Light pollution extinguishes the stars
Astronomers, naturally, were among the first to be alarmed. Our brightening skies are gradually forcing on every astronomer a kind of professional blindness. The Mount Wilson observatory in southern California, a major facility with a 100-inch reflecting telescope, has been rendered virtually useless for deep-space work by the growth of Los Angeles. Even the large observatories on Hawaii's Mauna Kea, almost 14,000 feet above sea level and one of the world's most pristine astronomical sites, are beginning to feel the effects of light pollution. Amateur astronomy, once a backyard hobby, is becoming an expensive and peripatetic pursuit; its devotees are spending more and more of their time and money traveling to conferences in Nebraska, Australia, and other places that are still dark enough for them to see from. If the trend continues, one can imagine astronomy students of the future who have never seen the universe through a telescope with their own eyes.
But with the slow creep of light pollution has come a far wider, and perhaps more profound, loss to the human spirit. The night sky has inspired rapture and wonder at least since the beginning of recorded human history. Golden stars in a midnight-blue sky adorn the ceilings of ancient Egyptian temples; stars figure in the Anasazi petroglyphs. From Stonehenge to the Hubble telescope, humans have gone to great lengths to make sense of the sky, and from those efforts have come some of our greatest scientific revolutions.
Yet the night sky has now been lost to millions of people. Under ideal conditions, the sky is crowded with visible stars, about 2,500 in all, that loom large and close and extend to the horizon in all directions; if there is no haze, the Milky Way, too, will stretch all the way to the horizon. That sight is granted now to fewer than 10 percent of all Americans. Even in a thinly populated suburb or a small village, at roughly double the natural level of sky brightness, much is lost: the contrast and delicate details in the Milky Way, the vast number of stars, and the sense that the stars are large and nearby. In a moderately illuminated suburb, the night sky has only 200 to 300 visible stars. In large cities, people are lucky if they can see more than a few dozen.
Children who live in cities are astonished when they get to summer camp for the first time and find out what the stars really look like. Some grow up without ever having the chance. In my own introductory astronomy classes, the number of students who have already seen the Milky Way before enrolling has dropped, in just 20 years, from half to a handful.
Light pollution also interferes with ecological functions that are keyed to celestial patterns. Bright lights on tall buildings or reflecting off low clouds can confuse migratory birds. The British Trust for Ornithology estimates that at any given hour on any given night, 10,000 English robins are serenading a false dawn. The circadian rhythms of some plants can change under 24 hours of bright light, as when deciduous trees near streetlights retain their leaves too late in the year.
There is also the waste of energy involved in lighting the night sky. The International Dark-Sky Association, organized in 1988 to find and publicize solutions to the problem of light pollution, estimates that the light shining above the horizontal plane--some one-third of the total nighttime illumination--costs more than $1 billion annually in the United States alone. Most of that electricity is still being generated by coal-fired power plants, the source of massive environmental destruction in the form of acid rain, smog, mining damage, and greenhouse gas emissions.
As with most energy waste, there is a cost-effective path back to sanity. Even on Manhattan Island, with its Great White Way and towering office buildings, streetlights are, collectively, the brightest source of wasted light. And streetlights are easily fixed. Municipalities can save themselves substantial amounts of money just by calling a halt to their efforts to illuminate the universe--which does a good job of that on its own.
One of the most common streetlights in use today, the cobra-head fixture, draws 150 watts. A fixture with reflective backing and full-cut-off shielding will illuminate streets and homes just as thoroughly and draw only 100 watts. The same principle applies to the 175-watt, unshielded mercury vapor lamp that has been widely peddled in suburbs and rural areas as a safety measure: A 50-watt metal halide lamp with a reflective shield does the job even better. Because they cut down on glare, shielded fixtures are safer for driving, and they actually make it easier for pedestrians and homeowners to see their surroundings.
Fixtures like these are now recommended by the Illuminating Engineering Society of North America and are widely available on the market. And they are coming increasingly into use as municipalities begin to pass light-pollution ordinances. The city of San Diego has saved over $3 million annually because of its light-pollution ordinance; if Connecticut passes the law it is now considering, it is likely to save $10 million every year.
In Sanibel Island, Florida, one of the strictest outdoor-lighting ordinances in the world has restored night to the city. Even though--or perhaps because--it is a vacation community in southwestern Florida, where tremendous development pressure is eating up the remaining natural landscape, Sanibel Island has a highly developed environmental awareness. By night, this city of 9,000 is remarkably dark. No streetlights shine along Periwinkle Way, the main business artery that runs down the center of the crescent-shaped island, or on any of the side streets leading to the shores. An occasional light shines here and there, usually from a house or yard.
The sky over Sanibel is almost as dark as that over the large mountaintop observatories in the Southwest. To visitors unaccustomed to the dark, the effect is first startling, and then a pleasure. Few communities are likely to be able to reduce outdoor lighting to the same degree as a small, prosperous town on an island. But those that do, even those that make a start, will rediscover Byron's 'night / Of cloudless climes and starry skies.'
Excerpted with permission from The Amicus Journal (Winter 1996), a quarterly publication of the Natural Resources Defense Council. Subscriptions: Nonmembers $10/yr. (4 issues) from Natural Resources Defense Council, 40 W. 20th St., New York, NY 10011