1. Eating poisonous lichen (Parmelia molliuscula) kills humans and other animals.
2. It grows and damages walls and buildings.
3. They damage marble stone buildings and monuments.
4. Lichens called Usnea and Evernia cause skin diseases, allergies, asthma etc. in humans.
5. Damages the durability and beauty of windows and doors and wood.
6. Damages host plants like Cladonia, Amphiloma, Usnea etc.
7. Usnea lichens help spread wildfires from one tree to another.
8. Letharia vulpina lichen contains toxic substances and is used to kill wolves.