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You probably know the drill well. First I pulled on the long johns, then the thick wooly socks, snow pants, a wool sweater, windbreaker, wool hat, ski boots, and—finally—puffy mittens. With a quick look at the thermometer (-5°F), a short drive to the trailhead, boots in ski bindings, hands through pole straps, and I was off!
Bright sun sparkled merrily over the rolling hills as I shushed along, working hard to glide over the cold, hard snow. In no time, I’d warmed right up, and my core temperature felt more like July than January.
Humans have gotten used to a tropical climate over the millennia, and we try to recreate it wherever we go. Whether it’s a wood stove crackling cheerily, our metabolisms burning edible fuels, the car heater turned on full blast, layers of wool, down and fleece trapping warm air around our bodies, or a trip to Florida, we tend to survive the winter by avoiding the cold.
Not everything has that luxury. Clinging to the bark of almost every tree in the forest is an organism that does just the opposite. “Lichens master the cold months through the paradox of surrender.” writes David George Haskell in his wonderful book The Forest Unseen. He compares lichens to the Taoist story of a man who jumps off a waterfall and, to everyone’s amazement, returns safely to shore. When asked how he did it, the old man answered, “I go down with the water and up with the water...I survive because I don’t struggle…”
Lichens don’t fight the cold, dry, winter air. Unlike wintergreen leaves, they have no waxy coating to slow evaporation. They don’t hide roots deep in the unfrozen ground like the oaks. They don’t try to fire up their metabolism to produce internal warmth like the chickadees, and they don’t grow layers of soft fur to retain it like the ermine.
Instead, lichens allow themselves to gain and lose water as the relative humidity fluctuates. During dry spells, a lichen thallus (leaf-like structure) might only contain 15-30% water, and it goes dormant. Freezing temperatures don’t seem to bother them, and at least one species can even photosynthesize at -4 degrees F. In fact, lichens have survived at least eighteen months in the hostile environment of outer space. While orbiting the Earth on the outside of the Space Station, lichens experienced wide temperature fluctuations and the full intensity of UV rays from the Sun. Back on Earth, given water and sunshine, they began photosynthesizing with no residual effects.
On a warm, damp day, the lichens I skied past will do the same thing. Their dusty-green, opaque surfaces are filtering out sunlight today, to protect inner cells from sunburn. But, with as little as 60% relative humidity, moisture will seep back into their cells, the surface will become translucent, and photosynthesis can resume within minutes.
“Plants shrink back from the chill, packing up their cells until spring gradually coaxes them out. Lichen cells are light sleepers. When winter eases for a day, lichens float easily back to life,” writes Haskell.
This incredible flexibility to surrender to ambient conditions makes lichens excellent colonizers of harsh environments. On mountaintops, the tundra, fresh rock faces, gravestones, and even mine tailings, lichens are the first signs of life. Vegetation dominated by lichens covers nearly eight percent of the Earth, largely in the Arctic tundra. What makes them so tenacious?
Lichens are actually a partnership between two or three different types of organisms. They are a cross-kingdom alliance. A fungus plays host, providing a stable home for a photosynthetic partner. Algae or cyanobacteria (formerly known as blue-green algae) set up shop inside the leaf-like structure, and use the Sun’s energy to make food for them both.
Without the photosynthetic partner, the fungus could not grow in rocky habitats that lack organic matter to decompose. When scientists try to culture the fungus by itself, they end up with a slow-growing lump. Without the fungus, the algae would be severely restricted in is habitats as well, needing constant moisture to survive and reproduce.
Together, the fungi and algae in lichens are the quintessential example of a mutualistic symbiosis, where both partners benefit from a close, living relationship. Lichens are also a lesson in Taoist philosophy, exemplifying the concept of “Wu Wei,” that was demonstrated by the old man in the waterfall. Wu Wei means allowing things to flow naturally, without combative or egotistical effort.
A good skier can use Wu Wei as well. Extending the glide, relaxing on the back swing, using momentum, and coordinating movement and breath are all hallmarks of great technique. My more casual technique also includes pausing to enjoy the view (and catch my breath) at the top of a hill, smiling at the bright pink sunset, and finding inspiration in the winter woods.
For over 45 years, the Cable Natural History Museum has served to connect you to the Northwoods. Come visit us in Cable, WI, at 13470 County Highway M. The current exhibit, “Deer Camp: A Natural and Cultural History of White-tailed Deer,” opened in May 2013 and will remain open until April 2014.
Find us on the web at www.cablemuseum.org to learn more about our exhibits and programs. Discover us on Facebook, or at our blogspot, http://cablemuseumnaturalconnections.blogspot.com/.