Lichens are a unique combination of fungi and algae which survive by accumulating nutrients from the air. Because they lack roots, stems and leaves, they can grow almost anywhere.
Scientists have long known that lichens are very sensitive to air pollution. For example, they were used to estimate the nuclear fallout from the Chernobyl reactor meltdown in the nineteen eighties.
Lichen tissue functions like a natural filter by accumulating air borne pollutants as they are deposited on the lichen surface. Conventional methods for measuring air pollution require the installation of expensive, immobile air sampling equipment. These devices collect airborne particles in one specific place using filters which are removed and analysed in the lab.
However, the same technique for analysing pollutants can be used on lichen samples collected in many different locations.
Recent studies at Brigham Young University now show that the amount of pollutant taken up by lichens, reflects the amount of pollutant in the air. For example, the amount of copper absorbed by lichens in an industrial smelting region compared well with the known copper levels. The expectation is that when lichen samples are analysed to see what other elements are present, the quantity of other pollutants in the air will be accurately estimated.
So next time you take a hike, remember you may be treading on some precise air quality monitors – lichens.