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Also featured in the Summer 2025 edition of Tree Tips

 

The Impact of Nighttime on our Environment and Health

 

Night hikes are one of my favorite activities we offer at TFT and are often a favorite of many participants too. We lead small groups through the forest at night while doing various sensory activities that connect to discussions about nocturnal animal adaptations. We begin at sunset and end in complete darkness…no lights allowed! During my night hikes, after participants have the opportunity to sit silently in the dark for several minutes, we gather together, and I talk to them about the importance of natural darkness and how darkness is a natural resource worth conserving. 

 

We generally think of dark night skies as a scenic resource, valued by professional and amateur astronomers as well as casual stargazers. Often forgotten is the importance of natural darkness for ecological function and overall human health and wellness. A naturally dark sky is integral to many natural processes and since the invention of electric light, the night has been getting progressively brighter.

 

Light pollution is the human-made alteration of outdoor light levels from those occurring naturally. When we over-light, fail to use timers and sensors, or use the wrong color of light, we can negatively affect many parts of our world, including migratory birds, pollinators, sea turtles, and mammals, including humans. Light pollution can come from cities, outdoor lighting, electronic advertising, parking lots, and many other sources. Fortunately, there’s a growing awareness that the ways we stave off the dark can have harmful effects too.

 

EFFECTS OF LIGHT POLLUTION

Wildlife and Ecosystems

Nocturnal animals sleep during the day and are active at night. Light pollution radically alters their nighttime environment by turning night into day. Predators use light to hunt, and prey species use darkness as cover. Glare from artificial lights can also impact wetland habitats that are home to amphibians such as frogs and toads, whose nighttime croaking is part of the breeding ritual. Birds that migrate or hunt at night navigate by moonlight and starlight. Artificial light can cause them to wander off course and toward the nighttime landscapes of cities. Every year millions of birds die colliding with illuminated buildings and towers. Migratory birds depend on cues from properly timed seasonal schedules. Artificial lights can cause them to migrate too early or too late and miss ideal climate conditions for nesting, foraging, and other behaviors. 

 

Light pollution can dim the magic of fireflies—too much artificial light disrupts their ability to find mates and communicate.

 

Many insects are drawn to light, but artificial lights can create a fatal attraction. Light pollution directly interferes with multiple insect species’ development, movement, foraging, and reproductive success. Declining insect populations negatively impact all species that rely on insects for food or pollination. 

 

Tree Health

Trees are just some plants that can be affected by light shining on them every hour of every day. Trees use sunlight for energy, but they also use it as a signal. This signal helps them regulate their growth and seasonal changes. A study conducted in Poland found that artificial light at night caused trees to develop their buds faster. Leaf development was also affected as that process was accelerated by 20 days due to the level of light pollution. They also concluded that exposing trees to light can affect their nutrient content. Trees are central to many insect and bird survival, but they also provide a necessary urban canopy to protect humans by mitigating heat and cleaning our air. Protecting them by lowering the light levels is just one way to ensure these pillars of our ecosystem can thrive in our neighborhoods and cities.

 

Crime and Safety

There is no clear scientific evidence that increased outdoor lighting deters crimes. It may make us feel safer, but it has not been shown to make us safer. Outdoor lighting is intended to enhance safety and security at night, but too much lighting can actually have the opposite effect. Visibility should always be the goal. Glare from bright, unshielded lights decreases safety because it shines into our eyes and constricts our pupils. This can not only be blinding, but it also makes it more difficult for our eyes to adjust to low-light conditions. Smart lighting that directs light where it is needed creates a balance between safety and minimizing our impact.

 

Human Health

Research suggests that artificial light at night can negatively affect human health. With increased light at night, our biological clock fails to do its job. This can have long-lasting effects and can lead to a lot of health consequences down the road, like cognitive decline, heart disease, and cancer. It has to do with how light inhibits the production of melatonin, an essential hormone regulating our sleep cycle. Further studies conducted by Harvard Medical School found that blue light (emitted from electronics or LED lights) at night is more potent at suppressing the secretion of melatonin, suppressing it twice as long as other forms of light.

 

Night Sky Heritage

The natural night sky is our common and universal heritage, yet it’s rapidly becoming unknown to the newest generations. More than 80 percent of the world’s population lives under light-polluted skies, and more than one-third of all human beings can’t see the famed Milky Way. On an existential level, we are disconnected from the night sky now more than ever. Dark skies give us more opportunities to connect with nature, for indigenous communities to reclaim their connections to the night sky, and for darkness and the stars to be accessible to all those that live under it.

 

Dark Sky Places

The International Dark Sky Places program was founded in 2001 with Flagstaff, Arizona as the first officially accredited Dark Sky Place. The program is designed to create physical spaces to encourage enjoyment of the night sky and to educate communities on best practices when it comes to lighting policies. There are five different designations for the possible types of dark places: communities, parks, reserves, sanctuaries, and urban night sky places. Each designation comes with its own criteria. 

 

The process often starts with one individual who gathers a community around them and says, “look, we have something special here that we value: darkness. We value the night, and we don’t want light pollution to grow here.” As more communities rally to protect the night sky, more official dark places are created.

Wisconsin has a designated Dark Sky Place, Newport State Park on the tip of the Door Peninsula. Recognizing the value of its dark skies, for the past 25 years the Park has undertaken public outreach and education on astronomy and the importance of natural darkness to local wildlife. Newport was designated as a Dark Sky Park in 2017.  See more about DarkSky International at https://darksky.org/

Newport State Park, nestled on the tip of Wisconsin’s Door Peninsula, offers serene wilderness, rugged Lake Michigan shoreline, and some of the darkest night skies in the Midwest.

 

How We Can Reduce Light Pollution

Light pollution has a fairly obvious fix: just reduce the amount of light. We can continue the activities we want to do outside at night, while still protecting the planet and reducing light pollution overall. There are five principles for lighting, and if people follow those, we would make quick strides in reducing light pollution.

• Only light necessary areas
• Use shielded lights that face downward
• Control brightness levels
• Use warm-colored lights

Control how long lights stay on through dimmers, motion sensors and timers

By applying these principles, properly designed electric lighting at night can be beautiful, healthy, and functional. Projects that incorporate these principles will save energy and money, reduce light pollution, and minimize wildlife disruption.

 

I hope you better understand the significance of preserving the dark night sky for wildlife, plants, and human health and well-being. The night sky is a natural, cultural, and historic resource that closely intertwines humankind with the nocturnal environment. Get outside this summer and enjoy the night – no lights allowed.

 

Article by Jenny Sadak, Trees For Tomorrow Environmental Educator