Breaking the protective layer not only allows disease in, but it may also cause cellular damage if the cut penetrates below the bark, disrupting its ability to transport nutrients through xylem and phloem.In Dalarnas, Sweden, tree carvings from the 17th century called fäbodsristning, made by girl shepherds, have been documented by the local museum.[9] In 2021, a collaborative project to find and trace histories etched in boab trees in the Kimberley region of Western Australia was launched.It has been speculated that at least some of the symbols represent the dead, based on the fact that in some, the figures have their knees pulled up to their chests, in the position that deceased Moriori were buried in dunes.[12] Basque immigrants from the Pyrenees came to work as shepherds in the mid-19th century, and, spending long hours alone in forests, etched drawings and poetry into the aspen trees with a knife or even their fingernails.The ancient oak in the Santa Lucia Mountains in San Luis Obispo County had the outline of a lizard-like being with six legs, nearly 3 ft (0.91 m) tall, carved into its trunk, and included a rectangular crown and two large circles.In the 1970s, anthropologist Travis Hudson's book Crystals in the Sky combined his observations of the rock art of the Chumash people with cultural data recorded by ethnographer John P. Harrington nearly a century earlier.