Feature The Dark Side of Light

by Joe Bower

Las Vegas it’s not. But the small city I live in, Kalamazoo, Michigan, still puts on quite a light show. As night falls, thousands of lamps flicker, blink, pulsate, and shine. Incandescent, fluorescent, mercury-vapor, metal halide, and halogen. White, red, blue, yellow, orange. We’ve got them all here in Kalamazoo. You should see them from the hill near my house. It’s a sight, especially during the holidays. But if you’re ever admiring the spectacle, I hope you appreciate the costs involved in staging it. n Leaving the lights on is more expensive than you’d think. It not only costs a chunk of change, but it also takes a surprising toll on the environment. The proliferation of artificial lighting threatens wildlife, ruins habitat, fouls the air, squanders resources, and blocks our view of the heavens. No wonder the pervasive problem has come to be called light pollution. 

Astronomers were the first to notice this problem. About 30 years ago they began to be frustrated as sky glow, the eerie radiance that emanates from settled areas and has spread with urban sprawl, began impairing their ability to see the stars. 

Today as few as one in 10 Americans live in areas where they can see the 2,500 or so stars that should be visible under normal nighttime conditions. In most big cities, you’re lucky to glimpse a few dozen–on a good night. But light pollution isn’t just an
urban problem. In Springfield, Vermont, a controversy has erupted over the economically depressed town’s decision to permit the construction of a prison; the lights from the site, it is feared, would mar the view from Breezy Hill, one of New England’s best places for stargazing. Each year since 1926, thousands have flocked to Breezy Hill for a celebration of the stars called Stellafane. David Levy, an astronomer, has led the protest against the proposed prison. "Stellafane is a magical place, a sanctuary to the stars," he wrote in Sky & Telescope magazine. 

Although light pollution’s impact on stargazing is as clear as day, its effects on other environmental elements are just coming into focus. The evidence shows that artificial lighting has dire consequences for animal behavior, particularly on the ability to navigate at night. 
Sidebar: Lights Out, Live Longer

As far as your health goes, turning out the lights may not rank with, say, exercising three times a week or eating five servings of fruits and vegetables a day. At least not yet.

But research increasingly indicates that our bodies do better when they’re kept in the dark during sleeping hours.  Exposure to light at the wrong time of day has been linked to many maladies. Last year, for example, researchers at the University of Pennsylvania and at the Children’s Hospital of Philadelphia released a joint study that found that children younger than 2 who slept with a night-light on were more likely to develop nearsightedness during childhood and teenage years. "There’s no doubt, light is a powerful regulator of human physiology," says George C. Brainard, a professor of neurology and the director of the Light Research Program at Philadelphia’s Jefferson Medical College. 

Exposure to bright light at night can disrupt the internal clocks that make our various circadian cycles tick. Such cycles affect behavioral rhythms, daily changes in blood and urine chemistry, and the production of melatonin, a hormone involved in wake/sleep cycles and body-temperature fluctuations that is produced at night by the pineal gland. Connected by nerves to the eye, the pineal gland is very light-sensitive, and sudden or continuous exposure to a bright light can suppress the production of melatonin.

In the short term, the disruption of biological rhythms can produce grogginess, depression, and impaired thinking.  In the long term, though, things aren’t so clear. Some scientists, such as Robert Hahn of the Centers for Disease Control and Prevention in Atlanta and Richard Stevens of the Energy Department’s Pacific Northwest National Laboratory, theorize that chronic disruptions in melatonin production–such as those caused by sleeping in a room that’s bathed in a streetlight’s glow–might contribute to the development of "hormone-related" cancers, including breast cancer. Recent studies of blind people in the U.S., Sweden, and Finland have all shown that among those with the most severe loss of vision there is also a lower incidence of breast cancer. "At this point, the epidemiological studies strongly suggest that light exposure may be a risk factor for breast cancer," says Brainard.  "What is needed now is careful, controlled studies to test this idea."

Until a lot more light is shed on the subject, the medical establishment isn’t likely to issue a prescription on how to treat nighttime illumination. Still, advises Brainard, "it’s probably better for your health to sleep in a dark room."
–J. B.

The hundreds of species of migrating birds that fly after the sun sets, including most songbirds and many shorebirds, are prime examples. Normally they rely on constellations to guide them during their twice-yearly migrations. But scientists speculate that when they fly near urban areas, the bright lights short-circuit their steering sense. Numerous reports have documented birds flying off course toward lights on buildings, towers, lighthouses, even boats. "Both birds and insects demonstrate positive phototaxis," says Sidney Gauthreaux, a Clemson University biologist. "To put it simply, birds are attracted to light much like moths are to a flame. But the reasons are unclear. They may use it as a reference and home in on it." When birds suddenly reach the light’s source, they often seem to become confused or blinded by the glare, which can be disastrous.

Birds may slam into windows, walls, floodlights, or even the ground. On the night of October 7, 1954, for instance, 50,000 birds were killed when they followed the beam of a guide light at Warner Robins Air Force Base in Georgia–straight into the
ground. The problem is particularly acute when the weather is bad. On a rainy, foggy Labor Day weekend in 1981, more than 10,000 birds collided with the floodlit smokestacks at Ontario’s Hydro Lennox Generating Station, near Kingston. And on January 22, 1998, between 5,000 and 10,000 Lapland longspurs crashed into radio transmission towers near Syracuse, Kansas. 

