The Grand Canyon’s walls chart 17 million centuries, a third of this planet’s lifetime, and eons of water and wind have shattered them. From the main stem of the canyon, where the river laces through so far below as to often be silent and invisible, side canyons branch off, then splinter into their own side canyons. The puzzle is further complicated by ledges, which routinely cliff out, forcing would-be hikers to climb up or rappel down to another.

"You're constantly moving in and out, and you're constantly moving up and down, and you're moving that way more than you're moving laterally—it's a really frustrating way to travel," says Kevin Fedarko who, with photographer Peter McBride, section-hiked the length of the Grand Canyon over 14 months.

Efficient travelers float the canyon's 277 river miles in about four weeks. On foot, Fedarko and McBride's route totaled 700 or 800 miles.

"It becomes very difficult to calibrate because you're going in and out of so many side canyons," Fedarko says. "So we're not actually sure how far we walked."

They sweltered through summers, shivered through storms that frosted cliff edges with inches of snow, and bled from cactus spines and blisters. While hiking hundreds of feet above the river, water often came from potholes filled by recent storms, sometimes so shallow they required plastic medical syringes to tap.

"It's a place almost 6 million people go to every year to look in to, but there's almost no way to walk from one end to the other—at least not easily—so that means the interior is filled with all these secrets that very few people go to or set eyes on," Fedarko says. "It's a secret in plain sight."

McBride, filming the adventure, caught Fedarko referring to the experience as an ongoing river of pain, a stern epithet for a canyon that so obsessed him that it compelled him to quit his job as an editor at Outside Magazine and leave Santa Fe to work as an apprentice raft guide, rowing a boat carrying human refuse through some of the Colorado River's fiercest rapids. The experience informed his book, The Emerald Mile: The Epic Story of the Fastest Ride in History Through the Grand Canyon.

Fedarko, it seems, likes to suffer for a good story. He's writing up this latest trek for a book as well, while McBride works on a feature-length film. Both are striving to tell the story of the Grand Canyon in a way that makes the case for protecting it; despite benefitting from some of the country's strongest conservation laws, preserving the Grand Canyon makes for a daily fight. Fedarko takes that campaign to the KiMo Theater (7 pm Thursday Sept. 21. Free. 423 Central Ave. NW, Albuquerque, 505-768-3522), a teaser to a 2018 National Geographic lecture tour.

The Grand Canyon, Fedarko says, "is a place that's viewed by many if not most people to be kind of sacrosanct and permanently protected, and yet is beset by a whole range of development threats from literally every cardinal point."

On the east, a developer has proposed a tramway to the confluence of the Little Colorado and Colorado rivers, a site considered sacred to the Hopi, Zuni and Navajo. A cable system of gondolas would take thousands of people a day to a walkway, restaurant and amphitheater on the canyon floor. South of the rim, a 2,200-home development has been proposed that could drain the area's aquifer, choking off the springs that create idyllic oases deep within the canyon. Hundreds of helicopter tours come from the west, filling the air with thrumming noise. Uranium mines to the north have already rendered streams radioactive, and pose a risk of contaminating the Colorado River for its millions of downstream drinkers.

Threats to the Grand Canyon aren't new, says Roger Clark, program director for the Grand Canyon Trust. Over 30 years, that organization has fought coal-fired power plants graying the park's vistas; hydroelectric dams impeding a flood-driven ecosystem; helicopter tours once able to hover so close to Thunder River, a spot where water comes roaring out of the sandstone, that the waterfall couldn't be heard. Some campaigns have gone on for so long they've outlived the people who initially undertook them.

"What's going on today is a continuation of people finding different ways to make money off of Grand Canyon National Park and, in some ways, to exploit it," Clark says.

Developers have argued some of these projects increase public access, but Fedarko contends that that ignores a key point about our national parks.

"If you provide access in such a way as to damage or impair the very thing that is drawing people into the parks," he says, "you have negated the reason for protecting it in the first place."