Long before "light pollution" entered the lexicon, Carlos Lastreto worried about it.
The California ornithologist had heard rumors that migrating birds were dying around lighthouses. In 1917, he and colleagues from the Audubon Association of the Pacific wrote to federal lighthouse keepers, asked them to keep track of the deaths of night-migrating bird at the 37 lighthouses along the coast, then tallied the results.
The survey largely absolved the lighthouses. But after 85 years of population growth and urban sprawl in the United States as well as more rigorous studies about the biological effects of light scientists across the country are becoming increasingly concerned about the effect that inefficient use of artificial lights may be having having on plants and creatures great and small.
In the process, they are adding a slowly growing set of voices to an issue already of considerable interest to professional and amateur astronomers, states and cities that want to cut energy bills, and just about anyone who heads out into the backyard on a clear night to find the stars or watch an aurora, only to find them shrouded by the sky glow.
"We're in jeopardy of losing the whole night sky this century," warns Dan Green, an astronomer at the Smithsonian Astrophysical Observatory in Cambridge, Mass.
At issue is the widespread use of increasingly efficient but powerful outdoor lights along highways, at malls, in housing developments, and even in rural areas that shine out and up, as well as down, often spreading the light where it isn't needed. Wasted outdoor lighting adds roughly $1 billion a year to the nation's energy bill, according to the International Dark-Sky Association in Tucson, Ariz.
For homes and small businesses, lighting research has spawned halogen and metal-halide lights that pack a more-luminous punch in a smaller package than their incandescent ancestors, and they are cheaper to run, Mr. Green explains. So more people install them. During the past decade, he continues, homebuilders have put finishing touches on new construction by hanging large, clear-lensed coach lights by the front door or mounting them on posts at the ends of a driveway, while unshielded floodlights bathe garage entrances and back decks with more light than they need.
Meanwhile, many cities and towns line their streets with unshielded lights, often with little background knowledge of how the light will behave in combination with the lighting already present.
"Many communities don't even know how many streetlights they have," he adds. "Police say we need a light at this intersection, and the town puts one in" without examining whether lighting levels already are adequate.
In the 1950s and '60s, astronomers began to press for city ordinances to curb light pollution that was affecting major telescope facilities, such as the Kitt Peak Observatories south of Tucson. Sky glow not only was brightening the dark skies that drew astronomers to the area initially. The light also was difficult to filter.
But in the 1970s, as research into light's effect on organisms' "biological clocks" and nocturnal behavior patterns, more biologists took closer note of artificial lighting's effect on a range of organisms, according to Melissa Grigione, an environmental science professor at the University of South Florida in Tampa.
During the past 25 years, she says, much of this work has focused on small amphibians, reptiles, and birds.
Captivated by light from skyscrapers and radio towers, for example, night-migrating birds were found to orbit them until they dropped out of the sky from exhaustion or after colliding with other birds in the migration flock or with structures. Since 1993, skyscrapers in Toronto alone have claimed 15,000 birds, including threatened and endangered species, according to the Fatal Light Awareness Program in Toronto.
In Florida, "it was shown early that sea turtles were really affected by light in an area," Dr. Grigione adds. Beaches along the state's Atlantic coast are breeding grounds for Western Atlantic loggerhead, leatherback, and green turtles. Researchers found that lights from roads and a lengthening necklace of condos and hotels along the beaches discouraged female turtles from laying eggs. If they did lay eggs, hatchlings would leave their shells and head toward the lights instead of the ocean, only to become roadkill or meals for terrestrial predators.
Now, she says, researchers are gaining the tools to examine light pollution's effect on less visible organisms.
To see what effect artificial light may have on lakes and ponds in urban areas, two researchers at Wellesley College in Wellesley, Mass., have developed techniques to measure the intensity and spectra of artificial light as it changes with depth. After looking at five New England lakes in a range of urban and suburban settings, Marianne Moore and Susan Kohler calculated that aquatic organisms can detect artificial light to a depth of roughly three meters (about 9 feet) and found that it could have a marked effect on their night maneuvers.
Small invertebrates that ordinarily rise to feed on surface algae at night become less active grazers in the presence of increasing amounts of light. As light-pollution levels rise, the results suggest that some of the region's ponds and lakes could experience more algae blooms and lower water quality.
Some worry that excessive lighting could undercut conservation efforts in states such as California, where ecologists have tried to ensure that corridors of land link habitats isolated by suburban development. The corridors allow groups of endangered or threatened species to follow their normal migration patterns or find new breeding partners.
Studies in California about the effect of artificial light on mountain lions, who tend to avoid bright lights, suggest that light pollution "could have a severe impact on the corridors" by discouraging the movement of animals that travel under the cover of darkness, says Travis Longcore, scientific director for the Urban Wildlands Group, an environmental organization in Los Angeles.
As the constituency for more conservation-minded lighting has grown, so have the number of states, counties, and towns that have built provisions into building codes requiring the use of shielded lights. So far, nine states have adopted so-called "dark sky" provisions, which are under consideration in 11 more.
IN California, where the state's energy crisis sparked a range of conservation measures, the state energy commission is getting public comment on proposed outdoor-lighting standards required by a statute enacted last year. Under the proposal, standards for commercial as well as government lighting would apply to new buildings and to projects that require more than half of a structure's outdoor lighting to be replaced.
"This really is an extension of the experience we gained from code changes for indoor lighting," says Mazi Shirakh, senior mechanical engineer with the Energy Commission. He adds that 40 percent of the estimated 4,000 megawatts the state has saved through conservation regulations since 1988 has come through changes in indoor-lighting codes.
The Smithsonian's Green, who has been active in trying to get similar legislation through the Massachusetts legislature, notes that once code changes appear at the state level, "they tend to cascade through the whole state." Moreover, the economic clout of states such as California provides a big incentive for lighting manufacturers to develop the fixtures to meet the requirements.
Emphasizing that groups such as his are not out to ban outdoor lighting, Green adds, "all we're asking is that lights be shielded and the output be reduced" to levels sufficient to do the job.
"Night is a place of its own," adds Catherine Rich, executive director of the Urban Wildlands Group. "We need to plan for the night."