How Light Pollution Threatens Minnesota's Wildlife and Dark Skies

Sep 18, 2023

LED lights use less energy than other types of bulbs, last longer, and cost less to operate. So, why is something with a decidedly better carbon footprint still so bad for the environment?

by Emily Sohn

June 8, 2023

6:47 AM

Illustration by Nicole Xu

Having spent part of her childhood in Duluth, Kate Hage remembers nights full of darkness—in a good way.

"I grew up looking at the Milky Way in my bedroom," says Hage, who coordinates the branding and strategy of a custom home builder in Minneapolis. "Now, there's no night sky anymore."

On her laptop, Hage has two pictures of Duluth taken from her childhood home in the Central Hillside neighborhood above downtown. In the first shot, from 2020, a warm amber glow shrouds the city's buildings on the edge of Lake Superior, but the brightest object in the picture is a full moon. In the second photo—taken three years later, after the construction of a new hospital and an area transition to LED light bulbs on buildings, parking lots, and streetlights—the entire city is lit up with white lights, as bright as a street fair.

Around the world, light pollution has increased dramatically in the last decade, with consequences ranging from ecological to existential. A rise in artificial light at night has been linked with negative effects on wildlife and human health, while depriving people of the opportunity to see the stars and experience all the wonder they evoke.

In Minnesota, the loss of darkness threatens one of the state's great natural resources, says Hage, who is a member of Starry Skies North, the local chapter of a global advocacy group called the International Dark-Sky Association. In 2020, the IDA named the Boundary Waters Canoe Area a Dark Sky Sanctuary, making it the largest of just 17 places designated as the darkest on earth. Soon after, the group named Voyageurs National Park and Quetico Provincial Park Dark Sky Parks, a status for less remote places.

To preserve the darkness and restore what's rapidly being lost, Hage and her cohorts at Starry Skies North are pushing back against light pollution in Minnesota. Their arguments are economic as much as they are aesthetic. Tourists fly to Scandinavia in the winter to see the northern lights, after all, fueling a booming astrotourism industry. Northern Minnesota could be the same kind of destination if more people knew about it.

"We have this unique, precious, amazing opportunity in Minnesota," says Hage.

The Loss of Night

Recorded observations of light's impact on the environment date back to ancient Rome, when people noticed that their fires affected animal behavior, says John Barentine, an astronomer and freelance dark-sky consultant in Tucson, Arizona. Gas, and later electric, lights altered the appearance of the night sky through the 1800s and into the 1900s, when observatories moved outside of cities to escape sky glow, followed by an accelerated brightening of nighttime as the 20th century went on.

Then came light-emitting diodes, or LEDs. A type of semiconductor, LEDs use less energy than other kinds of light bulbs typically used in streetlights and other outdoor fixtures, making their carbon footprint smaller. They last longer and cost less to operate. Those features make LEDs environmentally appealing in many ways, Barentine says, and society embraced them.

From 2016 to 2018, streetlights went from about 28 percent LED to about 49 percent, according to data from the U.S. Department of Energy. Cities were replacing streetlights and highway lighting with LEDs. Homeowners put them on their houses. And, as often happens when a resource becomes cheaper, Barentine says, people started lighting more spaces for longer periods of time with brighter lights.

LEDs come in a variety of color temperatures, but the bulk of controversy has surrounded bulbs with a color temperature at or above 4,000 Kelvin. At that level, lights begin to look like a cool white instead of a warm yellow.

To better understand how the shifting landscape of light is affecting our view of the night sky, researchers at the National Science Foundation's National Optical-Infrared Astronomy Research Laboratory recently analyzed citizen science data collected by a project called Globe at Night. For more than a decade, the project has asked participants around the world to compare what they see in the sky with a series of star maps. By assessing these changes in how many stars are visible from various places, researchers have learned how much brighter the sky has become.

Between 2011 and 2022, the sky grew nearly 10 percent brighter each year, the team reported earlier this year in the journal Science. Over the years, the changes quickly added up to a significant amount of brightness and loss of visibility of the sky.

"No place on earth is getting darker," says Paul Bogard, who teaches at Hamline University and wrote the 2013 book The End of Night: Searching for Natural Darkness in an Age of Artificial Light. "Wherever we go, we take our lights."

Drowning in Light

Migrating birds, disoriented by lights at night, circle buildings and fly into windows. Outdoor lighting affects plants that bloom only in darkness and pollinators that do their business at night. In the oceans, artificial light disorients baby turtles and interferes with fish reproduction. One study in the Arctic found that a boat's working lights altered fish and zooplankton behavior as far down as 600 feet.

"Every species that we look at, with very rare exception, we find an effect of some kind, and it's usually a negative effect," Barentine says. "Artificial light at night very clearly has a harmful effect on most biology."

