Every winter, Jim Gibson makes several trips to the Sierra Nevada, where he clicks into his Nordic skis and glides into the forest. When snow falls, the roads and trails disappear, presenting a frozen landscape that offers skiers like Gibson an unparalleled sense of freedom to explore the remote regions of the High Sierra.

A retired computer programmer from Campbell, Gibson has been Nordic skiing for 40 years. He says he skis cross-country for the peace and quiet — to escape the traffic, noise and air pollution in the city. “I enjoy going out into the woods where it’s primitive,” he says.

But the winter soundscape these days is not always so relaxing for Gibson, who is vice president of the Snowlands Network, a nonprofit that advocates for human-powered winter activities. One sound guaranteed to disrupt his quiet cruise in the mountains: the revving of a snowmobile motor. “To have a two-stroke internal combustion engine come zipping by at 15 to 30 miles an hour is very disconcerting,” he says.

Tension between snowmobilers and backcountry skiers in high-elevation winter terrain is long-standing. The motorized sleds make it easy to travel quickly on snow-covered terrain; skiers say motors disrupt the wilderness experience. As both activities grow in popularity, skiers and snowmobilers find themselves competing for fresh, untracked snow in high elevations — that increasingly elusive resource — on the same turf.

The issue has recently come to a head in the Sierra Nevada. For the first time, both groups have an opportunity to discuss how winter recreation is broadly managed across the mountains of Northern California.

Under a court-ordered mandate, the U.S. Forest Service is conducting an audit of all national forests that receive snow across the country to determine access privileges for motorized vehicles during winter months. When it’s done, the service will draw lines delineating where vehicles like snowmobiles and snow cats are allowed to go.

Beyond compelling skiers and snowmobilers to play nice, the outcome will determine the future of winter recreation in the U.S.’s premier outdoor destinations for decades to come. How the process unfolds in California is expected to ripple across the country — especially in Wyoming, Montana, Colorado and Alaska, where relations between skiers and snowmobilers are similarly tense.

“For people who are out on these forests in the wintertime, this is really the first opportunity that the public has had to talk about how (recreation in) the forest should be managed in the winter,” says Hilary Eisen, policy director for the Winter Wildlands Alliance, a national nonprofit that advocates for preserving outdoor recreation areas.

“This idea of public ownership — if you don’t have a plan for how you’re going to manage something, and everybody just thinks of themselves when they’re out there using it, you’ll lose that resource through neglect,” Eisen says. “Travel planning might be an opportunity for us to learn how to talk to each other again, or it might be an example of why we can’t talk to each other.”

Winter planning for over-snow vehicles is something every national forest that receives a certain level of snowfall will have to undergo, as of 2015. That’s when the Forest Service, under a court order stemming from a lawsuit brought by the Winter Wildlands Alliance, amended its travel management rule.

The Forest Service maintains operating agreements with ski resorts and cross-country ski centers and manages Sno-Parks, some of which have groomed trails for snowmobiles. But managing recreation beyond those boundaries, in the backcountry, had largely been ignored until now. Of the 155 national forests in the U.S., the alliance expects 77 will undergo winter travel planning.

A separate lawsuit filed by the Winter Wildlands Alliance, the Snowlands Network and the Center for Biological Diversity alleged a lack of information on the environmental impacts of groomed snowmobile trails in California. As a result, California’s forestlands will be the first to go through the process.

On the state’s docket: Lassen, Plumas, Tahoe, Eldorado, Stanislaus and Lake Tahoe Basin national forests, which comprise 4.7 million acres of prime landscape along the spine of Northern California. Environmental impact assessments have been ongoing throughout 2018, and supervisors in each forest face pressing deadlines to analyze public comments and publish final plans. Lassen and the Eldorado published their final plans earlier this year. A final decision for Tahoe is expected in January, while the planning period continues for the other forests.

“One of the things that I’m hoping for is that, through this process, people will become aware of a lot of other areas where they can recreate in the way they want to recreate,” says Eli Ilano, supervisor of the Tahoe National Forest.

Backcountry skiing is the fastest growing segment of the otherwise stagnant ski industry. In 2016, nearly 16 million people participated in human-powered winter recreation and spent $54 million on uphill equipment, according to the Winter Wildlands Alliance.

“It’s hard to say without getting hokey, but we need a place to go and walk the dog in the woods where you can get away from the sounds of traffic and motors and chainsaws and lawn mowers, and all that stuff,” says David Page, advocacy director for Winter Wildlands Alliance, a national nonprofit that advocates for human-powered snowsports on public lands, and a backcountry skier who lives in Mammoth Lakes. “It’s a basic part of the American spirit.”

