Lichens

Local Streams
Photos Courtesy USFS

What do you get when you cross fungus with algae? LICHENS!

Well, lichens are not creatures, per se, but they are certainly unusual organisms. Unlike mosses or liverworts, lichens are not true plants. They are not a single organism like other living things but a combination of two organisms living symbiotically together. Most of the lichen is composed of fungal filaments living among alga cells, usually green algae or cyanobacterium (previously called blue-green algae). Since fungi does not contain chlorophyll or have any other means of producing their own food, they rely on other organisms, such as algae, for nutrition. The algae uses sunlight to make sugars (food) that feed both the fungus and the algae. The fungus then creates a distinctive lichen body called a thallus that houses both organisms. Each fungi-algae combination creates a unique thallus that is identifiable from others.

There are approximately 3,600 known species of lichen in North America! Approximately a quarter of all known fungi world-wide are “lichenized”. Most lichens appear different from other fungi, like mushrooms, and have a texture that is usually more fibrous and stiff, compared to non-lichenized fungi, which are usually soft, fleshy and delicate to the touch. Also non-lichenized fungi lack algae and do not appear green in color.

Why are lichens so important to life? Lichens are ecologically important as they convert carbon dioxide in the atmosphere through photosynthesis into oxygen. They provide an important role in survival in harsh environments, as food and shelter. Many birds and small mammals, such as squirrels, use lichen for shelter and nesting material. They are also an essential winter food for many ungulates such as black tail deer, mountain goats and caribou, making up 90% of caribou’s winter diet. Other uses for lichens are as a human food source (beware some are poisonous), manufacturing of antibiotics and for dying wool. Lichens are very slow growing and many do not recover well from collecting or disturbance.

Lichens have evolved to live in a variety of climates and ecosystems, and have the ability to absorb everything in their atmosphere, especially pollutants. Pollutants such as heavy metals, nitric and sulfuric acids (acid rain) and carbon are absorbed into the thallus of the lichen. Toxins can be extracted to determine the levels of pollutants that are present in our atmosphere. When there is an excess of pollutants in the air, lichens are unable to survive. Utilizing this sensitivity to air quality makes them a dependable air quality indicator species. Throughout the world, lichens are being used to detect specific air quality changes, monitor for pollutants and track climatic changes. Scientists use this information to evaluate air quality and climatic trends and to assess ecological impacts to our air.

For more information about lichens visit www.fs.fed.us/wildflowers/ interesting/lichens