North Four Corners News ♦ April 2023

Nurturing Nature

Light Pollution and its Negative Impacts on Wildlife, Human Health

By Jennifer McGuire Cox

Thinking of adding lights to your driveway to keep better track of your cars at night?  Keeping your porch light on to feel safer around the house?  The cost is small and bulbs last longer than ever, so why not?  Yet while the introduction in recent years of cheaper light sources — such as LEDs — has made it tempting to use more lighting for outdoor purposes, regular exposure to light during nighttime hours not only hurts wildlife, but also has a negative impact on humans.

The Problem for Wildlife

Artificial light causes several problems for wildlife, especially those animals that are nocturnal (active at night).  This includes:

• Attracting different organisms (such as moths, frogs, and migratory birds) to places where they should not be.  This concentration of animals in one location can result in greater predation and mortality.  It also results in animals being trapped in the light, exhausting and sometimes killing them.  One billion birds alone are killed EACH YEAR during fall and spring migrations because of building strikes, with the brightest buildings having the highest number of strikes.
• Repels many organisms from their normal habitats, resulting in habitat loss.  Frogs, for instance, can’t relocate their vernal pool which is now under a bright light.  Light pollution reduces insect visits by 62 percent, which further hurts pollinators already in decline.  Moths, which are nocturnal pollinators, especially play an important role as pollinators in the ecosystem.
• Changes the day and night patterns of organisms.  This can alter reproductive cycles, not allow enough times for repairs to their bodies, and generally result in the organism not getting enough sleep and being lethargic.  This could mean they are not as healthy and at greater risk of predation.

In addition to wildlife, exposure to artificial light also impacts plants and trees.  Different plants need different photoperiods, or certain lengths of night and sunlight, to grow properly.  Increased light exposure impacts pigment formation, leaf shedding, bud dormancy, and behavior of pollinators.  In the case of trees, those leaves closest to light sources stay on the longest, sometimes weeks longer, in the autumn months when the leaves of trees change color and fall.  This could result in stressed plants and trees, or plants that do not grow properly.

Human Impacts

The damage from artificial light doesn’t stop at wildlife.  Humans, while feeling safer in locations that are lit, need darkness as well.  Humans need dark conditions to produce melatonin, a hormone that is necessary for the body to repair its cells.  Serious interruption to the circadian rhythm and day/night pattern interferes with this production and has been found to result in higher rates of some cancers.  Artificial light exposure, especially at night, has also been linked to increased rates of insomnia, headaches, cardiovascular disease, diabetes, anxiety, obesity, depression, and vision problems.

The Rise of LEDS

LEDs (light-emitting diodes) have become widely available and popular over the last 15 years.  Their popularity stems not only from their longevity but the fact that they use a fraction of the electricity as traditional incandescent light bulbs.  However, not all LED light bulbs are great for humans and wildlife.  LED light bulbs in the blue and purple-rich wavelengths have been shown to pose serious risk to the environment and human health, as the longer wavelengths bounce around the sky and atmosphere, appearing brighter to wildlife, possibly even blinding them.

What You Can Do Help

If you must use artificial outdoor lighting, consider the following:

• Keep the light low, mounting the fixture as low to the ground as possible to avoid unnecessary light spread.  Be a good neighbor and don’t shine light right into your neighbor’s bedroom window!
• Shield your light fixtures so that the bulb/light source cannot be seen.  This cuts down on the amount of glare seen by animals, which results in less chances of them being trapped, repelled, or otherwise impacted by artificial light.  Also, make sure the light points down.
• Make sure you’re using lights designed for nighttime use.  This includes wavelengths in the long range, such as reds and oranges, as the light will appear dimmer to animals as opposed to other colors.  Avoid blues and purples.
• Don’t overdo it on wattage.  Use only as much as you truly need.  Extra light doesn’t necessarily make you safer, as bright glares from lights results in darker shadows and actually makes it harder to see.
• Rethink your outdoor lighting.  Do you really need to have your backyard lit all night, for instance?  Can you eliminate any lighting?
• Do you need to have a light on all night?  Can you turn off your porch light when you go to bed in the evenings?  Especially consider this during fall and spring migrations to limit bird strikes.

[Both graphics are from the City of Fort Collins, Colorado, and used with permission.]   ■

Dark Skies 2002