In Pacific Northwest forests, lichens provide essential winter forage for deer and elk and also nesting materials and habitat for rodents, birds, and invertebrates. Although lichens are often the first organisms to populate a landscape and many species can survive in the most barren environments, lichens with the greatest ecological value tend to be the most sensitive to excess atmospheric nitrogen. In areas with high levels of human-generated nitrogen, ecologically beneficial lichen species are disappearing and "weedy" species are thriving. Because lichen are innately sensitive to nitrogen, scientists use lichen community composition as an early indicator of encroaching nitrogen pollution.
Based on science by Linda Geiser, and Sarah Jovan.
Oliver, Marie. 2011. Canaries in a coal mine: using lichens to measure nitrogen pollution. Science Findings 131. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 6 p.