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2.1 Introduction

Lichens are important traditional medicines in many different cultures. This information has been made available to us from the contributions of hundreds of traditional knowledge holders in communities across the world. It is our responsibility to respect and value the knowledge that has been given to us. This paper is a tribute to the wealth of traditional knowledge that exists about lichens.

There have been a few previous reviews on the traditional uses of lichens for medicine. The traditional uses of lichens in Europe were reviewed by Smith (1921), with later contributions by Llano (1948) and Richardson (1974). Sharnoff (1997) compiled the first global review lichen uses, which was added to by Crawford (2007). Upreti and Chatterjee (2007) reviewed the medicinal uses of lichens in India and republished Sharnoff’s (1997) database on medicinal uses elsewhere. Wang and Qian (2013) recently reviewed the medicinal uses of lichens in China. The current paper includes all the medicinal uses recorded by these previous authors, as well as many additional records. It is the most comprehensive review to date, but it is still far from complete.

2.2 Cultures That Use Lichens

There are records of medicinal uses of lichens in cultures in Africa, Europe, Asia, Oceania, North America, and South America. The majority of these uses are in North America, Europe, India, and China, but this is most likely because that is where the majority of the ethnographic work has been done. Interestingly, no records have been found for any traditional use of lichens in Australia.

It is difficult to determine the prevalence of lichens in traditional medicine across the world. Most ethnobotanists and ethnographers have ignored cryptogams, both historically and currently.

If the ethnographic literature on a culture does not mention lichens, it might be because that culture does not utilize lichens. However, it might also be because the ethnographer’s culture does not value lichens, and the ethnographer therefore did not notice and record the value of lichens in the culture that they were documenting. In the cultures for which traditional uses of lichens have been recorded, there are usually between one and three medicinal lichens. There are more records of lichen use among cultures in temperate and arctic areas and less in the tropics. This probably represents the relative dominance of lichens in these zones.

A few ethnobotanists have recognized the cultural value of lichens, and their work has been invaluable in documenting lichens in traditional medicines. These workers include, among others, N. J. Turner (Canada), M. R. González-Tejero (Spain), L. S. Wang (China), and D. K. Upreti (India). As a result, there is an overrepresentation of these geographic areas in this current analysis.

2.3 The Lichens That Are Used in Traditional Medicine

This paper documents a total of 52 different genera of lichens that are used in traditional medicines. The most commonly used genus of lichen is Usnea, which is used across the world for medicine, although it is often used synonymously with other arboreal hair lichens. Despite its worldwide importance, Usnea is not traditionally one of the dominant medicinal lichens in Europe. Numerous other genera of lichens have particular importance in certain parts of the world, as is shown in Table 2.1.

Table 2.1 Lichen genera commonly used in traditional medicine

2.3.1 The Folk Taxonomy of Lichens

All cultures develop a folk taxonomy of living organisms that allows people to make sense of the world around them. Folk taxonomies are unique to a specific culture and usually reflect its particular environment and values. Some cultures have a very detailed folk taxonomy for lichens. The traditional taxonomy of the Saami recognizes lichens as being a distinct life form from mosses and divides lichens into three different generic taxa and numerous specific taxa (Nissen 1921). Other cultures placed less value on lichens, which is reflected in a much more simplistic folk taxonomy for lichens. European botanists in the fifteenth century lumped all lichens, and many other cryptogams, into a single life form category of moss.

Folk taxonomies can be very accurate, but they are often different than the scientific taxonomy. This mismatch between folk and scientific taxonomies is particularly prevalent in lichens. For instance, the Saami folk genera of jægel includes Cetraria, Cladina, and Stereocaulon, but excludes Parmelia, which is placed in the folk genera gadna. The scientific taxonomy would lump Parmelia and Cetraria together in Parmeliaceae and exclude Cladina and Stereocaulon. Another example is the common practice within folk taxonomies of classifying lichens according to their substrate. There is often a folk genera that includes all arboreal hair lichens (and sometimes mosses), which are then divided into different species depending on what type of tree they are growing on.

One of the biggest challenges in ethnolichenology is that a folk taxon of lichens that has cultural significance may not be synonymous with any scientific taxon. This means that if a culturally important lichen is identified according to the scientific taxonomy without understanding the folk taxonomy, it may be recorded as the wrong lichen. For example, a botanist recorded that the Saami used Usnea plicata for blisters, but maybe the lichen that he saw only happened to be U. plicata, and the Saami actually used any species of Alectoria, Bryoria, or Usnea that was growing on a birch tree.

