Lichens can grow on bare rock, or on living trees too. They use the branches only for support. They can survive in very harsh environments.
Some lichen found in the Western Ghats is a major component of the curry powder. Now,I believe it is forbidden to gather those lichens from the forest.
Lichens warn us of pollution in the air. They are useful for assessing pollution levels.
I thank Mrs.Nesbitt, the founder of ABCWednesday, and Roger and his team who so ably are carrying it forward.