The loss of starry skies: 'Growing problem' of light pollution

A few years ago, in the fall, I went camping in the Boundary Waters Canoe Area Wilderness on a string of clear nights. When the sun set, there was no moon and the stars came alive in the sky, billions of them stretching from one horizon to the other. In the dark, I lay on a warm rock near the water for a long time, watching meteors flare and satellites circle the earth before turning in.

Later, I got up in the night, stepped out of my tent and looked north. The big dipper still hung there, only it had spun, like someone reached down and turned it with a giant hand. For a few seconds I stood there, struck by the palpable sense of being on a planet spinning through space.

A few days later, I was back in Minneapolis, where I would look at the night sky and think of all the stars I couldn't see. Instead, there I saw a bluish haze with a few bright points. This is what's known as the "skyglow" and it's something that increases every year, blocking more of the cosmos from our view.

According to a 2017 study published in the journal Science Advances, nighttime artificial light increased at a rate of 2.2 percent each year from 2012 to 2016 — a 9.1 percent overall increase worldwide.

"It's a growing problem," said writer Paul Bogard, author of "The End of Night: Searching for Natural Darkness in an Age of Artificial Light." "Pretty much everywhere is getting brighter, and almost nowhere is getting darker. That's true in Minnesota, in the United States, and all over the world."

And it has been truer since the advent of LED streetlights, which tend to be on the higher end of Kelvin — initially around 6000K — with a lot of blue light in their spectrum. Kelvin is the scale used to describe the "color temperature" of a light source. The highest Kelvin temperature lights (5000K and higher) have a blue hue, while lights with a lower temperature (2000K-3000K) tend to be yellowish.

Blue light travels more easily through the atmosphere than the yellow of the old sodium light, causing more skyglow. It can also have serious effects on humans and wildlife.

The association's stated mission is combating light pollution.

Artificial light can disrupt everything from bird migrations to insect breeding to salmon spawning. But it also affects humans: In 2016, the American Medical Association warned that blue spectrum light more than 3000K (from our bulbs and our screens) has a serious circadian impact on human health, and noted that sleep disruption can increase the risk of cancer, diabetes, cardiovascular disease and obesity.

All of which are reasons why in 2016, when the city of Duluth announced it was going to replace the old sodium streetlights, which had a Kelvin of 1870, with new 4000K LEDs, there was a public outcry. The skies over Lake Superior, Superior National Forest and the Boundary Waters are the some of darkest in the state and the country.

"Duluth is on a huge migratory path," said Randy Larson of the dark skies group's Lake Superior chapter. "And the artificial light completely disrupts bird migration. It also affects the insect population. We've seen a massive decrease in lightning bugs in North America. The light also casts out into the water, and affects aquatic life, and we're right on Lake Superior. Local astronomers told us that with anything over 3000K, they weren't actually able to see the stars anymore, and we're ending up with a huge skyglow."

Eventually, the city agreed to use newer bulbs that were 3000K or less and is working on a pilot project with other less-blue LEDs.

One battle the association recently won was in Tuscon, Ariz., where the city reduced its skyglow 7 percent by switching from the old sodium lights to 3000K LED streetlights, which it runs at 90 percent of their maximum power, resulting in less light but streets that feel just as bright.

"More and more people are becoming aware of the issue," Bogard said. "And it's a problem that we know how to solve. It's not like climate change, or toxins in the soil, or these overwhelming problems that you don't know where to start. We could start tonight."

Throughout history, humans have used the stars to navigate across oceans and prairies. But in the era of global positioning systems, many think we don't need them for orientation. Yet whenever I'm Up North staring at sky, I can't help feeling like without the stars, we are at risk of losing our way.

"We've taken what was once one of the most common human experiences — walking out your door and coming face to face with the universe — and made that one of the most rare of human experiences," Bogard said. "The night sky has inspired people forever: in science, religion, philosophy and art. And we're losing that."