• What is a lichen?
    A lichen is a symbiotic relationship between an algae, fungus and sometimes a cyanobacteria. Lichens grow on trees, on soil, and on rocks. Over 1000 lichen species have been documented in the Pacific Northwest.

    Why are lichens ecologically important?
    Lichens are important for ecosystems because they provide nesting material for numerous bird species and are an important a food source for many animal species. In addition, some species of lichens are nitrogen fixers and are an important part for forest ecosystem health.

    Why are lichens scientifically important?
    Lichens are bioindicator species that allow scientists to understand the long-term nitrogen-based air pollutants deposited in an area. Nitrogen-based gases are emitted from transportation and other human activities. Some lichen species are sensitive to air pollutants and other species are tolerant. A scientist can assess if the air has high nitrogen-based pollutant loads based on which lichen species are present. There are three classifications of lichens: 1) Eutrophic - (tolerant to pollutants), 2) Mesotrophic (medium tolerance), and 3) Oligotrophic (sensitive to pollutants). If an area has high proportions of Eutrophic species that can indicate high amounts of nitrogen-based pollutants are falling in that area.

    Why is a lichen biomonitoring important?
    It is important to document which lichen species are present in an area to understand the long-term  air pollutants in a given area. High levels of nitrogen-based air pollutants cause ecological harm and also are associated with human health impacts. The Summer of 2019 a Wilsonville High School student, Shelby Parrack, launched a long-term biomonitoring study to document lichen species on the CREST property and at Grahams Oak Nature Park. Eleven species were found, with the majority of species categorized as Eutrophic lichens. This documentation can provide a baseline dataset to be compared to in future years. Future research efforts can identify if lichen biodiversity is declining and if the decline is associated with air pollutants.


    List of lichen documented lichen species (Summer 2019)

    Candelaria concolor - Eutroph
    Cladonia fimbriata/chlorophaea - Eutroph
    Evernia prunastri - Eutroph
    Hypogymnia tubulosa - Mesotroph
    Parmelia sulcata - Eutroph
    Physcia adscendens - Eutroph
    Platismatia glauca - Mesotroph
    Ramalina farinacea - Eutroph
    Xanthomendoza fallax - Eutroph
    Xanthoria polycarpa - Eutroph
    Xanthoria parentina - Eutroph