Light Pollution Harms Bats, which Eat Harmful Insects
In he first part of this series on light pollution, Mary Dawson talked about Watoga State Park seeking to be designated as a Dark Skies Park and provided an overview of the effects of light pollution. Now, in part two, Megan Dister, an AmeriCorps Volunteer assigned to the Marlinton-White Sulphur Springs District of the Mon Forest, explains how light pollution can also cause harm to bats, which are nature’s eliminators of harmful insects.
“Bats are some of West Virginia’s most environmentally friendly mammals and they help out humans too by eating pesky insects like moths, wasps, beetles, gnats, mosquitoes and midges” Megan said. However, as human populations spread and grow, we are impacting these important little creatures.”
“One way we are hurting our bat populations is through light pollution. Most people have heard of air or water pollution, but light pollution is also a serious issue for both humans and wildlife, like bats. Light pollution is the inappropriate or excessive use of artificial light.”
“Nocturnal animals like bats are especially impacted because they spend time at night hunting, mating, and moving around. They also have almost no cones in their eyes, which normally help animals deal with bright lights.”
“Because bats are adapted to living in the dark, light pollution affects bats both directly and indirectly by impacting their habitats and behaviors. Due to artificial lights bats might not emerge from their roost or delay their emergence because they are more confused about the time of day. This means their foraging time is shorter and they might miss the largest abundance of insects at dusk. In addition, if light directly illuminates a roost this can cause bats to abandon the roost, cause bats to die, and/or force bats to use suboptimal exits. When a roost is fully lit predators are better able to attack bats and bats may use different exits that put them more at risk for predation. Moreover, artificial lighting of bat colonies is linked to reduced juvenile growth rates. This can lead the colony to be more at risk from other threats. Bats are slow to reproduce and live a long time, so population declines are especially harmful to them.”
“Light not only affects bat roosts, but also their commuting routes. When artificial light spills into bat commuting routes bats may have to use different routes that put them more at risk for predation. It might also increase their flying time causing increased energy use. Sometimes there may not be another commuting route, so bats are forced to abandon their roost and typical foraging areas.”
“Additionally, light pollution affects bat hibernation by disturbing hibernating bats and forcing them to use more energy while hibernating, reducing their ability to survive the winter.”
“Mating is affected by light pollution because many bats mate by swarming in specific sites. If the swarming site is disturbed by light pollution it could significantly affect breeding behavior.”
“All of these impacts of light pollution on bats are very concerning, but the good news is there are ways you can help! Number one is avoiding the use of outdoor artificial lighting unless it is absolutely necessary. But if you do use outdoor lights you can make your lighting more friendly to bats by following three steps: reduce, direct, and limit. You can reduce your lighting intensity, so it will not be as impactful to bats. You can direct your light so it’s only lighting necessary things and not bat habitat. And finally it’s easy to use motion sensors or timers to limit the amount of time light is used therefore reducing its impact on bats.”
Keep listening to Allegheny Mountain Radio for the third part of this series about the effects of light pollution. In that final segment, Clinton Gabbert, of the Greening Youth Foundation who also works with the Mon Forest, will explain how light pollution can harm our nighttime pollinators.