There are over 20,000 lichen species on Earth and lichens collectively make up a whopping 8% of the Earth’s biomass. You would think lichens would have a larger presence in our collective awareness, but they don’t. If they are everywhere, why don’t we know them?
First, they aren’t always easy to see. Then, when we do see them, they can look like mold, algae or even dried paint. Once you start looking for lichens, you will see what a curious, rich world they inhabit even as they remain in the same space indefinitely.
Some species of lichen look like spray paint on a tree.
In the case of lichens, opportunity and evolution make for strange bedfellows. Lichens are the curious living arrangement between algae and fungi. It’s all a matter of “room and board.”
The fungi create the room (structure) and the algae provide the food (sugar). The result is a mutually symbiotic relationship in which the fungi derive energy through sugar manufactured by the algae. The algae are sheltered from the elements and live near the lichen's surface to have access to light for photosynthesis.
A lichen shares the landscape boulders near the Marion Andrus Learning Center at the Arboretum.
Lichens thrive in a wide variety of harsh conditions and are “extremophiles,” a word comprised of the Greek for “extreme” and “love.” The map lichen (above) and the elegant sunburst lichen (below) were two species sent into orbit for 14 days on the outside of a space vehicle. After an incredible journey, the lichens remained viable upon their return to Earth.
The elegant sunburst lichen variety is out of this world.
Lichens only need sun and water to grow. Some lichens survive on atmospheric water provided by morning dew or heavy fog. When moisture evaporates from the lichens, they stop growing for the day! Some lichens only grow in the winter, when the leaves fall off the trees and expose the lichen to sunlight while rain or snow provide moisture. Unlike moss, lichens grow on any side of a tree. Lichens frequently grow along or throughout a moss clump, because moss holds moisture for lichens.
Lichens and moss hang out together.
Lichens are considered to be their own ecosystem. The slow-growing organisms play the “long game” of survival and if conditions are not right, they will stop growing and wait. Lichens can survive almost everywhere. Lichens grow from the edge of the North and South Poles to the highest mountains and hottest deserts. Gray reindeer moss, actually a lichen, is a food source for grazing reindeer and is used as an additive for bread in some Scandinavian cultures, it is found on the tundra, in boreal forests and in central to northern Minnesota.
Gray reindeer moss is a lichen in the Cladonia genus.
Minnesota has upwards of 750 different lichen species and over 20,000 lichen species worldwide. There are many areas of the Arboretum where visitors can discover lichens if they look closely. The Arboretum’s Lake Tamarack — located just west of the Arboretum’s main entrance on Highway 5 — and Spring Peeper Meadow — located off of 82nd Street — also host many species of lichen.
Whereas fungi and mushrooms destroy the structure that they grow on, such as rotting wood, soil or leaves, lichens (lichenized fungus) live on the surface of many substrates. Many lichens are more complex with additional fungi, cyanobacteria or yeasts making up the lichen. Lichens grow on undisturbed surfaces of trees, rocks, soil, metal and even plastic as long as the lichen has access to sunlight and moisture.
This nitrogen-tolerant lichen colony is on a tree at Arboretum’s Lake Tamarack.
Lichen scouting is a hobby much like birdwatching, lichens are both local and well-traveled! Lichens are monitors of good air quality, and that’s why there are so many more lichen varieties “up north” where the air is cleaner.
Many lichens growing in central and southern Minnesota are nitrogen tolerant. Because lichens have no cover or protective coating, they are directly exposed to heavy metals. The types of lichens that can grow in these areas are limited. In fact, lichens are used to measure air quality associated with high traffic volume, industrialized exhaust, agriculture or ranching.
If you want to learn more about lichens here are two upcoming opportunities. No previous knowledge about lichens is necessary!
On Nov. 2, bio-engineer Tanner Barnharst and I will be presenting a class in basic lichen identification and lichen scouting at the Arboretum. Registration is required, but there is no limit to the fun!
Tanner and I will also present a class through the University of Minnesota Extension Master Naturalist program on Oct. 25. Participants do not have to be a Minnesota Master Naturalist to attend the class. It’s an entire day of lichen learning with lunch included with the required registration.
Lichens are a hobby and interest open to everyone. Won’t you become a Minnesota lichen scout?
Zan Tomko is an artist, horticulturist, Minnesota Master Naturalist and a co-founder of the iNaturalist Minnesota Lichen Map Project. More information about the Minnesota Master Naturalist program is available on their website.