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How an effort to reduce fossil fuel use led to another environmental problem: Light pollution

Sumeet Kulkarni, Los Angeles Times on

Published in News & Features

The light produced by incandescent bulbs had warmer amber or yellow colors, "more in tune with firelight, the only light aside from starlight we knew," said Robert Meadows, a scientist with the Natural Sounds and Night Skies Division of the National Park Service. LEDs, in contrast, give off cooler bluish-white tones that exacerbate light pollution for the same reason that the sky is blue.

Sunlight contains the full spectrum of colors, and air molecules happen to be the right size to scatter the shorter blue wavelengths more effectively than any other. This causes blue light to spread more readily in the atmosphere, giving the daytime sky its familiar color.

After the sun goes down, the same thing happens with LED light that spills wastefully into the sky: It gets diffused to a greater extent and increases "sky glow," the combined radiance of city lights.

Travis Longcore, an urban ecologist at UCLA, estimates that artificial lighting causes the night sky in Los Angeles to shine 1 1/2 times brighter than a night lit by a full moon. All creatures are affected by the brighter nightscapes, especially those who cannot close the blinds for a sound sleep.

"There are many, many species who don't go out and forage during the full moon because it's too bright and they know they're going to be vulnerable to predators," he said.

According to the National Audubon Society, 80% of North American migratory bird species fly at night, and they're confounded by city lights.


Even species that stay put are forced to relocate their homes. A recent study led by Longcore found that Western snowy plovers, a threatened species of shorebird, look for safe roost sites in darker areas of Santa Monica Bay when mostly empty parking lots are illuminated with floodlights all night long.

The survival of wild species depends on the variabilities of the natural world — day and night, seasons, the lunar cycle. Take them away, Longcore said, and you inevitably start alienating species from their natural habitats.

Snakes, for example, are most active and hunt prey during new moon nights. The disappearance of the California glossy snake and the long-nosed snake from Orange County has been attributed largely to the increase in ambient light.

Humans, too, are vulnerable to light pollution. Artificial light blocks the production of melatonin, a hormone that regulates sleep cycles, and disrupted sleep cycles have been linked to an array of health problems. The American Medical Association warned in 2016 that high-intensity, blue-rich LED lights were "associated with reduced sleep times, dissatisfaction with sleep quality, excessive sleepiness, impaired daytime functioning, and obesity."


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