Limiting Light Pollution Is Ongoing Challenge

When an earthquake knocked out the power in Los Angeles in 1994, people were puzzled by the starry sky. Ed Krupp, director of Griffith Observatory, recalls, “People saw something they’d never seen before in an urban environment—or never in their lives. We got two or three dozen calls. They wanted to know, Did the earthquake cause it?”

“The skies are very much a part of our intellectual survival. But people have lost touch with the sky,” says Krupp. It’s a loss felt across the industrialized world as light pollution has increasingly brightened the night sky. Already, for one-fifth of the world’s population—in the US, it’s more than two-thirds and in Europe, half—the Milky Way is no longer visible, according to Italy’s Pierantonio Cinzano of the Light Pollution Science and Technology Institute in Thiene and the University of Padua. Artificial sky glow comes from light that shines upward—from roadways and commercial, industrial, public, and residential properties.

Streetlights and stars

Cinzano models light pollution. From satellite data, he determines the intensity of light sources on Earth and then computes how much light is scattered from particles in the atmosphere, taking into account the distributions of gases, aerosols, temperature, and other factors. For projections, he assumes light use will continue to grow at its present rate. By 2025, for instance, he calculates that fewer than 100 stars will be visible in most of Italy’s population centers (red or farther down the scale in the figure below). His projections for the whole of Europe and for the US likewise show increasing light pollution. “The night sky is very endangered,” he says.

“Usually people think that light pollution is a problem only for astronomers, but this is not true,” says Cinzano. Among the other casualties of light pollution are the general public’s diminished view of the night sky, animals from fireflies to frogs to migrating birds, and human health—recent studies show increased rates of cancer when circadian rhythms are disrupted by too much light at night. “In 10 years we will have more biologists and medics at our meetings than astronomers,” predicts Malcolm Smith, president of the International Astronomical Union’s commission for the protection of existing and potential observatory sites. For now, though, he says, “astronomy acts as a canary in the mine for the rest of humanity.”

Ground-based telescopes can’t beat light pollution. Astronomers can avoid it by observing in the infrared instead of the visible spectrum, or they can partially compensate with a larger telescope, but, as Bob Brucato, former assistant director of Palomar Observatory, puts it, “there is no filtering in principle. Photons are the same whether they come from a star or a streetlight.” Adds Chris Luginbuhl, an astronomer at the US Naval Observatory Flagstaff Station, “As light pollution has originated and accelerated for the last 50 or 70 years, astronomers have gone to more and more remote areas—to remote mountaintops and remote countries. There are no further places to run.”

Given that dark skies are the bread and butter of astronomy, it’s perhaps surprising how few astronomers actively fight for them. Astronomers account for only a few percent of the nearly 11 000 members of the International Dark-Sky Association (IDA), a group that seeks to raise awareness about, and find solutions to, light pollution. The astronomers who still observe from polluted areas are “preoccupied with how it affects their observatories,” says Cinzano, but most go to “privileged dark skies and think, wrongly, that they are untouched by the problem.” Adds Smith, “Imagine a 25-year-old astronomer hearing about opportunities to work on light pollution and the acceleration of the universe. It’s not hard to guess what most people will choose.”

Fragmented fight

For the most part, the battle against light pollution takes place at the local level. In west Texas, for example, McDonald Observatory has teamed up with the Nature Conservancy to buy nearby land and resell it with restrictions on lighting. Northern Italy has some of the toughest laws for preserving starlit skies. And in April the UK parliament passed a law declaring exterior floodlighting a “statutory nuisance.”

“There are hundreds, if not thousands, of light pollution ordinances nationwide,” notes IDA cofounder Dave Crawford, an astronomer based in Tucson, Arizona. Typically, they limit upward-shining light, overlighting, and light trespass—the shining of light onto neighboring property. Near some observatories, laws call for low-pressure sodium lights, whose emissions in the 589 nm doublet astronomers can work around.

IDA is drafting a model lighting ordinance to be tailored by communities for their specific needs. The MLO is supposed to be unveiled later this year. Says Nancy Clanton, a lighting designer and member of the drafting team, “We want to piggyback on the green-building movement, which is exploding.”

Slow and nasty

Not surprisingly, it’s easiest to rally support for curbing light pollution in areas where there’s a clear environmental threat—such as to sea turtles on the Florida coast—or where astronomy is a boon for the economy. In Chile, “astronomy is a billion-dollar-a-decade industry,” says Smith. When he moved to that country in 1993 to head the Cerro Tololo Inter-American Observatory, the light pollution had, he says, “increased substantially” since a previous stay in the early 1970s. “On the horizon, you could see the faint glow of La Serena, 60 kilometers away. That was an early warning.” Now, thanks to a 1999 ordinance, by this October all street lights in three northern regions of the country must comply with restrictions on upward-shining light. “If the legislation is effective, it will increase the lifetime of telescopes in Chile by more than 20 years,” Smith says.

The Big Island of Hawaii, home to the 10-m Keck telescopes and—like northern Chile—a candidate to host a future larger telescope, “has a strong ordinance” for controlling light pollution, says Richard Wainscoat, a University of Hawaii astronomer. Still, he says, “we are right on the edge of light pollution affecting us. I’m worried about the future. It’s a very slow, nasty increase. Better shielding and better regulation of noncompliant lighting are needed to cut down on per capita light pollution. That would allow for many years of population growth on the island while still preserving the dark night sky for astronomy.”

Ordinances are one thing, enforcing them is another. “It’s like keeping Jell-O down; stuff pops up all over,” says Crawford. In southern Arizona, for example, where astronomy brings hundreds of millions of dollars into the state annually and the skies are widely considered a natural resource and tourist attraction, the billboard industry has for years fought to win exemptions from local outdoor lighting codes.

“The gutting of lighting codes could be devastating,” says Buell Jannuzi, deputy director of Kitt Peak National Observatory near Tucson. “It’s a never-ending education effort to explain to people why it’s important to regulate lighting. Most people understand that light going up into the sky is not making you more safe.” And by not sending light up, he adds, “you save energy and money in the long run. The irony is that it’s a win-win situation.”

Indeed, a few years ago, IDA estimated that the US was spending $1–2 billion annually on wasted light. In Chile, new shielded fixtures will save the town of Monte Patria about $1.3 million over a decade, Smith says. By shielding, “you can usually end up with about the same amount of light on the ground for about half the cost,” adds Bill Wren, a dark skies consultant. “In another energy crisis or two, the light pollution problem could solve itself.”