By Faith Maranion
The first time I went climbing outdoors began with a road trip to Wisconsin; it was my first visit to Devil’s Lake State Park during autumn. A canopy of leaves hovered above the road leading into the park, while the surrounding trees embraced visitors with blazing oranges, fiery reds, and fading greens. Leaves fell from above, dancing from side to side in rhythm with the autumn breeze. Reaching the ground, they gently settled into inviting piles. Our tires drove over them with a crunch against the gravel. Rolling down my window, the crisp and fresh air filled my senses, but my attention quickly turned to the loud and abrupt bird calls — which I now know came from the great blue heron rookery. I couldn’t see these birds, but I heard them. I could hear their deep and rowdy shouts, their long wings beating against the trees, and the falling branches hitting the ground beneath their nests.
I was not essential to that ecosystem, but I changed the environment in more ways than I could see. As environmentally conscious travelers in natural areas, we are often careful not to litter or visibly harm the surrounding ecosystem, but we may forget to consider our sheer noisiness. From the buzzing of electronics to the hum of our car engines, we make noise wherever we go. Thinking back on my trip, I can still hear the traffic sounds on the road leading into the park and the music blaring from the car radios. While the noise created by one individual may not have drastic effects, the cumulative and sustained noise produced by entire populations of humans alters the way wildlife species live, even the lives of the birds who fly above us.
While I didn’t get the chance to see a great blue heron that day, I did have a view overlooking the Devil’s Lake, still and calm with only one kayak in sight. I wondered what this view looked like before becoming a popular park — before the hikers, climbers, and visitors, before the parking lots, paved roads, and widening trails. I wondered what it sounded like before the presence of humans — before the car engines, traffic sounds, and roaring aircraft. From such a height, I could see the park in its entirety: air, water, flora, and fauna combining. With 115 bird species year-round and an additional 133 during migratory seasons, Devil’s Lake State Park is a reminder that the residents and visitors most essential to this ecosystem are not the 3 million people who visit the park each year, but the non-human species who call this place home.
Birds are unique species that hold essential ecological roles within their natural habitats. No matter which trophic level they belong to, birds are important members of their ecosystem as predators, pollinators, scavengers, seed dispersers, and ecosystem engineers. The health of an ecosystem depends on birds’ ability to plant and spread seeds, dispose of decaying waste, control the insect populations, and pollinate plants.
Birds are also of economic value to humans by providing ecosystem services, or “natural processes that benefit humans.” These include providing resources like food and feathers, regulation of disease through scavenging, and cultural services such as bird watching and photography. While humans profit off the monetary value that can be generated from these services, birds are worth much more than what they can economically offer humans: their intrinsic value as a species, their essential ecological roles, and how other species depend on birds. When noise pollution interferes with the presence and behavior of bird species, the entire ecosystem feels its effects.
While not as obvious as other forms of pollution such as air or water, noise pollution is defined as any interfering noise that is harmful to humans and non-human species. Our world is filled with sounds, even without the presence of humans, but there is a difference between anthropogenic and natural noise. Sources of loud natural noises include wind, water, and animal sounds, which animals are familiar with and have adapted to: tree branches rattled by the wind, streams rippling over rocks, and the early morning chorus of birds.
However, sources of anthropogenic noises like machinery, aircraft, and traffic can influence an animal’s ability to hear and interact with its environment — equipment that pounds and whirs, airplanes taking off for flight, and car engines humming. Animals are facing sound conditions beyond the natural noise they are used to; due to noise pollution, sound levels have doubled in 63% of U.S. protected areas. Protected areas are defined with the goal of ecosystem conservation by minimizing the effect of human activity, but noise pollution isn’t often considered in these effects.
Although all species are affected in some way by noise pollution, multiple studies have been conducted to research the effects of noise on bird species. In 2015, a research group from the Department of Biological Sciences at Boise State University published a study investigating the effects of traffic noise on songbird species. This research group created a “phantom road” in southwestern Idaho by playing traffic sounds at stopover sites, or places where birds stop during their long flights. Using audio files recorded at Glacier National Park, the team created a playback to emulate representative frequency levels of traffic noise near protected areas.
Looking at the behavior of 51 songbird species with a total sample size of 9,924 birds, the study observed that 31% of the songbird population avoided the area affected by the phantom road. Instead of stopping to rest and eat during their migratory journey, many songbirds had avoided the site, suggesting that these birds had assessed this habitat to be unsuitable. The other 69% of the songbirds did not remain unaffected by the noise, though: Their overall body condition, which correlates to the energy the bird has for migratory flights, and their ability to increase this body condition, were reduced compared to the birds in the control conditions without the traffic noise playback. The roads that we build, especially ones in the path of migratory flights, alter the behavior and well-being of bird populations.
In addition to influencing their migratory behavior, noise pollution alters the way in which birds communicate with one another. A joint study by researchers at Leiden University and Groningen University analyzed the acoustic behavior of birds of the great tit species (Parus major) in a national park in the Netherlands. For male-female communication, low-frequency songs are more attractive to female birds. In the presence of low-frequency noisy conditions, male birds are faced with two choices: singing at lower frequencies, which may result in not finding a mate because they are not heard, or singing at higher frequencies, at the risk of pairing with a less desirable mate. In environments with low-frequency noise such as those near cities and highways, male birds have been observed to sing at higher frequencies to be heard over this noise.
The presence of anthropogenic noise alters the typical mating behavior, as well as the reproductive success of this bird species. This study’s findings identified effects of urban noise that extend beyond the great tit species. While male great tits can immediately shift their song frequency, other bird species such as pigeons and cuckoos do not share this ability. Since some bird species cannot adapt to anthropogenic noise, these bird populations could face decreased breeding success.
Although total elimination of noise pollution is impossible, preventive measures and further regulatory enforcement can mitigate its effects. Since the 1970s, the U.S. Environmental Protection Agency has attempted to place noise limits on industries through the Office of Noise Abatement and Control. The goal of the Noise Control Act of 1972 is to reduce the effects of noise pollution that threatens human well-being by coordinating research, establishing noise standards for commerce, and informing the public. However, these goals have remained unfunded since 1982 because of a desire to transfer greater responsibility to state and local governments. Meanwhile, few states have addressed this issue of noise pollution, and jurisdictional boundaries limit the scope of state involvement.
Most of the efforts in regulating noise pollution have been motivated by protecting the health and safety of humans, so the well-being of non-human species is not the top priority. Nonprofit organizations such as Quiet Use Coalition and Alaska Quiet Rights Coalition have stepped up for non-human species and their ecosystems. These organizations preserve quiet areas and protect public lands and wildlife from noise pollution by working with land agencies, educating the public, and advocating for protective policies. They play a key role in spreading awareness to the public about noise pollution and how it can alter animal behaviors and the health of ecosystems.
As individuals who contribute daily to noise pollution, we should be aware of our noise levels when in protected natural areas while also advocating for policies that can propel systemic change. To substantially mitigate the effects of noise pollution, federal and state noise controls that specifically address the conservation of wildlife must be implemented and properly enforced. While we may not always consider the noise pollution we create as a human population, the birds are listening — to our noise and to our silence.
About the Author …
Faith Maranion is a senior from South Elgin, Ill. She studies Civil & Environmental Engineering and is currently studying abroad in Copenhagen, Denmark. Upon graduating, she is interested in working in the field of drinking water treatment.
This piece was written for ESE 360, the introductory course in the Certificate in Environmental Writing, in Spring 2022.