A two decades ago, there was little scientific interest in the effects of artificial lighting on the wild. Scientist who noticed the phenomenon of night glow were mostly astronomers that complained about lights interfering with their observations of the night sky. If you live in an urban zone, you may not remember the last time you saw the Milky Way arched across heavens. Seeing the stars in a truly dark sky such as in the Australian Outback is a revelation of the non-biblical kind. The effect of artificial night lights in now receiving increased study, and the news for animals and plants is not good.
Much of the planet's surface is lit at night and the surface area affected is growing at about 6% a year. Studies show that artificial lighting at night disrupts natural behavior of animals and insects. From migrating birds thrown off course and turtle hatchlings diverted from the sea to insects uselessly fluttering around a llight bulb until they drop dead from exhaustion human's penchant for lighting up the night is posing an increasingly serious threat to biodiversity. A third of bee and butterfly species are in decline, beset by disease, toxic pesticides and climate change.
Plants are also affected by night lights. Much pollination goes on at night by bats, moths, beetles and other insects; almost nothing was known about night pollination until a Swiss researcher, Eva Knop, began studying the affect of artificial lighting on night pollination. Insects account for 88% of plant pollination and 39% of crop pollination worth an estimated $361 billion in the US, so its an important question to answer. Ms Knop and her colleagues installed artificial illumination over half of the fourteen Swiss meadows in her study. For two consecutive summers when the meadows were in bloom they walked the fields at night collecting any pollinating insects they could find. The study, published in Nature, provided the first clear evidence that artificial lighting deters pollinating insects, thus harming the plants that depend on them to reproduce. One plant, cabbage thistle, which is usually heavily visited by nocturnal pollinators produced 13% less fruit in lighted fields compared to dark ones in the study. Fortunately cabbage thistles are visted by day time pollinators and can self pollinate too, but the these paths are not enough to make up for decreased night pollination by animals and lead to less genetic
diversity.
It unlikely humans will give up their need for night illumination, but it can be used more sensitively. Use of motion detectors for some optional lighting will illuminate walls of light that repeal some insects such as moths. Spacing street lights farther apart will also help, as would using longer wave length lighting. LEDs are replacing other street lighting because of their efficiency, but the blue wavelengths emitted are particularly attractive to insects. Changing the lights color will do less harm.