Q. I have heard that light pollution causes migrating birds to become disoriented. Will the fairy lights (small solar lamps) that people put out alongside sidewalks affect any animals?

A. The simple answer is, yes: Any artificial change we make to a natural situation is likely to affect some animals and plants. Certain nocturnal beetles and moths living in the immediate vicinity may have their lives disrupted. But small lights in a suburban area are relatively benign compared to some of the other lighting problems around the world.

Many small birds migrate at night, and some use the stars to navigate. Not a good plan when flying over Charlotte, Miami or Atlanta. Seasonal timing and spatial positioning of lighting can make a difference in some situations. Nesting sea turtles may become confused when approaching brightly lighted housing on a beach. A few weeks later hatchling sea turtles trying to make their way to the ocean at night head the wrong way because they are following lights inland. High, unnecessarily bright streetlamps cause orientation problems for moths and other night-flying insects. Small porch lights may attract a few nocturnal visitors but create far less overall light pollution than other efforts to light up the night sky. Our infatuation with bright lights robs us of the wonder that comes from millions of animals that depend on total darkness, except for the moon and stars, as part of their life cycle. Nocturnal biodiversity is much higher than most people are aware.

Many Americans who live in brightly lit urban areas may not know of nearby wild areas that remain dark at night. Sadly, they have not seen stars for years. I recall a poignant scene in Miami the night after a power outage from a hurricane had ended. I left a restaurant behind a family with a little boy who said, “Daddy, make the sky light up like you did the other night.” It was probably a while before he saw another star.

But like any environmental issue, more than one perspective exists. Not everyone agrees on what constitutes a problem, much less an effective solution. One issue that often arises involves outdoor lights to reduce crime. According to the International Dark-Sky Association, a nonprofit organization that promotes public education on night sky conservation, “There is no clear scientific evidence that increased outdoor lighting deters crimes.” Much of our outdoor lighting that affects wildlife is not necessary. For example, most rural and suburban areas would be safe enough without bright streetlamps or yard lights. What is the attraction of a 50‑foot‑high glaring mercury lamp in the backyard of an otherwise serene countryside? A motion-sensor light would be far more effective.

Some recommendations for outdoor illumination include lighting up only the area of interest and not burning lights more brightly than necessary. Keeping lights on only when in use is readily accomplished in many situations. Such approaches are not only better environmentally but also economically. A further recommendation is to shield lights and point them downward. Nocturnal birds that migrate in spring and autumn surely get no benefit from—and may even become disoriented by—unnatural lights pointing up at them. Consider any outdoor lighting in the context of what impact it may have on natural phenomena, in the sky as well as on the earth.

The loss of the night sky is also of increasing concern to astronomers. Anyone observing Orion or Scorpio and their starry entourage from a dark desert, beach, wildlife refuge or even an unlighted neighborhood is aware of how outdoor lights rob us of spectacular nighttime skies. Many of the nation’s large observatories are already threatened by night‑sky illumination associated with urban development. The saying “it is better to light one candle than to curse the darkness” is excellent advice. But the idea of eliminating the darkness with perpetual artificial daylight is absurd. Let’s use outdoor lighting sparingly.

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