Lichens are found throughout the world, often occupying areas where no other plant can become established. They are found in their greatest numbers in the Alpine and Arctic regions, where they are the dominant form of vegetation.
Lichens are the products of two distinct groups of plants. Together fungi and algae (seaweed is an algae) combine to produce lichens. Most rocks you will come across have an abundance of these plants. Lichens are almost the only plants able to survive the severe conditions at high altitudes.
In Antarctica, where there are very few flowering plants, more than 400 species have been found. In warmer climates lichens are common in old fields and forests, on rotting logs and on tree trunks. However, few species survive near large cities. Unfortunately, lichens are very sensitive to industrial smoke and gases.