Even in places where climbers can get permission, the process is often difficult. Typically, a climber has to apply for a permit every time she wants to climb on public land. And because the sport is still so new, many officials are unfamiliar with it and unsure how to handle permit requests.

While some national forests and a few cities, such as Boulder and Evergreen, Colo., allow tree climbing, national parks remain strictly off-limits. Only forest ecologists and a handful of other researchers are permitted to climb trees in parks. This is because it is a ranger's "primary mission" to "protect the park," says Janet Cooper, special park use coordinator for Redwood National and State Park in California.

Researchers, Cooper says, have the training to minimize damage to trees, something that can't be counted on with recreational climbers. And a bunch of people dangling around in the canopy is bound to impact wildlife, particularly species like the endangered marbled murrelet, which nests in old-growth forests. Besides, says park spokesman Rick Nolans, opening national parks to climbing, at least in California, is unnecessary. "There're so many opportunities to climb elsewhere in California, it's not really a big deal for them to do so," he says.

But many climbers want to climb in national parks. Cooper notes that the Redwood office alone receives three to four calls a week from people asking about climbing trees in the park. The park denies all requests, a stance that veteran tree climber Jenkins respects. "Rangers are trying to preserve what's there," he says, "and have a hard enough time chasing tourists who don't behave well."

In the vast bottomlands of Georgia and Florida, 66-year-old "Swampy Joe" Maher often wades through water up to his "belly-button," paddles silently in his canoe, or catches a ride on a jon boat, in search of the perfect old-growth bald cypress tree. He travels light, often with just a backpack carrying little more than water, a few ropes and some mesh for a makeshift harness. When he finds a perfect tree, his "desert island" in the swamp, he glides up in his canoe, docks at the trunk and climbs the tree right from the boat. There is nothing around him for miles, no cars, no people, just tree after tree - and silence. "When I go out on what I call a ‘real' tree climb, I go to the swamps," says Maher. "I love swamps."

Maher, like hundreds of other tree climbers, doesn't ask permission first. He just does it. And for that reason, in the lexicon of tree climbing, he's considered a rogue. Rogue climbing has several offshoots - including ninja, or stealth climbing - which involve deliberate trespassing.

The term "rogue" is mostly a joke within the tree-climbing community, because it implies that simply climbing without permission is a renegade pursuit. But stealth and ninja climbing represent a murkier area. And not everyone in the woods shares the wilderness ethics of climbers like Maher, Teitelbaum and Jenkins, who practice "leave no trace" and wear muted colors - doing their best to avoid detection and lessen environmental disturbance.

"People hike out to a tree and one of the first things they do is begin stomping down all the surrounding vegetation," in order to clear the way for throwing a line into the tree, says Maher. Others see a dead tree branch and can't resist the desire to cut it off. "People within the recreational tree-climbing community have an idea that trees need to be ‘developed' for climbing," Maher says. "They will take handsaws and cut every dead tree branch or branch that is an impediment to climbing. Some people will go out into forests just to trim a dead limb because it's there. I get very annoyed with these people."

Rice, with the Georgia Department of Natural Resources, says ninja climbing harms the cause of tree climbers rather than helping it. "I don't support stealth or ninja," says Rice. "We have to look at that seriously. You have a responsibility to give people an idea of where you are," he says. "If they get caught, it just hurts the long-term effect of getting this approved."

But Jenkins sees stealth climbing as part of the sport's natural evolution. "Tree climbing is new," says Jenkins, "and because it's new, probably what's going to get policy to change is people climbing."

Back in Evergreen, Colo., I'm dangling 80 feet off the ground, trying to avoid touching the tree. Three children flank the tree lower down, yelling encouragement as I near the top of the climb. I'm using a technique that, on rock, would be called aid climbing. My legs, arms and abdominal muscles burn as I bring my knees to my chest and pull myself up the rope with all my might in a decidedly ungraceful maneuver. Thonk. My head bounces off the branch above me, but thanks to my helmet, I hardly feel the blow.

I've reached the end of my rope. This trip stops just above the main branches of the tree. Though I won't get to the top, seeing the world from a bird's-eye view is exhilarating. Life is pretty quiet up here, hanging with the branches. It's like a great view from a skyscraper, but instead of city streets jammed with ant-like cars, there's just the breeze and the sunshine. One of the kids asks if I'm going to come back down, but I'm in no hurry.

I flip upside-down to get the squirrel's-eye view and try unsuccessfully to "tree dance," swinging away and spinning a 360.

Teitelbaum stands in miniature on the ground, waiting for my signal indicating that I'm ready to descend. And the kids are anxious to head off for some afternoon swimming. I'm confident that the climb gave the children a greater appreciation for the trees that are all around them. Still, I'm all too aware of the impact we had, how we bumped and scraped our way up the tree trunk.

I take some comfort in the idea that "Gus Otis," like so many other trees, has survived centuries of storms, drought and even forest fires. Generations of animals have dug and scratched away at its bark; birds have come and gone, and who knows what else has happened to it. I suppose it can survive the attentions of a few tree-climbing, fun-loving humans. At least I hope so. Before descending, I take another moment to savor the quiet up among the branches, because even if the trees survive, this solitude may not.

Morgan Heim is a former HCN intern. She is a freelance journalist and photographer, who is currently finishing a master's at the University of Colorado's Center for Environmental Journalism in Boulder.