Forest Inventory and Analysis National Program

Program Features

Forest Health Indicators: Lichen Indicator

Lichens are symbiotic organisms, consisting of a fungus living with one or more photosynthetic partners (an alga, cyanobacterium, or both). The recent discovery of a third partner in some lichens, a yeast, suggests there is much yet to discover about these unique symbiotic organisms.

The U.S. Forest Service (USFS) collected over 8,300 surveys of epiphytic (''tree-dwelling'') lichen communities between 1989 and 2012 to serve as a baseline for tracking air quality, climate, and other change on forest land. Lichens are widely used as ''canaries in the coalmine'' for detecting air pollution and monitoring its impacts, a practice dating back to 1866. Lichens lack roots, deriving all nutrition and water from the atmosphere, making them especially vulnerable to air pollutants as well as climate changes and other shifts in habitat conditions that affect light, microclimate, and nutrient availability.

The Forest Inventory and Analysis (FIA) and Air Resources Management (ARM) Programs of the USFS collaborate to collect, distribute, and analyze the lichen data. The data have been used in over 90 publications, many aimed at meeting Federal Land Managers' needs for detailed information on air quality across forestlands.

National FIA Lichen Database

The National FIA Lichen Database (Version 1.0) unites, for the first time, all lichen community surveys conducted by the FIA and ARM Programs through 2012.

User Guide for the National FIA Lichen Database - Version 1.0

Download the National FIA Lichen Database - Version 1.0 (MS Access)

Lichen Critical Loads

Researchers commonly use lichen data collected by the USFS to develop Critical Loads (CLs) for nitrogen and sulfur pollutants. CLs define the amount of pollution that sensitive species and processes can tolerate without negative consequence. Thus, many land managers use CLs to evaluate the ecological effects of air quality.

Recent articles on lichen-based CLs include "Assessing ecological risks from atmospheric deposition of nitrogen and sulfur to US forests using epiphytic macrolichens." Supplementary materials for that article are available for download (.zip file).

U.S. Lichen Atlas

The National Atlas of Epiphytic Lichens uses the National FIA Lichen Database to map the distributions of over 450 lichens across U.S. forests and provides additional history on lichen monitoring efforts in the USFS.

The Lichen species distribution maps (Appendix 2) can be downloaded from the above linked National Atlas, or viewed directly here.

Additional Resources

• Additional data and information about lichens at the Forest Service can be found at the USFS Lichens and Air Quality Website (http://gis.nacse.org/lichenair/). Many sites that the ARM Program surveys for lichens also have elemental data - measurements of pollutants accumulated in lichen tissue. Those and over 4,000 other lichen surveys conducted using different field protocols, can be found there.


• Lichen research at the Forest Service and the importance of lichens in the measurement of air pollutants was highlighted in the video, "The pollution surveillance system growing on your street".