Lichen
Lichen are a fascinating group of organisms with time-tested survival adaptations that have let them exist on Earth for over 400 million years! With a wide range of species and adaptability to a variety of conditions, lichen can be found almost everywhere in nature……so I hope you like ‘em!
Lichen…what is it?
Lichen are epiphytic (they grow on other plants, supported by them, but not depending on them for food) and grow on trees, rocks and other surfaces all around us, whether they are in the woods or in our own backyards! They vary in size and can be seen as small specks on a leaf or twig, or as bright patterns sprawling across shingled roofs or boulders. Although they look like plants, they are actually composite organisms, meaning they are a combination of different organisms that grow together, forming a whole new organism. They form a ‘mutualistic, symbiotic relationship’; in other words, they each provide a benefit to the other. Lichen are composed of a fungus and a green alga, cyanobacteria, or both. The fungus supplies important nutrients, while the alga can photosynthesize, providing food and other nutrients to the composite organism. An impressive ability of cyanobacteria is to create oxygen as a by-product, even when it is in an oxygen-free environment. For this reason, lichen are one of the first organisms to grow in new ecosystems or after devastating ecological events as they do not require an existing oxygen-rich environment in which to grow, and actually create oxygen in which other organisms can live. They are one of the oldest organisms on Earth. Lichen are incredibly diverse, with up to 17 000 species worldwide and they come in almost every imaginable colour and shape.
Lichen are categorized according to their general structure, such as crustose (tightly attached to the substrate), fructicose (branchlets), foliose (leaf-like), leprose (powdery), gelatinous, filamentous, or byssoid (wispy). Lichen often appear green because of the photosynthetic chlorophyll they contain, though many lichen genera also contain usnic acid, a yellow pigmented acid that gives them a variety of yellow, orange, or red hues. These colours are enhanced after a rain.
Lichen: lungwort (Lobaria pulmonaria)
Ecology
One type of lichen found in Nova Scotia is lungwort. It is composed of a fungus, cyanobacteria, and a green alga, which gives it a vibrant shade of green when it is sufficiently hydrated. As with any lichen, lungwort can survive long periods of drought, and can even be stored indoors and still be rehydrated, years later, if placed in the sun. Lungwort is important as a nitrogen-fixer, and is therefore a vital source of nitrogen for other plants in the ecosystem. It is significant as a source of nutrients for smaller critters, like insects, and large animals, like deer and moose. Lungwort also provides nesting material for squirrels, birds, and other forest creatures. It thrives in rainy conditions with shaded areas to protect it, making it suitable for our Nova Scotia climate.
Origin of the Name
The common name for this species of lichen, ‘lungwort’, is also commonly used for a genus of flowering plant. Be careful not to confuse them; they are unrelated. The scientific name for lungwort is Pulmonaria, which comes from the Latin word for lung. This was given to the lichen species because the shape of its wavy, lettuce leaf-like outer edge looks a bit like the tissue of its namesake, lungs. Lungwort was also once considered by some to have medicinal properties to treat illnesses of the lungs, and though this has not been scientifically proven in modern times, the name stuck!
Lungwort and the Environment
Lungwort is very sensitive to air pollution and does not grow well in areas with high levels of contaminants in the air. If you see lungwort growing, it is a good sign that the area is healthy! It is common in many old growth forests. Unfortunately, this also means it is easily affected by changes in the environment, and, as more land is developed for human use, lungwort populations are decreasing in many parts of the world. In some regions, it is now considered a threatened species. Fortunately for lungwort, and for humans, reductions in acid rain after the 1980s assisted a rebound in its populations in many regions, including forests in Nova Scotia. With continued conservation efforts, this useful organism will remain a familiar sight in our province and beyond.
Human Use
Many blue or green lichens are edible and high in vitamins and minerals. They can be eaten fresh off the rocks or bark, or boiled. Orange and black lichen is generally not edible. Check with an adult before eating any of them!
Biomimicry
Many lichens have the amazing ability to dry out almost completely without dying. Researchers have mimicked this ability to create a dehydrated vaccine to make storage much more sustainable. After manufacturing, vaccines must often be stored for weeks or months during transport, or until they are needed. The ability of many lichen species to survive in prolonged dehydrated states has helped inform research and development in this area, leading to significant advances in vaccine availability and safety around the world.
Resources
Now it’s your turn! Try identifying different types of lichen on your next nature walk in Nova Scotia. Here is a useful resource to bring along: https://www.novascotia.ca/nse/protectedareas/docs/identifying.nova.scotia.lichens.pdf
Jokes
Why did the algae and the fungus get together?
Because they took a lichen to each other!
Why did the portobello go to the party?
Because he was a fun guy!
Why did he leave early?
Because there wasn’t mushroom!
-Sarah Silver Slayer
