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When my grandfather worked as a lighting engineer at General Electric’s Nela Park laboratory in Cleveland, who would have known that his development of outdoor street lights would lead to a worldwide environmental problem today. At night our planet is now bathed in artificial light, ranging from street lights and floodlights to burning gas flares in oil fields. There are few places that are truly dark at night. (See http://blogs.nicholas.duke.edu/sea-bird/star-light-star-bright/).
One look at a satellite picture of the Korean peninsula will show that night lights follow economic development. South Korea is one of the brightest places on Earth, whereas North Korea is bathed in darkness. Culturally, we insist on lighting for safer driving, fewer crimes, and night-time advertising. With the advent of LED lights, nights are certain to get even brighter.
Unfortunately, most of the rest of nature doesn’t share our illuminophilia.
In the early 1970s, I noted that the oak trees at Cornell University retained their leaves well into winter, but only on branches near streetlights on the campus. Apparently the onset of shorter days in autumn determines leaf-fall in some species. Later when I enrolled in a class in plant physiology, I learned that flashes of light during the night can induce flowering in plants that bloom in the spring and delay flowering in plants that bloom in the fall. Most organisms have evolved in an environment in which we expect sunlight during the day, and (at best) a little moonlight at night. Interrupt that pattern, and changes in their behavior will follow.
Numerous studies show that street lighting has negative impacts on the orientation of migrating birds, moths, and nesting sea turtles. Night lighting alters predator-prey relationships, and the behavior of predators. Some studies suggest an increased risk of cancer in humans in response to night-time lighting. As the sprawl of human habitation and the density of roads increase on the landscape, we find less and less natural habitat that is not subjected to some level of artificial night light.
There are actions that we can take. One study in Michigan showed that night-time bird mortality at lighted communication towers could be reduced 50 to 71% by removing non-flashing red lights. Lights to deter crime can be coupled to motion sensors, so they only turn on when nearby activity triggers them. Lights in office buildings can be turned off after night-time cleaning, saving money in the process.
For a better environment, douse the glimmer.
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