Sources of Human-caused Sounds in National Parks
Since parks were created in part for enjoyment by people, some human-caused sound is present in many park soundscapes. Roads, hikers, vehicles, and maintenance activities are some examples of human-caused sound that may occur in National Park .
Visitors who enjoy national parks using certain modes of access create sound characteristics that impact the experience of other visitors. When visitors view the park via an air or bus tour, an auto, a snowmobile or snowcoach, personal water craft, or motorcycle, intrusive sounds are created for people who have an expectation of quiet, solitude, or appreciation of natural sounds. Often, people who use these modes of access are not even aware of the impact on other people.
Individual sounds do not have to be loud, frequent, or otherwise dominant to have an impact. The total impact to park soundscapes and other resources is often due to the “cumulative effect” of all the sources of sound in a park. It is the combination of sound sources, the acoustic characteristics of each sound (frequency, amplitude, etc), and the physical character of the landscape that determine the impact. The key issue is determining the levels and types of sound that are appropriate or acceptable for different management areas within a park. Click on the pictures to hear some of the human-caused sounds affecting National Parks.
Cars, busses, and other motorized vehicles are one of the most dominant and pervasive sound sources in the national parks. A 1997 Memorandum of Understanding between the Secretary of Transportation and the Secretary of the Interior addressed the severity of the problem. It noted that “Congestion in many National Parks is causing lengthy traffic delays and backups that substantially detract from the visitor experience. Visitors find that many of the National Parks contain significant levels of sound and air pollution, and traffic congestion similar to that found on the city streets they left behind”.
The Natural Sounds Program is working with motorized recreational industries to educate their user groups on the importance of respectful and responsible use.
In many National Park units, the capacity of parking facilities at interpretive or scenic areas is well below demand.
On occasion, National Park units must close their gates during high visitation periods because the existing infrastructure and transportation systems are at, or beyond, the capacity for which they were designed.
Recently, parks have started to tackle the problem of vehicle congestion by slowly weaning visitors from their cars. At Zion National Park where visitation doubled between 1982 and 1997 to more than 2.6 million visitors per year, park managers said they had little choice but to ban cars during the park's busiest times and create a mandatory shuttle system. Before the shuttle system began operation, as many as 5,000 cars a day were lining up on holiday weekends to follow the road into the canyon which contained only about 450 parking spaces. According to park staff, the public response to the change, while initially very controversial, has become overwhelmingly positive. Visitors frequently comment that the park is much more serene and peaceful without the multitude of cars.
The Zion shuttle system carried 2.4 million riders last year resulting in a noticeable reduction in vehicular sound levels. The peace and quiet not only had a positive impact on visitors, the effects were also seen in wildlife health and behavior. Over the years, several wildlife species had moved further and further from the main roads to avoid the sound of buses, cars, and other vehicles. Now it’s peaceful enough in the valley that visitors have reported seeing mountain lions from the shuttle buses.
In recent years, the number of airplanes and helicopters flying over national park units has increased dramatically. Aviation activities over parks include general aviation, commercial passenger flights, park maintenance, and fire and emergency operations. Much of the increase in flights over the national parks can be attributed to the growth of the air tour industry. In the 1990s, Congress began to address the increasing number of sightseeing air tours by mandating the Federal Aviation Administration (FAA) and the National Park Service to manage air tours over the parks. The National Parks Air Tour Management Act of 2000 requires the development of Commercial Air Tour Management Plans (ATMP) for each park in which air tours are conducted. with the exception of the Grand Canyon and its environs, Rocky Mountain National Park, and lands in Alaska.
The FAA and Park Service signed a Memorandum of Understanding for the ATMP program in 2004 and recently completed a detailed plan for implementing the program and developing ATMPs. Currently, ATMPs are being developed for Lake Mead National Recreation Area, and Hawaii Volcanoes, Haleakala, Kalaupapa, Mt Rushmore, and Badlands National Parks. For more information on the National Parks Air Tour Management Program, visit the FAA website http://www.atmp.faa.gov/.
The use of snowmobiles and other winter activities in the national parks has been the subject of intense controversy for many years. This controversy has been most pronounced in Yellowstone and Grand Teton National Parks. The effects of snowmobiles and snowcoaches on park soundscapes have played a key role in the winter use planning process. On November 22, 2000, NPS issued an EIS and record of decision that was to phase snowmobile use out of the parks and replace it with snowcoach access. The rationale for this decision was based on impacts primarily to air quality, the soundscape resource, wildlife, and visitor experience, which cumulatively were determined to be impairing park values. After publishing a supplemental EIS in 2003, NPS produced an interim rule permitting snowmobiles in the parks while capping their numbers, requiring cleaner and quieter machines, and access by guided tour. These measures were intended to mitigate impacts on sound, air quality and wildlife.
On November 4, 2004 the National Park Service approved another assessment and Finding of No Significant Impact (FONSI) for the Temporary Winter Use Plans and Environmental Assessment for Winter Use in Yellowstone and Grand Teton National Parks and the John D. Rockefeller, Jr. Memorial Parkway. The Final Rule implementing this decision was published in the Federal Register on November 10, 2004. This decision allows 720 snowmobiles per day in Yellowstone, all commercially guided. In Grand Teton National Park and the John D. Rockefeller, Jr., Memorial Parkway, 140 snowmobiles would be allowed. With minor exceptions, all snowmobiles would be required to meet NPS best available technology (BAT) requirements. The plan will be in effect for three winters, allowing snowmobile and snowcoach use through the winter of 2006-2007.
