Listening to Yellowstone, Day 5: Winter soundscapes, snowmobiles, and howitzers

From Wikimedia Commons

Yellowstone's winters have long fascinated visitors. Though winter tourism was rare before the 1920s, hunters were known to roam the snow-covered park at the time of its establishment and continued to track buffalo, wolves, and other animals long after hunting was banned by the U.S. Army in 1886. By the 1990s nearly 150,000 people visited the park each winter to ski the Upper Terrace of Mammoth Hot Springs, snowshoe with park rangers, and watch the wolves prowl Lamar Valley.

By far the easiest way to navigate the park during winter is by snowmobile or snowcoach, a necessity, really, considering how few of Yellowstone's roads are plowed during the winter. Visitors first entered the park on oversnow vehicles (OSVs) in 1948 using a snow plane -- imagine an airboat with skiis and a cockpit -- followed in 1955 by the first snowcoaches and in 1963 by the first personal snowmobiles. As winter use increased during the 1960s, park officials promoted the use of OSVs by grooming roads and trails for use.

Thirty years later, 100,000 visitors entered the park on OSVs, leading to long lines of snowmobiles at the park's entrances. Rangers manning the entrances were forced to wear masks to protect themselves from the fumes. The sound was deafening.

Last October, in the wake of a decade-long study of Yellowstone's winter soundscape, winter-use policies were further revised and will take effect by the 2015-2016 season. Current limits call for no more than 110 "transportation events" per day, defined as either one snowcoach or seven snowmobiles with limits of 60 snowcoaches and 50 snowmobiles, far fewer than the nearly 2,000 snowmobiles per day witnessed in the 1990s. Most conservation groups prefer the use of snowcoaches as they carry more people and, thus, reduce the number of OSVs in the park.

Though the NPS conducted its first winter-use and environmental studies of Yellowstone in 1990, officials placed no restrictions on OSVs entering the park. In 1999, conservation groups including the Greater Yellowstone Coalition (which has monitored winter-use issues for more than fifteen years) proposed limiting, or outright banning, recreational snowmobiling in Yellowstone (as well as all other national parks). In 2004, the Park Service limited commercially-guided tours to OSVs equipped with best available technology (BAT) in terms of noise pollution, lowering the daily number of snowmobiles to 720 and snowcoaches to 78. The NPS set further limits in 2009, lowering snowmobile numbers to 318.

One major unresolved issue is the use of explosives to manage avalanches in Sylvan Pass, just inside the park's East Entrance. Currently, park rangers use a 105mm howitzer to blast snow from the surrounding peaks. As the Greater Yellowstone Coalition has noted, the little-used pass (only 110 people entered the park from the East in 2011-2012) contains some "300 unexploded ordnances" at a cost of roughly $1000 per visitor. For photographs of the howitzer by Yellowstone Gate author Ruffin Prevost, see here.

The park published the results of its first officialsoundscape study after the 2003-2004 season. The report is a fascinating read (and thankfully not overly technical). Separating the park into two acoustic zones (open and forested), park scientists placed monitors along popular OSV routes and in the backcountry to collect soundscape data. Their studies focused on two metrics: 1) the amount of time per day (between 8am and 4pm) when non-natural sounds were audible, and 2) the decibel levels of non-natural sounds. The NPS set not-to-exceed levels at 50% for time and 70dBs for destination areas (e.g., Old Faithful) and groomed roads and trails. NTE levels for backcountry areas were 10% and -6dBs below natural ambient sound.

The data from the 2003-2004 report are rather shocking: at Old Faithful, levels were exceeded for all but two days during the winter season, and backcountry levels were exceeded every day during which data was taken.

By 2011-2012, sound levels in the park were much lower due to BAT regulations and limits on transportation events. Still, human-made and motorized sounds permeate the park. The average noise-free interval at Madison Junction (near the park's west entrance) was a mere 3m 21s during between 8am and 4pm.

The Greater Yellowstone Coalition and other conservations groups continue to monitor the park's winter soundscape and are hoping to further reduce the number of OSVs entering and using the park.