Lichen is a composite consisting of an alga and a fungus. Alga undergoes photosynthesis to produce food which is also shared to the fungus. Fungus is responsible for protecting the alga and absorbing water from the air. There are many different species of lichens, some are very sensitive to air pollution, and some are less sensitive. Therefore, lichens are used as air pollution indicator organisms. When air is clean, lichen diversity is high; when air pollution level is high, there will be less lichens or even no lichen at all.
|A lichen species only grows under clear air||A lichen species which also grows under high air pollution level|
Information and photos are provided by Ho Koon Nature Education cum Astronomical Centre