Cladonia rangifernina
Cladonia rangifernina or 'The Reindeer lichen'. Photo: Carly Anderson Stewart

Lichens are a symbiosis between two organisms

Lichens are organisms that result from a symbiosis between a fungus and algae. Probably, there are many other additional tiny organisms involved, such as other fungi or bacteria. The main fungal partner provides a humid house for the algae, which in turn feeds its fungal partner through photosynthesis.  This symbiotic system is one of the main sources of food for the reindeer.

Foliose lichen growing on a rock
Foliose lichen growing on a rock. Photo: US Forest Service

Reindeer lichen grows in all climates

The reindeer lichen is a light-colored, grey lichen from the family Cladoniaceae. It is a widespread species that can thrive on the ground in both hot and cold well-drained, open environments. In Sweden Cladonia rangiferina is frequent and abundant in pine forests and tundra regions (Ahti et al, 2013). Sonia Merinero, a former DEEP researcher, is working with lichens in boreal forests and the Arctic and has shared her knowledge about them.

The global warming is making it hard for the reindeer to get food

A reindeer eating lichen
A reindeer eating lichen. Photo: Marko Junttila

“Lichens, including Cladonia rangiferina, are nearly 90% of reindeer food in the winter. They need to dig through the snow to find this resource. Unfortunately, more frequent warmer winters coupled with heavy rainfall instead of snowfall, a consequence of global warming, is making it harder for the reindeer to access their food”, explains Sonia.

The winter rainfall is followed by a cold spell, which traps the lichens under ice. Reindeer cannot break the ice layer with their hooves and need external help:

“In Lapland, for example”, says Sonia, “the snow-freezing or the conversion of snow into ice, is often so heavy that the locals have to collect lichens in summer to supply food for the reindeer in winter. Otherwise, they could starve to death.”

A reindeer in Lappland
Reindeers in Lappland. Photo: Hearth my Backpack, travel blog

Reindeer has been a key component of high latitude ecosystems for at least 2 million years (Forbes & Kumpula 2009). In Sweden reindeer herding is an important economic and cultural resource: “It is wild and semi-domestic fauna that belongs to the Sami people. Traditionally, they use the reindeer for meat and fur. Their herds are also a tourism attraction”, notes Sonia.

Lichens keep our environment healthy

Lichens are essential to the environment. They fix nitrogen and carbon which are essential nutrients for ecosystem, especially for plants. Lichens enrich the soil by trapping water, dust and silt. When they die, lichens leave organic matter in the soil, which helps other plants to grow better. Lichens are a succulent dish for slugs and snails, which makes them important in food webs. Lichens also serve as a habitat for small invertebrates, like spiders, that constitute important food for larger animals, like birds, according to Sonia Merinero.

Some insects have adapted their appearance to look like lichens. This way it’s harder for predators to recognize them.

An insect camouflaged as a lichen
An insect camouflaged as a lichen. Photo: Pavel Kirillov

Because lichens are quite sensitive to air pollution, some scientists use them to assess the air pollution levels coming from industrial plants and traffic in urban areas. The disappearance of lichens at a site is an early warning sign of harmful pollution (Blue, 2017).

Lichens don't kill trees!

Even though these symbiotic systems bring so many benefits to their surroundings, some people think it does more harm than good. Since lichens are more visible in winter and often grow on dead trees, many people think they are killing them:

“Some lichen species quickly colonize dying trees because the bark properties like pH and the higher availability of light on leafless trees is favorable for them. This leads to the idea that the lichens kill the trees. This is not true, however. In reality, they've just found a nice place to establish themselves”, explains Sonia.

Lichens on a dead twig.
Lichens on a dead twig. Photo: Jim McCulloch

How can humans use the lichens?

Some lichens are used as food. In times of hardship, some Native American tribes would eat the hairy Bryoria lichen. Some lichens were also fed to pets during hard times (Chaudhary et al, 2017).

Bryoria lichen
Bryoria lichen. Photo: Willem van Kruijsbergen

Not all lichens are edible though. Some can even be poisonous. The Wolf lichen, for example, has been used in Europe to deter wolves by poisoning them. Some Native American tribes have used it for poisoned arrowheads.

Wolf lichen (Letharia vulpina)
Wolf lichen (Letharia vulpina). Photo: J.Hollinger

Other lichens have been used as dyes. Mixed with such substances as pine sap or water or burnt to ash before usage, lichens provide the colors of yellow, brown, green, orange, purple and red. Examples of dye lichens include Lobaria pulmonaria, Parmelia saxatilis, Parmotrema, or Umbilicaria.

Lichen dyes
Lichen dyes. Photo: Roxanne Evans Stout

Lichens are also used in deodorants, toothpaste, salves, extracts and perfumes. In Japan they are used in paint due to their anti-mildew properties. Usnea is used in research for its antibiotic properties (US. Forest Service). 

Written by:  Liene Rozenstrauha, liene.rozenstrauha@su.se and based on interview with Sonia Merinhero, sonia.merinero@su.se.

References:

  1. Ahti, T. Roland Moberg, R. Stenros, S. (2013).  Nordic Lichen flora. Svenska Botaniska Föreningen, Uppsala.
  2. Blue, M., L. (25 April 2017).  What Two Roles Do Lichens Play in an Ecosystem? Retrieved on 22.01.2020 from https://sciencing.com/two-roles-lichens-play-ecosystem-8789.html - how lichen protect the ecosystem (nutrients etc. 3 paragraphs)
  3. Chaudhary, R.P., Devkota, S., Werth, S. et al. Indigenous knowledge and use of lichens by the lichenophilic communities of the Nepal Himalaya.  Journal of Ethnobiology Ethnomedicine 13, 15 (2017).
  4. Forbes, C., B., Kumpula, T. (2009). The Ecological Role and Geography of Reindeer (Rangifer tarandus) in Northern Eurasia. Geography Compass, (3), 4, pp. 1356 – 1380. Retrieved on 22.01.2020 from https://onlinelibrary.wiley.com/doi/10.1111/j.1749-8198.2009.00250.x
  5. US. Forest Service. Lichens – Did You know? Retrieved on 22.01.2020 from https://www.fs.fed.us/wildflowers/beauty/lichens/didyouknow.shtml