Folk taxonomies of lichens are intrinsically linked with the traditional methods of identifying lichens. It is very common to identify lichens based on where they are found. Lichens are often thought to imbibe their desirable properties from the substrate on which they are growing. For example, Nuxalk consider alectoroid lichens to be better medicine if growing on alder, the Gitga'at consider Lobaria oregana to be better if on fir, and the Ancient Greeks thought that Evernia was better if growing on cedar. The medicinal properties of a lichen species may change depending on where it is growing. However, this may also be a clever aid for identification. Many lichens have specific microhabitat preferences, and selecting lichens from only a specific substrate will result in preferentially selecting certain species.

Another interesting identification method is employed by the Quichua of Saraguro, Ecuador, who have determined that an effective medicine requires seven different colors of rock lichens. It is possible that there is a synergistic effect between the different lichen species. It is also possible that collecting seven different species makes it much more likely to collect the correct one.

2.3.2 Development of Lichen Taxa in Western Science

The meaning of the word lichen has changed over time, which can make it complicated to identify culturally important lichens in old documents. Lichen comes from the Ancient Greek Λειχήν (leikhēn), the first record of which is from Theophrastus in 300 B.E. (Richardson 1974). Theophrastus was probably referring to thalloid liverworts, but subsequent Ancient Greek authors may have used that name for a lichen (see Ancient Greek use of Ramalina spp.). Early European botanists lumped together a variety of cryptogams into the same taxon, usually including lichens, mosses, liverworts, fungi, seaweed, and sometimes even coral. de Tournefort (1694) was the first European author to distinguish lichens by the name lichen, but he also included some thalloid liverworts in his taxon and excluded some lichens. It was Dillenius (1742) who reorganized the lichen taxon to make it synonymous with our modern concept.

The taxonomy and names of lichens have changed radically since Dillenius and are continuing to change in contemporary times. This can make it difficult to determine what lichen is being discussed in ethnographic literature. To add further complications, most authors know very little about lichens and thus frequently use names that are outdated or even just completely wrong.

The genus Usnea was created by Dillenius (1742). Linnaeus (1753) described five Usnea species, but lumped them all together in his all-encompassing genus Lichen. They were moved to the Usnea genus by Weber and Wiggers (1780). Four of the original species are often mentioned in ethnographic literature: Usnea barbata, U. florida, U. hirta, and U. plicata. The number of Usnea species has now increased to around 350 species (Thell et al. 2012), so any reference to one of the original Usnea species in old herbals or ethnographies is suspect. Of the original five, only Usnea hirta occurs in North America (Esslinger 2014). References to Usnea barbata are particularly ambiguous, as the taxonomy of this species is still confusing and still being determined (Articus 2004).

The pendant Bryoria species were originally all lumped together as Lichen jubatus (Linnaeus 1753), which became Alectoria jubata (Acharius 1810). The taxonomy of Bryoria was not well understood until Brodo and Hawksworth (1977) created the genus Bryoria, so references to specific Bryoria species prior to that are ambiguous.

The Parmeliaceae is a large and diverse family of lichens that includes many culturally significant lichens. This family currently contains around 80 genera and over 2,000 species (Thell et al. 2012). Five culturally significant genera of Parmeliaceae were described before 1810: Usnea, Parmelia, Cetraria, Alectoria, and Evernia. By 1903, Letharia and Pseudevernia had been split from Evernia, and Parmotrema and Hypogymnia had been split from Parmelia, although historically not all authors have recognized these genera. The taxonomy of Parmeliaceae remained relatively constant until 1965, when the genus Cetraria began to be split into numerous different genera. The genus Parmelia was also split up starting in 1974. This splitting was mostly completed by the early 1990s, by which time there were over 80 genera in the family (Thell et al. 2004). Recent molecular work has resulted in some genera being lumped and others split, such that Thell et al. (2012) recognize 79 genera. Currently, the original genus Parmelia is divided into 32 genera and Cetraria into 22 genera.

For practical reasons, lichenologists sometimes lump the morphologically similar genera that were previously included in Parmelia and Cetraria back together into the categories of parmelioid (Hale and DePriest 1999) and cetrarioid lichens (Randlane et al. 2013). These morphological groupings are not entirely monophyletic (Thell et al. 2012), but they can still be useful. A third morphological grouping of Parmeliaceae lichens that is often used is the alectorioid lichens, which include several similar-looking genera of hair lichens that were previously lumped together in the genus Alectoria. The genus Usnea is sometimes included in this category.

