When most people think of pollution, they think of the visible effects: smog, the rainbow sheen of gasoline on water, and billowing exhaust pipes. Most people do not stop to think very much about light pollution. In most cities, though, it is simply a matter of going outside and looking up at night. You likely won’t see many stars, and are far more likely to be looking at a street light, throwing its glow both down into the street and up into the sky.
People are not well-adapted for darkness. We’re very visual, requiring the bright light of the daytime to operate effectively. To compensate for this lack, we’ve engineered the night to make it more suitable for us. We’ve filled it with light.
At first, it was really only astronomers who complained that much about the skies filled with light. However, there was never much research done into how all this light affects humans, and the world around us.
Lately, however, scientists have started to study the effects of light pollution. It is largely the result of bad lighting design, which allows artificial light to shine outward and upward into the sky, where it’s not wanted, instead of focusing it downward, where it is. Ill-designed lighting washes out the darkness of night and radically alters the light levels, and along with that, light rhythm to which many forms of life have adapted, including us. Wherever human-generated light spills into the larger world, some aspect of life is affected, whether that is migration, reproduction, or feeding, or even something that we aren’t even aware of yet.
We’ve treated this vast expanse of night sky as if it was unoccupied space, with no consequences to our actions. Nothing could be further from the truth. Just in the mammals alone, the number of nocturnal species is amazing. Light is a powerful biological force, and on many species it acts as a magnet. The effect is so strong that scientists speak of songbirds and seabirds being “captured” by searchlights on land or by the light from gas flares on marine oil platforms, circling and circling in the thousands until they drop. When migrating at night, birds tend to collide with brightly-lit tall buildings.
Everyone has seen moths and other insects gathering around streetlights, yard lights, and even flashlights. Feeding at those insect clusters is now ingrained in the habits of many bat species. For others, however, perhaps more light shy, it has seen a decline in their numbers as larger proportions of insects are consumed by bats that do not shun the light. Other nocturnal mammals, such as desert rodents, fruit bats, opossums, and badgers, must forage more cautiously under the permanent full moon of light pollution as they’ve become easier targets for predators.
Some birds, like blackbirds and nightingales, among others, will sing at unnatural hours because of artificial light. Scientists have determined that long artificial days, along with artificially short nights, can induce early breeding in a wide range of birds. And because a longer day allows for longer feeding, it can also affect migration schedules. The problem is that migration, like most other aspects of bird behavior, is a precisely timed biological behavior. Leaving early may mean arriving too soon for nesting conditions to be right.
Many human activities have unintended consequences. In many cases, there just hasn’t been enough information, and no one thought to look into it. The answer could be as simple as better light design, or as unpopular as turning off some of the lights. Perhaps our night might get a bit darker, but for many species that means that they will get healthier, and safer.