There are many ways to exist on this planet. Humans, for one, like to live in social groups. While we may love to be alone from time to time, for the most part we enjoy being around these groups, be it friends or family, classmates or coworkers. In the realm of plants and fungi there are more social species too, and a great example of a forest friendship is that of lichens.
Pronounced “like-ens”, these strange growths that appear on trees, rocks, and other surfaces are actually fungi and algae or cyanobacteria living together. It’s a symbiotic relationship, one in which both the fungal and the photosynthetic receive benefits from sticking together. The fungus obtains nutrients from the photosynthesizing algae, which make their own food, and in return the algae receive protection in their environment with the help of the fungal filaments, and the geographic range of both species is extended. Some species of lichen fungi can even fix nitrogen, making it easier for algae to uptake that vital nutrient.
But things aren’t always friendly. The presence of a fungus, a natural decomposer, means that the algae will lose some photobiont cells where their food is made as they are penetrated by the structures of their fungal frenemy. Luckily, these cells are continuously produced, so it’s a small price to pay. Lichens are so successful that they can be found almost everywhere on the planet, from the tundra to the tropics, taking on many different forms along the way. When push comes to shove, it helps to work together.
Since lichens can be found in almost every biome on Earth, it’s not hard to find them in your own backyard. Looking on tree trunks and on rocks is a great place to start. The diversity of forms allows lichens to adapt to all sorts of living conditions. They’re also indicators of good air quality, so if you see some be sure to take a deep breath while you take a liking to the lichens!