Yellowstone Soundscape Report Full of Surprises

The shear bulk of the 91-page study reporting on how much noise over-the-snow vehicles generated in Yellowstone National Park last winter is impressive.
But once you wade deep down into the text and charts and graphs you begin to peel away layers of narrative that obfuscate the real message: Even despite a weakening of standards, even with less than half the daily allotment of 720 snowmobiles cruising through Yellowstone, "best available technology" snowmobiles frequently exceed Yellowstone's noise thresholds
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The report is one in a series looking at how over-the-snow traffic in Yellowstone impacts the park environment, wildlife, employees and visitors. Already there's been a report on wildlife responses to snowmobiles and snowcoaches, and any day now the park is expected to release a report on emissions from those vehicles.
These reports are annual snapshots of multi-year studies, so it's impossible to say they are definitive. Plus, they're employing data collected during below-normal snow years that saw below-normal snowmobile traffic, so how can anyone say they accurately reflect how Yellowstone will be impacted by daily traffic of 720 snowmobiles coursing through a snow-laden landscape that forces elk and bison to congregate along roads groomed for those snowmobiles, not to mention two or three dozen snowcoaches?
The soundscape report, which was written from data collected when the park witnessed, on average, 206 snowmobiles per day, is troubling on a variety of fronts. For instance, on page 2 the "abstract" says that "the sound level and the percent time oversnow vehicles were audible remained substantially lower than oversnow vehicle sounds from the 2002-2003 winter-use season."
OK, but how about a comparison with the 2003-04 season? Was that sentence in the abstract a typo, or was the comparison intentionally not made to the 2003-04 season?
Last winter the park required snowmobilers to travel in guided groups and ride supposedly quieter 4-stroke machines that represented the "best available technology," so one would think that the winter of 2004-05 would most definitely be quieter than the winter of 2003-04. But that doesn't appear to be the case.
On page 18 of the report you'll find that "within the developed area at Old Faithful, the average daily percent time audible for snowmobiles and snowcoaches was 69 percent. This compares to 61 percent during the previous winter-use season."
Things seemed a little better along the Mary Mountain Trail, a backcountry site, where on average during the winter of 2003-04 audible over-the-snow vehicle noise was recorded 32 percent of the time compared to 26 percent of the time last winter. However, the recording site used for the winter of 2004-05 was located 8,000 feet away from the groomed Old Faithful-Madison Junction road, while the site used the previous winter was only 1,000 feet from that road, which makes me guess that things actually were louder here than the report suggests.
At the Lone Star Geyser site, over-the-snow vehicles were audible 4 percent of the time, on average, last winter, versus an average of 3 percent of the time during the winter of 2003-04. At Madison Junction, oversnow vehicles were audible for 24 percent of the two-day President's Day weekend during 2004, and 61 percent in 2005, the report points out.
Things don't sound quieter, do they? And remember, this data come when, on average, there were just 206 snowmobiles traveling in the park each day, not under the currently allowed limit of 720 machines.
There's another curious twist in the report that I'm trying to understand. Prior to the winter of 2004-05, Yellowstone's Winter Use Plan specified that noise above 70 decibels from over-the-snow traffic in developed areas of the park, such as Old Faithful, wasn't to be heard more than 50 percent of the time between 8 a.m. and 4 p.m. However, last winter that standard mysteriously changed dramatically.
The current guidelines say that an "adverse major effect" of noise pollution in developed areas of the park doesn't occur until sounds above 70 decibels are heard 75 percent of the time -- a 50 percent weakening of the previous guideline. And even with that weakening of the guidelines, over-the-snow traffic last winter frequently exceeded the noise thresholds.
I've placed several calls to Yellowstone officials to question them about the latest soundscape report and am waiting to hear back. In the meantime, I discussed the study with Bill Wade, a long-time Park Service employee who now is chairman of the Coalition of National Park Service Retirees' executive committee. He guessed that the change in noise standards is tied to the noisiness of even the four-stroke snowmobiles.
"They'll probably justify that by saying it's part of the so-called 'adaptive management approach' to doing things," Wade told me. Too, he wonders what the impacts will be if 720 snowmobiles visit the park on a daily basis, as the current Winter Use Plan allows.
"If we're already seeing certain impacts, if some of these kinds of things are creeping up to the point where they have to change the standard now with generally only about a third of the snowmobiles that they propose, then the question that arises is what is it going to be like when they get up to those kinds of numbers?" said Wade.
I have another concern with the soundscape report, one that ties in directly with what Park Service officials in Washington are trying to do to the agency's Management Policies. The introduction to the soundscape report points out that the "2001 National Park Service Management Policies state that natural soundscapes (the unimpaired sounds of nature) are to be preserved or restored as is practicable."
But in Washington, the revisions to the Management Policies significantly water that provision down.
"As you well know," Wade told me, "in the proposed revisions, they've dropped out the emphasis on natural soundscapes and natural quiet. Again, it raises the question of what should be governing things here, the levels of use, or the standard that's been set by Management Policies in the past or the (National Park Service) Organic Act or research or science and you adjust the use so it doesn't exceed the standards? That doesn't seem to be what they're doing."
And while the Park Service seems to be extremely patient and hopeful that the snowmobile industry will be able to produce a clean, quiet snowmobile, in a recent PowerPoint presentation the agency noted that when the "best available technology" concept was established, both the Interior Department and Park Service "expected that snowmobile emissions would continue to improve...However, there have been no improvements in snowmobile air or sound emissions since 4-strokes were introduced in 2001."