Much progress has been made in setting standards for classification and mapping of U.S. (and Canadian) vegetation as led by ESA’s Vegetation Classification Panel. Over 6,000 different types of vegetation are being proposed in the United States, an important milestone for conservation of habitats, threatened species and biological diversity. This symposium brings together scholars who confront a wide range of data showing change in vegetation. The session begins by looking at the central theory and models of vegetation change at a large scale. These may be driven by natural processes, change in climate, and new human strategies for carbon retention. The session continues by considering change brought about by intensive forest fire at a large scale in Canada. Several papers will examine regional case studies of change to elucidate the mechanisms (and their interactions) leading to natural change in classification. Permanent change is evident in the cases of dominance by invasive species (such as novel shrubs and wetland graminoids) facilitated by nearby logging or cultivation. These examples need to be viewed from the perspective of our knowledge of how the autecology of functional traits facilitates spread or resists invasion, and is in turn influenced by change in the frequency of intense drought, fire, or winter cold.