Birds that are distracted by tower lights also may end up crashing into one another. "Around communication towers with constant lights, birds curve, circle, pause, and hover around the lights," Gauthreaux explains. They are apparently trying to orient their flight to the light, which they mistake for the moon or a star. "Over time there’s a buildup of migrants [all trying to adjust their course], raising the possibility of hitting guylines or other birds." 

Nobody is certain of the total number killed across North America. But Michael Mesure of the Fatal Light Awareness Program (FLAP), a Toronto organization working to publicize the problem, estimates that at least 100 million birds are killed annually by manmade structures. "More birds die each year through collisions than died in the Exxon Valdez spill," he says. A tall building in the path of a migration can claim hundreds of lives. One example: From 1982 to 1996, 1,500 migrating birds have smacked into Chicago’s McCormick Place Exposition Center. 

Although few nocturnal migrants seem immune to light’s dark side–for example, dead or injured members of 141 different bird species have been found at McCormick Place–songbirds may be most at risk, Mesure says, because they fly at low altitudes dominated by artificial light.

Passerines are not the only order of birds waylaid by lights. The Newell’s shearwater, an endangered Hawaiian seabird, is particularly vulnerable. After their parents abandon their cliffside nests in October and November, fledglings make their first flights by relying on their innate attraction to light to guide them. Normally, because of the light’s reflection on water, they fly out to sea, toward the horizon. But when the moon is neither full nor visible, many of the shearwaters instead glide toward lights in seaside resorts and towns. Disoriented, hundreds crash into structures or drop from the sky. In 1998 volunteers gathered 819 shearwaters on the island of Kauai. Most were exhausted or injured, though fortunately, only 77 died. 

Other animals are threatened by light pollution, too. Hatchlings of at least five sea-turtle species found in Florida rely on an instinctive attraction to light to guide them to water. But lights on or near the beach can confuse the turtles and cause them to head in the wrong direction. Scientists have seen hatchlings cross parking lots, streets, and yards–transfixed by shining streetlights or porch lights. "Their reliance on light is so strong that they’ll continue heading to a light source, even if it’s an abandoned fire that burns them alive," says Blair Witherington, a Florida Marine Research Institute scientist who studies sea turtles. Disoriented hatchlings usually die from exhaustion, dehydration, or predation. Many others are squashed by cars. 

Insects cannot seem to resist this fatal attraction either. Most people know that moths find lights irresistible. But what they may not realize is that the energy moths expend in this way can cost females the chance to attract a mate. What’s more, it can interfere with locating prime spots to lay their eggs, thus giving larvae inadequate conditions to develop, according to Michael Collins, a lepidopterist at the Carnegie Museum. Some entomologists speculate that the proliferation of outdoor lights has contributed to the decline of numerous saturniid moth species in the northeastern United States.

Visual orientation is just one sense disrupted by artificial light, though it probably isn’t the only one, says Mere-dith West, an Indiana University professor specializing in avian development. Studies of animals raised in controlled settings, like laboratories and poultry farms, indicate that lighting can affect certain "photo-periodic" behavior, including foraging and reproduction.  "Animals are very sensitive to light," West says. "Lighting is a powerful stimulus on behavior. If there’s enough of it, it can make them act in ways they wouldn’t normally." If enough light is present–say, in a well-lit neighborhood–it’s possible that animals living there would be stimulated to act as they do during longer days. Overexposure to light may explain reports from English researchers about robins singing at night if there are streetlights in their territories, or why some birds build nests during the fall,
instead of spring: Their internal clocks have gone haywire. 

Adult female sea turtles will not emerge from the water to nest and lay eggs on beaches that are bathed in artificial light. Many behaviors influenced by changing light–from night to day and the seasonal increases of longer days–involve hormones.
"Anything that alters the hormonal system will bring enormous changes," West says. "Hormones regulate growth and immune functions. But they’re not produced all the time. If they don’t shut down, you overload the body. It can’t get rid of them.
Hormones are toxic in the wrong amounts." Indeed, a 1998 study at the Mary Imogene Bassett Research Institute in Cooperstown, New York, found that cancerous liver cells in lab rats grew rapidly when they were constantly exposed to light.
Side Bar: Light Right

You can help turn down lighting’s environmental impact

Lights Out Turn off lights whenever you leave a room. Close window blinds at night to prevent lights from shining outward. (During the day, open them for old-fashioned sunshine.) Turning off a few lights makes a big difference in
conservation. For example, running five 100-watt lightbulbs for 10 hours a day uses 5 kilowatt-hours of electricity and costs, on average, about 40 cents. If you use these lights at this rate every day, that adds up to more than 1,800 kilowatt-hours and about $150 a year. To generate 1,800 kilowatt-hours, a typical coal-fired power plant has to burn one ton of coal.  Environmental Defense (formerly EDF) has an online program that calculates the pollution generated by your use of electricity (www.edf.org/programs/energy/green_power/x_calculator.html). 

