The Friendly World of Lichens

By Lynne Bittner

Robert Louis Stevenson

The Vernal Equinox is a of couple of weeks away and it is still about a month before the early spring wildflowers in our woodland begin to emerge - and as usual, this time of year I am preoccupied with looking for green and growing things. Recently, I’ve become acquainted with the fascinating (but often overlooked) world of lichens and suddenly, I see them everywhere! On trees, rocks, on my house and roof shingles- both wooden and asphalt (much to my husbands chagrin). They can grow on almost any undisturbed surface provided they have the right conditions of light, moisture and clean air. It is at this time of year when they become luminous - absorbing the early spring sunlight in combination with moisture from the thaw; their pale sage color turning incandescent against the gray bark and rock surfaces.

Basically, a lichen is a dual organism, comprised of two and sometimes three separate organisms living permanently together: a fungus, an algae and/or a photosynthesizing bacterium called a cyanobacterium. A fungus by definition is: a mushroom, mold, mildew, rust, smut, etc. characterized chiefly by its lack of chlorophyll ... subsisting upon dead or living organic matter... a spongy morbid growth.... Yuk! Not an appealing thought to ponder. However, when a fungus is paired with an algae or photosynthesizing partner, a small ecosystem is created unto itself. The fungus provides the physical structure and the ability to absorb hydration and nutrients from the atmosphere. It also provides its bedfellows with shade and protection from drying out by enclosing them cozily within the body of the lichen. In turn, the algae supplies nutrition through its ability to use sunlight’s energy to convert carbon dioxide and water into food for them both. Somewhere down the multi-millennial road (around 400 million years ago) they worked out this friendly arrangement that has been so successful, they cover about eight percent of the terrestrial surface of the earth.

With the remarkable ability to extract nutrients from the air, lichens can flourish in places not fit for man nor beast - even surviving extended exposure in outer space. In fact in 2005, they were exposed to the vacuum of space for 15 days - enduring cosmic radiation and widely fluctuating temperatures, and found to be in perfect health with no discernible damage. Here on earth, they tolerate extreme cold and drought, and can be found thriving in areas that are so hot, dry or sterile that nothing else will grow. However, because of this quality, they will also indiscriminately absorb and concentrate many toxic substances -making them extremely vulnerable to pollution. For example, sulfur dioxide when emitted from the combustion of fossil fuels kills the non-fungal partner, and without it’s photosynthesizing companion, the fungus part soon dies. Thus, their presence - or lack of, is an important indicator of air quality. I am happy to report that here along the banks of the Battenkill, the lichen population is burgeoning, with a diverse amount of species growing all over the place - most especially on the oak trees along the river’s edge. 

There are several categories of lichens, the most quickly recognized are the sage colored patches on rocks classified as crustose which are flat and paint-like. This variety is the hardiest and can tolerate the highest levels of pollution. Lichens from the foliose or leafy, category- slightly resemble foliage, while fruiticose lichens are branched and shrub like. These tend to be more sensitive to pollution. They vary in shades of greens, grays, yellows, reds and oranges to black. My favorites are the lilliputian ‘British soldiers’ with their bright red caps that grow on the shale outcroppings on our property along with the sage green pixie cups.

Lichens grow very slowly and some live a long, long time. In fact there are ones that are 4,000 years old that live in the Arctic moraines. We have much to learn from their patient, tenacious lives, as they have an impressive story of survival to show us.  

Lichens & toadstool.

A moss like lichen or liverwort