Chocolate Rim Lichen

The Chocolate Rim Lichen (Protoparmelia badia) is a crustose lichen in the family Parmeliaceae, found on exposed siliceous and acid rocks in montane and subalpine environments across Europe, North America, and other temperate and boreal regions. Crustose lichens form a tightly adhering crust directly on rock surfaces and lack the lobed margins of foliose lichens, making them impossible to remove from substrate without destroying the thallus. Protoparmelia badia forms a thin, pale grey to brownish-grey thallus with conspicuous reddish-brown to dark chocolate-brown apothecia (disc-shaped reproductive structures), from which the common name derives. The species is typical of well-lit, clean-air rocky habitats such as mountain summits, upland heathland, and acidic outcrops. Like many lichens, it is a pioneer coloniser of bare rock surfaces and contributes to the initial stages of soil formation. The IUCN classifies P. badia as Near Threatened, reflecting concerns about declining populations linked to air pollution — lichens are renowned biological indicators of air quality, being highly sensitive to sulphur dioxide, nitrogen oxides, and ammonia — as well as climate change effects on montane habitats and disturbance from rock climbing and other outdoor recreation.