Lichen is everywhere we turn: rocks, tree trunks, soil and manmade surfaces like the flat, crusted lichen on the roof tiles in the photo above. We've all seen it, and most of us know there are many varieties of lichen, but for a substance that is found on every continent on Earth--including the Antarctic--we actually know very little about it.
For instance, what do we classify lichens as? What category, family, species? During a recent hiking expedition with friends, the debate began as soon as we took a breather against a pile of lichen-covered boulders.
"It's a fungus," ventured one of us. Another disagreed, declaring it more of an algae-like substance. Turns out they're both right. When a fungus pairs with algae (most commonly green algae) or cyanobacterium (also known as blue-green algae) the result is a dynamic duo (AKA lichen), relying on nature's "buddy system" of symbiosis--each organism helping the other to mutual benefit. Fungus provides the moist, nutrient-rich substrata for the algae to anchor to, while algae has the ability to photosynthesize, turning sunlight into valuable chemical energy that can fuel the lichen. That's all any of us really need to survive: a place to call home and a nice meal, right?
There are four basic lichen types (think body types for lichens): foliose lichens are the ultra-skinny supermodels of the lichen world: two-dimensional leaf-like waifs, while Fruticose lichens are pendulous, three dimensional, and a bit sloppy looking, lacking distinguishable upper and lower surfaces. Crustose lichens form a crust over their substrates, like rocks, trees, and sidewalks. The lower surface of crustose lichens attach firmly to many surfaces and form brightly colored patches of a thick, rough naturalized texture. Kind of like a person with a bad skin condition. And then there's Squamulose lichens, which can't decide exactly what to look like, so they take a few characteristics of both foliose and crustose growth forms. Their shape is scale-like, and they attach by the lower surface like tiny shingles.
Okay, so now that we know what lichens are made of, and what most of them look like, why do we actually need to know it? I mean, honestly, do lichens really DO much that helps us? You may be surprised. I know that I was. First, and perhaps foremost, lichens have the ability to "fix" atmospheric nitrogen (kind of like bean plants do in soil), which allows the vital chemical element to reach other plant life. When it rains, nitrogen is leached from both living and dead lichens and is available to plant life in the immediate areas. When lichens die, they contribute decayed organic matter to the area they inhabited, which enables mosses and seeds from vascular plants to begin developing among the pockets of new soil. Cool cycle-of-life stuff. Maybe not worthy of the Lion King's "Mufasa speech," but special enough to get a quote by Thoreau: I find myself inspecting little granules as it were on the bark of trees � little shields or apothecia springing from a thallus � such is the mood of my mind � and I call it studying....
On a more practical note, lichens also contribute to the food chain (Caribou love 'em, though they aren't a tasty treat for humans), have antibiotic properties that have been used in ointments to aid healing in superficial wounds, and can be found in deodorants, laxatives, expectorants, tonics, and healing pastes. Research with lichens around the world is suggesting these organisms hold promise in the fight against certain cancers and viral infections, including HIV.
All that wonderful stuff makes me wonder what can't lichens do? Well, contrary to popular belief, lichens growing on living things, like tree trunks, can't kill trees or other vegetation. With a few very rare exceptions, lichens are more helpful to plant life around them than harmful. So cozy up to these composite colonizers, and be thankful they're around. Like many of us, they need three vital things to survive: undisturbed surfaces, time and clean air (kind of like me on a lazy Sunday morning). Be happy when you encounter lichens because it means you're in a neighborhood that's clean enough to support this amazing dual organism.
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