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 are usually flat and live on rock. Foliose lichens are leafy, and can live on rocks or trees. Fruiticose lichens are shrub-like, more three-dimennsional, 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.
Many crustose lichens grow exceedingly slowly and live for thousands of years. Representatives of a species called the map lichen (Rhizocarpus geographicum) have been aged in the arctic at 8,600 years, by far the oldest living organisms on the planet. They are easily aged because many species grow at constant rates. 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.