Mother Nature's pollution monitors.

Lichens, a curious symbiotic partnership between an alga and a fungus, are very susceptible to atmospheric pollutants, such as sulphur dioxide. They are, therefore excellent natural indicators of levels of pollution. They are also extraordinarily beautiful.

One of the first people to notice this was one William Nylander who in 1866 published observations about the lichens in Paris, particularly those of the Jardin du Luxembourg, a large public park. He noted that in general lichens didn't seem to like cities and that urban lichens often showed incomplete development. According to Nylander lichens could give a good indication of the quality of the air and so constituted a very sensitive "health meter" for the surrounding air. Based on his observations about the numbers of lichen species (and numbers of thalli) found in various parts of Paris he concluded that Paris' healthiest area was to be found within the Jardin du Luxembourg. The richness in lichen species and quantity within parts of that park was such that, had you wished to see anything comparable, it would have been be necessary to look outside the city, in the cleaner country air.

The lichen flourishing on this concrete post Xanthoria parietina would suggest that here in Newburgh on Ythan we can breath relatively safely!