In April 2021, astronomy educator John Heasley set out to see just how dark the skies were in southwestern Wisconsin's Vernon County.
He measured the brightness of the night sky in three public recreational areas — Wildcat Mountain State Park, the Kickapoo Valley Reserve and Tunnelville Cliffs State Natural Area — and was delighted by what he found.
For years, Heasley and other night sky enthusiasts in the region had dreamed of getting the properties designated as an international dark sky park , a title that signifies excellent stewardship of the night sky and attracts star-seeking visitors interested in astronomy — or just enjoying stars not visible when there is too much light. The measurements he took that spring showed the skies were easily dark enough to qualify for the designation.
But by fall 2023, that had changed. His measurements found that sky brightness had increased by 50% or more in some areas — too bright to qualify.
"It was a blow. It was a disappointment," Heasley said. "We had done so much work to create this international dark sky park."
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He and others believe the culprit is increased outdoor use of LED lights, which communities around the country are switching to en masse because they last longer and eat up less energy than traditional bulbs. Research is beginning to show that comes with a price: the bluer, brighter light that LEDs emit could be brightening the night sky by as much as 10% each year, one study found . And the impacts extend beyond stargazing. The brightness can disrupt the nighttime patterns of people and animals , which can have health consequences.
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Dark sky park designations come from the International Dark Sky Association, which began a "dark sky places" program in 2001. Parks are one of its categories , which range from sanctuaries (remote areas with little to no light encroachment) to urban night sky places (which are in urban areas but take significant steps to still provide an "authentic nighttime experience").
To date, the association has certified more than 200 dark sky places, resulting in more than 61,000 square miles of protected night skies in 22 countries. Wisconsin has just one such place: Newport State Park , at the tip of Door County on the shores of Lake Michigan, which has had the designation for seven years.
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The application process is stringent and can take years. Dark sky parks must have robust educational programs to teach the public about the harms of light pollution. On top of that, getting dark enough skies often requires changing light fixtures. That has happened at Kickapoo Valley Reserve and Wildcat Mountain State Park, which have changed about 60 fixtures. There are no lights at Tunnelville Cliffs.
Local power engineer Scott Lind led the effort, painting the sides of omnidirectional light fixtures so the light would only shine down, and using photographic gels to soften the light coming from recently replaced LED bulbs. Today, Heasley said, "We've made all the light changes we can make" on those properties.
The problem is the land outside them.
Even when sky brightness readings met the qualifications to be a dark sky park, light domes from the small surrounding towns and villages were visible from the three properties, Heasley told the Journal Sentinel in 2022. Those communities have been slowly making the transition from high-pressure sodium streetlights and other outdoor lights to brighter LEDs.
It's not that residents haven't been receptive to helping protect their starry skies — in fact, the nearby village of Ontario put lower-temperature LED bulbs in its streetlights when switching over to help keep things dark. (Lower-temperature LEDs, typically around 3000 Kelvin or lower, emit less blue light and give off a warmer glow.)
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Still, it just isn't dark enough anymore.
Lind pointed to a 2021 study led by National Park Service staff in Chelan County, Washington, which had just switched its streetlights from high-pressure sodium to mostly 3000 Kelvin LEDs. Sky glow increased after the transition, the researchers found, in one place by as much as 60%.
Since light pollution can travel more than 100 miles from its source , municipalities from farther away could also be making an impact, Lind added.
The Chelan County study — and the sky measurements in his own area — were a "wake-up call," he said. He hopes to use what happened as a teaching moment "to show how drastically things are changing, and quickly."
Preserving starry skies is a multifaceted effort
Just because the dark sky park designation may be out of reach for now doesn't mean Lind and Heasley are giving up.
While they can't approach places like Ontario and ask them to get new lights again, Lind acknowledged, they can develop relationships with other communities that haven't yet transitioned to LED lights for outdoor fixtures — and when it's time to do so, urge them to consider a lower temperature, such as 2200 Kelvin.
Businesses and municipalities can also dim LED lights or turn them off completely if there are certain times they don't need to be lit, Heasley suggested.
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Lind and Heasley are also interested in raising broader public awareness of light pollution and the importance of keeping night skies dark. One way they'll tackle that is through the work of a new group, DarkSky Wisconsin , which launched this summer.
Though it's in its infancy, chapter president Sam Saeger said the group's ultimate goal is to work with municipalities to write rules that preserve starry skies. What happened in Vernon County shows that protecting them takes everyone, she said.
Heasley said he tries to reframe his disappointment by thinking about the work he and others have done to enhance stargazing opportunities at the three properties. People need public places to see the stars and other cosmic phenomena, he said, so they'll "fall in love with it and help speak up for it."
"What I like to say is, starry skies await you in Vernon County along the Kickapoo River," Heasley said. "They're still there."
Madeline Heim is a Report for America corps reporter who writes about environmental challenges in the Mississippi River watershed and across Wisconsin. Contact her at 920-996-7266 or mheim@gannett.com.
This article originally appeared on Milwaukee Journal Sentinel: A second dark sky park in Wisconsin was within reach. Then light pollution increased.
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