Lichen Heaven

Author, teacher and bioregionalist, Stephanie Mills offers this essay to Nature Change readers on the curious life of lichens in Northern Michigan and one of our region’s expert lichonologists, Julie Jones Medlin.

One recent raw April day the widely capable biologist Julie Medlin, a botanizing sidekick of hers, and I prowled through some rich woods on a nearby two track. Although a few ephemeral spring wildflowers like hepatica, Dutchmen’s breeches, and trout lilies had put forth buds, these forbore to open, for no pollinator in their right mind would or could be out and about in such cold.

“On a day like today the lichens are probably the prettiest things here,” says Medlin,  author of  Michigan Lichens (1996, Cranbrook Institute of Science Bulletin 60) now alas out of print. A Michigan native, Medlin got her B.S. from the University of Michigan and her M.A. and Ph.D. from Western Michigan University. Possessed of a keen eye and boundless interest in every natural thing, she spotted the lichens Parmilia, Physcia milligrana, Usnea, and Evernia mesomorpha, among others along our walk. Seen through Medlin’s hand lens, one lichen’s tiny complex identifying characters leapt out. We saw a minuscule diadem of white spore-bearing structures ranged around a sage-colored cup, one of hundreds of such cups in a lichen growth, or thallus, on the bark of a roadside tree. It was pretty, indeed.

The octogenarian Medlin is compact, rosy faced, white-haired, overflowing with energy, acuity, and skills.  She’s instinctively generous, provident.  Following our walk, and before she departed from my place, she’d unobtrusively bestowed on me a bag of dried apple slices, a couple of chicken legs from the lunch she’d packed along, and one of the dozens of day-glo pink pussy hats she’s knitted to give away while watching TV. Retired from teaching anatomy and physiology in the Biology Department at Northwestern Michigan College a decade ago, when Medlin’s not in the field botanizing —nowadays she’s learning the ferns—she’s home gardening with native plants, out photographing, playing pickle ball, vocalizing with the Grand Traverse Chorale or the Singing Sisters, and sometimes playing the bassoon.

Medlin’s lichenology began during her student days at WMU, where she did an air quality monitoring study using lichens, which though resilient in the harshest climates, are extremely vulnerable to air pollution and acid rain. Captivated by the lichens themselves, she began studying and photographing them wherever she was, up north in Michigan or at her mother’s place in Mt. Dora, in north central Florida.

“I spent hours and hours and hours looking at the lichen.  I documented and collected down there.” Yet when she went back some years later, she said, “They were gone.”

Although she produced a valuable book on scores of Michigan’s most common lichens, and having had “a blast” doing it, Julie Medlin modestly disavows expertise. “I’m strictly an amateur,” she says, “pretty much self-taught.”

Our walk on that Leelanau County two-track led us through a patch of hardwood forest that has lost most of its ash trees but still retains maples, hemlocks, beech, poplar, a lushly flowering floor and other biodiversity as well.  “Lichen heaven,” Medlin called it. Lichens were everywhere she looked:  Painted on tree trunks, encrusting fallen branches, sprouting off twigs.  She’s mastered, and sometimes forgotten, more lichen identities than most ordinary mortals ever knew existed. And there are many to know: estimates of the number of lichen species in the world range from fifteen to twenty-five thousand. Although I marveled at her ability to recognize not just the obvious differences among the many lichens she noticed, but to name the family, if not genus or species, she bemoaned her memory lapses.

Strange and wonderful, lichens are not plants.  “They’re a very unusual thing…a dual organism,” says Medlin. Lichens are mutualists, or symbionts, an archaic partnership between fungus and either algae or cyanobacteria.   Algae are members of the plant kingdom, cyanobacteria of the kingdom Monera, and fungi have a kingdom all their own.  Kingdoms denote the most fundamental kinds of differences among organisms, primordial branchings of the tree of life towards radically different ways of existing.  Yet back in the distant mists of time, many millions of years ago, it was the wont of some of those disparate beings to team up and lichen.  Algae and cyanobacteria both have chlorophyll, which allows them to combine sunlight, water, and minerals, and CO₂ to make sugars for the hungry fungi.  Fungi are weirdly predatory, sending their threads, or mycelia, and their enzymes into organic matter, bare earth, or solid rock to dissolve and transform their ground.  The fungal part of lichen enmeshes and shelters the alga or bacterium and is nourished by it.  “The fungus captures a photosynthetic partner and hangs on to it so it will produce food.”

