MOAB, Utah (ABC4) — Last week, park rangers with Yosemite National Park shared a video of Wilderness Restoration Rangers toppling over a large stack of rocks. The park said park visitors should absolutely knock the rocks over, sparking some confusion.

The stacks of rocks are known as a rock cairn.

Yosemite National Park officials said the cairns are a sign of human impact. According to the Leave No Trace ethics for the national park, the goal is to leave no signs of human impact on the land and to respect creatures living in the parks. Building the cairns also disturbs small insects, reptiles, and microorganisms living beneath the rocks.

However, not every rock cairn at every national park should be dismantled.

Arches and Canyonlands National Parks spokesperson Karen Garthwait said when used appropriately, the ranger-built rock cairns are beneficial to visitors to mark designated hiking trails.

“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,” said Garthwait. “We also ask that visitors not create their own sculptures out of the rocks that they find and collect.”

Following the same, Leave No Trace ethics tailored specifically for Arches and Canyonlands, Garthwait said people come from around the world to see the natural beauty of the parks’ rock formations. The “spontaneous sculpture gardens” distract from the park’s natural beauty.

Visitors who take building rock cairns into their own hands can also cause unintended damage to the park’s ecosystem. Garthwait told ABC4 walking off-trail to gather walks could damage fragile biocrusts and disturb the animal habitat.

Garthwait said rather than knocking anything down, visitors should report any suspicious rock stacks or sculpture gardens just like they might report graffiti around the park. Once reported, staff can assess it and remove it safely.

As for how to tell a ranger-built rock cairn from a visitor-made one? It’s a little hard to say.

“Appropriately sized rocks are not uniformly distributed on all trails, and some trails require taller cairns if the desert terrain is uneven or has challenging sight lines,” said Garthwait. “That said, ranger-built cairns tend to have at least three levels of rocks, are built for stability, and are positioned so that you can see the next one at a linear distance from the previous one.”

Garthwait explained that rock stacks that are grouped together like a garden or contain any vertically balanced rocks that look “precarious” are more than likely to visitor built.

Sometimes a rock “garden,” as Garthwait called them, can form next to an official cairn.

“[That] is why it’s best not to knock anything down here, but just report it to a ranger,” said Garthwait.