For many of us, it’s hard to imagine what it was like outside at night before the introduction of artificial lights. Have you ever walked through the woods or in a meadow at night dependent solely on star and moonlight? It can be a challenge until your eyes adjust. The darkness is full of mystery and tends to amplify sound; the unknown can play tricks on us. On cloudy nights, the clouds provide insulation that makes noises seem closer than they are. Natural darkness can also instill a sense of peace and wonder. What is really out there?
Recently, the mid-December full moon was bright on the freshly fallen snow and I took some wonderful late night walks with moonlight as my only light source. The walks were brisk and invigorating. Each time I went out, I became less fearful of the night and more conscious of the health benefits: breathing that cold, clean air, getting my legs in shape for ski season, better sleep.
Celestial bodies and meteor showers are much easier to identify once your eyes have adjusted to the night sky. If you’re lucky enough to live in an area where light pollution is at a minimum, it opens up a whole new sky and landscape to explore. Sadly, a large majority of the U.S. population has already lost the ability to see the Milky Way with the naked eye due to light pollution, which is brightest on the east coast. When viewed from space, it looks like a fairly thick line of light along the coast and slightly inland from Florida to southern Maine.
Light pollution, which affects the circadian rhythm in humans, also impacts the sleep-wake cycle in nocturnal animals including bats, owls, foxes, and flying squirrels. Breeding cycles, foraging behaviors, and migratory routes of wildlife including insects, turtles, birds, fish, and reptiles have been similarly affected. Almost two thirds of migratory birds travel during the night, using moon and starlight to navigate. Light pollution interferes with their ability to stay on course and many never make it to their winter nesting grounds.
Plants are also affected by artificial light. Plants take cues from the amount of light and darkness they are exposed to each day, so prolonged exposure to light pollution prevents many shrubs and trees from adjusting to seasonal change at the right time, disrupting their flowering and fruiting cycles.
If we can live with less night light, the entire natural world (including humans) will benefit from a return to darkness after the sun goes down.