Why are lichens important?
Lichens allow algae to live in environments that would normally be too harsh. The fungi protect the algae from hot, sunny conditions, provided that there is enough water to last through dry periods. Algae is responsible for producing most of the world’s oxygen, so the more places that algae can inhabit, the better.
They also play a role in controlling pollution, as they are effective bioindicators. They are very sensitive to atmospheric pollutants such as carbon and sulphur, and they will readily absorb them. Any changes in lichens reflects the air quality around them, and extracts can be taken from them for analysis (more info can be found here).
Lichens have been used by people for centuries as food, medicine, cosmetics and even for embalming. Lichens often contain mildly toxic substances, but these can be washed or boiled away, while the lichens themselves are rarely poisonous. Examples of edible lichens include Iceland moss (Cetraria islandica) and reindeer lichen (Cladonia spp.). The latter is harvested partially digested from the rumens of reindeer and called “stomach ice cream” according to Wikipedia…
Photo: Alectoria sarmentosa by Leif Stridvall.