Lichens

This area of the buckeye grove is covered with lichens, which are said to cover 6-7% of all the trees and rock on Earth. There are thousands of variety of lichens, but they are composite organisms — that is, they are actually communities of a type of algae and a type of fungus that exist together as a single unit. They can exist in the harshest arctic and desert environments, but are very sensitive to air pollution since they get much of their nutrients from the air itself. For this reason, lichens have been used as inexpensive pollution indicators. Some lichens actually break down the rock they are attached to, thus eroding it and creating soil.