Ecological Dynamics on Yellowstonea (TM)s Northern Range discusses the complex management challenges in Yellowstone National Park. Controversy over the National Park Servicea (TM)s approach of natural regulation has heightened in recent years because of changes in vegetation and other ecosystem components in Yellowstone's northern range. Natural regulation minimizes human impacts, including management intervention by the National Park Service, on the park ecosystem. Many have attributed these changes to increased size of elk and other ungulate herds. This report examines the evidence that increased ungulate populations are responsible for the changes in vegetation and that the changes represent a major and serious change in the Yellowstone ecosystem. According to the authors, any human intervention to protect species such as the aspen and those that depend on them should be prudently localized rather than ecosystem-wide. An ecosystem--wide approach, such as reducing ungulate populations, could be more disruptive. The report concludes that although dramatic ecological change does not appear to be imminent, approaches to dealing with potential human--caused changes in the ecosystem, including those related to climate change, should be considered now. The need for research and public education is also compelling.