Cliff Spencer knows what it's like to be singled out. The tall, slim 54-year-old is superintendent of Colorado's Mesa Verde National Park, and one of just a handful of African-Americans in the upper echelons of the National Park Service. Some years ago, when Spencer ran Arizona's Petrified Forest National Park, he strolled through the visitor center on the way to his office. When he reached his desk, a ranger was on the line: "Cliff, some people want to meet you." It was a black family from Atlanta, visiting several parks on their way to the Grand Canyon. "We've never seen a black person in uniform in any of the parks we've visited," they told him. "Do you mind if we take a picture of you?"

Spencer understood: It was probably the only such photo they'd get. In his 30-year career, Spencer has gotten to know many major Western parks and monuments, including Lake Mead, Point Reyes, White Sands, Petrified Forest and now Mesa Verde. But no matter where he's gone, brown-skinned rangers and tourists have been scarce. Even as the nation becomes increasingly diverse, park visitors and staff remain overwhelmingly white. Spencer's rise at the National Park Service is one of the agency's success stories, but also highlights its struggle to reach more minorities.

"There were two things I knew growing up," Spencer says. "I really loved the outdoors, and there was a whole country out there to see, and I wanted to go." As a child in inner-city L.A., Spencer went to summer camps in Griffith Park and discovered that archery, horseback riding and hiking were more fun than hanging out on the street. He attended college at California State, Northridge, majored in recreation administration, and got chosen for a program that gave minority students a chance to work at the nearby Santa Monica Mountains National Recreation Area.

If anyone understands the importance of having Americans of all races appreciating public lands, it's Spencer. "I would love to get to the time," he says, shaking his head, "when a black ranger is not a big deal, not cause for a double take." At Mesa Verde, he's reached out to nearby communities of color – the Navajo, Southern Utes and Ute Mountain Utes on whose ancestral lands the park sits. Tribal representatives helped design the new visitor center, a handful of Native interpreters guide tourists, and Native students have opportunities to intern. And yet Spencer, as the busy overseer of the nation's largest archaeological preserve, seldom writes "increase diversity" on his daily to-do list. "I think about it occasionally," he says, "but there are just so many other things going on. That's not an excuse, but I don't think I'm doing a very good job of promoting it."

Unfortunately, parks and other public lands are facing an array of challenges, and without increased support from citizens, these lands may be in jeopardy. "If Congress decides that it doesn't want national parks, they will go away," warns John Reynolds, who spent 36 years as a Park Service planner and regional director. Just last summer, Sen. Tom Coburn, R-Okla., suggested "removing" less-visited parks and putting new parks under private management. During last fall's federal shutdown, states like Utah took over some national parks, fueling calls from some locals for permanent control. In March, the U.S. House of Representatives voted to gut the Antiquities Act, which several presidents have used to protect lands that later became national parks, including Grand Canyon and Grand Teton. And underfunding remains a chronic problem – the agency's budget doesn't even keep up with inflation, and it staggers under a nearly $12 billion maintenance backlog.

Given these threats, "we can't allow millions of people, generations of people, to not experience parks and to have no connection to them," says Spencer. "When those people get into positions where they'll influence policy and hold the purse strings, they won't understand what parks are and how important they are."

Thus, the Park Service's diversity dilemma. Despite years of rhetoric about the importance of the issue, the agency's on-the-ground actions have failed to keep pace. In 2016, the Park Service will celebrate its centennial, and the stakes have never been higher. "Some of the things we are seeing now are symptoms of waning relevancy," says agency director Jon Jarvis. "The flattening of our budget, sequestration cuts, the political pressures on the Park Service to allow everything from extractive usage to more motorized recreation. Rather than continuing to treat the symptoms, we need to go for the cure – and make that connection with all people."

Today, a handful of pioneering urban parks, such as Boston Harbor Islands National Recreation Area in Massachusetts, and Golden Gate National Recreation Area in San Francisco, are using innovative programs to reach out to under-represented communities. Can they lead the rest of the massive park system into the future and help a new, more diverse generation find relevance in America's "Best Idea" – before it's too late?