Lichen are good biological indicators of air pollution and will die when exposed to air pollutants such as sulfur dioxide. Lichens can live in hot, dry places as well as in arctic conditiions. They live on rocks, on the ground, and on trees. About 15,000 kinds of lichens have been described. They come in many colors and shapes.
Sizes range from one mm to more than three meters.
Left undisturbed, lichens may live for centuries. One arctic species was found to be about nine thousand years old. They are easily collected at any time of the year, and identification of different species is not diffucult. With the help of a science teacher many projects with lichens are possible. Have fun with lichens.