Lichens are a Sign of Fresh Air

I can think of no other organism with the modesty of lichens. They add richness to every outdoor scene, yet seek little recognition and get none.

The country church stripped of its lichens would lose its charm; it would appear less alluring, too new and wrong. Look beneath the stained-glass windows of many rural churches and you will get a glimpse of the decorative job that lichens do. Windows that were framed in lead leak traces of this poisonous metal down with the rain after each downpour. Lichens are sensitive to these pollutants and are killed off, leaving a line of naked stones beneath the windows.

Lichens are also sensitive to airborne pollutants, so the more lichens we see the happier we should be – they are whispering that the air is pure. Walk from any town into the surrounding countryside and the lichens will appear to multiply before your eyes. But only if we give them the courtesy of noticing them and few do.

The fussier any organism is, the stronger the clue it contains. There is one family of lichens that is particularly sensitive to air quality. These ‘usnea’ lichens are typically pale grey-green in colour, with thin intertwined hair-like threads. Usnea hangs from tree branches, but only in places with the freshest air. In places like Wistman’s Wood in Dartmoor the stunted oaks are draped in it.

Usnea hangs on a tree like a medal, awarded to the area for its purity.

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