Where to find lichens?

Lichens will grow on almost any surface including trees, rocks, earth and artificial surfaces such as concrete and tarmac. Lichens grow best in light  where they are not competing directly with tall grass, shrubs and climbing plants. Lichens that are highly sensitive to air quality and have been used to detect sources of pollution. In the past, when the air in many places was highly polluted by sulphur dioxide, few lichens could survive, creating lichen deserts around many industrial and urban areas. Lichens are now returning to British towns and cities, and they can still provide a great deal of information about our air quality.