Lichen as Air Pollution Bioindicators

Lichen is an organism composing of algae and fungi in a symbiotic relationship with a complex structure and a self-sustaining micro-ecosystem. They can live on different substrates, which among them are concrete or rock, bark, and leaf. Each lichen species would differ from one another, based on the substrate they live on, the composition of the lichen itself, and many other environmental factors.

Lichens can be used as bioindicators for air pollution. If an area is polluted, then it would be hard to find lichens. Likewise, a lot of lichens means that the air quality is good and there are little to no air pollution. In Jakarta, the place where I live, there are no lichens. Although, I had found one lichen living on the bark of my starfruit tree at home. Since moving to Daugavpils, Latvia, I can easily see a variety of lichens with different colors on trees. It can then be easily concluded that Jakarta is a city that has a lot of air pollution, whereas Daugavpils has cleaner air.

How does lichen as an air quality indicator work then? Would it just be that as long as there is lichen, there is no air pollution? Lichen consume water from the air, if the air contains sulfur dioxide (SO₂) it then becomes acid. So the variety of lichens that can be found in an area would correlate to the actual air quality. This is based on the lichens tolerance to the environment. Some lichen can handle a lot more acid (air pollution), while others cannot survive even the littlest of acid (air pollution). It is an outdated technique, but in my opinion it is something interesting to look out for.

Special thanks to my lecturer Rolands Moisejevs, a lichenologist that teaches at Daugavpils University who taught me all this knowledge in class.