As public service announcements go, it's on the fun side: Yosemite National Park posted a video of someone knocking over a stacked pile of rocks—a cairn—and encouraged visitors who come across them to do the same, reports SFGate. Why? Yosemite rangers say these structures violate leave-no-trace principles. This "dramatically oversized cairn is a mark of human impact and is distracting in a wilderness setting," says the park statement. "Building rock cairns also disturbs small insects, reptiles, and microorganisms that call the underside home!" However, the announcement has created a bit of controversy—and confusion.
Officials at other national parks disagree with the knock-it-down approach. For example, a spokesperson for Arches and Canyonlands national parks in Utah tells ABC4 that visitors should leave such cairns in place, because some have been built by rangers as navigational guides. Also, even if people are knocking down an unsanctioned cairn, they might cause more damage to the surrounding environment by toppling it. "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," says Karen Garthwait.
It's a tricky subject, writes Adam Roy at Backpacker. One thing all the parks agree on is that hikers should not build new cairns. As for the question of whether they should knock down existing ones, well, "it depends on the situation," writes Roy. Some are indeed vital for figuring out a correct route. When in doubt about whether one in place is useful or mere decoration, the best thing to do is find a ranger and ask, he advises. (More Yosemite National Park stories.)
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