NPS has begun preparation of a long-term plan for managing winter recreational use in Yellowstone and Grand Teton National Parks and the John D. Rockefeller, Jr. Memorial Parkway. The purpose of the Winter Use Plan and Environmental Impact Statement (EIS) will be to ensure that park visitors have a range of appropriate winter recreational opportunities, while ensuring that these recreational activities are in an appropriate setting and do not impair or irreparably harm park resources or values. The EIS will consider a variety of different alternatives for managing snowmobile and snowcoach use in the parks.
According to some estimates, the number of personal watercraft (PWC) in America has increased to more than 1,300,000. This increase has resulted in more frequent conflicts between users of PWCs and other park visitors. Often these conflicts focus on impacts to the soundscape resource.
Studies have suggested that PWC sound is different from that of motorboats. The most important difference is that jet skis continually leave the water. This magnifies their sound impact in two ways.
First, minus the muffling effect of the water, the PWC engine’s exhaust can be more than 15 dBA louder than a motorboat. Second, each time the PWC re-enters the water, it smacks the surface with an explosive “whomp”, sometimes with a series of them depending largely on the speed at which the machine is operating.
PWC sound can also prove detrimental to nearby wildlife. Studies have shown that PWC, which lack low-frequency, long distance sounds, do not warn surfacing birds or mammals of approaching danger until they are very close, causing panic and flight.
Currently only 87 national park units allow motorized boating. The National Park Service has adopted a rule that permanently prohibits PWC use in 66 of those units. Five other park units—Cape Cod National Seashore, Cumberland Island National Seashore, Delaware Water Gap National Recreation Area, Indiana Dunes National Lakeshore, and Whiskeytown National Recreation Area adopted permanent closures for PWCs in 2002.
Park operations include a number of sources that affect natural soundscapes. Parks that are engaged in comprehensive planning through a General Management Plan (GMP), a GMP amendment, or a soundscape management plan should evaluate all sources of human or mechanical sound, and determine which of those are necessary to the purposes of the park. For those sources, the park should further determine measures that will be taken to mitigate and minimize the impact to restore the natural soundscape in accordance with NPS policies. Some sound from park operations are inevitable, however parks are working to find “quieter” ways of performing necessary tasks and actions through better technology, appropriate timing, and best management practices.
Denali National Park serves as an example of how parks can minimize sound from park operations. Denali is located in the heart of the Alaska wilderness. It contains some of the most remote places in the National Park system. But not long ago, for Park employees and visitors at Wonder Lake Ranger Station, nature was less than peaceful. A noisy 30-kilowatt diesel generator that powered the station and its buildings ran 24 hours a day. As part of its planning process, the park staff set out to mitigate sound caused by the generator. The Park Service installed a bank of batteries that limited the generator run-time to only 6 to 8 hours every fourth or fifth day to recharge the batteries. As a result, the impact from the generator was greatly reduced and the soundscape was enhanced.
The National Park Service (NPS) and the U.S. Air Force (USAF) have built relationships thorough participation in regional Airspace and Range Council meetings. Both agencies have benefited from the increased collaboration over the last decade. NPS has hosted backcountry trips in Sequoia and Kings Canyon National Parks for the purpose of developing relationships between senior military officers and park managers in a setting that provides the opportunity for solitude, tranquility, and the ability to hear natural sounds. The relationships that have developed have resulted in collaborative problem solving and enhanced cooperation, which can be built upon to solve future issues.
As a result of the cooperative relationship between the NPS and USAF, the two agencies developed a tool to identify and address mutual agency needs in regard to military overflights of National Park units. A “Sourcebook” was written and published to provide information and procedures to military commanders and NPS superintendents. The sourcebook currently covers four park units in the Pacific West region. Additional versions covering other regions are under development.
Throughout the U.S. there is a continuing demand for new, larger and safer airports and aviation support facilities. Many of the proposals for increased safety and capacity at US airports can directly or indirectly affect National Park units. In such cases, Park Service staff must work closely with the FAA to minimize impacts to park soundscapes. For example, the St. George, Utah Municipal Airport, is located near six national park units Bryce Canyon, Grand Canyon, and Zion national parks, Cedar Breaks and Pipe Spring national monuments, and Lake Mead National Recreation Area.
Similarly, the expansion of commuter service at Hanscom Field has caused significant public controversy regarding the potential impact to historic properties. Hanscom Field is located just north of Minute Man National Historical Park, site of the opening battles of the American Revolution, and is surrounded by four historic communities: Lexington, Concord, Lincoln, and Bedford. Visitors to these sites should be able to experience a soundscape that is as similar to the late 1700s as possible.
Other parks potentially affected by sound issues from airports include: Big Bend National Park, Devils Postpile National Monument, Cedar Breaks National Monument, Devils Tower National Monument, Death Valley National Monument, Eugene O’Neill National Historical Site, Glen Canyon National Recreation Area, Grand Teton National Park, John Muir National Historical Site, Joshua Tree National Monument, Lake Mead National Recreation Area, Manzanar National Historical Site, Montezuma Castle National Monument, Mojave National Preserve, Parashant National Monument, Petroglyph National Monument, Pinnacles National Monument, Pipe Spring National Monument, Point Reyes National Seashore, San Antonio Missions National Historical Park, Sequoia Kings Canyon National Park, Yosemite National Park and Golden Gate National Recreation Area.