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LAKE TAHOE — The rope tow is long gone. The parking lot is empty. Instead of the bustling chatter of a happy crowd of skiers, there’s just silence.

But the landscape of the abandoned Powder Bowl ski area still bears witness to its past, more than two decades after its closing.

Throughout the Sierras there are dozens of abandoned resorts that hark back to a different era, when snow was plentiful and skiing a favorite pastime. With increased competition from bigger resorts and a decline in skiers, many have closed and the scars they have left behind may have dramatic impact on our watershed.

Some Powder Bowl runs remain exposed and scarred, where heavy machinery scraped off topsoil, seeds, vegetation and boulders, leaving just a grassy field. Others, built more gently, are lush with diverse vegetation, slowly being reclaimed by the surrounding forest.

Not all ski runs are created environmentally equal, according to research of California and Nevada’s abandoned ski resorts by restoration ecologist Jennifer W. Burt, formerly of UC Davis, in the Journal of Applied Ecology.

How they recover — or don’t — can influence water quality, wildlife habitat and determine whether a scar cut into a mountain is reclaimed by the surrounding area or remains a blemish in the midst of natural beauty. The issue casts a shadow over the future, as climate change and shifting leisure pursuits are expected to trigger additional closures.

Runs that are built by “grading” — scraping, smoothing and compacting the soil with bulldozers and other big equipment — show no predictable recovery even 40 years after abandonment, Burt found.

But runs that are “cleared” — cutting plants but leaving roots and topsoil intact — bounce back to host a tapestry of saplings, shrubs, wildflowers and insects.

“We need to take the long view of things,” said Burt, who currently works at GEI Consultants, Inc. in Rancho Cordova. “Soil formation takes geologic time. When we remove soil, without active restoration, it takes a long time to recover.”

Mountains are cold, dry and fragile places, where damage heals slowly. Any disturbance has downstream consequences.

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“Slope construction can dramatically affect the whole watershed,” said Jenny Hatch of the environmental watchdog group Sierra Nevada Alliance.

Ghostly remains of small ski areas are scattered around the Sierra, often out of public view.

Relics of a simpler time, they tug at our heartstrings, with memories of a relaxed weekend of fun. But they were no match for spiraling costs, economic downturns, unpredictable winters and competition from great glittering resorts like Squaw Valley and Mammoth Mountain.

Dozens of small to mid-size resorts sprang up during the postwar skiing boom, “almost anywhere there was a little hill, using garbage can lids as slides,” recalled Norm Sayler of the Donner Summit Historical Society. “Then you’d hook up a toboggan. There were little rope tow things built everywhere.”

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Roadshow: How many hours do you allot for a Friday drive to Tahoe? A lot of snow fell in the 1950s and 1960s, and it was a wonderful time to ski. An estimated 82 resorts opened from 1940 to 1960, with 107 more in the 1960s. But the 1970s were tough times for ski area operators. A recession hit hard, followed by the oil crisis. Liability insurance costs skyrocketed.

Then came California’s great drought of the mid-1970s, when resorts fell prey to the whims of Mother Nature, said Sayler, who built the first chair lift at Donner Ski Ranch in 1955 and owned the ski area until 2000.

“They were built in lower snow areas, that didn’t get the snow,” he said.

And these modest day-use areas for beginner budget-minded skiers didn’t have the financial banking of large flashy “destination resorts” with more advanced terrain.

So crowds dwindled, and an era ended. Abandoned areas include the fabled Edelweiss, a mile past the town of Twin Bridges, where famed U.S. Ski Team and World Cup racer Spider Sabich and his fearless friends, dubbed “The Highway 50 Boys,” learned to race. It is now Camp Sacramento.

Iron Mountain, located on Highway 88, the same road leading to Kirkwood, struggled through years of bankruptcies and finally closed in 1993. Peddler Hill, just below Iron Mountain, also closed.

Other long-gone areas include Tannenbaum on Mt. Rose Highway, which closed in the 1980s. Echo Summit, whose 200 foot rope tow was first operated with the help of an old Dodge transmission, has been closed nearly 20 years.

Construction techniques have changed over time, Sayler said. Early on, ski areas were built in natural fields; work was largely confined to mowing grass, clearing brush and cutting random stumps.

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As time went on, techniques advanced, he said.

“The predominant practice shifted from clearing to grading, or bulldozing ski runs to create a smooth under-snow surface, stripping the slope of vegetation, stumps, rocks, roots and seeds,” said Burt. “The topsoil is scraped and the soils are compacted.”

Grading has more up front costs, but is popular for good reason: Slopes require less snow to open, so areas can expand the “shoulder” season of early and late winter, when there’s less snow. Grading also can correct slopes that are too steep or rocky.

A hike up Powder Bowl, a modest place that operated in the shadows of Squaw Valley and Alpine Meadows from 1961-1984, reveals the differences.

One former run is blanketed only by grass. Here, the ground was graded — scraped smooth with a bulldozer, Burt said. On another, cleared by chainsaws, you’re tugged and scratched by thriving young Jeffrey pine, cedar and fir trees. There are tangles of ceanothus, currants and other shrubs, as well as clouds of mosquitoes.

Burt conceived of the study while on a summer hike in 2005 along the Pacific Crest Trail, through the Sugar Bowl ski area.

“As I crossed ski runs, I noticed how diverse their plant communities were and made the connection that different construction could have wildly different effects on the ecology,” she said. It became her doctorate thesis at UC Davis.

The U.S. Forest Service, where many of these closed, sometimes bankrupt, ski areas are located, said operators are responsible for returning ski area lands to their natural state, through revegetation and other environmental restoration practices. The level of restoration needed is not prescribed and is up to the local Forest Service officer.

Today’s ski operators are more sensitive to mountain ecology and environmental concerns, said Mike Livak, executive vice president, Squaw Valley Alpine Meadows.

Few new slopes are under construction, he said, adding it’s been years since a new area was created at Squaw or Alpine. The resort’s last big project was to remove weak trees to reduce fire risk. In 2000, the resort analyzed every area of its holdings, and is improving conditions by adding organic material, irrigating, seeding and mulching, he said.

“We want to protect the mountain,” said Livak. “People come here to experience it’s natural beauty. We want to make it as great as it can be.”

Yet the number of declining resorts raises the specter of more abandoned runs. The number of ski areas has declined from a peak of 546 in 1991-92 to 463 in 2015-16, according to the National Ski Areas Association. Visits also have fallen, from 60 million to 52.8 million. Interest in the sport is stagnating, as Baby Boomers are aging, and young people aren’t fully replacing them.

Meanwhile, the climate is warming, with shorter winters, late snowfall and early melts.

Choices now will shape tomorrow’s landscape, said Burt.

“As more ski areas become abandoned, there should be some effort taken to actively restore graded slopes,” she said. “They don’t recover on their own.”

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