The word”cairn” comes from the Scottish Gaelic meaning stone man. It may conjure images of faith, purpose, and spiritual journeys. In the backcountry, cairn making is a popular trend and it’s easy to understand why people are attracted to these adorable stones that are shaped like children’s building blocks. With shoulders hurting and black flies buzzing through ears, hikers will examine the stones around her, and then try to select one that is just the right mix of tilt and flatness in depth, breadth and width. After a few near misses (one that’s too large, another that’s too small), the purist will pick the one that sets perfectly in place, and the subsequent layer of the cairn becomes complete.
However, what a lot of people don’t realize is that cairn building can have an adverse environmental impact, especially when it’s done near water sources. When rocks are removed from the edge of a river, pond or lake, it disturbs the ecosystem and destroys the habitat for microorganisms that support the entire food chain. The rocks could also be carried away from the edges of a river, pond or lake by erosion, and end up in areas in which they could harm humans or wildlife.
In light of this, the practice of making cairns should be avoided in areas where there are endangered or rare reptiles, amphibians, or mammals or plants and flowers that require moisture locked under the rocks. If you build a stone cairn on private land it could be in violation of federal or state regulations protecting the natural resources of the land and cause fines or even arrest.
http://cairnspotter.com/here-are-some-interesting-facts-about-cairns