Wherever stable and reasonably well lit surfaces occur in nature, so will lichens. A bizarre partnership of fungus and algae, lichens will grow on soil, rock, and even trees. Although they give the appearance of being parasitic on their vegetative hosts, lichens are anything but, being self-reliant in feeding themselves through photosynthesis in their algal cells. The algae, in turn, benefits from the ability of the fungus to better find, soak up, and retain water and nutrients.
Preferring a somewhat drier habitat, lichens often occupy niches where nothing else will grow, and appear throughout the park landscape. For wildlife such as deer, squirrels, mice, and bats, these plants have become important in providing food and shelter. Additionally, lichens can be used in dating rock surfaces, and secondary compounds produced by the organisms are used in medicines, natural dyes, and perfumes. Several studies have shown the sensitivity of lichens to environmental pollution, and they have become excellent instruments for assessing levels of air toxins, thus providing a value tool for park staff to monitor the park’s habitat quality.