Light pollution's effects #1:
Energy Waste
No doubt you've seen pictures taken of Earth at night from space, like the one below, or looked down on the sparking lights of a city at night from an airplane. Every light source you see directly from on high represents electricity being wasted. Any outdoor fixture that directs some of its light above horizontal is sending light not onto the ground, where it should be going, but rather directly into space.
For 20 years, the International Dark-Sky Association has argued that such poorly designed outdoor lighting wastes tremendous amounts of electricity. The IDA's most recent estimate, based on government statistics of energy use and conservative assumptions about lighting use, concludes that each year roughly $2 billion in electricity is lost to space from the United States alone.
As society has become more nocturnal, our need for nighttime illumination has increased. Along the way officials and business owners began to equate "more light" with "better safety and security" — even though objective proof of such a relationship did not (and does not) exist.
You might think that the most egregious sources of light pollution are businesses that flood their properties with light — fast-food restaurants and gas stations come to mind. Their lighting is often harsh, obtrusive, and wasteful, all in the guise of customer convenience, safety, and security. Some McDonald's franchises have even tried to attract customers with searchlights so powerful that they created problems for aircraft in their vicinity.
Yet a far more serious problem is municipal streetlighting, which accounts for roughly one third of all light pollution in the United States. Many cities and towns are upgrading their streetlights these days -- though not always for the better. (See "Streetlight Basics" for more information.)