Although lichens are tolerant to a wide variety of habitats and conditions, they are very susceptible to air pollution. Because of this, lichens are good bioindicators of air pollution levels. A strong lichen presence reflects low air pollution levels and in areas where air pollution is a problem, lichens absorb the contaminants and can serve as a record of the pollutant type.
Lichens are difficult to identify without a microscope because the exact fungal and algal combinations can vary even within a single lichen body. Despite this, the different growth forms lichens take are easily identifiable. Foliose lichens have a broad leafy structure while crustose lichens take on a lower profile, scab-like appearance. Squamulose lichens have a tightly clustered gravel like appearance and fruticose lichens have freestanding and branching elements.
Visitors to Richmond National Battlefield Park are likely to overlook these inconspicuous organisms, however, the interesting biology and useful environmental information lichens present warrants closer attention.