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When I moved to the Ozarks for graduate school in 1989, the place terrified me. First there was the Pig Trail, which is what the locals call the stretch of highway between Alma and Fayetteville, Arkansas. As I embarked on the steepest stretch of it, I saw a sign that read, “Caution: Eleven people killed on this road in the last two years.” The sign changed every year or so to update the count. Even though the Ozark mountains are more like hills, they were steep enough to make me wince; I’d come from the prairies to the west, so the precipitous roads and drenching humidity of this territory struck me as unnatural. It didn’t help that some of the locals pronounced “Fayetteville” as “fateful.”
My discomfort may help explain a sort of optical illusion I encountered shortly after moving into my home in the woods. One night I glanced out a window and was startled to see that the tree trunks looked completely different from how they had appeared the day before. Instead of dull brown, they were a ghostly gray verging on green and flecked with gold. The next day, exploring those woods, I found the trees still had the new colors of the night before. Their gold flecks were abundant, and I had a hard time distinguishing that gold from the glints of sunlight that filtered through the canopy. Then it struck me: The shimmering color I was seeing belonged not to the tree trunks themselves but to the lichens that covered the bark from top to bottom, made vibrant by the bright sunshine.
The trees never changed back; I soon learned that this was the way of the woods in the Ozarks. My eyes had opened to the life-form that dominated the look of my new surroundings. All around, the trees’ external surfaces were hidden. The forest was painted in the colors of lichens.
I was hardly the first to be baffled by lichens. For hundreds of years, naturalists didn’t quite comprehend what they were. Originally these odd forms were thought to be part of the plant kingdom, which is why we still see lichens collected by botanical gardens. Eventually, microscopy enabled scientists to identify lichens as composites of mutually beneficial fungi and algae. Because fungi take the more dominant role and cultivate photosynthesizing algae for food, in return providing them a shady, moist, vitamin-rich environment, scientists have classified lichens based on their fungi species. Their identity came into dispute again when blue-green algae, a frequent component of lichens, were reclassified as cyanobacteria, a kind of bacteria that obtain energy through photosynthesis. But as it turned out, whether the fungi were harvesting algae or cyanobacteria, the symbiotic modus operandi of the lichens proved to be the same. Perhaps Trevor Goward, the lichen curator at the University of British Columbia Herbarium, describes them best. “Lichens,” he says, “are fungi that have discovered agriculture.”
My walks in the Ozark woods impressed upon me the lichens’ diversity and the confusion they can create. Sometimes their identity was clear. A lichen species known as British soldiers sports distinctive, bright red caps atop green stalks. Old man’s beard can run more than three feet long and hangs from trees in the manner of Spanish moss. But without a microscope to see green clusters or strings of photosynthetic organisms running like arteries through the fungal flesh, you cannot always tell you are seeing a colony of lichens. A colony might look like a plant, an uncomplicated fungus, or even a patch of rust: here a fence speckled in autumnal reds and yellows, there some orange lace spread on a stone. Behind my house I found a fallen tree carved with a set of leathery lichenous steps.
There are an estimated 20,000 lichen species, living on every continent in practically every environment that supports life. In the Ozarks and elsewhere, a handful of biologists now see lichens as sources of unique chemical compounds and as sentinels of environmental change—and also as enduring biological puzzles.
“We’re still in our infancy in understanding the lichen biota of the world,” says botanist Doug Ladd, who has spent the last 15 years tramping through the woods with colleagues from the New York Botanical Garden and The Nature Conservancy to assess the array. Their area of interest includes my local hotbed of lichen activity: the Ozark Plateau, which covers most of Missouri, the northern third of Arkansas, the eastern edge of Oklahoma, a tiny corner of Kansas, and a nibble of Illinois.
Ladd and company have visited every county in that region. They have searched sunny patches of rock and shaded bits of forest, weathered fence posts and sheltered caves, grassy glades and the faces of cliffs. Some lichens they have uncovered are smaller than grains of sand. When they come across a crusty specimen, they use chisels or knives to cut a sample of the lichen and its substrate, sealing it all in a paper bag. Sometimes, Ladd says, a particularly interesting find—say, Phoebus hydrophobias, a bright orange lichen that he describes as a “mad-dog sunburst”—elicits a triumphant whoop from the team.