Snowmobiling is on the rise as well. The International Snowmobile Manufacturers Association says the industry pumps $26 billion into the U.S. economy each year. More than 1.2 million snowmobiles are registered in the country. “The reason why I live here is because there is such great balance,” said Dennis Troy, a land-use planner and snowmobiler from Reno. “I can have quiet recreation or I can load up my sled.”

Skiers typically avoid snowmobiles, especially in avalanche terrain, due to concerns about safety, noise and air pollution. But snowmobiles travel much more freely, and encounters have become more common in the the Sierra Nevada. “Over the last couple of decades, snowmobiles have gotten (so much) lighter and more powerful that, at this point, there is really nowhere that a person on foot can go that a person on a machine cannot get to,” Eisen says.

Many snowmobilers see winter planning as a no-win proposition that would only restrict their land access. Troy says he would like to keep the status quo, allowing snowmobiles to ride in the same places they always have.

Only 2 percent of the Tahoe National Forest’s 871,495 acres restrict motors and mechanized equipment year-round. The draft environmental impact statement for the forest, published last April, proposed a 36 percent cut to snowmobile terrain.

When Troy heard about the proposition, he moved quickly to form the Sierra Snowmobile Foundation, a nonprofit geared toward preserving access for snowmobiles in the Sierra. “The snowmobile community wasn’t at the table when those discussions were taking place,” Troy says. “Once the decisions are made, when areas are closed down to snowmobiling, they’re never opened back up.”

Castle Peak, at the top of Donner Summit in Tahoe National Forest, is a popular launchpad for both snowmobiles and backcountry skiers and has become a lightning rod in this debate.

Troy’s group is pushing to keep the Castle Peak area open to snowmobilers. The Snowlands Network and Winter Wildlands Alliance, however, submitted a request to keep them out. Some local backcountry skiers opt for a compromise — only the north-facing chutes off the peak would be closed to snowmobiles, which would keep the prized terrain for skiers.

Shortly after opening the Tahoe National Forest draft plan to public comment last spring, Ilano shut down the online comment submission portal. The dialogue had turned ugly; human-powered advocates, including Page, received threats after pushing for snowmobile restrictions.

“I wasn’t expecting the level of interest and the level of intensity and emotion,” Ilano says.

As with so many public-policy debates in the country recently, the rhetoric of the winter planning process has become increasingly politicized and polarized. In the most rural parts of the Sierra Nevada, environmentalists, human-powered recreationalists and liberal-leaning, pro-regulation groups are being pitted against locals who live in rural, conservative regions that don’t want a government agency telling them where they can and cannot ride their snowmobiles.

“What was really eye-opening to me was the level of animosity that motorized interests have against the forest service and federal government,” says Gibson, who attended public meetings on each of the forests in Northern California. The vast majority of participants at those meetings were pro-snowmobile, he says. “I feared for my own personal safety when I would go to these meetings.”

There are radicals on both sides of the argument, Troy says. “You really just need to bring a realistic approach,” he says. “Yelling and kicking and screaming isn’t going to do anything.”

Seven months have passed since the public comment period for Tahoe National Forest draft plan closed, in May. Ilano is due to issue his final decision by Jan. 4.

“We’ll put out another balancing act, if you will, for how to manage everyone who wants to recreate in those areas, and we’ll go from there,” Ilano says. “We have outstanding winter recreation opportunities on the Tahoe (National Forest), and I want to make sure that everyone, no matter what they want to do, has a place to do it here. I think we can do that.”

As skiers and snowmobilers await a decision in the Tahoe National Forest, they have begun to study the draft environmental report for the Plumas National Forest, which is open for public comment until Jan. 25.

From her home in Montana, Eisen of the Winter Wildlands Alliance has watched the process in California unfold from afar. It will likely serve as a barometer for regions around the country that will be directly affected by the Forest Service’s winter planning mandate, including her home state.

The tug-of-war is a case study in the tragedy of the commons, she says.

“Everybody can agree that public lands should be public,” Eisen says. “It’s one of the awesome things about being American — we all own these public lands. ... But if we don’t pro-actively manage them to make sure that we can all share them in a way that is meaningful, and not just a free for all, then are they really public if just a few users are dominating them?”

Julie Brown is a freelance writer in the Lake Tahoe area. Email: travel@sfchronicle.com