Artificial Lighting and its Effects on Wildlife

by Anne Duzan

Summer evenings used to be when young children would capture fireflies in their hands or jars. Frogs and toads would call out; spring peepers, chorus frogs, and bullfrogs announced themselves through the warm season. Insects would flit by, and moths would flutter around flowers. Bats would fly in crazy paths, catching bugs. Swallows, owls, and other birds active at night would dive and swoop for food. Animals would come out of their daytime hiding spots to browse for food or social activities.

In some places, it’s still this way. But increasingly, the areas where dusk becomes dark have become places where artificial light sources replace sunlight. Constant light has dramatically affected the world around us. Firefly populations have crashed in cities and suburbs, frogs and toads are silenced, moths are caught by the lightbulbs, and bats and birds have lost their food sources and the dark in which to find them.

LIGHTING AFFECTS NATURE

Many animals, such as opossums, skunks, and raccoons, are active mostly at night but sometimes during the day. Some birds fly at night, with several species responsible for pollinating crops. Moths and other insects are active at night, as well as certain frogs and toads. These animals and insects use the cover of darkness to find their food, safely eat, mate, help avoid predation, and live more safely.

The presence of artificial light reduces the habitat available for these animals. Attracted to the artificial lighting, some bird species become trapped in cities along their migration path. They then find warm places within the urban area and stay instead of moving on to their ecological niche at the end of their migration. The result is that they don’t reproduce. In another example, in many southern U.S. beaches, you’re asked to keep your curtains closed, and outdoor lights turned off at certain times of night to allow newly hatched sea turtles to find the ocean. And it’s not just steady artificial lighting that affects wildlife. Vehicle lights passing over a dark area disrupt the blinking patterns of fireflies for half an hour or longer. The disruption means fewer fireflies in future generations due to shortened courting and mating times. Fireflies are also affected by steady lighting outdoors, as their blinking patterns are much harder to see in bright places.

BALANCING LIGHT AND DARK

We have become reliant on light being available at all times of the day. Many people believe that light at night will deter crime. However, light glaring from the wrong direction may mean we can’t see someone making their way through a fence gate or hiding in the shadow at the side of a house, just like we can’t see the drivers behind headlights on the road at night.

The front of a residence may be brightly lit from the ground to showcase the building and the surrounding plantings, while shadows hide the rest of the property. Is this bad or good? When designing a site, sometimes we intentionally incorporate shade and shadows, so the concept of good versus bad darkness may not apply. Instead, we can enhance a space with artificial lighting that showcases its beauty, illuminates pathways in the dark and promotes safety. This can be done without disrupting the feeding and reproduction patterns of insects, birds, and other animals. As for intruders, perhaps we should outfit them with headlamps or flashlights! Or, we can just install video cameras.

NURTURING NATURE

Do pathways need to be lit to mimic daytime light levels? Do houses have to be illuminated from dusk to dawn? Can we use a lower light intensity to assist safe passage through a space? We can often design with a ‘less is more’ attitude towards artificial lighting.

Using light fixtures that shine light downwards and outwards—instead of up—and using lower wattage options can be used creatively when designing the space. Uplighting trees and buildings gives a beautiful ambiance and sense of space during a summer evening event. But turning off the lights afterward will help the birds, insects, and other animals living in the canopy.

Many studies have looked at the effect of artificial lighting on the populations of birds, sea turtles, small mammals, and insects. The consensus is that certain light wavelengths are better than others for wildlife at night. Generally speaking, “warmer” wavelengths that we perceive to be yellow, orange, or red are better for wildlife than “cooler” wavelengths such as blue.

You may be familiar with your computer monitors or device screens changing from a cool daylight color to a warmer hue in the evening. This is important to wildlife as they respond to light wavelength through evolutionary processes, such as birds’ reaction to finding a brightly lit city along their migration paths, as mentioned above. We can use this idea in lighting the landscape to benefit people and animals.

By specifying lighting with warmer wavelengths—using light strategically along pathways and patios and turning off the light when people won’t be around—we can also save energy. Using lights at lower wattages helps with savings. Solar lighting is an excellent option to save energy and still have enough artificial light. Various solar lights are available, including floodlights that can be controlled remotely, motion sensor lights, deck post cap lights, lanterns that can be hung from trees or hooks, café lighting, decorative string lights, and pathway lighting. Depending on the model, some solar lights have enough battery power to last a few hours, while others have enough storage capacity to provide light all night.

We can use light and darkness to add time-based visual interest to our designs and delight our clients. But artificial lighting has repercussions beyond human concerns, such as disrupting wildlife activities and over-using energy. Sustainable ways to use light in our designs, from choosing how to illuminate an area, selecting lights with warmer wavelengths, turning off the lights when they are unnecessary, and using lower wattage options or solar lighting, will help not only our clients’ wallets but also the wildlife in the landscape.

Anne Duzan is the owner and designer of Daisyenne Designs, LLC, focusing on ecological and sustainable design. Daisyenne Designs, LLC is based in southeastern Pennsylvania.