Humans make quite a racket, and all of the excessive noise we make is not just a problem in urban areas. About 14 percent of the land mass in the United States has been afforded some kind of legally protected status, and noise pollution is noticeable even in these more remote areas where manmade disturbances are supposed to be kept to a minimum.
According to a study published this month in the journal Science, the noise pollution from airplanes, highways, industry, and resource extraction is encroaching ever further into U.S. protected areas designed to preserve habitat for biodiversity.
Rachel Buxton, a post-doctoral researcher at Colorado State University's Warner College of Natural Resources and lead author of the study, led a team of researchers that recorded sounds at 492 sites across the country in order to quantify the extent of noise pollution in the U.S. Using baseline sound levels for each study area established by machine learning algorithms that took into account geospatial features of the area, the researchers determined that anthropogenic noise pollution exceeds three decibels (dB), essentially doubling background sound levels, in 63 percent of the nation's protected areas. In 21 percent of protected areas, the team measured 10 dB of noise pollution, close to a 10-fold increase over background levels.
Wilderness areas with some of the highest levels of protections were found to have the lowest amount of noise pollution, though 12 percent of those areas still experience manmade sound levels at least three dB above natural levels, the researchers found—"indicating that they are not entirely 'untrammeled by man' as defined by the Wilderness Act," they wrote in the study.
Three decibels of sound may not seem like much, but, according to the researchers, that's enough to reduce the area that natural sounds can be heard by anywhere from 50 to 90 percent—meaning that natural sounds that can normally be heard from 100 feet away, for instance, can only be heard at a distance of 10 to 50 feet.
"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," Buxton said in a statement. "These acoustic resources are just as magnificent as visual ones, and deserve our protection."
Noise pollution causes cognitive impairment, distraction, stress, and altered behavior and physiology in ways that directly influence both wildlife and humans.
Reduced capacity to hear natural sounds detracts from the restorative properties of spending time in nature, Buxton and her co-authors note, and also negatively affects wildlife. By distracting or scaring animals, reducing the ability of prey species to hear predators, or interfering with mating calls, noise pollution in any given area can result in changes in species composition. Even plants can be affected if the rodents and insects that disperse seeds and pollinate flowers alter their behavior or location due to excessive noise.
"Noise pollution causes cognitive impairment, distraction, stress, and altered behavior and physiology in ways that directly influence both wildlife and humans," Buxton and her co-authors write in the study. "Moreover, noise pollution that alters the distribution or behavior of key species can have cascading effects on ecosystem integrity."
Buxton adds that, while she and her team were surprised by the prevalence of noise pollution in U.S. protected areas, they "were also encouraged to see that many large wilderness areas have sound levels that are close to natural levels. Protecting these important natural acoustic resources as development and land conversion progresses is critical if we want to preserve the character of protected areas."
The study showed that high noise pollution levels tended to be concentrated in specific parts of U.S. protected areas, suggesting where noise-reduction tactics might be most effective. Some protected areas have already undertaken efforts to reduce noise, such as adopting shuttle services that reduce traffic and establishing specific zones where visitors are encouraged to enjoy nature in silence while also creating noise corridors that align flight patterns with roads to keep noise pollution from being pervasive throughout the area.
The researchers found that there was 56 percent less noise above natural levels in critical habitats within protected areas that have adopted stringent noise regulations compared to measurements taken in habitats in unprotected areas.
"Numerous noise mitigation strategies have been successfully developed and implemented, so we already have the knowledge needed to address noise issues," George Wittemyer, an associate professor at Colorado State University and the senior author of the study, said in a statement. "Our work provides information to facilitate such efforts in respect to protected areas where natural sounds are integral."
This story originally appeared at the website of global conservation news service Mongabay.com. Get updates on their stories delivered to your inbox, or follow @Mongabay on Facebook, Instagram, or Twitter.