Zion soundscape study aims to preserve canyon's quiet

Phil Taylor

If a yellow warbler calls out in the canyons of Zion National Park, and no potential mates can hear it, did it make a sound?

It does, according to National Park Service officials, who this month are crafting a soundscape management plan to make sure other warblers, park visitors and potential predators can hear it, too.

The noise plan aims to define both the existing ambient soundscape and set scientific standards for future management decisions that could impact acoustics in the park, said Jock Whitworth, superintendent at Zion.

"The deep canyons in Zion really amplify both natural sound and also high-flying aircraft," said Whitworth, adding that commercial aircraft can be heard about every seven minutes from some of the park's higher altitudes and backcountry areas.

When completed in the fall, the Zion plan will become the first noise action plan to be incorporated into park management rules and will be a crucial tool in how the agency manages more than 120,000 acres of new wilderness added to Zion as part of the 2009 public lands omnibus package, Whitworth said.

"Eighty-five percent of Zion went from recommended wilderness to legislated wilderness," he said. "That gives us another reason to want to preserve natural sounds."

Park planners will be assisted by data from solar-powered sound monitors placed throughout the park since 2001 that have recorded everything from waterfalls flowing into the Virgin River to bighorn sheep ramming heads in the backcountry, said Frank Turina, senior planner for the agency's Natural Sounds and Night Skies Program.

"These are the kind of sounds that are unique to Zion that need to be protected for future generations," he said.

Those natural sounds will be measured against the anthropogenic sounds of aircraft, motor vehicles, and potential energy development and off-highway vehicle use across Bureau of Land Management holdings surrounding the park, Whitworth said.

The park held three public meetings this month to gather input for its study and will accept written comments through the end of next week. Whitworth said he is hoping to issue a finding of "no significant impact" as part of an environmental assessment (EA) to be released in October.

Building on research

National parks have long been managed as refuges where visitors can find solace from the artificial clamor of cities and suburbs.

But recent studies are shedding new light on the disruptive effects that outside noises can have on such experiences. More important, biologists say, artificial noise can disrupt wildlife behavior and functions, such as mating rituals and predator-prey dynamics, as well as nocturnal species.

A recent study published in the journal Trends in Ecology and Evolution found that increased noise from activities such as transportation, resource extraction, motorized recreation and urban development have reduced the distance over which acoustic signals can be perceived by animals.

"Noise management is an emergent issue for protected lands, and a potential opportunity to improve the resilience of these areas to climate change and other forces less susceptible to immediate remediation," according to the study by scientists at the National Park Service and Colorado State University (Land Letter, March 18).

Artificial noises can be heard during more than 25 percent of the time between 7 a.m. and 10 p.m. at more than half of the sites monitored by NPS in 14 parks. And despite prohibitions on motor vehicles and other disruptive activities in wilderness areas, such sanctuaries are not immune from artificial noise because many are located below major flight corridors, the agency found.

For wildlife -- including birds, primates, marine mammals and some rodents -- artificial noises inhibit, or "mask," ambient sounds and have caused species to shift their vocalizations to acclimate to the new environment.

Whitworth said predators in Zion, such as owls, gray foxes and mountain lions, require quiet environments to hunt prey just as other species, such as rodents, need to hear rustling sounds to evade capture.

"Unnatural sound distracts certain animals," Whitworth said, adding that certain frog species have been observed to change their croaking patterns in the presence of artificial noises.

Sound planning in action

Whitworth said noise impacts are already factored into management decisions involving trail work at Zion, with particular attention given to the newly designated wilderness areas.

The use of helicopters to transport equipment and supplies, for example, is allowed only when jobs cannot be done safely without them. In addition, employees must remove trees using crosscut saws instead of chainsaws when possible, Whitworth added.

One of the biggest improvements to natural acoustics at Zion happened in 1997, Whitworth said, when the Park Service banned private vehicles from the park's main roads, eliminating an estimated 1,300 cars that used to drive through Zion Canyon each day.

A fleet of propane-powered buses was established to eliminate traffic and parking problems, protect vegetation, and restore tranquility to Zion Canyon. The buses also help mitigate the visual, acoustic and environmental impacts of Zion visitors, which numbered a record high of more than 2.7 million in 2009.

"The traffic up there was so bad," said Bryan Faehner, associate director for park uses at the National Parks Conservation Association. "Everybody would just drive in circles waiting for someone to leave. So rather than turn the entire canyon into a parking area, they put in the shuttle system."

Not surprisingly, sound-monitoring equipment showed that the bus fleet reduced the amount of time that human-caused sounds are audible by about 50 percent, according to park officials. Many visitors also reported an increase in sightings of wildlife such as coyotes, bighorn sheep and rarely seen mountain lions, he said.
Curbing outside noise

While sound management is expected to improve conditions inside the park, Whitworth and others warned that NPS has limited authority over noises that occur outside parks -- even those that occur on federal lands.

Resource management plans at Utah BLM's Kanab field office to the east of the park and St. George field office to the west do not prohibit oil and gas development or off-road vehicle use in areas bordering the park, despite requests by park officials to ban such activities.

Zion planners provided visual sketches of what oil rigs would look like from park boundaries in the drafting of the Kanab office's recently revised RMP, Whitworth said.

"We do work cooperatively with them on how they manage zones," Whitworth said, adding that he sees a very low probability for mineral development near the park considering the recent controversy involving oil and gas leases issued near national parks during the Bush administration. Those leases were later withdrawn by Interior Secretary Ken Salazar.

In Colorado last year, two environmental groups sued the Fish and Wildlife Service after it permitted a Canadian energy company to drill a pair of 14,000-foot-deep wells on the Baca National Wildlife Refuge about 2 miles west of Great Sand Dunes National Park, the nation's quietest national park according to the agency (Land Letter, Oct. 8, 2009).

With respect to air traffic, Karen Trevino, program manager for the agency's sound and night skies program, said the Park Service is working with the Federal Aviation Administration to tailor flight plans over national parks as authorized under the National Parks Air Tour Management Act.

A bill passed by both chambers of Congress last week to reauthorize the FAA included a provision from Oregon Sen. Ron Wyden (D) that would clarify the respective roles of both NPS and FAA in implementing the flight plans.

"I see this as a first step in keeping our national parks free of noise pollution that can ruin visitors' experience of our national treasures," Wyden said in a statement, adding that his amendment would give NPS the authority to deny air tours over some parks where air tour management plans have not been completed.

The House and Senate versions of the bill are being resolved in conference this week.

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Source: Land Letter

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