Fewer Lichen Species Grow Near the Red Dog Mine Haul Road in Alaska

Lichens lack roots and an outer epidermal layer, so they take in nutrients and pollutants alike. That makes them useful gauges of the air they live in. In Cape Krusenstern National Monument, lichen communities are used to monitor mine-related heavy metals carried as dust along the Red Dog Mine haul road, and recent findings confirm that the closer lichens grow to the road, the fewer species there are.

What a lichen is

A lichen is a composite organism: a fungus and an alga and/or cyanobacteria growing together in a symbiotic partnership. Lichens are a conspicuous, colorful part of Alaska’s vegetation and one of the most species-rich groups of organisms in the Arctic. They are highly sensitive to environmental conditions, including airborne contaminants, the chemistry of what they grow on, and climate, which makes them good indicators of environmental change.

They live in every kind of ecosystem, from intertidal zones to mountaintops, even on nunataks, the exposed rock outcrops of icefields, and they grow on soil, rock, bark, wood, barnacles and buildings. Wildlife use them for food, shelter and nesting material, and they play a role in hydrological and mineral cycles, notably nitrogen fixation.

The common freckle pelt lichen (Peltigera aphthosa) is often found over mossy ground, rocks, or under trees. NPS Photo / James Walton.

Many species, some new

Recent inventories in Arctic Alaska parks found high lichen diversity. Across the Western Arctic Parklands, over 500 lichen species have been discovered, including at least 16 newly described in Alaska or North America and three newly described to science. Many of the species are circumpolar and also found outside the Arctic, though most are confined to Arctic-alpine habitats.

The boreal pixie-cup lichen (Cladonia borealis) can be found on soil and rock in arctic and alpine regions. NPS Photo / Nina Chambers.

Patterns in Arctic lichen communities have drawn attention because shrub communities are expanding and fires are becoming more frequent and more extensive, both linked to declines in lichen abundance. Lichens are often a major part of the forage caribou eat, including the Western Arctic Caribou Herd, one of the largest free-roaming herds in North America, so losing lichen habitat could have substantial consequences for the ecosystem and for local subsistence communities.

The arctic finger lichen (Dactylina arctica) can usually be found in mossy tundra, often in late snowmelt areas. NPS Photo / Nina Chambers.

Reading the air

Because some lichen species are both abundant and sensitive to change, they can reveal long-term trends in the wider ecological community, including the effects of changing air quality. Lichens depend largely on the atmosphere for water and nutrients, and with no outer epidermal layer they cannot tell nutrients from pollutants, so they absorb both. Even low levels of certain pollutants make particularly sensitive species decline or die, so the makeup of a lichen community is a good indicator of ecosystem health.

Lichen species richness along the Red Dog Haul Road rises with distance from the road (red to blue in order of increasing richness). Map from the National Park Service article.

Six kinds of lichen. NPS Photos / James Walton.

Sources

• James Walton, National Park Service, Lichens of the Arctic, Alaska Park Science, volume 16 (Science in Alaska’s Arctic Parks); the source gives a herd estimate with no date, which is left out; rewritten in hubnx's own words.