Snow continues to blanket the landscape, despite our surprising (and welcome) jaunt of warmer weather, and I often wonder at the well-fed deer trotting through my backyard. With so many species laying dormant for the winter, what are these brave souls eating? My question was answered—in part—by watching them nibble lichen from the trees by a local creek. I confess to often skipping over the lichen section of my otherwise well-worn copy of Plants of Coastal British Columbia (Pojar and Mackinnon). Despite my neglectful studies, it's hard to overlook the grey-green strands of witch's hair draped copiously over tree branches at the edges of old-growth forest.
Contrary to their somewhat unappetizing appearance, lichens are an important food for deer and caribou through the winter. Lichens, especially those in the Alectoria and Cetraria genera have a surprisingly high glucose content. Some enterprising early peoples in Russia even processed certain species of lichen to make a molasses-like sweetener.
Before you go out and start harvesting lichen to sprinkle in your coffee (likely, I'm sure), be warned that lichens bio-accumulate pollutants. Bio-accumulation is the gradual build up of a toxic substance in a living organism. Due to this tendency to bio-accumulate, hair lichens such as witch's hair (Alectoria sarmentosa) and old man's beard (Usnea sp.) are great indicators of air quality. Lichens don't have roots to help them source nutrients from soil—they absorb water, nutrients, and pollutants from air through their outer skin. Toxins taken in remain in the lichen for a long time, and so, testing cuttings can reveal the levels of pollutants in their system, and in the environment around them.
Although lichens are generally equipped to reproduce through fruiting bodies (appearing in A. sarmentosa as cute, little, brown saucers), most of its spread is caused by stormy winds dislodging pieces of it and blowing the wandering chunks from tree to tree. Their strands lengthen over time, growing to the tune of only few millimetres to a few centimetres per year!
Another quirk of lichens is that they are not single organisms. Lichens are formed through a mutually beneficial symbiotic relationship between two organisms. In lichens, a fungus (the mycobiont) and an alga (the photobiont) work together. The alga component is usually a green alga or blue-green cyanobacteria that works as the photosynthesizer of the team. The alga harvests energy from the sun (something the fungus can't do) and turns it into carbohydrates for growth and reproduction. The fungus gets a constant source of nourishment through "farming" the alga and in return, the alga secures a protected environment.
Wet days are often the best days to go looking for lichens. When the conditions are dry, they turn dormant, becoming brittle and fading to a more demure display. If wet, the foliage plumps and turns more intense shades of green, brown, or black.
When the surrounding air is clean, lichens become abundant. If you spot a host of these beauties draped on the trees around you, make sure to take a nice deep breath and enjoy.
Naturespeak is prepared by the Whistler Naturalists. To learn more about Whistler's natural world, go to Whistlernaturalists.ca.