Lichens are widely recognized for their relative sensitivity to air pollution compared to plants.  As a corollary, lichen-based critical loads of atmospheric deposition have been touted as protective of the broader terrestrial flora.  Lichens are less well known for their ecological roles.  But, in fact, the roles they play are broadly exemplary of the many ecosystem functions and services provided by other forest and rangeland vegetation. Thus, lichen responses to air pollution can be used to illustrate the risks, from a land manager’s perspective, of exceeding terrestrial critical loads of atmospheric deposition. Here, we use lichen species known or likely to occur in Superior National Forest in a case study to show how species level air pollution responses can be used to assess risks from deposition on biological diversity, extirpation of rare species, and the ecological functions and services provided by those species.