In “Degraded Darkness”, Ben Harder, the general manager of health and science for U.S. News & World Report, says: “It’s tempting to assume that artificial light distresses only a few exquisitely sensitive species. But mounting evidence suggests that disappearing darkness undermines our best conservation efforts.”
More and more ecological and health issues are being identified that are caused by artificial light at night. Almost every living thing on this earth has functions dependent on living in an environment with a pattern of light and darkness. Dusk causes the beginning of a chemical process that each living things health and existence is dependent upon. That process would normally create a spike in the amount of melatonin between midnight and 4 AM. Very small amounts of light can suppress the production of melatonin enough to affect a plant or animal’s normal chemical balance and activities. Even nocturnal animals have a normal melatonin spike in the early morning hours that artificial light will suppress. Although the way they produce melatonin differs, all plants and animals are dependent on a day-night cycle that should not be disrupted by artificial light at night.
Research shows additional significant negative effects of artificial light during the hours of natural darkness on many animals. Nocturnal frogs suddenly exposed to artificial light stop all activity and sit motionless even hours after the light has been turned off. Birds are drawn to artificially lighted towers and skyscrapers where hundreds of thousands of them die each year from collisions or exhaustion. Their vision and internal magnetic compasses seem to become dysfunctional in the artificial light. Artificial lights lead baby sea turtles off course and many die before they can get to the ocean. Salamanders and dung beetles lose their ability to navigate. Artificial light interferes with fireflies, which generate light for sexual communication.
Plants have a wide range of photoreceptors that perceive and respond to light signals. Night blooming plants fail to bloom disrupting the insects that use them as food. The list goes on and on. Almost all living organisms have a dependence on a circadian rhythm. Daily cycles of light and darkness and the number of hours of each trigger key occurrences in their lives.
To summarize, the consequences of artificial light at night for the natural world include general disruptions in daily and yearly activity cycles, habitat, and navigation. Additional effects are seen with changes in competition and predation, as well as reductions in dispersal, foraging, and reproductive opportunities.
We know what habitat destruction by bulldozer looks like. We don’t begin to know all the alterations and disruptions that are caused by our modern habit of profusely using artificial light at night.