and lead constellation tours.

People are now attending star parties at Death Valley, going on moonlight hikes at Bryce Canyon in Utah, and viewing the same constellations at the observatory of Chaco Culture National Historical Park in New Mexico that some believe inspired the location of ancient Pueblo villages.
Against this magical stage, rangers are not only enlightening people about the heavens, but they’re also unveiling the ugly truth about artificial light at night. It’s a sky spoiler that, more important, disturbs the natural rhythms of animals, disrupts ecosystems, wastes energy, and affects the health and well-being of humans.

  • Image about National Parks Service
Long exposure taken of the night sky in Denali National Park in Alaska
Gary Schultz / Alaska Stock LLC
Light pollution began with the invention of the lightbulb more than a century ago, but it has steadily worsened over the past few decades, thanks to a growing population and the incandescent detritus of suburban sprawl. A satellite map of the United States shows the Eastern Seaboard lit up like Times Square — and the rest of the country isn’t much better.

“As much as we humans would like night to be day, for millions of years we’ve had a dark night,” says Travis Longcore, science director of the L.A.-based Urban Wildlands Group and co-editor of Ecological Consequences of Artificial Night Lighting. “We can mess with that, but it comes at a cost.”

Many of the species on Earth are nocturnal, and artificial light disrupts the darkness they need in order to hunt, hide from predators, navigate and reproduce. Artificial light causes prey to be more visible to predators and migrating birds to fly off course. For humans, being exposed to artificial light at night may affect our moods, lead to anxiety and trigger factors that make us fat. It may even increase our risk of certain cancers, according to research done by Richard Stevens, Ph.D., a professor and a cancer epidemiologist at the University of Connecticut Health Center.

Light pollution is caused by excessively bright outdoor lights that shine upward or sideways — the kind at mall parking lots, on billboards, at stadiums and even on your porch. Stray light or excessive artificial light increases the brightness of the night sky, washing it out and obscuring the stars.