By Nancy Anderson
Extension Master Gardener℠ Volunteer of Transylvania County and Purdue Professor Emeriti of Biology

To understand how artificial light pollution at night harms nature, consider what light does to animals and plants that rely on cues from visible light. Light helps plants locate the sky, and neighboring organisms, and respond to seasonal changes. In sunlight, animals are attracted to the colors of flowers but at night in the dark when colors are not visible, the pollinators seek shelter. They hide when no conspicuous red flowers are visible to attract birds, orange flowers are not seen by beetles, flies, or bumblebees, and when bees cannot find blue, violet or yellow flowers because it’s dark. But artificial night light can distract such pollinators from seeking shelter. Furthermore, some white flowers attract pollinators such as moths in the dark. For example, white Mayapple blossoms reflect enough dim light for Slantline Mayapple Moths to find them as a place to hide as the night sky darkens. Unfortunately, such moths are often found exposed to predators on walls near an artificial light that makes them disoriented, taking away their protective camouflage.

As seasons change, so does the light from the sun. In summer the sun’s path is higher above the horizon, the length of a day is longer, and natural sunlight is more intense than in other seasons. In winter, the sun’s path is lower and farther to the south, days are shorter, and the sun’s light intensity is weaker, so plants receive fewer hours and less intense light, and the night hours are longer. These changing conditions cue land plants to seasonal changes so that they can produce leaves at a time of year when more light is available. Right now, a “short day” is signaling deciduous plants to drop their leaves. Unfortunately, artificial night light can disorient a deciduous tree, making it fail to detect the time to drop leaves. In spring, when days get longer, a short night signals some seeds to break dormancy and start to germinate. In the presence of bright artificial light these seeds may germinate before the season is warm enough for growth, killing the seedlings.

Besides confusing plants and creatures like the Mayapple Moth, artificial light may also disorient bird migration and disrupt the reproductive cycles of various amphibians, reptiles, and insects like Blue Ghost Fireflies that depend upon dark skies for timing their seasonal behaviors.

Light Pollution Map from Lightpollutionmap.info

Unfortunately, dark sky regions needed by plants and animals for their survival are becoming increasingly rare. In this satellite map, the light pollution indicated by red and pink shaded areas, confuses plants and animals about the timing of the seasons. Overall, there has been a worrisome +14% increase in night sky illumination on average across the US, with most of that change happening during the past 4 years. Compared with Knoxville (top left), Greenville (lower right), and Asheville-Hendersonville (red strip), Brevard (thumbtack) is surrounded by areas with a dark night sky. In fact, a 278 square mile area around Brevard has experienced a 16% decline in night illumination over the past 10 years, which is good news!

Safety is the main reason why people add light to their landscape, but that does not mean that a safe area must be flooded with unnecessary light. In fact, the safety-related dangers for people are from poor visibility at night caused by glaring lights, and not just from the dark. Artificial light is not safe when it is blindingly bright. A smart lighting choice protects the “dark sky” without “dark ground” by focusing light downward toward a road or path. Look around to see how dark Brevard’s night sky looks. Easy solutions include shielding lights to reduce glare and dimming lights to provide the right amount of light. Our region’s dark sky trend will continue with smart lighting choices using new types of illumination. For example, the rechargeable cordless Zafferano brand Pina Pro Table Lamp (available from Amazon.com) focuses light downwards without glare.

A Pina Pro Lamp can be taken outdoors at the end of May for a Blue Ghost Firefly excursion. Blue Ghost Fireflies are found hovering just above ground leaf litter on humid dark nights for the first few days of June in our nearby woods. In pitch black dark with lamps turned off, these dim fireflies will stay lit for up to a minute, creating the appeal on a totally dark night of fairy lights gliding above the forest floor.

To continue preserving our amazing nature, live in harmony with our wonderful plants and creatures by minimizing light pollution that might disrupt their survival and, therefore, our enjoyment of nature.

Visit these links for more information:
Mayapple Moth
Earth Observatory
James Madison University – Light Pollution
LightPollutionMap
LightPollutionMap – Brevard