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Most environmental pollution comes from humans and their inventions. The electric bulbs are thought to be one of the greatest human inventions of all time. However, too much of a good thing has started to negatively impact the environment. Light pollution, the extreme or inappropriate use of outdoor artificial light, is affecting human health and wildlife behavior. There is a global movement to reduce light pollution, and everyone can help.

Light pollution is a global issue. This became particularly obvious when the World Atlas (地图册) of Night Sky Brightness, a computer-generated map based on thousands of satellite photos, was published in 2016. Vast areas of North America, Europe, the Middle East, and Asia are glowing with light, while only Siberia, the Sahara, and the Amazon are in total darkness.

Artificial light can wreak havoc on natural body rhythms in both humans and animals. It interrupts sleep and confuses the circadian rhythm (生理节奏) — the internal, twenty-four-hour clock that guides day and night activities and affects physiological processes in nearly all living organisms. One of these processes is the production of the hormone melatonin (褪黑素), which is released when it is dark and is prevented when there is light. An increased amount of light at night lowers melatonin production, which results in lack of sleep, headaches, stress, anxiety, and other health problems. Blue light, in particular, has been shown to reduce levels of melatonin in humans. It is found in cell phones and other computer devices, as well as in light-emitting diodes (LEDs), the kinds of bulbs that have become popular at home and in industrial and city lighting due to their low cost and energy efficiency.

Studies show that light pollution is also impacting animal behaviors, such as migration (迁徙) patterns and habitat formation. Because of light pollution, sea turtles guided by moonlight during migration get confused, lose their way, and often die. Large numbers of insects, a primary food source for birds and other animals, are drawn to artificial light and are instantly killed upon contact with light sources. Even animals living under the deep sea may be affected by underwater artificial lighting. One study looked at how animals in sea responded to brightly lit panels put under water off the coast of Wales. Fewer filter feeding animals (滤食性动物), such as the sea squirt (海鞘), made their homes near the lighted panels. This could mean that the artificial light is altering ocean ecosystems.

The good news is that light pollution, unlike many other forms of pollution, is reversible (可逆的) and each one of us can make a difference! Now, many people are taking action to reduce light pollution and bring back the natural night sky. Individuals are urged to use outdoor lighting only when and where it is needed, to make sure outdoor lights are properly shielded (遮挡) and direct light down instead of up into the sky, and to close window blinds, shades, and curtains at night to keep light inside.