Across the country from Walden and more than 150 years after Thoreau, Travis Longcore, and Catherine Rich have created the Urban Wildlands Group in Los Angeles. Dedicated to “the conservation of species, habitats, and ecological urban and urbanizing areas,” Urban Wildlands ranks light at night high on its list of concerns.
“Back in 2002,” Longcore tells me, “if you had Googled ‘impact of light on wildlife,’ or ‘wildlife and night lighting,’ you basically got nothing except maybe birds and sea turtles.” In 2006, Longcore and Rich set about to change that by editing Ecological Consequences of Artificial Night Lighting, a collection that gathered the current research on light pollution and ecology. Along with articles on birds and sea turtles, the pair added pieces on bats, moths, fireflies, reptiles, amphibians, salamanders, fishes, and seabirds. Even so, most striking about this impressive anthology is that it remains remarkably thin—their section on “Mammals” has two papers, for example; their sections on “Fishes” and “Plants,” one each. For although, as they write, “natural patterns of darkness are as important as the light of day to the functioning of ecosystems … as a whole, professional conservationists have yet to recognize the implications.”
With at least 30 percent of all vertebrates and more than 60 percent of all invertebrates worldwide nocturnal, and with many of the rest crepuscular, those implications are enormous. While most of us are inside and asleep, outside the night world is wide awake with matings, migrations, pollinations, and feeding—in short, the basic happenings that keep world biodiversity alive. Light pollution threatens this biodiversity by forcing sudden change on habits and patterns that have evolved to depend on light in the day and darkness at night. (In just one example, circadian photoreceptors—those same ones on which we humans rely—have been present in the vertebrate retina for at least 500 million years.) Aside from crazy-looking ancient fish and their bottom‑of‑the-ocean ecosystems (and those of caves or soil), every creature on this planet has evolved in bright days and dark nights. None has had the evolutionary time to adapt to the blitzkrieg of artificial light.
Significantly, Longcore and Rich make a distinction between “astronomical light pollution” and “ecological light pollution.” They define the latter as “artificial light that alters the natural patterns of light and dark in ecosystems.” Longcore says, “We had to do that, because the idea of ‘light pollution’ is very much an astronomy/astronomer focus. You could have a dark sky-compliant light—pointed down—and still do a lot of damage.”
Light at night impacts wildlife in five primary areas: orientation, predation, competition, reproduction, and circadian rhythms. If we have heard anything about light at night and wildlife, we’ve probably heard about orientation. This is the problem of insects drawn to streetlights, of migrating birds being attracted to lit‑up city buildings or communication tower lights, or of beach-born sea turtles heading the wrong way—toward streetlights and hotel signs—and ending up crushed by truck tires or plucked easily by predators.
Introduce artificial light to a dark environment several billion years in the making and suddenly some species find themselves exposed to increased predation—and so reduce their foraging time. Introduced light means new pressures of competition between species, some of which adapt better than others. Artificial lights confuse reproduction cycles—the flashing attraction signs of fireflies, for example—or the internal circadian rhythms that synchronize the internal processes of birds, fish, insects, and plants, just as they do for humans. Beyond individual species, these light/dark rhythms also shape seasonal changes such as migration. Entire ecosystems shift as the length of light changes through spring, summer, fall, and winter. As one biologist told me, “We have levels of light hundreds and thousands of times higher than the natural lamp during the night. What would happen if we modified the day and lowered the light a hundred or a thousand times? Of course, the damage would be much worse. But it is a metric. You cannot modify half the time without consequences.”
Every day in the United States alone more than 1 million birds and animals die on the nation’s roads and highways, and because so many species are nocturnal or crepuscular, more than one-half of this carnage occurs at night. These nighttime collisions are incredibly costly to humans as well. In fact, at least statistically, deer are far more dangerous than mountain lions or bears or, certainly, wolves. Every year in the United States more than 200 people are killed in deer-vehicle collisions, the most dramatic result of the more than 1 million annual deer-vehicle collisions that cause 10,000 personal injuries and cost more than $1 billion in damages (and, of course, the deer do not fare well, either). Studies show that increasing highway lighting to reduce such collisions is ineffective, and actually makes it far more difficult for wildlife active at night, at dusk and dawn, to avoid collisions. Animal eyes that see so well in darkness or dim light—blessed with more rods than cones—are blinded by our headlights and streetlights. “On the issue of designing highway lighting to minimize road kill mortality,” writes Paul Beier in Ecological Consequences of Artificial Night Lighting, “our knowledge of mammalian vision is sufficient to conclude that, from the animal’s perspective, less is better.”
Less light on our roads, fewer streetlights and not so bright, is not only better for wildlife but safer for us—we drive slower and pay more attention when we have to rely on our headlights.
But how to do with less light on our streets and highways? One innovative concept comes from a design cooperative in San Francisco called Civil Twilight. Their award-winning idea: streetlights that respond to moonlight, or “lunar-resonant streetlights.” Relying on LEDs and highly sensitive photosensors, they would allow the level of brightness from the streetlight to balance the level of light from the moon. On nights when there is no moon, or just a crescent, the streetlights would provide enough light for pedestrians and drivers. On full-moon nights, the streetlights would dim to barely on. Civil Twilight estimates that their idea could save more than three-quarters of the money spent on streetlights, as well as bring the ambience of moonlight back to our streets.
The idea borrows from an old one. In the 18th and 19th centuries, street lighting was still intimately tied to the changes in seasonal light and the moon’s monthly phases. In Paris, even after the advent of gas lighting in the 1840s, two kinds of lanterns were used, one that burned all night, and another that was lit only when the moon in the streets didn’t offer enough light. Even into the early twentieth century, many municipalities planned their lighting schedules in relation to the moon. Long before Paris was the City of Light, it was, as every city in the world, a city of moonlight.
And to enchanting effect. In Nocturne: A Journey in Search of Moonlight, James Attlee explains, “Just as in a black-and-white photograph, the lack of colour visible by moonlight makes the architectural structure of the landscape more apparent.” Goethe saw this while touring Rome in 1787:
Nobody who has not taken one can imagine the beauty of a walk through Rome by full moon. All details are swallowed up by the huge masses of light and shadow, and only the biggest and most general outlines are visible. We have just enjoyed three clear and glorious nights. ... This is the kind of illumination by which to see the Pantheon, the Capitol, the square in front of St. Peter’s and many other large squares and streets.
It’s an effect we no longer experience today. Too often in modern cities the moon, overwhelmed by artificial lights, makes its crossing unnoticed. And so we forget the wild beauty of this natural light, or worse: We never miss it because we have never had the chance to learn.
Excerpted and adpated from The End of Night, by Paul Bogard, out now from Little, Brown.