Starker than partnership, another way to understand this relationship, says Medlin, is as “controlled parasitism.”  The alga or cyanobacteria is the host, the fungus the parasite.  Because the trick in parasitism is not to kill off the host “It knows enough not to bite the hand that feeds it.”

Patient and venerable, lichens would seem to be almost indestructible, withstanding drought and extremes of humidity and temperature, reproducing by fragments or spores, wresting sustenance from bare ground. Some have long slow life spans, expanding by maybe a centimeter a century. Some have lived for thousands of years. The long-term, nearly planet wide presence of lichens suggests a durable, but not invincible design for living. Bad air can undo them.

Able to colonize naked sand, rock faces, and other barren terrains, lichen are world-making organisms. “As they grow,” write Dorion Sagan and Lynn Margulis, “they slowly turn solid rock inside out into crumbling soil and living earth.” These inconspicuous beings work at the leading edge of making the planet habitable for larger, more complicated forms of plant life and animal life, like Homo sapiens.  Yet it is rare to accord them their due significance.

Once alerted to these unassuming wonders, every trip to the woodpile or the occasional visit to a cemetery can become a microcosmic biodiversity outing.  Now I notice their myriad forms—some are like minute goblets, some are granular, some are flat and crumbly, some crisp and bristly, some form as medallions splayed across a tree trunk.  Their generally soft colors are varied—gray-green, ivory, black, ebony, taupe, and the occasional blaze of saffron.  They cling closely to, and sometimes penetrate and break the surfaces that feed them—twigs, bark, granite boulders, old marble headstones.

Looking more closely at a familiar fallen fence post lichen, British soldiers, or Cladonia cristatella, I began to ponder the how and why of the evolution of their different shapes and hues.  What’s the advantage to sending up a reproductive structure, a podetia with a red top, or apothecia? Or of being discreetly ruffled at the edges, like the gray-green rosette on that pine out my window? What determined those forms?

“Not many people care about lichens,” writes Medlin.  It takes, she says, “a little curiosity.”  Returning to Michigan Lichens, I’m struck by the intensity of her endeavor.  There was vocabulary to master, for one can’t distinguish these subtle organisms without being exact about their parts, which are unlike those of plants.  There was cultivating an eye to examine and appreciate these smallish, varied forms, and recognize their particular characters; it took skill and art to photograph and portray them in all their diversity and beauty, which is not of an obvious kind. This field guide, dedicated to her parents and produced while she was teaching at Northwestern Michigan College is, as perhaps most field guides are, clearly a labor of love.

What’s tragic is that such passionate, low-tech, open-air, pursuit of natural science has lost status, respect, or much place in education. Beglamoured by technology, regimented by teaching to the test, schools and colleges are so fettered by numbers and quantification that direct sensory experience of the wonder and mystery of nature gets short shrift. For the young or old to ignore or abstract the living world is to miss a great power of truth and beauty.

Julie Medlin has been plant walking for much of her life.  Her love for sharing natural history is unabated. While her children were growing up, Julie, then a single mother, brought them along.  “I used to drag my kids out because I always wanted to botanize.  They acted bored to death but it’s amazing what they did learn.” Her own offspring weren’t the only ones learning.  Many years later a chance meeting with a young friend who’d tagged along on one of those expeditions revealed he’d gone on to become a biologist himself.

No telling how many others Medlin and her kind have awakened to natural history. Given a little curiosity—and a naturalist’s company on a path, natural history can claim your human interest, and why wouldn’t it? It is, after all, the kind of rich and detailed understanding of the lives and relationships—the ecologies—that has sustained our kind from the beginning.