A possible air traffic mitigation plan can be found in an example from Rocky Mountain National Park in Colorado. According to Kurt Fristrup, NPS senior scientist, when the FAA allowed a minor shift in route away from the wilderness section of Rocky Mountain National Park, “the restoration of natural silence in certain areas was profound” (Levin 2015, 17). This example from Rocky Mountain National Park provides a potential plan that could be implemented for soundscape restoration with the FAA and National Park Service working together in the quest for natural quiet in Yosemite National Park.
Environmental Impacts
Noise pervades nearly every corner of the United States and it is having a detrimental effect on the environment. “Pervasive flight traffic coupled with an extensive road network eliminates natural quiet across almost the entire country” (Mennitt, Fristrup and Nelson 2013, 3). Barber et al. focus their efforts on protected land to illustrate how anthropogenic noise is not only in developed areas but in most natural areas, especially along roadways. It is estimated that 20 percent of the contiguous United States are ecologically affected by the noise of road network. They propose that when anthropogenic noise pollution affects the ecology of an area and soundscape research must be done at the landscape scale (Barber, Burdett, et al. 2011, 1283). This approach attempts to force recognition of the enormous scale of the problem, that few natural areas have escaped the reach of anthropogenic noise.
Soundscapes can be an indicator of biodiversity and reflect habitat losses. “Human domination of natural habitats has resulted in the loss of biodiversity. With the loss of habitat and biodiversity, areas lose their natural sounds.” (Dumyahn and Pijanowski, Soundscape Conservation 2011, 1327) Barber et al discuss several studies to bolster the need for further research: reduced breeding success among birds living near roads, altered vocalization by birds, squirrels, and frogs and road avoidance by bats. Their research offers suggestions to reduce noise, sound barriers, overpasses, and longer underground roadways, with the latter have the added benefit of increased habitat connectivity (Barber, Burdett, et al. 2011, 1288). Further research in this area may not only provide an answer to reducing noise but increasing habitat. “Some researchers have used the acoustic signals from biophony to serve as a proxy for biodiversity estimates.” (Dumyahn and Pijanowski, Soundscape Conservation 2011, 1333) Environmental impacts on the biophony create disturbance natural soundscape. The biophony is an important component of a healthy soundscape and the opportunity to gauge biodiversity by recording is a way to illustrate how anthropogenic noise impacts wildlife.
Fewer species in the environment that generate biophony create a void in the soundscape. Soundscapes have given researchers a new way to check the health of an ecosystem.
Noise and Wildlife
The effects of anthropogenic noise on wildlife are far-reaching. The acoustic environment is an important component of a healthy ecosystem. While there are standard noise thresholds for people, there are no such guidelines for wildlife and habitat exposure to noise (Barber, Burdett, et al. 2011, 1289). The types of anthropogenic noises that affects wildlife on land come from oil and gas exploration, wind energy production, jet and air traffic, with road traffic being the largest contributor to noise in natural areas. “Motorized transportation noise has been found to mask, or limit the perception, of acoustic signals” (Dumyahn and Pijanowski, Soundscape Conservation 2011, 1330). Songbirds near oil and gas development have significantly less pairing success, bird density and bird species diversity (Lynch, Joyce and Fristrup 2011, 1299). Even quiet human activities such as hiking and skiing result in habitat degradation. Barber et al (2009, 184) explored ways that people impact wildlife beyond the expected transportation, infrastructure, and energy production. “A recent meta-analysis of ungulate flight responses to human disturbance showed that humans on foot produced stronger behavioral reactions than did motorized disturbances.” (Barber, Crooks and Fristrup 2009, 184) This study presents other ways people impact wildlife beyond the expected transportation, infrastructure, and energy production. Noise can mask alarm calls and the sounds of both predator and prey. Noise masks sounds of prey rustling used by predators to locate prey. Robins use only sound to locate worms below ground, many bats use sound to capture prey and owls, hawks, and lemurs listen for the rustling of leaves to find prey. Prey animals listen for the sound of predators and the alarm call of others to avoid detection. Additionally, many animals eavesdrop on the alarm calls of other wildlife to alert them of approaching predators. A recent study of red squirrels found that they listen to the communication calls of blue jays for cache pilfering. In response to noise, some wildlife have shifted their signal types: begging calls of chicks, alarm signals in ground squirrels, echolocation cries of bats and sexual communication signals in birds, cetaceans, and anurans (Barber, Crooks and Fristrup 2009, 183). The sounds and calls produced by an animal is a signifier for its overall health and suitability as a mate. “Unfortunately neglected by ecological investigations for long a time, sounds have an important role in detecting early signs of animal stress connected to climate change from the scale of individual species, populations, communities, and landscapes” (Krause and Farina 2016, 246). These studies highlight the importance of animal communication and how anthropogenic noise interferes with their environment and has far-reaching impacts on the ecosystem.
