Lessons learned from the lichen

Lessons learned from the lichen

Photo by Jeffrey Hamilton on Unsplash

Originally published 23 April 2002

There is a low mist in the woods. It is a good day to study lichens,” wrote Hen­ry David Thore­au in his jour­nal on the last day of 1851. To tell the truth, any day is a good day to study lichens, as Thore­au would have acknowl­edged. “I could study a sin­gle piece of bark for hours,” he wrote else­where in his jour­nal. He meant, of course, a piece of bark cov­ered with lichens.

Win­ter or sum­mer, as oth­er crea­tures come and go, lichens endure, in their rain­bow of col­ors, their mul­ti­plic­i­ty of forms, their prodi­gious capac­i­ty to thrive in the least hos­pitable envi­ron­ments. They col­o­nize grav­el­ly ground, bare rock, con­crete walls, tomb­stones, and nooks and cran­nies of the plan­et snubbed by every oth­er creature.

Lichens are nature’s graf­fi­ti artists, paint­ing every exposed sur­face with swaths of color.

Some of the most engag­ing lichens in our area require get­ting down on hands and knees: British sol­diers, pix­ie cups, rein­deer moss (which is not a moss at all), and pink ground lichen (bub­ble-gum lichen, my stu­dents call it, nail­ing the col­or) — tiny forests that invite explo­ration. A mag­ni­fy­ing glass helps.

To look for lichens is to “go gnaw­ing the rails and rocks,” wrote Thore­au. The per­son who stud­ies lichens grows fat where oth­ers starve, he said — like the lichens themselves.

Unfor­tu­nate­ly, there are few guide­books to help us as we go a‑gnawing. My col­lege library has sev­er­al shelves of books on algae, and more shelves on fun­gi, but only a few vol­umes on the com­bi­na­tions of algae and fun­gi known as lichens. How for­tu­nate we are then to have the mag­nif­i­cent new Lichens of North Amer­i­ca by Irwin Bro­do, Sylvia Sharnoff, and Stephen Sharnoff (Yale Uni­ver­si­ty Press, 2001), which has got to be one of the most beau­ti­ful nature guides ever published.

I’m not sug­gest­ing that you rush out and buy the book. For one thing, it costs $70 (although worth every pen­ny). For anoth­er, at almost 9 pounds you are not like­ly to car­ry it in your back­pack. For­get the rails and rocks: This is a book to savor in a com­fort­able chair, prefer­ably with the book rest­ing on a stur­dy table.

And what makes the book so savory are the col­or pho­tographs, more than 800 of them, almost all tak­en by the Sharnoffs. Who would guess that low­ly lichens could be so beau­ti­ful? Per­haps only bee­tles dis­play such a range of col­ors, and no oth­er class of liv­ing things has such a vari­ety of forms.

A lichen is usu­al­ly referred to as a sym­bio­sis of an alga and a fun­gus, which means that the two live togeth­er for mutu­al ben­e­fit. The alga makes nutri­ents with sun­light, pho­to­syn­the­sis, which a fun­gus can­not do. The fun­gus pro­vides the alga with a steady water sup­ply, pro­tec­tion from excess light, and a chance to live in habi­tats — dry rocks, exposed tree bark — where it could not sur­vive on its own.

But all things con­sid­ered, it would appear to be the fun­gus that gets most out of the col­lab­o­ra­tion. Liche­nol­o­gist Trevor Goward goes so far as to say that lichens are “fun­gi that have dis­cov­ered agriculture.”

What he means, I sup­pose, is that lichen fun­gi have domes­ti­cat­ed algae the way we domes­ti­cat­ed corn and cat­tle. After all, humans could not sur­vive with­out the nutri­ents pro­duced by plants, or the flesh and flu­ids of ani­mals that eat plants.

Lichen fun­gi feed on the algae that they have enticed or trapped into col­lab­o­ra­tion. They suck nutri­ents from the algae, some­times killing them. It is only because alga cells repro­duce faster than they are con­sumed that a lichen can exist at all; oth­er­wise the lichen would “eat itself alive.”

If the alga and fun­gus com­po­nents of a lichen are cul­tured sep­a­rate­ly, they appear pret­ty much as mono­chrome goos, lack­ing the hues and form of the orig­i­nal lichen. It’s the fun­gus’s genes that deter­mine the struc­ture of the lichen. The alga some­how turns its part­ner’s genes on or off, but when if comes to the won­der­ful lichen shapes you see on rock or rail, it’s the fun­gus that’s in charge.

As appre­ci­a­tors of beau­ty, we humans also gain from the lichen sym­bio­sis. The breath­tak­ing pho­tographs in Lichens of North Amer­i­ca raise the ques­tion: Why the beau­ti­ful col­ors? The hues of flow­ers attract insects for pol­li­na­tion; the col­ors of birds attract mates. It is less clear why lichens dis­play such gaudy col­ors, but, on a misty morn­ing in the woods, those lit­tle flecks of pig­ment — British-sol­dier red, bub­ble-gum pink, bright yel­lows and oranges — are welcome.

Thore­au even took home a moral les­son from his lich­eniz­ing: “It fits a man to deal with the bar­ren­est and rock­i­est expe­ri­ence,” he wrote. He might have added: Such is the resource­ful­ness of all life.

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