85 Light Pollution-Mid

Light Pollution FOCUS Question What causes light pollution, and how can people reduce its effects?

Bright City Lights Vincent van Gogh was famous for his night paintings. The painting Starry Night Over the Rhone shows bright stars above the waters of the Rhone River in Arles, France. Van Gogh painted this masterpiece in 1888, but he likely could not have done so today. Most of those stars would have been dim or invisible to him because of light pollution. The glow of illuminated signs, streetlights, stadium floodlights, and other lights have created a veil of light between Earth and space that blocks our view of the stars.

Since the discovery of fire, people have turned to light for safety. Darkness hid danger from wild animals as well as human rivals. Ancient cities used streetlamps made from torches for security and navigation. In 1417, London illuminated its streets with lanterns. By the early 1800s, major roads in cities from Baltimore to Paris were lit by gas streetlamps. The widespread availability of electricity presented an even better option to light up the night. Electric lamps spread light across wide areas. Police and the general population saw light as a great tool to reduce crime and travel-related accidents. It was also good for businesses. Shops no longer had to shut at dusk; they could continue to serve customers after dark.

Unfortunate Effects Along with these positive effects, however, came some negative consequences. Lights require energy. The longer lights are on, the more energy needs to be produced. Power plants that burn coal to generate electricity run longer, pumping more smoke into the air. Outdoor lighting also affects the atmosphere in another way. Many light fixtures send wide arcs of light up into the sky. When many such lights shine simultaneously in an area, they create skyglow, a widespread hazy illumination of the night sky. Astronomers were the first to notice this effect. Light from cities made it difficult to locate and track objects in space, even with their powerful telescopes. Word Wise The term light trespass refers to light that falls where it is not wanted, intended, or needed.

Animal Activity Not being able to see the stars poses problems for animals, too. Migratory birds use the stars to guide their seasonal travels to and from nesting and feeding grounds. Bright lights, especially those on high hillsides, cause birds to become disoriented, making them fly until exhausted or crash into lit buildings. Outdoor lighting seems to make nocturnal animals— those that are awake at night— believe it is still daytime. Prey animals such as mice use darkness as a cover. When the Moon is full, they reduce their feeding activity to stay safe from predators. Artificial lighting confuses the animals. They stay hidden more often, which leads them to forage less and get less food. Predators such as owls that rely on mice as a food source have less to eat as well because they can't find the mice.

Skyglow can also affect animals in other ways. Male frogs and toads sound their mating calls after dark. If true dark comes later or not at all, mating doesn't occur, which reduces the population. Insects such as moths and beetles are drawn to white light, which mimics sunlight and moonlight. Many die from exhaustion as they flit about exterior lights. Even sea creatures are affected. Sea turtles hatch from eggs in the sand and then head toward the ocean The turtles locate the ocean. by looking for light reflecting off the water's surface. Artificial lights shining on shoreline buildings often confuse the hatchlings and send them scurrying in the wrong direction.