Gabe Garcia and John Miller stood the other day at the rim of Cucamonga Canyon, dwarfed by the spires of peaks with names that evoke old, wild California — Timber, Telegraph, Bighorn.

They were supposed to be alone.

They were not.

"Red shorts! White shirt!"

Garcia, a San Bernardino National Forest district ranger, barked the description to Miller, his Forest Service colleague, who yanked a pair of binoculars to his eyes.

The hikers were there, sure enough, but far away, deep in the folds of the canyon. From the spot where Garcia and Miller were standing, 40 miles east of Los Angeles, there wasn't much chance of catching them. But if the hikers were caught, they'd face a federal citation that could bring a $5,000 fine and six months in prison — for walking through public land, on a path taken thousands of times before.

Things are different this year in the San Bernardino National Forest. Cucamonga Canyon, a wildly popular natural area above Rancho Cucamonga, has been closed to the public by the Forest Service.

The problem, and the reason for the closure, is fire. Not a fire that has already happened — a fire that might happen. For the first time in decades, according to the Forest Service, Cucamonga Canyon has been closed for the duration of wildfire season to the people who own it, to save it from them, and from itself.

With California seemingly in a now annual state of heightened wildfire danger, this unusual step could become increasingly common. Similar fire-protection closures have been ordered in New Mexico and Arizona, according to Forest Service officials in Washington.

"This is the most extreme fire-prevention tool that we have," Miller said. And Garcia said he's weighing using it, during this most extreme fire season, to close several other wilderness areas to public access.

"That's the $64,000 question," Miller said. "Is this a part of our management strategy? If we're set up to be in a multiyear drought, it definitely will be something we'll consider."

Garcia stabbed the toe of his dusty boot into the ground beneath a yerba santa shrub. He pointed to its leaves, which were browning at the edges and curling up. "It's just out of water," he said.

Firefighters have been bracing for a terrible fire season since the spring. The year has brought one ominous sign after another. There were significant spring fires in Inyo County, for instance, long before that part of the state typically sees that kind of activity. State fire officials reported in April that they had recorded 150 more blazes — well before fire season — than at that point in 2012.

Veteran firefighters tend to ascribe personalities to fires, and those conversations have taken on an ominous tone this year. Miller was among the authorities who responded to the Summit fire near Banning earlier this year — and he watched as a routine brush fire exploded over 3,000 acres in little more than a day, and burned straight through the night. "In May!" he said with astonishment.

"The fire activity this year has just been different," Garcia said. "These things are just not wanting to come under control."

The fire season already includes the 400-plus-square-mile Rim fire in and around Yosemite National Park, which was ignited in mid-August by a hunter's illegal campfire. It has become one of the largest fires in California history, so large that its effect on patches of the Stanislaus National Forest is likely to last for decades.

Against this backdrop, Cucamonga Canyon began to look like a trail of gunpowder strewn through the thirsty mountains.

Cucamonga Canyon, which many people call Sapphire Falls, after the stream-fed pools that serve as the hike's turnabout, has seen heavy use for decades. But in recent years, the area's popularity has exploded spread through social media; on a hot day, despite limited parking adjacent to residential streets, it's not unusual to find 100 people gathered at the main stream pool alone.

Some of those people are not in it for an untainted nature experience.

The rock walls surrounding the main pool, and scores of large rocks along the walking path there, are covered with graffiti. Alcohol use is rampant; beer cans and empty 12-pack boxes are a common sight. And during a recent survey, forest officials found evidence of more than 70 illegal campfires in the flats below the falls.

A fire there, on a busy day, would be a disaster. The area is in year two of a severe drought; this year, authorities have recorded a quarter of what is considered a normal level of precipitation. Hikers, meanwhile, have one way in, and one way out. They are surrounded on all sides by dense, dry vegetation. The canyon's steep walls would act as a furnace, funneling flames directly toward the spots where people gather.

Garcia knows this much: "I'm not going in there. Not right now."

And so, in August, with a heavy heart, Garcia made the difficult decision to shut it down — closing 1,650 acres to public use until the area is saturated with rain. That could be soon, but it could be in 2014 too.

"It's the people's forest — they should have access to it," Garcia said. "But in the end, I didn't have much of a choice. It's hard."

scott.gold@latimes.com