Ethnolichenology

Ethnolichenology is the study of the relationship between lichens and people. Lichens have and are being used for many different purposes by human cultures on every continent, with the possible exception of Australia. The most common human use of lichens is for dye, but they are also frequently used for medicine and food. Different human cultures across the world have also found many other more novel uses for lichens.

Lichens for dye
Lichens are a common source of natural dyes. The lichen dye is usually extracted by either boiling water or ammonia fermentation. Although usually called ammonia fermentation, this method isn't actually a fermentation and involves letting the lichen steep in ammonia (traditionally urine) for at least 2 to 3 weeks.

In North America the most significant lichen dye is Letharia vulpina. Indigenous people through most of this lichen's range in North America traditionally make a yellow dye from this lichen by boiling it in water.

Historically, traditional dyes in Scotland were very important. Brown lichen dyes (called crottle) and red lichen dyes (called corkir) were used extensively to produce tartans.

Purple dyes from lichens were historically very important throughout Europe from the 15th to 17th centuries. They were generally extracted from Roccella spp. lichens imported from the Canary Islands, Cape Verde Islands, Madagascar, or India. These lichens, and the dye extracted from them, are called orchil (variants archil, orchilla). The same dye was also produced from Ochrolechia spp. lichens in Britain and was called cudbear. Both Roccela spp. and Ochrolechia spp. contain the lichen substance orcin, which converts into the purple dye orcein in the ammonia fermentation process.

Lichens for medicine
Many lichens have been used medicinally across the world. A lichen's usefulness as a medicine is often related to the lichen secondary compounds that are abundant in most lichen thalli. Different lichens produce a wide variety of these compounds, most of which are unique to lichens and many of which are antibiotic. It has been estimated that 50% of all lichen species have antibiotic properties. One of the most potent lichen antibiotics is usnic acid, as a result Usnea spp. are commonly used in traditional medicines. Other lichens commonly featured in folk medicines include Iceland moss and Lungwort.

Lichens for food
There are records of lichens being used as food by many different human cultures across the world. Lichens are eaten by people in North America, Europe, Asia, and Africa, and perhaps elsewhere. Often lichens are merely famine foods eaten in times of dire needs, but in some cultures lichens are a staple food or even a delicacy. Two problems often encountered with eating lichens is that they usually contain mildly toxic secondary compounds, and that lichen polysaccharides are generally indigestible to humans. Many human cultures have discovered preparation techniques to overcome these problems. Lichens are often thoroughly washed, boiled, or soaked in ash water to help remove secondary compounds.

In the past Iceland moss was an important human food in northern Europe and Scandinavia, and was cooked in many different ways, such as bread, porridge, pudding, soup, or salad. Bryoria fremonii was an important food in parts of North America, where it was usually pitcooked. It is even featured in a Secwepemc story. Cladina rangiferina, or reindeer lichen, is a staple food of reindeer and caribou in the arctic. Northern peoples in North America and Siberia traditionally eat the partially digested lichen after they remove it from the rumen of caribou that have been killed. It is often called 'stomach icecream'. Rock tripe is a lichen that has frequently been used as an emergency food in North America.

In India, and other centers of curry powder production, garam masala sauce contains certain lichens used as bulking agents.

Other human uses of lichens
Lichens have been and are still being used for many other purposes, including
 * Alcohol production (for fermentable carbohydrates, as catalysts, and/or as flavour/preservatives)
 * Cosmetics (for hair, and/or sweet smelling powders)
 * Perfumes (see Oakmoss)
 * Decorations (including costumes and artwork)
 * Fibre (clothing, housing, cooking, sanitation)
 * Animal feed (both fodder and forage)
 * Fuel
 * Industrial purposes (production of acid, antibiotic, carbohydrate, litmus)
 * Tanning
 * Hunting/fishing (to find prey, or to lure them in)
 * Navigation
 * Insect repellent/insecticide
 * Preservatives (for food or beer)
 * Poison (arrowheads, wolves)
 * Mummies (see Pseudevernia furfuracea)
 * Rituals
 * Magic
 * Tobacco
 * Narcotics
 * Hallucinogens