Lichen: Sign of Life

Ever seen this greenish grey thing on a tree? You might think that it's a kind of fungus that we should remove. Hummm, actualy lichen consists of 2 symbionts: fungus and algae. They cannot avoid pollution, so their existance proves how clean the air in the area where you find them.

And as a matter of fact lichen only grows 1 mm - 1 cm / year! So please, let them grow…