Geophony has the ability to interfere with animal communication through its many forces. Pijanowski et al (2001, 1224) explain how loud river water sound can influence the bird calls, favoring birds that whistle as it can penetrate the sound of the river more effectively. After a large rain storm, rivers may overwhelm the biophony until the water level recedes and the waters quiet. When it is heavily raining or windy, many animals, frogs, birds, and insects, stop producing sound altogether until the storm passes. The geophony is an integral part of the soundscape and influences and interferes with sounds produced by the biophony.
Field Recording
Field recording involves taking recording equipment into the field to capture the natural soundscape. Gallagher (2015) identifies this as the natural recording style, one which is used to capture the vibrations of wildlife, plants, habitats, and ecosystems. These are mainly used for television nature programs, scientific field research, and wildlife enthusiasts. “In this style, the audio presence of humans is usually erased as far as possible, avoiding human voices, the noise of cities, transport systems, and so on.” (Gallagher 2015, 565) Using different recording techniques, soundscapes may expand the methods for documenting the environment in new, yet to be discovered, ways.
Dumyahn and Pijanowski push for more research on the impact of noise on humans and wildlife and to add value to conservation efforts (Dumyahn and Pijanowski, Soundscape Conservation 2011, 1324). The study reports the national parks are quieter than urban and suburban communities but that noise is still audible for a significant part of the day. Lynch et al. (2011) developed a method for identifying natural quiet, defined as the baseline ambient sound level or the acoustic environment without anthropogenic noise. As earlier noted, the National Park Service considers natural ambient sound synonymous with natural quiet. Audio recordings from National Parks are analyzed using software that produces a spectrogram, a visual representation of sound, to identify the sound signatures of noise (Lynch, Joyce and Fristrup 2011, 1302). Field recording can further reveal what is missing from the frequency range. Fewer or missing species in the biophony creates a void in the soundscape that is measurable. One study used the frequency band to analyze where vocalization gaps occur. Used in this way, the soundscape can serve as a bioassessment tool to detect shift in ecosystem function (Dumyahn and Pijanowski, Soundscape Conservation 2011, 1322). Researchers then look for what would normally be in that frequency range to identify what bird, amphibian, or insect is missing from the landscape.
Field recording can be used to identify species diversity by separating out the vocal calls of specific wildlife. “Compared with visual technologies like camera traps or video monitoring systems, audio systems offer omnidirectional coverage that is not immediately limited by the presence of obstructions or vegetation.” (Fristrup and Mennitt 2012, 16) While many animals remain hidden, their uninhibited vocalizations can be recorded and an estimate can be deduced. Moreover, animal behavior is not altered by the human observer which may be affect their vocalization. Bioacoustical refers to the sounds produced by living organisms and is referred to as biophony. “Bioacoustical monitoring can document many parameters of interest-occupancy, temporal activity patterns, spatial patterns of movement, population density, breeding activity, and possibly-when long term individual recognition is possible-individual survivorship and reproductive output” (Fristrup and Mennitt 2012, 23). During research in Papua New Guinea, Eddie Game, Nature Conservancy’s lead scientist says “Bioacoustics give the researchers a broad picture of what’s going on in the ecosystem without them having to painstakingly count individual animals, the way they would in a traditional fauna survey” (Hansman 2015, 3). Sound analysis and machine learning tools allow the collection of data valuable for biodiversity across a wide range of spaces (Gage, et al. 2017, 73). The ability to record the vocalizations of birds, insects, and mammals allows for a minimally invasive method to monitor the health of an ecosystem.
Audio recordings create a lasting record of the soundscape. “Recordings can be permanently stored, functioning as a ‘museum voucher’ allowing future comparisons and analyses” (Campos-Cerqueira, et al. 2017, 9922). These recordings may capture the last call of a species as it falls to the changing environment, or the unique sound of a foghorn in a light house that will be washed away and lost to climate change. It may record the last complete soundscape of an intact ecosystem such as Krause recorded before the logging around Lincoln Meadow in Sequoia National Forest (Comstock and Hocks 2016, 169). These recordings become sad reminders and acoustic fossils of lost ecosystems.
