Lichens: Reading to Learn About Nature's Partners

Lichens: Two Living Things in One

1Have you ever seen a crusty orange or gray-green patch on a rock or a tree trunk? It might look like old paint or a dry stain, but it is alive. It is a lichen (say LY-ken). Lichens grow in forests, in deserts, on mountains and even in icy places near the poles.

2A lichen is not just one living thing. It is two living things working together as a team. One partner is a fungus, a relative of mushrooms. The other partner is usually an alga, a tiny green living thing that can make food from sunlight. The alga lives inside the body of the fungus.

3Each partner helps the other. The fungus builds a tough body that holds onto rock or bark. This body soaks up water from rain and fog, so the alga inside stays damp and safe. In return, the alga uses sunlight to make food. It shares that food with the fungus, which cannot make food on its own.

4Lichens come in three main shapes. Some are flat and crusty, like a coat of paint stuck tight to a stone. Some are leafy, with wavy edges you can lift with a fingernail. Others are bushy and look like tiny branching shrubs or hanging beards.

5Lichens grow very slowly. Many grow only a little each year, so a large patch on a boulder may be very old. As they grow, lichens make weak acids that slowly break rock into tiny bits. Over a very long time, these bits help make soil where plants can grow.

6Animals use lichens too. In the far north, caribou dig through snow to eat a bushy lichen often called reindeer moss, even though it is not a moss at all. Some birds tuck bits of lichen into their nests. Lichens even help people. Many kinds cannot grow where the air is dirty, so scientists study lichens to learn how clean the air is in a place.