Published online 7 July 2010 | Nature | doi:10.1038/news.2010.339

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In search of dark nights

Astronomers and conservationists team up against bright lights.

starry nightNights dark enough for star-gazing are important not just for astronomy, but for the health of many species.CORBIS

Artificial light at night can disrupt everything from astronomers' views of the stars to the path-finding abilities of migrating animals. The impacts of artificial light on wildlife was the focus of a symposium at the 24th annual International Congress for Conservation Biology, held 3–7 July in Edmonton, Alberta.

Unusually, the symposium was funded by a group of Edmonton astronomers - the Royal Astronomical Society of Canada Edmonton Centre, which includes both professionals and amateurs. The society also invited the speakers to planet-gaze at their observatory and chat about their common problem, light pollution.

The symposium was the latest manifestation of a growing collaboration between astronomers and conservationists, aimed at extinguishing unnecessary night lighting. Astronomers want to see the night sky better, whereas conservationists want to spare wildlife the disorienting effects of a sky illuminated at all hours of the day and night.

Lights at night have long been known to confuse migrating birds, which are drawn mothlike to the beams. Some crash into brilliantly lit skyscrapers, lighthouses or offshore oilrigs. Many others are lured off course by the glow of cities on the horizon.

Sea-turtle hatchlings, too, are dazzled by bright light. Normally, they move away from the dark shadows of dune vegetation and towards moonlight or starlight reflected on the sea. In the presence of bright artificial light, they end up wandering in the wrong direction on the beach.

Rhythmic disruption

Researchers presenting their work at Edmonton added further examples of species affected by brightness in various ways. Some, like the turtles and migrating birds, become visually bewildered, whereas others, such as voles, can have their circadian or seasonal rhythms disrupted by artificially lengthened days, leading to rising levels of stress hormones.

Speakers also showed evidence that frogs and snail larvae grow at different rates under natural and artificial light. Beach mice on bright shorelines may have to restrict the areas in which they forage, to avoid predators. Salamanders, too, are reluctant to leave their hideaways at night under the glare of artificial light, and certain bats won't fly in bright areas, which limits and lengthens their commutes to food.

Not all lights have the same effects. Astronomers and conservationists are looking closely at the increasing popularity of LED lights, for instance. LEDs are more energy efficient than many alternatives, which carries environmental benefits. But LEDs that include light from all wavelengths are also closer to sunlight than traditional bulbs and are therefore more disruptive to many species.

Permanent full moon

"You talk about global change — one of the most visible changes in the last 100 years is night lighting," says Travis Longcore, science director of the Urban Wildlands Group, based in Los Angeles, California, and organizer of the Edmonton light symposium. "We've turned major swathes of the globe into permanent full moon, or more."

Longcore works with the International Dark-Sky Association, based in Tucson, Arizona, to encourage dark-sky preserving policies in cities, parks and elsewhere. The association was founded by two Arizona astronomers, says spokeswoman Johanna Duffek, and initially attracted only astronomers as members. In the last decade, however, it has also embraced the conservation agenda.

"It helped our cause," she says. "[Before] we had people saying, 'I am not an astronomer, so what do I care if you can't see the stars?'"

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Duffek stresses the energy savings of smarter lighting, and says that lower levels of light in urban areas can actually be safer. "By shielding the light you are eliminating horizontal glare detrimental to pedestrians and cars." The bonus, she adds, "is that you can actually see the night sky".

The Starlight Initiative, based in La Palma in the Canary Islands, mentions the effects of night light on wildlife in its 2007 Declaration in Defence of the Night Sky and the Right to Starlight, which asserts that "an unpolluted night sky that allows the enjoyment and contemplation of the firmament should be considered an inalienable right of humankind equivalent to all other environmental, social, and cultural rights, due to its impact on the development of all peoples and on the conservation of biodiversity".

Longcore himself, living in lit-up Los Angeles, has to wait for special events like the observatory party to get a good look at the heavens. But like people all over the world, he once spent hours gazing at the night sky in wonder.

"I grew up in Maine," he says. "We had the northern lights. I could go outside in the backyard and lie in the grass and have that universal human experience." 

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