Lichens have been known to indicate air pollution levels for well over one hundred years. The levels of air pollution in certain areas preclude the existence of the more conservative species. Rich’s lichen surveys in Chicago have hinted at this. It’s unfortunate, but clearly some of the lichen species present in the days of the Calkins surveys, are now rare, extirpated, or extinct due to our pollution. It is well documented that lichens are sensitive to sulfur dioxide, which is associated with the burning of the less refined fossil fuels such as coal and diesel. However, nitrogen oxides produced by car exhaust have been shown to cause their demise as well. It’s possible many other pollutants can limit the variety of lichens we find, and this is due to lichen use of air as a nutrient source. It’s simple, you eat poison and you die. One of my favorite related quotes from Michael Cohen is “I thought I saw a blue jay this morning, but the smog was so bad that it turned out to be a cardinal holding its breath”.

I’ve put a clip of research here, and will eventually post a list of the authors, sites and more good research articles.

Some of the species listed above are not present in our area. However, Wilhelm’s key mentions Graphis scripta, and Opegrapha varia as being common in the days of Calkins, but now quite rare. It would seem that air pollution is the culprit behind this trend. It’s also possible that the above mentioned Ramelina was here, but there is some confusion on the scientific name.          Well, there’s a start.