Lichens of the Arctic

By James Walton, National Park Service

Lichens are a conspicuous and colorful component of Alaska’s vegetation and one of the most species-rich groups of organisms to inhabit the Arctic. A lichen is a composite organism consisting of a fungus and an alga and/or cyanobacteria growing together in a symbiotic partnership. Together they are intimately connected to their environment. Lichens are highly sensitive to environmental conditions including airborne contaminants, substrate chemistry, and climate and are good indicators of environmental change.

They can be found in all types of ecosystems, from intertidal zones to the tops of mountains—even on nunataks (the exposed rock outcrops of icefields). They grow on soil, rock, bark, wood, barnacles, and buildings. Lichens are ecologically important as food, shelter, and nesting material for wildlife; and play important roles in hydrological and mineral cycles, notably nitrogen fixation.

Recent inventories conducted in Arctic Alaska parks have revealed high lichen diversity. Across the Western Arctic Parklands, over 500 lichen species have been discovered, including at least 16 that are newly described in Alaska or North America and three that are newly described to science (Holt and Neitlich 2010, Nelson et al. 2015). Many of these species are circumpolar and also distributed outside the Arctic, though the majority are confined to Arctic-alpine habitats.

Lichen species are an important component of the many biological communities across Arctic Alaska. Recently, patterns in Arctic lichen community composition have received attention in response to expanding shrub communities and increasing fire frequency and extent, both of which are linked to declines in lichen abundance. Because lichens are often a major component of forage consumed by caribou, such as by the Western Arctic Caribou Herd estimated at 234,000 individuals, and is one of the largest free-roaming herds in North America, the consequences of lichen habitat decline could be substantial for the ecosystem and the local subsistence communities (Joly et al. 2010).

Because certain lichen species are both abundant and sensitive to changes in the environment, they can serve as useful indicators for detecting long-term trends in the larger ecological community, including the effects of changing air quality. Lichens lack roots and largely rely upon the atmosphere for their water and nutrients. Because they do not have an outer epidermal layer, they cannot discriminate between nutrients and pollutants, and absorb both.

When exposed to even low levels of certain pollutants, particularly sensitive species will decline or die, making lichen community composition a good indicator of ecosystem health. In park units such as Cape Krusenstern National Monument, lichen communities are being used to monitor mine-related and fugitive dust-borne heavy metals along the Red Dog Mine haul road. Recent findings confirm that lichen species richness decreases the closer they are to the haul road (Figure 1; Neitlich et al. 2017).

You can learn more about lichens and other non-vascular plants in Alaska’s national parks by reading the recent article: Moving beyond the Minimum: The addition of nonvascular plant inventories to vegetation research in Alaska’s national parks.

References

Holt, E. A. and P. N. Neitlich. 2010.
Arctic Network Lichen Inventory Dataset. Geospatial Dataset—2166259. Available at: https://irma.nps.gov/App/Reference/Profile/2166259.

Joly, K., F. S. Chapin III, and D. R. Klein. 2010.
Winter habitat selection by caribou in relation to lichen abundance, wildfires, grazing, and landscape characteristics in northwest Alaska. Ecoscience 17(3):321–333.

Neitlich, P. N., J. Ver Hoef, S. B. Berryman, A. Mines, and L. Geiser. 2017.
Effects of heavy metal–enriched road dust from the Red Dog Mine haul road on tundra vegetation in Cape Krusenstern National Monument, Alaska. NPS Natural Resource Technical Report. Submitted.

Nelson, P. R., B. McCune, and D. K. Swanson. 2015.
Lichen traits and species as indicators of vegetation and environment. The Bryologist 118(3):252-263.