I found some interesting facts about Christmas fern here, and I quote from that site: "Christmas fern may grow in large, extensive colonial masses but more typically is found in clusters of two or three individuals. Growing ferns and the accumulated detritus of past sterile fronds form a dense covering mass over the soil surface. This mass helps to stabilize the underlying soil and prevent or lessen erosion. It also generates a protective, concealing habitat for a number of ground feeding and ground nesting bird species. Because of their complex chemical composition, ferns are eaten by very few browsers or grazers."