Consider the patterns of lichen growth. Describe how you could use the patterns of lichen growth to estimate the changing levels of sulfur dioxide in the air at different distances from the industrial estate.
Lichens are life forms that live in a symbiotic relationship in the environment they are found in. They may grow on plants or rocks, and are considered pioneer organisms because they are often the first type of plant life to establish in the environment.
Lichens show a sensitivity to compounds that are emitted from factory smoke stacks, such as sulfur dioxide. Sulfur dioxide is a primary pollutant that will mix in the atmosphere with water vapor to form acid rain. The acid rain has a debilitating effect on both animal life and plant life, such as lichens.
One would reasonably expect to see a severe drop-off in lichen growth in environmental areas surrounding factories that emit waste pollutants such as sulfur dioxide. The further away from the industrial setting one goes, the less likely one would expect to encounter acid rain as precipitation. This would promote the existence of plant growth like lichens. In pastoral settings, far away from the belching smoke stacks of industry, lichen growth and participation in the environmental setting would be restored to its maximum effect.
Lichens are very sensitive to the presence of sulfur dioxide, a common pollutant. When sulfur dioxide dissolves in water, it forms highly acidic ions, which can be easily absorbed by lichen and which disrupt photosynthesis. Generally speaking, there will be fewer lichens (both number of plants and number of species) the closer one is to an industrial, pollutant-producing area. More lichens will be present as distance from the industrial area increases because the concentration of pollutants also drops with increasing distance. However, there may be patches of healthy lichen growth found inside industrial areas. These healthy patches are normally the result of a distinct micro-climate which forms around an area protected from pollution. Such an area can be formed by a protective barrier of other plants (such as a cluster of trees) or a geographically sheltered area (such as a ravine).