Less well established but also raising concerns are laboratory studies suggesting that exposure to artificial light at night interferes with our circadian rhythms, altering the timing of hormone production, causing insomnia and contributing to health problems such as cancer, diabetes, and slowed healing from strokes, wounds, and inflammation. In the real world, data is still accumulating, Barentine says, but it's an active area of research.

Also up for debate is whether extra lights actually equal added safety. Some studies show that light reduces crime. But like the blinding beam of a car's headlights, bright LEDs can create glare that can obscure objects outside the illuminated area and make it hard for people's eyes to adjust, argue dark-sky advocates. At the very least, Bogard says, shining lights up into the sky doesn't make anyone any safer.

Light pollution is a social justice issue, studies suggest. In the United States, a 2020 analysis found that Black, Asian, and Hispanic people tend to live in neighborhoods that are twice as bright as predominantly white neighborhoods.

"Nobody's calling for no lights," Bogard says. "We’re just calling for thoughtful, intelligent light."

Taking Action

Reducing light pollution isn't complicated, according to Barentine. In Tucson, where he lives, the city operates its new 3,000 K streetlights at 90 percent capacity until midnight, when it dims them to 60 percent. The shift has darkened the night sky and saved money without an uptick in safety concerns or complaints, Barentine says.

More than a dozen states have passed legislation to reduce light pollution, including Minnesota. Most municipalities have taken no such steps. Those that try often lack in enforcement. Even if one city makes an effort, light pollution drifts from one community to another like smog. Light from Duluth is now visible from Port Wing, Wisconsin, 50 miles away down the south shore, Hage says. Two Harbors and other communities now make their own halos of light.

One of Starry Skies North's priorities is to reduce light pollution in Minnesota through outreach—a booth at the State Fair, talks at libraries. For her part, Hage has been talking with business owners in Duluth and Minneapolis about smart ways to alter their lighting decisions. In conversations with Odyssey Resorts, Target, Essentia Health (owner of the new hospital in Duluth), and other businesses, she shares information and offers support for keeping the night sky in mind while choosing lights during construction or retrofitting with inexpensive solutions like shields that block light from shining up.

Scott Vesterstein is one business owner in Duluth who is trying to fight back against the creeping glare of artificial lighting. A native of Duluth, Vesterstein is president and owner of Fitger's, a complex of shops, restaurants, and a hotel on the waterfront in Duluth. He has installed wildlife-friendly lighting outside of Fitger's and on the apartment buildings he owns. In one case, he cut 20-foot light poles down to 10 feet so they wouldn't shine into residents’ windows or bother neighbors.

Back in 2016, Vesterstein saw the city's engineering plans specifying a shift to 4,000 K streetlights. In response, he posted a petition at Fitger's to request that the city light only areas that need it, only when needed, and with lights no higher than 3,000 K, among other requests. More than 3,000 people signed the petition, he says. He also hosted a seminar at Fitger's that drew experts from around the country to talk about the impacts of harsh lighting on wildlife, including the migrating birds that fly through Duluth and often slam into buildings and ships parked in the port.

Vesterstein has noticed changes in his hometown that motivate him to keep northern Minnesota dark. "I can't remember the last time I’ve seen a firefly," he says. "I used to be able to go and catch them. You can't do that anymore."

The battle to make a dent in Minnesota's growing glow is full of both obstacles and momentum, Hage says. In Minneapolis, Starry Skies North has been vocal in opposition to a $9 million budget proposal that would add more light to some neighborhoods as a safety measure. Xcel Energy already replaced 24,000 streetlights in Minneapolis with LED bulbs from 2017 to 2019, and the city is converting thousands more. Adding light where needed is OK, the group argues, but there are ways to do it better.

In Duluth, Hage is particularly focused on Essentia, which lists dark-sky priorities on its website. It also has engaged in encouraging conversations, but Hage feels there's still more work to be done. Essentia says it plans for all of the hospital's exterior lights to point down and to meet or exceed standards and guidelines set by the International Dark Sky Association, LEED, and other groups, in order to protect bird safety and address public concerns about skyglow.

People tend to be receptive when they learn about light pollution, says Hage, who lives on a wetland where neighbors used to keep their lights on all night. After she knocked on doors in her neighborhood and talked about the impacts of artificial lights at night on great horned owls and other creatures living in the area, people responded.

"I got that entire street to knock their lights out with a very simple, non-confrontational conversation," she says. "This is a profoundly simple issue. We’re talking about light bulbs."

Unlike air pollution and other environmental issues, addressing excess light has instantaneous effects, Barentine adds.

"We can literally solve this problem tomorrow, if we chose to do it, because we know how," he says. "What we’re missing is the political will to take action."

by Emily Sohn

June 8, 2023

6:47 AM

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