Name one way humans use lichens?

Humans use lichens as a source of food, primarily in certain regions of the world. Some species of lichens, such as the species of _Parmelia_ and _Cladonia_, are traditionally consumed in various cultures, particularly in Scandinavia and parts of Asia. Their use as food is often driven by necessity during periods of food scarcity or in remote areas with limited access to other food sources. Lichens typically require specialized processing methods to reduce potential toxic substances and improve their palatability.