close-up of green lichen on rock
Look for the bright greens and oranges of lichens on Glacier peaks

NPS/Tim Rains

The 30% of Glacier Park that is often characterized as "barren" rock isn't necessarily barren at all. The multi-colored "splatters" seen on the surface of many rocks and mountain sides comprise hundreds of species of lichens. Other species colonize tree bark or even the soil surface. They thrive in some of the most harsh environments on the planet, often found where nothing else can live.

Lichens are composed of two different life forms, a fungus and an algae which coexist in an odd symbiosis, forming an entirely new organism called a lichen. The fungus provides structure and mineral-gathering capability, and the algae provides photosynthesis to make food for both. Which fungus combining with which algae determines which species of lichen.

Lichens come in three basic styles:

  • Crustose lichens, usually flat and live on rock
  • Foliose lichens, leafy and can live on rocks or trees
  • Fruiticose lichens, shrub-like--more three-dimensional and often live on trees

Lichens gather many of their nutrients from the air and need unpolluted air to thrive. Abrupt changes in lichen numbers and species assemblages are often a reliable early warning of shifts in air quality. Glacier Park's vast array of lichens indicate relatively pristine air quality by modern standards.

Lichens have been used to estimate minimum ages for exposed rock surfaces. Because species such as Rhizocarpon geographicum show consistent growth rates under specific conditions, the ages of the oldest lichens on exposed rock give an approximation of the time when the rock was first uncovered. Glacial geologists use the ages of lichens to estimate the time of retreat of a glacier.

Besides being food for deer, elk, squirrels and other wildlife, lichens have many uses as food and dyes for humans. The colors in Harris Tweed fabric are still lichen-dyed. Smooth rock tripe can be boiled, cleaned and then roasted as a nutritious potato-chip-like food. Hanging tree lichens (black horsehair lichen, green old man's beard lichen) are still used by the Kootenais, Salish and Blackfeet as a traditional food.

Last updated: May 26, 2022

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