Thu October 15, 2009
Earth Notes - Lichens
Flagstaff, AZ – Earthnotes: Lichens
In the woods and around town, crusty growths cling to bare rocks, hang from tree branches, and hug the ground. Painted in shades of dusty green, sulfur yellow, and pumpkin orange, these subtle organisms are lichens, hardy colonizers of some of the harshest environments on Earth.
The ultimate survivors, lichens can grow where it's dry, wet, windy, hot, or frigid. On the Colorado Plateau they survive in the driest deserts, in pine forests, and on the alpine tundra of our highest peaks. Beard lichens drape from ponderosa pine branches, while others such as Parmelia, Cladonia, and Collema [KO-LEE-MA] have no common names.
Lichens are a convenient marriage between fungus, algae, and cyanobacteria. The fungus provides the form, while the algae furnishes the food. As one lichenologist puts it, "Lichens are fungi that have discovered agriculture."
Birds and mammals line their nests with strands of lichen, insects hide among them, and some animals eat them. Lichens contribute valuable nitrogen to soil, and some can prevent soil erosion. An amazing array of biochemicals makes lichens useful to people too. Navajos make a dye from the ground-growing "vagrant" lichen. Other people have used them to make poison arrow points, bake nutritious breads, and formulate antibiotic salves.
Lichens grow slowly some less than half an inch in a thousand years. Knowing their growth rates, scientists can date glaciers and rockslides. Durable but sensitive, lichens are also indicators of air pollution they need clean air. The next time you see one, you might think about saluting it for its endurance.