Rock Tripe Lichens
Introduction
"Rock tripe is the common name for various lichens of the genus Umbilicaria that grow on rocks.[1] They are widely distributed, including on bare rock in Antarctica, and throughout northern parts of North America such as New England and the Rocky Mountains." - Wikipedia: Rock tripe
Types of Rock Tripe & Their Locations
All species of Umbilicaria lichen grow on bare, sunny exposed rocks, usually on nearly-vertical faces on rocky ridges.
"Umbilicaria americana is normally found on sheer granite rock faces such as cliffs and huge boulders. It prefers to grow in wet forested areas in sheltered sites. In really well suited sites, this lichen is abundant, covering entire rock faces. Look for it on the underside of smooth rock outcrops near a river or lake, or in wet forests." - USDA: Frosted rock tripe
Emery rock tripe "tends to grow, sometimes in groups or patches, in desert areas or in other arid and dry climates in western North America and South America. While typically brown, some varieties in northern California and the Pacific Northwest grow a bright red. The leaf-like cap of the lichen tends to be very smooth and is host to many small black spots." - TM Parks Foundation: Emery Rock Tripe
Umbilicaria torrefacta "is a boreal lichen species with a mainly northern and western distribution. It is found from Alaska south to California, and east to the Lake Superior region and the high mountains of New England. In Minnesota, U. torrefacta is known from a single population documented in Cook County in 1980. At the time of its designation as a state special concern species in 1984, its distribution in the state was uncertain and the known locality was not threatened. However, further searches have not yielded any new locations in the state, and the single known population in is being subjected to increased rock-climbing activity. For these reasons, U. torrefacta was subsequently reclassified as state endangered in 1996." - Department of Natural Resources: Umbilicaria torrefacta
Edibility
Rock tripe has historically been a useful emergency/famine food, but it is now considered a delicacy eaten in salads or deep fried.
"They are edible when properly prepared; soaking extensively and boiling with changes of water removes the bitterness and purgative properties.[2][3] They have been used as a famine food in extreme cases when other food sources were unavailable, as by early American northern explorers.[2]
Umbilicaria esculenta is commonly used as a food in Asian cuisine and a restorative medicine in traditional Chinese medicine. It is called shi'er (石耳 "rock ear") in Chinese cuisine, iwatake (岩茸 "rock mushroom") in Japanese cuisine, and seogi (석이(石耳)) or seogibeoseot (석이버섯) in Korean cuisine." - Wikipedia: Rock tripe
Threats
Rock Climbing
"The preferred rock outcrop habitat for this lichen is also attractive to rock climbers, who are drawn by the physical challenge. Consequently, recreational use of the rock faces that harbor this rare lichen presents a serious threat to the only known population in the state." - Department of Natural Resources: Umbilicaria torrefacta
Harvesting
These grow so slowly that they can't be considered a general food source. Overharvesting could very quickly wipe them out.