There is a low mist in the wood –

It is a good day to study lichens

Henry D. Thoreau

January is Bark Appreciation Month.  It’s the time when the earthy gray blue and ochre patches of lichen become vivid accent colors.

Snowshoeing in Governor Dodge Park last Sunday, I became riveted by the gorgeous splashes of colorful lichen all around me.  It is always there, quietly covering the motionless places in the landscape: rocks, trees, grave stones.  But I’ve been too focused on other things to really look at it.  Suddenly I wanted to be a lichenologist.

Today I hauled home a massive library book called Lichens of North America and lost myself in 795 oversized pages – many with gorgeous photos of lichen that look like they came from the planet Zorg.  You can see breathtaking images of lichens taken by the photographers Sylvia and Stephen Sharnoff in their Lichen Portrait Gallery.

Lichen is not one, but two creatures:  fungi teamed with algae.  Like most relationships, it’s complicated.  The fungus is the dominant partner providing the algae with shelter and moisture, and essentially living off the hard photosynthesizing work of the algae.  If the algae can’t grow faster than it is being eaten — no more lichen.  And like most relationships, it somehow seems to work.  There are any number of particular fungi and algae who are willing to dance this dance, and they create enough different lichen to fill more than one massive book.  They cover the world.

This dynamic duo has lived long and prospered from the arctic to the tropics.  Lichens have been called Nature’s pioneers because they are often found happily colonizing bare rock.  They also love tree bark, which is dry and hard – a lot like rock.  It’s their kind of neighborhood.  Basically they seek out places where the more vigorous types of plants and animals won’t move in and outcompete them.

Over time (I know this well, having repeatedly scrubbed my grandparents’ gravestones) they can do a number on rock, but apparently they don’t harm trees.  They live very lightly on bark and never penetrate to the area where the trunk or branch is conducting is treeish transport of food and water.  If there seems to be a suspicious amount of lichen on dead or dying trees, that’s because the lack of healthy leaves gives the lichen a more generous portion of light to grow by.

Here in Wisconsin, lichen and trees take turns using the sun.  Leaves grow in the summer, and lichen really takes off in the winter.  As long as it has enough moisture and light, it can grow.  If it gets too dry, it slows down and goes dormant.

Lichen are more than just another pretty face.  They are also useful.  They provide valuable forage for elk, caribou, and (in my neck of the woods) deer.   Birds and rodents use lichen to upholster their nests.

Some scientists use lichens as canaries in a coal mine.  They absorb minerals from the air and can be hit hard by certain pollutants, so they are being used as bio-indicators in a nation-wide sampling grid by many researchers, including the U.S. Department of Agriculture and the U.S. Forest Service.

...The Alaskan Forest Inventory and Analysis crew prepares for the 2006 lichen certification exam. Photo by Sarah Jovan

While it is true that lichens can live in almost any environment, it is also true that each of thousands of different lichens is supremely adapted to its precise niche.  Many lichens are poor dispersers and have strict habitat requirements.  So now I have added lichen to my climate-change-worry list.  (see my post  Climate Change in My Backyard )

One study I read concluded, “All in all, climate change has considerable potential to depress lichen biodiversity.”

Let’s hope not.  And let’s all try a little harder — for the lichen.