No. Species in the genera Letharia and Vulpicida are some of the more common poisonous macrolichens. Many other lichens are important food sources for a variety of organisms, including humans.
To quote "Lichens of North America", 'few lichens are poisonous' (but include the ones mentioned by Geastrum). Fewer, though, I think are considered delicacies, so survival food at best for all but a few. If you've ever sampled the lichen that tastes like powdered aspirin, you'll seek out edible green plants instead.
Thank you for the responses. Powdered aspirin, definitely not gourmet cooking. JA Cambece JA Cambece Law Office