We are not Reindeer. I want to point this out before I go into lichen as food.
For several years, I have been told that lichen that grows on bark and rocks can be eaten. It took a survival stew made by a friend of mine for me to believe it. You do have to be careful what surface you scrape it from since it will grow on poisonous trees as well as edible ones. You can even drop in the rocks with lichen growing on it into water to make a lichen tea. Remember to not try to eat or drink the rocks.
I DO NOT recommend eating lichen except for in emergency survival situations. It is not good for humans to eat more than once in a while, and it takes a long time for it to grow back. It also tastes foul if you do not combine it with another food.
Finding food index