At Montana’s Medicine Rock State Park, visitors have a rare opportunity to look up at the night sky and see an awe-inspiring display of planets and constellations, as well as the Milky Way, our spiral-shaped galaxy that contains about 100 billion stars, according to the National Aeronautics and Space Administration. It is a magnificent sight, but those of us that live in or near cities with artificial lights beaming out of buildings and cascading over parking lots and highways, may never get the pleasure.

“Because of light pollution, up to 80 percent of people living in North America are unable to see the Milky Way where they live,” says Sabre Moore, executive director of the Carter County Museum, in Ekalaka, Montana. “Medicine Rock State Park is designated as an International Dark Sky Sanctuary, and the Carter County Museum has committed to safeguarding it in perpetuity.”

The park’s sanctuary certification was issued by the nonprofit International Dark-Sky Association, based in Tucson, Arizona, with a grassroots network throughout the world. The organization offers five dark-sky designations based on stringent outdoor lighting standards and relies on the help of community stakeholders, such as Moore, who serves as a volunteer dark-sky preservation advocate. At Medicine Rock, she helps to hosts sky-parties for people to enjoy the celestial show and learn about the negative impacts of light pollution.

Threats Posed by Artificial Lighting

The skies around cities are hundreds, if not thousands, of times brighter than they were 200 years ago, according to 2017 research published in Science Advances. In addition to robbing us of the Earth’s nocturnal skyscape, outdoor illumination negatively affects many plants and animals, including humans. Human-made lighting threatens approximately 30 percent of nocturnal vertebrates and 60 percent of nocturnal invertebrates, and it “is increasingly suspected of affecting human health,” writes scientist Christopher Kyba, lead author of the report.

The mechanisms by which these life forms are affected vary. For example, when birds migrate, they fly into buildings that are lit up at night. Scientists estimate that at least 100 million bird deaths in the United States annually are related to light pollution. “Bobcats and bats rely on the cover of darkness for their survival and are also being affected,” says Moore, adding that artificial light interrupts human circadian rhythms, thereby affecting our REM [rapid eye movement] sleep, which is vital for our well-being. The flight patterns of night-active insects are disrupted by outdoor lighting, which partially explains their declining numbers worldwide.

A Simple Switch Saves Turtles

It is possible to reduce these negative impacts, as the Sea Turtle Conservancy has proven. By getting people to modify the positioning and types of lights used in buildings along Florida and Texas beaches, the nonprofit has been able to rescue loggerheads, leatherbacks and green sea turtles from the brink of extinction.

Female turtles have evolved to instinctively lay their eggs on the beach, allowing the hatchlings to emerge at night and head toward the light of the horizon into sea. Humans, however, have interrupted this natural course with artificial light emanating from the windows of high-rise condominiums, garden spotlights and outdoor lamps.

“When hatchlings erupt out of their nests in the middle of the night, the bright horizon today is in the direction of the land. They go the wrong way into roads, parking lots, swimming pools or dunes, where they are run over by cars or subject to predation,” explains David Godfrey, executive director of the conservancy.

Researchers have discovered that lights with longer wavelengths that are amber, orange and red in color do not disturb the turtles, as opposed to outdoor fixtures that emanate shorter-wavelength blue and white light. According to Godfrey, the good news for these sea creatures is, “LED can be programmed to emit the specific wavelength you want.”

The conservancy works with coastal counties, beachfront property owners and others to switch to turtle-friendly lighting, and the National Fish and Wildlife Foundation often provides grants to pay the retrofitting costs. As a result, Godfrey reports, there has been increased nesting in areas with changed lighting and greater survivorship by the hatchlings.

“We are saving tens of thousands of hatchlings every season, and homeowners are seeing a reduction in their utility bills. People love it. They’ve found the longer wavelengths are more pleasing to the eyes,” Godfrey asserts. “Since we know that light pollution affects various other forms of wildlife and humans, the managed use of lighting at night is something that everyone should pay attention to.”

Tips to Address Light Pollution

• Avoid blue-light fixtures.
• Turn off unnecessary lights in the evening.
• Use dimmers, timers and motion detectors.
• Close curtains and blinds at night to stop indoor lights from beaming to the outdoors.
• Visit Lights Out: Recovering Our Night Sky, an exhibit at the Smithsonian National Museum of Natural History, in Washington, D.C. (NaturalHistory.si.edu/exhibits/lights-out).
• Get involved at GlobeAtNight.org, a citizen-scientist group that monitors light pollution.
• Support dark-sky designated areas (Tinyurl.com/DarkSkyPlace).

Sheryl DeVore is a frequent contributor to national and regional publications and has authored six books on science, health and nature. Learn more at SherylDeVore.wordpress.com.