Should You Knock Over Cairns or Leave Them? Even the National Park Service Can’t Agree.

In a viral PSA, Yosemite National Park urged hikers to knock over rock cairns. Days later, staff at Canyonlands and Arches asked hikers not to. What's a backpacker to do?

Photo: Jordan Siemens / Stone via Getty

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Should you leave cairns alone or destroy them? Ask that question to a group of backpackers and you’re likely to spark the kind of argument that strains tramilies. Some hikers pass rock stacks by without touching them, while others kick down every pile they see. Now, as it turns out, even the National Park Service doesn’t have an easy answer.

Last week, staff at Yosemite National Park brought the debate over rock-stacking to the forefront when they posted a video  of a volunteer pushing over a head-high cairn on their social media, sending each rock crashing to the ground. The caption seemed to encourage visitors to do the same.

“Should you knock this over?? Yes!” the park wrote. “Why did Wilderness Restoration Rangers dismantle this rock cairn? According to Leave No Trace ethics when we recreate in wilderness spaces, our goal is to leave no signs of our impact on the land and respect other creatures living in it. Unfortunately, this dramatically oversized cairn is a mark of human impact and is distracting in a wilderness setting.” 

While the message noted that cairns can be useful as navigational tools in the right setting, it said that building them also disturbs the microorganisms, animals, and plants that rely on rocks for shelter. Instead, park staff suggested, visitors should “dismantle and refrain from building rock cairns when [they] visit Yosemite.”

Yosemite’s post blew up online, getting traction across both outdoor and mainstream media. “Yosemite rangers give the green light for hikers to knock down cairns,” read one headline on SFGATE, while a Bay Area NBC station posted that Yosemite had told visitors to “Stop building, knock over rock cairns.” But even as the cairn-haters were rejoicing, staff at other parks were raising objections. 

In an interview with Utah’s ABC4 on Monday, Karen Garthwait, a spokesperson for Arches and Canyonlands national parks, said that cairns are a necessary part of trails in those parks, marking routes for visitors across otherwise unsigned hard-to-navigate terrain.

“We ask that visitors do not disturb them, knock them down, add to them, or build their own, as that can lead to other visitors getting lost in the desert,” Garthwait said. “We also ask that visitors not create their own sculptures out of the rocks that they find and collect.”

So are warring cairn and anti-cairn factions about to spark a civil war within the NPS? And if so, which side should you enlist in? As it turns out, the choice may be easier than you think. Yes, the way that the parks decided to share their message was confusing, but when you get to the root of it, all three parks’ positions on whether you should knock over cairns more or less boils down to this: It depends on the situation.

In some situations, cairns are tremendously useful navigational tools. That’s especially true on hikes through rocky areas like Arches and Canyonlands, where the trail is often more of a notion than an actual path and installing traditional signage is difficult. In that case, ranger- and trail worker-built cairns can keep hikers on track and prevent them from wandering off. The problem comes when random hikers decide to take matters into their own hands and start stacking rocks either for fun or as improvised navigational aids. At best, those piles are an eyesore; at worst, they can lead hikers off the trail, damaging plant life or getting people lost.

Telling the difference between hiker-saving cairns and someone’s Instagram art project isn’t always easy. If you’re trying to decide whether to show a cairn the bottom of your boot, we suggest following these simple rules.


If there’s a lesson to be learned from this week’s Cairn Discourse, it’s that park rangers are the experts on what’s going on in their own parks. Find a ranger or call the visitor’s center and ask what you should do if you see a rock pile. Hiking somewhere more remote? Find a trustworthy local hiker and ask if the cairns there are for navigation or decoration.

Never Build New Cairns

One thing Yosemite, Canyonlands, and Arches agree on: Hikers shouldn’t be building new cairns. A lot of invertebrates, lizards, fish, fungi, and more thrive in the cool, sheltered conditions underneath stones; peeling them up puts those denizens at a disadvantage, even if you disassemble your stack later. Unless you’re volunteering on a trail crew, leave the rock stacking to the experts.

But Sometimes It’s Obvious

Hikers use cairns by navigating from pile to pile. If there are dozens of stacks of rocks clustered on one summit or riverbank, it’s a fair bet that they’re not doing anything but taking up space. Channel your inner Jean-Claude Van Damme and kick ‘em down.

From 2023