City Lights Are Obscuring Our Starry Nights SCIENCE JOURNAL by Robert Lee Hotz
Palomar Mountain, Calif. VIDEO: http://link.brightcove.com/services/link/bcpid452319854/bctid1690279119 Around the world, the night sky is vanishing in a fog of artificial light, which a coalition of naturalists, astronomers and medical researchers consider one of the fastest growing forms of pollution, with consequences for wildlife, people's health -- and the human spirit.
About two-thirds of the world's population, including almost everyone in the continental U.S. and Europe, no longer see a starry sky where they live. For much of the world, it never even gets dark enough for human eyes to adjust to night vision, reported an international team that mapped the geography of night lighting.
"Our children grow without seeing what is possibly the most extraordinary natural wonder," says Italian astronomer Fabio Falchi, one of several U.S. and Italian researchers who used military satellite images to compile the first comprehensive global atlas of night-sky brightness -- a 2001 orbital survey published in the Monthly Notices of the Royal Astronomical Society.
A natural nightscape has become as rare as an unspoiled wilderness. In Borrego Springs, Calif., a small town surrounded by 600,000 acres of desert in California's largest state park, the midnight sky is a tourist attraction. On a clear night, the curtain of stars almost seems to brush the ground.
Astronomers have long lobbied for local lighting reforms so they can continue to study the universe through wavelengths of the night sky. "We convert that starlight into knowledge," says Dan McKenna, superintendent of the Palomar Observatory here in the mountains 60 miles northeast of San Diego.
The International Dark Sky Association [http://www.darksky.org], founded by astronomers 20 years ago to promote sky-friendly lighting, has recruited 12,000 members in 75 countries. "We are about good lighting, not no lighting," says IDA technical adviser Peter Strasser. IDA experts are meeting Friday with congressional aides in Washington, D.C., to air their concerns.
But this light brigade is hard-pressed to keep pace with population growth, urban development and the changing technology of lighting. In the brightly lit cities that half of humanity now calls home, a half dozen stars may be visible on a clear night. In the darkest rural areas, about 2,000 stars typically may be visible -- half the number seen in centuries past.
"Wherever you look there is a glow, even on the darkest night," says Karl Dunscombe, who controls the Palomar observatory's 200-inch Hale telescope.
Even in Death Valley, one of America's most unspoiled parks, the night sky glows with urban light. Only the moon outshines the neon halo of Las Vegas, 120 miles away, Chad Moore, U.S. National Park Service night-sky manager, reported last year in Publications of the Astronomical Society of the Pacific. After taking night-sky readings at 45 national parks, he found that the glare of city lights 200 miles away could visibly alter a park's night lightscape.
All told, the amount of artificial light world-wide -- as measured in lumens per capita -- has tripled since 1970, the Italian researchers calculated. "Almost all the populated areas of the planet are polluted" by light, Dr. Falchi says.
Many of us may find it hard to regard light as a form of pollution or darkness as an endangered natural resource, like clean air and water. But lighting the night on such a broad scale may be hazardous to human health, new research suggests.
Last month, Harvard Medical School epidemiologist Eva Schernhammer and her colleagues reported that nurses who regularly worked the night shift had a higher incidence of colorectal cancer than women who only worked daylight hours. Writing in the Journal of the National Cancer Institute, Dr. Schernhammer concluded that working a night shift in rotation at least three nights a month for 15 years or more may increase a woman's risk of colorectal cancer.
In January, Itai Kloog at Haifa University in Israel and researchers at the University of Connecticut reported in Chronobiology International that the incidence of breast cancer among women living in brightly lit neighborhoods was as much as 73% higher than among women in areas where night-time darkness was the norm. Lights at Night Are Linked to Breast Cancer Study Bolsters Theory About Interference With Production of Key Hormone http://www.washingtonpost.com/wp-dyn/content/article/2008/02/19/AR2008021902398.html
Many researchers believe exposure to artificial light disrupts our nighttime production of the hormone melatonin that, among other things, suppresses tumor development. Even two weeks of intermittent nightly light exposure can seriously curtail melatonin production, studies show.
Such research isn't sufficient proof that darkness keeps us healthy. The findings are persuasive enough, however, that the International Agency for Research on Cancer at the World Health Organization last December added the night shift to its formal list of probable human carcinogens.
Whatever their effect on people, night lights are the bane of wildlife, says Travis Longcore, science director of the Urban Wildlands Group in Los Angeles and co-editor of "The Ecological Consequences of Artificial Night Lighting." [http://www.urbanwildlands.org/ecanlbook.html] Bright night lights affect hundreds of species, from sea turtles to birds, whose breeding cycles and migratory patterns are disrupted by the false clues of artificial light. Millions of birds every year are killed, disoriented by outdoor lights.
Despite such concerns, we still lack reliable, systematic data about light pollution.
Not until 2001 did Dr. Falchi and his colleagues first catalog global patterns of artificial light. They are working this summer at the U.S. National Geophysical Data Center in Boulder, Colo., to update their world survey. This November, Dr. McKenna at the Palomar Observatory expects to begin field testing an automated sky-brightness monitor that can report light conditions reliably every minute. One day, it could form the basis for a global network of wireless sky sensors.
In lieu of new technology, however, researchers rely on the naked eye. In April, the National Optical Astronomy Observatory in Tucson asked people around the world to look up and report the brightness of the constellation Orion in their night sky. They collected more than 6,800 reports from 62 countries for the Globe at Night Project. Researchers are analyzing the data.
To preserve their natural lightscape, residents of Borrego Springs are making sure the town's 25 street lights are properly shielded, so that light doesn't spill into the sky, and urging neighbors to adopt more efficient, low-wattage lights.
By reforming lighting practices, they hope to become the second Dark Sky Community designated by the International Dark Sky Association [http://www.darksky.org] later this year (after Flagstaff, Ariz.).
"It's a real canopy over the desert," said Betsy Knaak, executive director, Anza-Borrego Desert Natural History Association. "That's not something you can expect everywhere any more -- to look up and see the stars." ________________________________________ RECOMMENDED READING
As night lighting becomes more pervasive world-wide, the International Dark Sky Association [http://www.darksky.org] is promoting sky-friendly lighting practices and local lighting ordinances that favor more efficient, low-wattage lighting.