Weeds are unwanted plants. However, one person’s weed might be another’s foraged salad delicacy. So it is with sound. Unwanted sound is noise, and as one writer with the Los Angeles Times stated, “It’s a noisy planet.” Sure, some sounds that are noise to one person are music to another. But in general, there is plenty of research now underway to support this sweeping statement. And all this noise is taking a toll on humans and wildlife alike, even in places where you might not expect it.
Acoustic researchers agree that noise pollution “is more severe and widespread than ever before, and it will continue to increase in magnitude and severity because of population growth, urbanization, and the associated growth in the use of increasingly powerful, varied, and highly mobile sources of noise.” Considered by the EPA to be a form of air pollution, the health and societal effects of noise can include sleep deprivation, poor concentration, and unsatisfying recreation and leisure experiences. Chronic noise has been found to negatively impact reading proficiency in young school children, and to increase feelings of aggression in older people. The cardio-vascular effects of constant exposure to air and vehicular traffic, jack hammers, and gunshots are intuitive. It is for these and many other reasons that a former Surgeon General for the United States, William Stewart, claimed that “Calling noise a nuisance is like calling smog an inconvenience. Noise must be considered a hazard to the health of people everywhere.”
Having had just about enough urban noise in your life, you might decide to visit a nice, quiet national park somewhere for a week of backcountry solitude. Just you and the sound of wind, water, and wildlife. Perfect choice, right? Turns out be a little harder to escape the cacophony than many people would like. Sometimes that’s because of the people out in the park themselves, as a multi-agency study headed by Robert Manning of the University of Vermont clearly illustrated. Humans contribute any number of noises to the wilderness experience, be it loud guffaws, large group chatter, or crying children.
The emerging discipline of soundscape ecology includes both wildlife and human dimensions. Psychoacoustic research (studies related to the human reactions to sound) has determined that 72 percent of visitors to national parks in the US list experiencing the sounds of nature as a very high priority. To assist with preservation of healthful psychoacoustic space, certain legislative measures have been enacted to restrict anthrophony (human generated sounds) in parks and wilderness areas. One such law was the National Parks Overflight Act of 1987 which requires the park service to report on the nature and scope of aircraft overflight problems.
But aircraft-related noises are just one contributor. Aside from a handful of car-restricted parks, most public lands permit entry of vast numbers of cars and motorcycles every day. As a result, noise levels along park transportation corridors today are sometimes 1,000 times the natural level. The United States National Park Service Soundscape Management unit conducts yearly research to determine problem areas and identify mitigation measures. They have their work cut out for them, because nowhere in the continental US is a human listener farther than 22 miles from a road. They recently concluded a 10-year study that estimates that noise pollution in parks is doubling every 2 decades.
New Zealand’s national parks face similar problems. Although the nation’s parks occupy almost a third of the country’s real estate, many extremely popular parks such as Fiordland have experienced significant noise pollution from fly-overs, resulting in conflict between ‘trampers’ (as they refer to hikers there), conservation agencies, and private small aircraft concessionaires catering to a segment of the tourism market.
There’s also a cultural component to the way we experience noise. South Korea is quite mountainous, and urban populations have easy access to numerous nearby parks for vigorous hiking with friends. And that is exactly what they do. Hiking for South Koreans is a social and physical fitness activity. High vocal noise levels are less relevant to the enjoyment of the resource for South Korean hikers than are motorized sounds, according to a 2011 study. The research revealed that South Korean park users felt greater levels of perceived crowding when exposed to motor noise, less perceived crowding in the presence of nature sounds, and that the presence of no sounds and the sounds of children’s voices were both perceived as neutral. Conversely, a 2016 study conducted in a US national park found that “the acceptability of those settings may improve for visitors if the sounds in the area consist of the sounds of nature, rather than the sounds of the visitors themselves.” Perhaps this explains my colleague’s exasperation during a trip to South Korea, where he attempted a popular mountain trail. As he explained when he returned to the US, as a solitude-loving American he was appalled at the crowds, the boisterous chatter, and the constant selfies. The local hikers seemed cheerfully indifferent to any need for solitude..
In Japan on the other hand, the birth place of Shinrin yoku (forest bathing), many find the silence and mindfulness meditation in the presence of trees to be health giving. A recent and fascinating cultural study by Y. Ogihara describes how Japanese society is becoming less collective and more individualistic. The Japanese seem to be increasingly comfortable with, and even demanding of, occasional solitary peace and quiet, almost on par with Americans. For those engaged in Shinrin yoku, noise is considered to be antithetical to the desired stress reduction experience. Since less than six percent of Japan’s territory is devoted to park lands, respectful silence in natural settings may be an adaptive social response to a perceived need for privacy and occasional solitude. Quiet forest bathers can hear the birds, and the birds can hear each other.
From loud traffic sounds, to noisy visitors, sound pollution can interfere with the reproductive cycles of certain sensitive species of wildlife. For instance, the dawn chorus of birds so carefully catalogued by Aldo Leopold at his Wisconsin shack has disappeared. An acoustic ecologist from the University of Wisconsin, Madison has recreated this extinct soundscape based on Leopold’s 70-year-old notes. It stands in fascinating and sad contrast to what is heard there now; the ever present muted roar of the nearby interstate, audible at every hour from Leopold’s fabled sanctuary. Although this muted roar doesn’t bother some species of birds, and in terms of absolute numbers of successful nests there may be no change, the diversity of avian species can be impacted, as illustrated by a 2009 study on nesting success and road noise. This alteration of species richness due to noise pollution may help to explain the diminished complexity of the dawn chorus discovered by the U of W research team.
This change is not limited to this locale. The endangered Sonoran pronghorn has altered its range to avoid the sounds of military jets; female frogs exposed to traffic noise have difficulty locating singing males; bats avoid foraging above noisy roads. In fact, zoologists identified the impacts of road noise on bats over a decade ago. There’s even evidence that noise can impact certain plant species. Australian researchers recently discovered that the roots of some plants are able to identify the sound of water and grow toward that sound. They also found that noise inhibits that response. National Park Service biologists recently noted that when adverse noise effects are combined with other stressors such as winter weather, disease, and food shortages, successful reproduction is impaired. Although little can be done by individual park visitors to reduce certain noises, like those from passing planes, it’s encouraging to note that some parks have been able to curb loud and intrusive visitor chatter with a simple sign instructing visitors that they are entering a quite zone. This simple measure has been used with success to reduce human vocalizations by 50 percent in designated areas of certain parks such as Cathedral Grove in Muir Woods National Monument.
Management strategies can also be effectively employed. Replacing private vehicles in Zion National Park with free propane powered and electric buses for visitors has facilitated improved traffic flow and visitor experience along with overall noise and exhaust reduction.
Time spent in quiet nature is good for man and beast. The loss of such opportunities is disturbing. “Next time you go for a walk in the woods, pay attention to the sounds you hear — the flow of a river, wind through the trees, singing birds, bugling elk,” suggests Dr. Rachel Buxton, a bioacoustics researcher at Colorado State University. Excellent advice, where possible.