The ability to see a clear sky in daylight has been part of the
American environmental ethic since at least 1977, when the Clean
Air Act Amendments established visibility in U.S. parks and
wilderness areas as an environmental goal of national priority. But
the night sky has had no such protection. The post-World War II
growth of the U.S. population and mushrooming development in the
countryside have brought with them an unchecked surge of light
pollution. The sky above a typical suburban neighborhood is now
about five to ten times as bright as the natural night sky; over
city centers, it may be as much as 25 to 50 times as bright as its
natural level.
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
