Wresting a living from the world is never easy. Heck, just making it through a desk-bound workweek is enough to wipe me out most of the time.
But it could be worse.
Imagine sitting throughout your life on a cold rock, making a living as best you can from air and the occasional drop of rain.
That’s the task lichens face everyday.
You might say that lichens found a niche that nobody else wanted. Or, as the lichens might say, they have a role on Earth that nothing else has the stamina and fortitude to fill. “The few, the proud, the lichens,” might be their motto.
The success of the simple lichen is really a tale of cooperation. Two life forms make a living together in a lichen, each benefiting from the work of the other, like a tiny, socialist utopia.
The first part of the intimate pairing is a green single-cell organism. I won’t be more precise than that, because there are variations in that green cells that go right over the head of a geologist. But the main point is that the green partner harnesses the energy in sunlight and uses carbon dioxide in the air to build carbohydrates.
The green cells would often not do very well on their own. Enter the second part of the pairing, the fungus cells.
Fungi are weird. You know that from eating mushrooms. They are neither fish nor fowl, neither animals nor plants.
The fungi in the lichen combine with the green cells to form a compound organism that’s more successful than either half alone. The green cells create the carbs, while the fungus does a couple of different things. The fungal cells make a stable structure for the lichen community and create chemicals that dissolve a bit of the rock the lichen sits on. That, in turn, makes a small amount of mineral nutrients that the fungi shares with the green partner.
The cooperation between cells in the lichen has been a great marriage, one that’s lasted for more than half a billion years and shows no signs of heading to divorce court.
As a geologist, I drag home a few rocks from around the Northwest every chance I get. When I bring the rocks into my house or office, the lichens on them dry completely. And then years pass.
“But they’re still alive, I’d wager,” said Professor Jack Rogers of Washington State University. “Just water ‘em, set ‘em in the sun, and watch.”
Rogers is a fungi expert. He was kind enough to come with me on a geology fieldtrip, so some students and I could learn more about lichens.
Occasionally, geologists use the size of lichens in our work. The diameters of lichen on a gravestone – a rock surface with a known age conveniently printed right on it – can show you how fast lichen grows in a particular climate. Say lichen on the east side of a tombstone from 1908 are all about an inch across. Using that knowledge, geologists can estimate how long a certain boulder or cliff face has been exposed to the sky, judging by the size of the biggest lichen on east-facing surfaces.
It’s elementary, my dear Watson.
There are many different lichens: gray and flakey, light green and spongy – and my own personal favorite, the strongly orange ones. Rogers knows them all and calls them each by their scientific names.
“Lichens are a sensitive indicator of air quality,” Rogers reminded me recently. “The Scandinavians have been watching them for centuries.”
As an American of Scandinavian lineage, I can testify we are an odd group with peculiar interests. Watching lichens isn’t our strangest pursuit.
“The lichens in towns died off when Scandinavians started burning coal,” Rogers said.
Raw coal smoke from a simple hearth is a good bit nastier than wood smoke. Some of us geologists actually like the smell of coal smoke on a winter morning, but sane people do not. Our industrial cities used to be pretty sooty places – and those in China still are, in large part because of coal smoke.
“But now the lichens in Scandinavia have grown back because the air quality has improved as folks quit burning coal for everything,” Rogers said.
That conjured up a new motto in my mind.
The lichens: the few, the proud, the canaries of our industrial age.