One result of the profusion of genera within Parmeliaceae is that any reference to an unidentified species of Parmelia or Cetraria in an older ethnographic work is very ambiguous. The categories of parmelioid, cetrarioid, and alectorioid lichens are very useful when dealing with folk taxonomies of lichens, so they will be utilized in the current work.

2.4 The Medicinal Uses of Lichens

Lichens are used for many different medicinal purposes, but there are some general categories of use that reoccur across the world. Lichens are often used externally for dressing wounds, either as a disinfectant or to stop bleeding. Other common topical uses are for skin infections and sores, including sores in the mouth. This importance of this use is apparent in the name lichen (from leikhēn, ‘what eats around itself’), which comes from the Ancient Greek practice of using a cryptogam to cure a skin disease.

Lichens are often drunk as a decoction to treat ailments relating to either the lungs or the digestive system. This is particularly common in Europe, but is also found across the world. Many other uses of lichens are related to obstetrics or treating gynecological issues. This may be related to the common use of lichens for treating sexually transmitted infections and ailments of the urinary system. Two other uses of lichens that are less common, but reoccur in several different cultures, are for treating eye afflictions and for use in smoking mixtures.

Many of the traditional medicinal uses of lichens are probably related to their secondary metabolites, many of which are known to both be physiologically active and to act as antibiotics. However, some of the traditional uses of lichens also rely on the qualities of lichen carbohydrates. In particular, the lichenins [β-(1→3)-(1→4)-linked d-glucans] are common in the Parmeliaceae and have a remarkable ability to absorb water and form a gel (Crawford 2007). Many of the traditional uses of lichens involve boiling the lichen to create a mucilage which is drunk for lung or digestive ailments or applied topically for other issues. Other lichen carbohydrates which may be important are the isolichenins and galactomannans, which are taxonomically widespread, and the pustulins that are found in Umbilicariaceae.

2.4.1 Medicinal Lichens of Europe

Lichens are used in traditional medicine across the world, and many cultures outside of Europe have traditional uses for lichens that are completely unrelated to Europe. However, European uses of lichens have been exported worldwide, and there are numerous instances where the European use for a lichen appears to be associated with its traditional use in a different culture. This dispersal of European uses of lichens is related to the general dispersal of other aspects of European culture across the world. One specific source of this bias may be that most ethnographers that recorded traditional uses of lichens are from a European background, and their personal cultural bias can affect what they have documented. Another source is that most literature on lichens is from a European background, and if it features any uses of lichens, those uses are generally European.

An understanding of the traditional use of lichens in Europe can therefore be important for understanding traditional uses elsewhere. The origins of the medicinal use of lichens in Europe dates back to the fourth and third century B.E., when medicinal lichens were recorded by the Ancient Greek scholars Hippocrates and Theophrastus (Lebail 1853). The use of lichens continued to be recorded by various scholars throughout the rest of the classical era, including Pedanius Dioscorides and Pliny the Elder (Rome, first century C.E.), Galen of Pergamon (Greece, second century C.E.), Paul of Aegina (Greece, seventh century C.E.), and Serapion the Younger (a twelfth or thirteenth century compilation). These authors discuss at least three different cryptogams that might be lichens, but the most important for subsequent pharmacopoeias was an arboreal fruticose lichen called splanchnon (“intestine”). According to the original writings of Dioscorides, splanchnon was not only a powerful medicine, it was also sweet-smelling and used as a perfume (López Eire et al. 2006).

In the middle ages, various Persian scholars like Rhazes (tenth century) and Avicenna (eleventh century) wrote about the medicinal properties of splanchon, and it was adopted into Unani medicine under the name ushna. This lichen is currently interpreted as being Usnea spp.

At the start of the modern era (~ fifteenth century), herbalism flourished in Western Europe, with many authors adopting Greek herbal knowledge. These Europeans lumped together all fruticose arboreal lichens into one taxon, which they called usnea (borrowing from the Arabic ushna), tree moss, or oak moss (Dorstenius 1540; L’Obel 1576; Gerarde 1597; Ray 1686; Quincy 1724; Culpeper 1788). This taxon was considered to be synonymous with the Ancient Greek splanchon, with all of its medicinal and perfume qualities. Parkinson (1640) accurately distinguished between numerous genera, but considered them all types of oak moss and attributed the same medicinal values to all of them.

It was not until the late 1700s that a distinction was made between the different genera of oak moss, at which time the name Usnea was only applied to our modern genus. From this time onwards, most authors decided that the medicinal values of splanchon were referring to Usnea (Lightfoot 1777; Willemet 1787; Adams 1847; Lebail 1853), although the same medicinal properties were sometimes applied to Evernia prunastri (Willemet 1787; Lebail 1853).

