I understand a bit about the topic of cairns, but more because I've heard people who love the outdoors debating the merits of them, about the upheaval of habitat that happens when people want to mark their path. Clearly, these cairns were little threat to habitat:
I thought of the other ways we try to mark our existence, to say, "Hey, I was here."
Some of those ways are more subtle: we create a garden, which won't last long without someone there to tend it once we're gone.
We've developed every sort of ritual to signify our passages.
We've tried so hard to deal with all that scares us, to scare away the haints.
In the end, all we can do is walk the path where we find ourselves.