Lichens play crucial ecological and practical roles despite being nonpathogenic to humans. Ecologically, they act as early colonizers that break down rock to produce soil, stabilize desert soils, and serve as a vital winter food source for caribou. In some lichens, cyanobacterial partners fix nitrogen, enriching the environment. Humans utilize slow-growing, long-lived lichens in food, as dyes, as environmental indicators of pollution due to their sensitivity, and to extract antibacterial compounds that hold potential medical value.