Question

why are lichens called as pollution indicators ?

Answer 1

Lichens are called as pollution indicators as they will never grow at the places where pollution level is high. So we get to know where pollution level has increased.
It was so simple

Answer 2

Lichens are called as pollution indicators because lichens are highly sensitive to air pollution and it dies of rapidly in dirty air.It acts as an indicator by not being there in polluted atmosphere.

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