Yangsook Chung, left, and Manlim Choi, from Salt Lake City, take a snapshot along a short trail at a scenic overlook off Trail Ridge Road, above tree-line at Rocky Mountain National Park in Colorado, Monday, July 14, 2014.

(AP Photo/Brennan Linsley)

The Wilderness Act has meant millions of acres of land in Colorado are protected against anything that would change their natural character; anything mechanical or motorized is banned from those areas. The law, signed 50 years ago today, established land that would remain “untrammeled” by humans. But Jonathan Jarvis, director of the National Park Service, says that's getting harder to do.

"The paradigm that we have managed our National Parks, and particularly our wilderness areas, very much of a hands-off, leave it untrammeled... is being challenged by, particularly, climate change," he says. "We are seeing anthropogenic changes in our protected areas, whether it's fires burning, exotic species coming in behind fires, glaciers melting in Glacier National Park."

"It is causing us to begin to rethink our management policies around wilderness and protected areas," he adds.

In Rocky Mountain National Park, where about 95 percent of the land is designated as wilderness, cheatgrass is spreading into higher elevation areas where it's not native, kicking out native plants and increasing the risk of a dangerous wildfire. "We are going to have to take some management actions to control that," Jarvis says.

Already scientists in the park are intervening on a limited scale by hiking into the wilderness to apply a spray treatment, which is loaded into backpacks. That allows park managers to target small infestations of cheatgrass while not violating the Wilderness Act's ban on using mechanized or motorized equipment.

"Obviously we want to have a very light touch," Jarvis says.

Adapting to the effects of climate change and pollution is just one of the strategies the National Park Service is employing, Jarvis says. The agency is also monitoring changes in the parks, trying to reduce NPS' own carbon footprint, and educating park visitors about the effects of climate change.

Part of adaptation is also restoring more native species, Jarvis says: "In order to have... long-term resiliancy in the ecosystem, we're going to need some redundancy: more places that are protected that provide refugia for species that are under pressure by climate change."

But the decisions Jarvis' agency is facing are made with a lot of nuance, as exhibited in a scenario laid out in an article published a few years ago in the research journal of the National Park Service, called Park Science. The article explores whether there needs to be changes to the definition of wilderness. It includes a hypothetical scenario, where a forested wilderness area experiences a massive crown fire that’s more severe than the area had seen historically. Subsequently rains cause a lot of erosion, and that means the big, native trees can’t grow back. As a result, shrubs and nonnative grasses adapted to that kind of landscape move in.

The article suggests that scientists could have thinned the forest, preventing the extensive damage from the wildfire, and then poses the question: Which landscape is more undisturbed, the one that got all the shrubs and nonnative grasses, or the one that was managed and maintains its tree cover?

Jarvis says he wouldn't want to thin the forest.

"I would say, in those scenarios, that it would be inappropriate to go into a wilderness area... and do that," he says. "Just because we're getting climate doesn't mean you take wilderness and put it over in the category of excessive manipulation, even if that does mean that we have a stand-replacing fire that might result in a change to that ecosystem," he adds.

Jarvis says the National Park Service cooperates with the other three federal agencies managing wilderness: the U.S. Forest Service, the Bureau of Land Management, and the Fish and Wildlife Service. "We talk about how can we work together to connect up the wilderness areas that are, you know, on Forest Service with potential wilderness areas in the National Park Service; what are the corridor that prong-horned antelope might need to move between those areas," he says.

Most important, Jarvis says, is to maintain the character of wilderness. "I think there is something very primal, something very rejuvinating about that. I like to tell my wife that humans only came inside recently," he says. "We spent millions of years in the outdoors, and there's something very deep in us that appreciates that. I think the way you connect with the origin of who we are as a species is in wilderness."

And even if the glacier in the background is melting, Jarvis says most people won't notice, adding, "If the glaciers are gone, you're still going to have an incredibly powerful experience with that place."