The national parks are pristine emblems of the American wilderness, attracting millions of visitors from around the world.

But there’s an unintended consequence of their popularity: those visitors generate more than 100 million pounds of garbage a year, most of which ends up in landfills.

Now, as the National Park Service approaches its centennial anniversary , three iconic parks—Yosemite, Denali and Grand Teton—are pursuing the ambitious goal of eliminating virtually all their landfill trash. The parks will try to recycle, reuse or compost their waste instead of throwing it away. ( Read about how American marketing saved the national parks. )

The "zero landfill" movement has been growing for a decade, attracting big businesses from Nike to Wal-Mart; food companies such as Kraft and Nestle; and city governments in Boulder, Colorado and San Francisco . Overflowing landfills and garbage-laden oceans are prompting a broad rethinking of how we deal with waste.

The car maker Subaru, an industry leader in zero landfill since 2004, is advising the three national parks and collaborating with the National Parks Conservation Association , a nonprofit group, helping drive the initiative.

But unlike Subaru’s manufacturing plant in Indiana, the national parks have little control over what goes in and out of their gates. And they’re at the mercy of nearby recycling industries, which often lack the infrastructure to handle large quantities of waste.

While achieving true "zero landfill" might be a stretch, parks leaders say they can get pretty close.

“What constitutes success for the zero-landfill initiative will be different for each park,” says Julie Klein, a sustainability consultant for the National Parks Conservation Association. “Experts in zero waste do look at it as a continuum.”

If the three pilot parks are successful, she says, more parks could adopt the model.

Small Drop in a Big Bucket

The zero landfill campaign is part of a broader attempt by the parks to combat climate change. It comes a year after government scientists published a report showing “extreme” climate change in national parks , which face hotter weather, loss of scenic glaciers, disruptions to wildlife, and rising sea levels.

While energy use and fuel consumption are driving climate change, landfills produce 20 percent of all methane, a potent greenhouse gas that causes 25 times more global warming than carbon dioxide.

“It’s a small drop in the bucket, but it’s an important drop,” says Clark Bunting, president and CEO of the National Parks Conservation Association.

View Images A hiker observes California’s Yosemite Falls, which attract almost 4 million visitors every year. Photograph by Bill Hatcher, Nat Geo Image Collection

Eliminating landfill trash, meanwhile, is no small task. Denali, Yosemite, and Grand Teton each face big challenges in making the change.

Alaska's Denali National Park is more than 50 miles from its closest recycling center, which can’t handle large recycling streams. One area recycling center temporarily shut down last year when a surge of plastic recyclables from the park’s food and hospitality partner overwhelmed its facility.

That helps explain why Denali dumps 80 percent of its trash in landfills.

And because visitors only come to Denali about 100 days out of the year, better facilities wouldn’t get much use. “It’s like trying to build the church for Easter Sunday,” Klein says.

Yosemite, which is nearby stronger recycling and composting markets in the Bay Area, sends just 30 percent of its trash to a landfill. Even so, the park’s landfill is reaching capacity, eventually pushing waste haulers to bigger, farther facilities.

Wyoming's Grand Teton recycles or reuses less than 30 percent of its waste and composts almost none, hauling most of its trash 90 miles to a landfill in Idaho.

With all those barriers, Klein says, “the parks can’t do this own their own.”

It Takes a Village

So the park service is looking to Subaru and other partners for help.

When Subaru went zero landfill more than a decade ago, “we started very simply by dumpster diving,” says Denise Coogan, a Subaru environmental and safety manager. By making an inventory of all their trash and tracing its origins, the car maker could separate and recycle the material more effectively. The tricky part, Coogan says, was finding enough recycling operators to take their excess steel, plastic, glass and other supplies.

The car company also reduced its excess material by 50 percent by eliminating unnecessary packaging, reusing containers, and cutting car parts more precisely.

The Park Service followed Subaru’s lead by conducting a waste audit this spring. Once it understands what kind of waste visitors create, the parks will devise plans to deal with it.

Coogan says the parks will have to engage their diverse group of stakeholders, including food suppliers such as Cisco and US Foods, regional trash and recycling operators, and tour businesses bringing visitors to the park. The goal is to reduce the trash coming into the parks so they have less to manage.

View Images A moose crosses a lake in Alaska’s Denali National Park, hours away from the nearest recycling center. Photograph by Michio Hoshino, Minden Pictures, National Geographic

Eric Smith, deputy superintendent of Denali, says communication among park stakeholders has often been disjointed and hopes a unified approach on zero landfill can facilitate real change.

“What I like about the public-private partnership," says the National Parks Conservation Association's Bunting, "is we’re marrying a private success to a public need.”

It isn’t the first time the parks have collaborated with industry.

Even before the Park Service was officially established in 1916, railroad companies played an integral role in bringing tourism to the parks. The transcontinental Northern Pacific Railway, built a “Park Branch” line to bring people to Yellowstone in 1883.

“Our first director, Stephen Mather, was very anxious to get Americans into our parks, pretty much in any way possible,” says Robert Sutton, chief historian of the National Park Service.

Today, with more than 270 million people visiting each year, Mather achieved his goal. But his success created another problem, which the parks are still trying to clean up.

WATCH: Yosemite National Park is one of America's first wilderness parks and visited by millions each year.