Buy Design Use lights that have shields on their tops or sides so that they illuminate only where they’re supposed to. Lights without shields, such as floodlights or globes, shine upward and sideways. Most exterior lights can be outfitted with shields. Fluorescent lighting is about four times as efficient as incandescent lighting. Though fluorescents are most popular indoors, their outdoor use is increasing. 

Be Clean Better housecleaning lessens the inclination to overlight. Dirt that builds up on room walls can reduce their reflectability, and dust that collects on lamps and fixtures can dull the light shining through. Together dirt and dust can reduce total illumination as much as 50 percent.

The Outside Scoop If you use yard lights, consider ones that will minimize your contribution to light pollution. The worst are mercury-vapor lamps, because they use excessive energy and they shine in all directions. The best are high-pressure sodium lamps and low-pressure sodium lights, which emit light with an orange hue. Metal halide lights, which emit a white light, aren’t as efficient as sodium lamps but offer better visibility. Incandescent bulbs are cheap but not particularly energy-efficient. If you want to use them, try low-wattage bulbs and outfit them with motion sensors, so they shine only when something comes near. Finally, equip your outdoor lights with photo cells, so they shut off during daylight hours, or try solar-powered lights, which rely on nature’s renewable energy. 

Keep Current Lighting fixtures are constantly being improved. Call the EPA’s Energy Star hotline (888-STAR-YES) for information on light fixtures that exceed federal energy-efficiency guidelines without sacrificing performance. In addition, be sure to visit the International Dark-Sky Association’s web site www.darksky.org for other helpful light-reduction ideas. 

–J. B.

Even if wildlife were able to ignore direct sources of light, lighting’s impact on the environment would still be unavoidable.  Burning coal and oil, according to the Environmental Protection Agency, generates most of the electricity for lights. The process is a dirty one that each year spews out billions of tons of carbon dioxide (CO2), a greenhouse gas; sulfur dioxide (SO2), an ingredient of acid rain; and nitrogen oxides (NOx), which cause smog. Sadly, much of this atmospheric pollution is produced for nothing. "One-third of our lighting is wasted because it shines upward or sideways, illuminating nothing but the bottoms of
birds and airplanes," says David L. Crawford of the International Dark-Sky Association (IDA), a 10-year-old anti-light-pollution group based in Tucson. Every year this waste squanders the equivalent of 8.2 million tons of coal or 30 million barrels of oil.

How did we reach this point? A big reason is a push toward overlighting. "People think brighter is better," says Crawford. To lure customers, retailers plug in bigger, brighter signs and entrance lights. In commercial buildings, more electricity is now used for lighting than anything else, even computers or air-conditioning. Urban sprawl has increased the number of lights on streets, billboards, and buildings. Meanwhile, homes are getting bigger and using more electricity. The average single-family home currently consumes 1,500 kilowatt-hours a year for lighting–40 percent more than it did in 1970. To produce that much electricity, power plants emit more than a ton of CO2, 13 pounds of SO2, and 8 pounds of NOx. "Most people are in the dark about lights," Crawford says. "There’s a total lack of awareness" of the consequences of lighting.

Of course, using less energy would reduce emissions. In addition, research in Toronto and Washington, D.C. shows that when building lights are dimmed or turned off, the number of fatally attracted birds drops dramatically. "If you have a tower without lights, you’ll cause bird collisions, but at least you won’t be attracting more birds to it," Gauthreaux says. 

The challenge for the government and environmental groups is to, no pun intended, enlighten people. The Environmental Protection Agency has created an energy-saving program, Energy Star, to help companies and residents reduce lighting use.  Several manufacturers have begun producing energy-efficient lights and appliances. FLAP launched a 12-step bird-friendly program that encourages buildings to turn down lights during migrations; it has been adopted at 100 buildings in downtown Toronto since 1997. FLAP organizers are leading similar efforts to raise awareness in Chicago and New York. And educational drives to publicize the impact of light on turtle hatchlings and seabird fledglings are now being sponsored by the National Park Service in Hawaii and by county governments in Florida. Some cities, including Tucson and Miami, are replacing inefficient streetlights with ones designed to focus the beam more sharply. In addition, last August two workshops at the American Ornithologists’ Union conference explored light pollution’s impact on birds. 

Meanwhile, lawmakers in hundreds of communities have passed ordinances that restrict lighting types, power, and use. Last spring Texas and New Mexico became the fourth and fifth states (along with Arizona, Connecticut, and Maine) to implement a statewide light-restriction program. The ordinances vary in scope, from banning certain types of streetlights or limiting their wattage to shielding security lights. Similar actions are being considered in other states.

Any dark-sky proponent will admit that the national impact of these programs is minimal. But Crawford of the International Dark-Sky Association believes that they’re a good start. "I liken lighting to smoking," he says. "All the evidence shows it’s bad.  But we have to educate people about the consequences. Smoking bans are coming quickly now. But the education that brought them about took a long time." 

Joe Bower lives in Kalamazoo, Michigan, and is a regular Audubon contributor.

© 2000  NASI

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