There are lichen that grow on rocks, organically painting their hard surfaces with a spectrum from fluorescent split pea to brick orange. Others are epiphytes, growing on branches and twigs and making them even more textured and green. Then there are some that colonize the top of a Volkswagen bus.
Yep, my daddy’s 1971 beat-up ride is becoming its own little ecosystem. I counted at least four different types of lichen growing
on it. This has been happening for years, and continues to make me very pleased. His bus sort of has celebrity status, up there with Herbie the Love Bug and that stupid Chevron “Techron” cartoon car (“ ‘Do people care? People….’ Ah, who are we trying to kid? Nope!”). Occasionally, when I visit my parents, people I’ve known for years will say, “Oh, that’s your dad? That guy with the moss [sic] growing on the top of his van?”. He tells me tourists are always snapping pictures of it, nature photographers in their own right. The VW bus turned environmental education tool.
There are approximately 14,500 different species of lichen, according to my Introductory Plant Biology textbook (ed. Stern, Bidlack, and Jansky). Do I know what the ones on the bus are? Definitely not. Someday it would be fun to take a lichenology course. For now, though, it’s more important to know three concepts about lichens than the taxonomy: what they are, they three forms they take, and how they’re used and affected by humans.
Aside from maybe the other biggie – pollination — lichens are the quintessential example of mutualism in nature. Not only are they the result of two species co-existing, but this tiny life form is the embodiment of two species helping each other to live better. And in the case of one of them, perhaps even to live at all. Just when you thought it couldn’t get any more hippie than plants self-propagating on a VW bus, we have this gushy mutual aid, this anarcho-communalism that actually works. So, the lichen lowdown? It’s a symbiotic relationship between a fungus and either a green algae or a cyanobacteria (see the difference here). The green algae or cyanobacteria plays the role of bread-winner, providing food for both organisms through photosynthesis. The fungi holds down the fort as the homemaker, protecting its photosynthetic partner from damagingly intense sunlight, absorbing and storing water and minerals for both species, and producing a substance that speeds up the rate of photosynthesis. Two separate kingdoms coming together for the good of the whole. If only politicians were more like lichen.
Because there are relatively few species of algae or cyanobacteria involved in creating a lichen, but each lichen has its own fungal species, lichens are thus ID’ed according to their fungal contributor. In a lab, it’s possible to isolate and grow the two species of one lichen separate from each other. When this is done, the algae or cyanobacteria grow faster than they do when partnered with the fungus, and the fungus grows into a totally different shape. Also, while the photosynthetic species can, in some cases, grow well independently of its lichen body, the fungal component is rarely found on its own.
Lichen are grouped into three growth forms. These are useful in their identification. All were easily found on the VW bus. In order from “shortest” to “tallest”:
- Crustose These are the lichen that look literally like a crust, almost flush with their host surface, be it rock or tree, soil surface or windshield wiper. Of the three kinds, crustose are the most strongly attached to their substrate – some have hyphae (fungal filaments that extend underground) penetrating up to one centimeter into rock, absorbing water and minerals. They’re often brightly colored, making a plain old rock look like the canvas of a mad abstract painter.
- Foliose Again, the name suggests the form: these are the leafy lichen. They are crinkled, overlapping, and growing slightly off the substrate. They are often a grayish-green. Foliose lichen are very loosely attached, and I feel like an asshole thinking of how many I’ve killed while absent-mindedly picking them off tree bark as though they were a skater’s scab or shard of stubborn Scotch tape.
- Fructicose These are the ones like witch’s hair, spindly fingers, crusty tentacles. The lichen with the most dimension, resembling little shrubs or hanging long and beard-like from tree branches, creepying up the forest should you be inclined towards the woodland spooks. You know Usnea? That’s a fructicose lichen. In the VW photos, the fructicose kind include the ones silhouetted on the roof, creating a 3-D mini-forest.
Only a very few lichens parasite their host plant by digging their hyphae in too deep. Most are not taking anything, but just innocuously chillin’.
And humans? Where do we fit into all these partnerships? Do we give or take anything to or from the lichen realm? Ethnolichenology is the study of how people use lichens. Can you imagine: Oh, yes, I’m an ethnolichenologist! Throughout the
ages lichens have been harvested and used as dyes. At the height of the Roman empire and into the 17th century, a purple dye known as “ochil” was extracted from a species called Roccella tinctoria, symbolizing power and regality even after humans decimated the mollusk populations from which a violet-colored dye was originally derived. A vibrant yellow hue comes from a species common on the west coast of the United States, Letharia vulpina. Not only was the toxic primary constituent, vulpinic acid, good for dying, it was also used to poison wolves and foxes (boo!), hence the species name. Lichens can also be potent medicine. One of the most well-known anti-biotics is Usnea, which can be found growing all over the world and is commonly called “old man’s beard” or “treemoss”. In traditional medicine, usnea is used to treat various fungal infections, for example. And, lest we forget the little people, lichen are commonly used by crafters as miniature shrubs and other landscaping in dioramas and dollhouses.
As the VW bus example illustrates, lichen are totally capable of living in less than ideal environmental conditions. Whether on arctic permafrost, desert rocks, or even manufactured substrates like glass or asbestos, these are pretty tolerant organisms. Lichen life can be harsh, and they’re very slow-growing as a result. They hang in there, though: some can live up to 4,500 years, according to my aforementioned textbook. Part of the reason lichen are so admirably tolerant is due to a gelatinous substance in their fungal body, which allows them to deal with spells of intense dessication in between wetter times. They can be unaffected by drought, becoming temporarily dormant and not photosynthesizing.
Yet one thing lichen can’t survive too well is air pollution. They’re especially vulnerable to sulfur dioxide, to the point that within a given area, the amount of lichen growing or disappearing corresponds to nearby sulfur dioxide emissions. I’ve always had a hard time owning old Volkswagens, since they don’t have catalytic converters and just spew pollutants out the tailpipes totally unabated. However, all the lichen thriving on the bus is alleviating my guilt a little — I mean, if these hypersensitive organisms can grow so close to a direct source of sulfur dioxide, it must not be all bad, right (I’m kidding…! Basically.)? Plus, as susceptible as they can be, lichens also have the power to destroy hard, solid relics — including Machu Picchu and Troy — through the action of their acids and tenacious longevity. Along with rust, lichens are slowly degrading my dad’s VW. Someday, there will be a pile of lichen-created soil on the side of Melrose Avenue where a hippie-mobile once resided. This, too, makes me feel a little better, a tiny victory for the argument that fixing up and reusing old cars is more “eco-friendly” than buying the newest, made-of-plastic trend in auto-efficiency every five years.
Because really, how “green(TM)” are you if your car doesn’t have lichen growing on it?