What is the relationship between lichens and air pollution?
In 1986, following the Chernobyl nuclear power station disaster in Ukraine, arctic lichens as far away as Lapland were tested and showed levels of radioactive dust that were as much as 165 times higher than had been previously recorded. In addition, a human connection was found between the nuclear disaster and lichens: The lichens—being efficient absorbers of air-borne particles—are a primary winter food source for reindeer (Rangifer tarandus) in Scandinavia, and reindeer meat is commonly consumed by humans who live in those regions of tundra. The accumulated level of radioactive dust containing radiocesium became so high in the lichens that the reindeer meat became unsuitable for human consumption—and tragically, hundreds of tons of reindeer carcasses were disposed of as toxic waste.
Because they absorb minerals from the air, rainwater, and directly from their substrate, lichens are extremely sensitive to pollutants in the atmosphere—especially sulfur dioxide—and thus can be used as bioindicators of air quality. In particular, lichens can absorb airborne pollutants in toxic concentrations. Thus, a high level of pollutants can cause the destruction of the lichens’ (in other words, algae’s) chlorophyll, which leads to a decrease in the occurrence of photosynthesis. Pollutants also upset the physiological balance between the fungus and the algae (or cyanobacterium), causing the lichens to degrade or completely die off.