Lichens as Air Pollution Biomonitors

Image via Wikipedialichens as biomonitors (Lichens of Ireland project)

Also discussed here: Monitoring Air Quality with Lichen as a Bioindicator (Abbie Walston, Mon’s clean air force, May 4, 2011)

And here: Lichen determination keys (Botanischer Garten und Botanisches Museum Berlin-Dahlem)

And here: Lichenland Lite (Northwest Alliance for Computational Science & Engineering (NACSE), based at Oregon State University.)

Lichens have long been known for their ability to indicate the state of air quality because pollutants accumulate in them. This results in either further growth or decay depending on the concentration and type of pollutant and lichen. A number of references have been collected here which allow one to assess the type of lichen.

Key Quotes:

“Some lichens will only survive in a clean environment, while others flourish with certain pollutants. For example, some species of the genus Xanthoria establish and grow abundantly in nitrogen rich areas, such as near farms or chemical factories, while species of the genus Usnea are sensitive to the amount of sulphur in the air”

“chemicals can freely invade them and interfere with their metabolic processes, often killing the lichen, but sometimes increasing their growth rate. Also, lichens are unable to excrete or secrete these chemicals and so they accumulate within the thallus. The lichen is therefore an excellent bioaccumulator”

“Hawksworth-Rose Sulphur Dioxide Pollution Scale:

Most Polluted (0) to Least Polluted (10)

0 = No lichens
1 = Desmococcus viridis (not a lichen, but a green alga)
2 = Lecanora conizaeoides
3 = Lepraria incana
4 = Hypogymnia physodes / Parmelia sulcata / Parmelia saxatilis
5 = H. physodes / P. saxatilis / Calicium viride / R. farinacea / E. prunastri / Platismatia glauca
6 = Parmelia caperata / Graphis elegans / Pseudevernia furfuracea
7 = Parmelia caperata / Usnea subfloridana
8 = Parmelia perlata / Normandina pulchella
9 = Lobaria pulmonaria / Dimerella lutea
10= Sticta limbata / Usnea articulata”

“Summarized list:

• No lichens present – very poor air quality
• Crustose lichens only – poor air quality
• Crustose and foliose lichens – moderate to good quality (based on number of different lichens)
• Fruticose, foliose and crustose lichens – very good air quality”

Related articles

• Lichens.. and Fungi.. March (forwildlife.wordpress.com)
• Lichen evolved on 2 tracks, like marsupials and mammals (scienceblog.com)
• Lichens may aid in combating deadly chronic wasting disease in wildlife (eurekalert.org)
• Study finds remarkable diversity of lichen species in Florida state park (eurekalert.org)
• Who's exposed - and what can they do about it? Biomonitoring for consumer products and workplaces (scienceblogs.com)
• Europe's Air Pollution is Shown in Online Maps (treehugger.com)