The air is still and heavy with a dense fog. My ears are alert, listening for the soft pad of paws on soil or the distinctive snap of a twig. My eyes are alert as well, searching for the tawny coat of a cougar or the darker one of a bear. The forest is thick with trees and bushes. Together with the fog, this prevents me from seeing far and leaves too much up to my imagination.
I understand the probability of encountering a cougar or bear is small, and the risk of being attacked by one is even smaller. However, that understanding does little when my mind has already decided my fate.
A while later, I round a turn. The fog lifts, the forest thins, and my fears fade. In their place, my mind fills with wonder. The trees stretch towards the sky and needles fill their upper branches. Their lower branches, however, are empty. Needles are energetically costly for trees. Because lower branches receive less sunlight, that cost is not worth the little energy the branches are able to produce. As a result, trees stop transporting resources to these branches, and they begin to die.
With this death comes an opportunity for life. Old man’s beard (Usnea) seizes this opportunity. Like other lichen, old man’s beard consists of a mutualistic relationship between a fungus and an algae. As there is more sunlight on empty branches than on branches full of needles, the algae is better able to photosynthesize. Thus, old man’s beard often grows on dead or dying branches.
Some small plants and saplings line the forest floor, but my eyes are drawn to the old man’s beard. Lazily draped over branches, with sun shining through its many holes, it is a beautiful sight. Closer up, it looks like it sounds it would- if old men had pastel green beards that is.
Yet, old man’s beard’s significance goes far beyond its looks. Found in most biospheres from the Arctic to the tropics, it was first described in 300 BC as a hair-growth stimulant, and it has since been used for everything from epilepsy to athletes foot. Moreover, lichens are sensitive to pollution. That being so, old man’s beard can be used as a bioindicator— identifying areas that may soon experience harms from pollution.
As I continue along the trail, the forest transitions to alpine meadow. Before me are mountain goat tracks, alpine flowers, and the occasional patch of snow. I stop for a moment, glance back, see the old man’s beard gently waving in the breeze, and continue on my way.