Long-term research should play a crucial role in addressing grand challenges in environmental stewardship. We examine the efforts of five Long Term Ecological Research Network sites to enhance policy, management, and conservation decisions for forest ecosystems. In these case studies, we explore the approaches used to inform policy on atmospheric deposition, public land management, land conservation, and urban forestry, including decisionmaker engagement and integration of local knowledge, application of models to analyze the potential consequences of policy and management decisions, and adaptive management to generate new knowledge and incorporate it into decisionmaking. Efforts to enhance the role of long-term research in informing major environmental challenges would benefit from the development of metrics to evaluate impact; stronger partnerships among research sites, professional societies, decisionmakers, and journalists; and greater investment in efforts to develop, test, and expand practice-based experiments at the interface of science and society.