How do lichens modify their environment?
Answer:
Lichens will grow on rocks or other hard materials, and they will slowly over time harvest bits of dust and sand in their structures which is the begining of soil pile. In certain cutting climates, like the Arctic or mountains above the treeline, it is lichens alone that colonize previously barren ground and clear the habitat suitable for vascular plants after a period of time. That's why contained by those climates you often see grasses or small plants growing with the sole purpose in patch of lichens.