03/05/2024
Lichens are complex creatures formed by the symbiotic association of a fungus with algae or cyanobacteria, exhibiting a wide range of colours and sizes. They resemble plants, with some leaf-like structures or branches without leaves, while others generate flakes that resemble peeling paint. However, they lack a traditional root system and instead thrive on trees, rocks, and pavement, obtaining nutrients from fog, wind, and rain. Without particular protective barriers, Lichens quickly absorb toxins and are among the first species to perish when pollution levels rise. Consequently, they serve as effective indicators of Air Quality.
Since the 1860s, lichens have been used as indicators of pollution hotspots. Botanists in Paris found that lichens flourish in regions with clean air and deteriorate in places with polluted air. Initial inquiries were primarily concerned with the immediate impacts of Sulfur dioxide (SO2) resulting from coal combustion. Scientists have gradually found that lichens are effective markers of the regional impacts of acid rain resulting from the long-distance transportation of Sulfur dioxide (SO2) and other pollutants from industries. Lichens are also susceptible to the presence of Ammonia (NH3) and nitrates [NO3-]( that are carried by airwaves from agricultural regions where fertilizers are applied. Additionally, they can acquire metals like Mercury (Hg) from emissions released by power plants, as well as Lead (Pb) and Zinc (Zn) from smelters involved in mining activities.
In the 1980s, the U.S. Forest Service initiated a lichen biomonitoring program. This program involves scientists collecting census data on the variety and quantity of lichens in several designated survey plots around the nation. They gather a selection of samples and dispatch them to a laboratory for elemental analysis to determine the specific kind and quantity of contaminants. The statistics assist federal agencies in establishing pollution objectives and identifying regions where these targets are not being achieved. Additionally, they aid state and federal authorities in evaluating emissions permit applications and current restrictions.
Interestingly, hummingbirds use lichens as a means of concealing their nests.
