Lichen-Eating Across the World, and Among the Lichenophilic Limbu of Eastern Nepal

Lichen are one of the most ubiquitous forms of life, found in some of the Earth’s most inhospitable environments. We have long known that lichen are composite organisms, formed from the symbiosis of fungi and either algae or photosynthetic bacteria. Recent research shows that they can be more complicated, sometimes composed of several species of multicellular fungus as well as different kinds of algae and many kinds of bacteria. Single-celled fungi are also sometimes involved; a widely reported 2016 study was summarized in one headline as, “Yeast emerges as hidden third partner in lichen symbiosis.”

 Some 20 percent of fungi species can “lichenize,” or incorporate algae or cyanobacteria to reap the benefits of photosynthesis. The Wikipedia article on symbiosis in lichen includes this quip by naturalist Trevor Goward: “lichen are fungi that have discovered agriculture.” Goward takes this idea several steps further on his own website: “lichens are fungal greenhouses; lichens are algal farmsteads; lichens are ecosystems; lichens are organisms; lichens are emergent property.”

Lichen produce and store carbohydrates, and as a result can be an important source of food for animals, most notably reindeer (including caribou) and northern flying squirrels. They are seldom eaten, however, by people. Although only a few kinds are poisonous, many have compounds that can cause unpleasant effects. More important, the carbohydrates that most lichen produce are indigestible by human beings. But some are both digestible and nutritious. Yet over most of the world, edible lichen are eaten, if at all, only as a famine food. Perhaps this will change. One food specialist now touts lichen as a possible survival resource for a post-apocalyptic future.

Historically, the main areas of widespread lichen consumption were Scandinavia, East Asia, and the Pacific Northwest of North America. In northern Europe, mis-named Iceland moss (Cetraria islandica) was once widely consumed, “cooked in many different ways, such as bread, porridge, pudding, soup, or salad.” Its bitterness can be removed by boiling and its carbohydrates are easily digestible. But as Scandinavians gained access to more diverse foodstuffs, Iceland moss dropped out of their diets. As the Wikipedia notes, “It is not in great demand, and even in Iceland it is only occasionally used to make folk medicines^, and in a few traditional dishes.”

Among many indigenous societies of the Pacific Northwest, a horsehair lichen called wila (Bryoria fremontii) was gastronomically important. Care had to be taken in gathering it, as B. fremontii sometimes contains vulpinic acid, toxic to human and most other mammals. Evidently, even the edible specimens produce a carbohydrate that is largely indigestible by people. If so, why would wila have been such a highly desired foodstuff? According to the Wikipedia, “It is theorized that these peoples may consume the lichen because when it is cooked with other foods, it may capture carbohydrates from these other foods that would otherwise be lost in the fire pit method used to cook it, increasing the carbohydrates by 23 to 122%.”

Globally, the most widely consumed lichen are the so-called rock tripes, grouped together in the genus Umbilicaria. As the Wikipedia article notes, “They are edible when properly prepared; soaking extensively and boiling with changes of water removes the bitterness and purgative properties.” In North America, Umbilicaria has generally been a famine food, but in parts of East Asia one variety is consumed on a regular basis, known as iwatake in Japanese and seogi beoseot in Korean. In Japan, traditional iwatake gathering was an arduous process (see the illustration below). This form of lichen is also valued for its medicinal properties. The Korean gastronomic website Maangchi emphasizes its health benefits:

Seogi-beoseot (rock ear mushrooms*) are a rare, precious Korean ingredient that’s prized for its medicinal properties. It’s found high up on rocks deep in the mountains, and is kind of in the shape of an ear, which is probably where it got its name. It’s picked from the rocks, dried, and sold in small quantities. It’s hard to find outside of Korea. [*Despite its Korean name, seogi-beoseot is not a mushroom.]

Among the world’s few lichen-eating cultures, one stands out above all others: the Limbu and related Kirati peoples of eastern Nepal. A recent article in the Kathmandu Post explores this Limbu proclivity:

The Limbus, an indigenous people from Nepal’s eastern hills, have interesting and unique food traditions. Wild edible lichen, known as yangben, is the community’s signature speciality. Limbus cook yangben with meat, especially pork, to make a variety of dishes. And one of the most loved delicacies is yangben-faksa, pork with lichen. Another popular dish is blood sausage, known as sargemba or sargyangma, which is made by adding lichen to minced meat…

Several different kinds of lichen are grouped together as yangben by the Limbu. A few scientific studies have been conducted on their consumption. In one research project,

Three lichen species …., Parmelia nepalensis, Ramalina farinacea, and R. conduplicans, were chemically analyzed to assess their food value. The lichens were found rich in carbohydrate, fat, crude fibre, and minerals. Their carbohydrate and protein contents were comparable to that of rice. If cooked mixed with other food, these lichens will provide various minerals in sufficient amount and add carbohydrate, protein, fat, and fibre.

Another study examined the “use of seven species of lichens belonging to four families” among several ethnic groups of eastern Nepal. Along with the Limbu, the Sherpa were found to be decidedly “lichenophilic.” Among these groups, one kind of lichen is used extensively to treat wounds; another is hung above the entryways of houses due to the belief that it “wards off evil spirit and maintains peace at home and among family members.”

According to the Kathmandu Post, yangben consumption is spreading to other ethnic groups in Nepal, leading to overharvesting. As it characteristic of lichen in general, growth is slow. The same article also notes that, “there are others who believe that the dust from vehicles that ply the roads built through rural forests have also barred the lichen from flourishing.” This thesis may have merit, as lichen are highly sensitive to air pollution. Lichen health is often used to gauge pollution severity; an organization called UK Air Pollution Information System (APIS) has even developed a mobile “lichen-app” that uses “lichens to assess atmospheric nitrogen pollution effects.”

Although the consumption of lichen has spread from the Limbu to neighboring ethnic groups, other Limbu delicacies seem unlikely to find much appeal outside their homeland. Consider, for example, wachipa, which probably tastes better than it sounds: “Wachipa is a special dish made by cooking rice, minced local chicken meat along with burnt downy feather follicles and offal. It has a unique bitter taste and aroma that you get from firewood roasted meat.”

As a final note on lichen, my quest to find maps of their distribution and used by humans was partially frustrated by the existence of the “map lichen,” or Rhizocarpon geographicum, which dominated most searches. As described by Wikipedia, “the map lichen is a species … which grows on rocks in mountainous areas of low air pollution. Each lichen is a flat patch bordered by a black line of fungal hyphae. These patches grow adjacent to each other, leading to the appearance of a map or a patchwork field.”

I am not sure how map-like map lichen actually are, but they can be strikingly beautiful.

  GeoCurrents will run one more article on the Limbu before turning to the recent Czech election.

This post is from GeoCurrents

GeoCurrents.info provides map-illustrated analyses of current events, delving into the often overlooked geographic and cultural contexts that shape these world developments. Led by Stanford University Senior Lecturer Martin W. Lewis and linguist Asya Pereltsvaig.