Oak moss was used to make a popular scented hair powder called Cyprus powder in Europe in the late 1600s (Bauhin and Cherler 1650; Zwelfer 1672). By the time European botanists could distinguish different genera, Cyprus powder was found to contain a variety of lichen genera, including Usnea, Pseudevernia, and other arboreal lichens (Amoreux 1787). At this time Evernia prunastri was the preferred lichen to use for perfumes in France (Amoreux 1787). In more recent times, oak moss refers to only Evernia prunastri and tree moss to Pseudevernia furfuracea, and these are the two lichen species harvested for perfume (Moxham 1986).

When Europeans first adopted Ancient Greek herbal knowledge, they were confused as to the identity of splanchon, but eventually decided that it was Evernia/Pseudevernia when used for perfume and Usnea when used for medicine. Dioscorides’ description of splanchon is ambiguous and its identity cannot be determined with certainty, but Richardson (1974) suggests that it is referring to Evernia prunastri and Pseudevernia furfuracea. He may be correct, as these lichens were used medicinally in Europe and North Africa from ancient times to present. Europeans have added medicinal properties to Usnea that were not originally associated with splanchon by the Ancient Greeks. Perhaps these medicinal uses for Usnea existed in Europe independent of the Ancient Greek writings, and this caused Europeans to wrongly associate the Ancient Greek medicinal uses of Evernia/Pseudevernia with Usnea.

Starting in the 1500s, the doctrine of signatures was an ubiquitous concept in European medicine. It was thought that plants looked like the organ or ailment that they cured and various lichens were adopted into the European pharmacopoeia as a result. The main medicinal lichens in early modern era Europe were Cetraria islandica, Cladonia pyxidata, Peltigera canina, Peltigera aphthosa, Usnea spp., Lobaria pulmonaria, Xanthoria parietina, and Evernia prunastri. For more details, refer to these lichens in the tables below. The widespread use of these lichens had been mostly abandoned by 1800, with the exception of Cetraria islandica, which has persisted as a medicinal lichen in parts of Europe until today.

2.5 Known Records of Lichens Used in Traditional Medicine

The following tables document all of the traditional medicinal uses of lichens for which the author has found records. Tables 2.2 and 2.3 provide a list of the different genera and an index to the table where they can be found. Tables 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 2.10, 2.11, 2.12, 2.13, 2.14, 2.15, 2.16, 2.17, 2.18, 2.19, 2.20, 2.21, 2.22, 2.23, 2.24, 2.25, 2.26, and 2.27 are organized taxonomically by lichen family and provide the details on each traditional use.

Table 2.2 Lichen genera used in traditional medicine
Table 2.3 Index to tables of lichen families used in traditional medicine
Table 2.4 Cladoniaceae used in traditional medicines around the world
Table 2.5 Lecanoraceae used in traditional medicines around the world
Table 2.6 Mycoblastaceae used in traditional medicines around the world
Table 2.7 Alectorioid lichens (Parmeliaceae) used in traditional medicines
Table 2.8 Cetrarioid lichens (Parmeliaceae) used in traditional medicines
Table 2.9 Parmelioid lichens (Parmeliaceae) used in traditional medicines
Table 2.10 Other Parmeliaceae lichens used in traditional medicines
Table 2.11 Physciaceae used in traditional medicines around the world
Table 2.12 Ramalinaceae used in traditional medicines around the world
Table 2.13 Stereocaulaceae used in traditional medicines around the world
Table 2.14 Collemataceae used in traditional medicines around the world
Table 2.15 Lobariaceae used in traditional medicines around the world
Table 2.16 Nephromataceae used in traditional medicines around the world
Table 2.17 Peltigeraceae used in traditional medicines around the world
Table 2.18 Teloschistaceae used in traditional medicines around the world
Table 2.19 Roccellaceae used in traditional medicines around the world
Table 2.20 Ophioparmaceae used in traditional medicines around the world
Table 2.21 Umbilicariaceae used in traditional medicines around the world
Table 2.22 Icmadophilaceae used in traditional medicines around the world
Table 2.23 Megasporaceae used in traditional medicines around the world
Table 2.24 Pertusariaceae used in traditional medicines around the world
Table 2.25 Verrucariaceae used in traditional medicines around the world
Table 2.26 Hygrophoraceae used in traditional medicines around the world
Table 2.27 Unidentified lichens used in traditional medicines around the world