Lichens Partnership Leads To Success
Durango Herald, Nov 10, 2005
Leigh Gillette, Program Director

Courtesy Leigh Gillette Some typical lichens found in Southwest Colorado include these three species of crustose lichen. Each is a different color: yellow-green, gray-green and black. There is also one species of moss (bright green, star-shaped).

Regardless of setting or season, you can find them: orange, gray and green blotches on tree trunks and historic buildings, whiskery green tufts of old man's beard" hanging from dead branches, boulders sporting strange leafy growths.

We're surrounded by lichens, and there's a story behind their success.

Once there was a fine carpenter named Freddy Fungus, and he could build a home using any material. But Freddy was helpless when it came to feeding himself, because he couldn't cook. Then along came chef Alice Algae, who could whip up fabulous food right out of thin air. But alas, Alice needed a home. When Freddy and Alice met they took an immediate lichen to each other. And although their marriage was sometimes on the rocks, they lived symbiotically ever after.

Freddy and Alice's tale is a classic way of describing the symbiotic partnership within lichens, unique "dual organisms" composed of fungus and algae.

Fungi are decomposers, feeding themselves by degrading plant or animal matter. The fungal world is incredibly diverse, from yeasts to molds to mushrooms. The fungus member of a lichen is usually a mushroom in the sac fungus family (ascomycetes).

Algae are single-celled organisms that make their own food through the sunlight-driven process called photosynthesis. In photosynthesis, algae capture solar energy, using it to combine carbon dioxide (from the atmosphere) and water into sugars. Common examples of algae are the green film inside a fish tank, "pond scum" and seaweeds. Algae require ample water and so are restricted to watery habitats.

In a lichen, fungus tissues form a tough, protective body laced with algae (or sometimes photosynthetic bacteria). The fungus receives food from the algae, and within the fungus, the algae receives protection from drying and damage. Lichens survive and thrive where fungus or algae alone cannot. Requiring only rainwater and air, they can occupy harsh habitats: bare rock, tree trunks, desert sands, concrete, even window glass! During droughts, lichens enter dormancy and dehydrate to 2 percent of their optimal moisture level. Once the rains return, lichens revitalize and resume their slow growth (1-2 millimeters/year).

Because of their self-sufficiency and toughness, lichens are easily observable everywhere on Earth. Worldwide there are 17,000 species of lichens. Colorado hosts roughly 600 species, and an amazing 350 species even survive in Antarctica!

But despite their toughness, lichens are fragile when exposed to pollution. Acid rain from fossil fuel combustion and smog destroys them. Accurate, economical air pollution studies are conducted by mapping the presence or absence of lichens in industrial areas. Lichen can also indicate other pollutants. When the Chernobyl disaster struck in 1986, Scandinavian reindeer (and humans that milked and ate them) began showing alarming accumulations of radioactive materials in their bodies. The cause? Lichens, a critical food source for reindeer, had absorbed radioactive fallout. This radioactive trace was one of the earliest indicators that there had been a nuclear accident.

We can all learn from lichen. Complex yet common, resilient yet delicate, they exemplify how partnership and perseverance add up to survival on planet Earth!