Since its establishment in 1980, the Long Term Ecological Research Network has been a major force in the field of ecology, asking core questions about how ecosystems work; establishing seminal ecosystem manipulation experiments; maintaining long-term datasets to ground their inquiries; and models to test them. With a wealth of high quality data and interdisciplinary scientific teams, LTER sites attracted a corps of young researchers who absorbed the culture of collaborative research, sustainable data practices, and engagement with end users and interested publics. The LTER culture seeded far-reaching independent projects such as NutNet, DroughtNet, GLEON, and Data Nuggets. Long-nurtured efforts to synthesize data across sites and develop testable models of key ecosystem relationships bore fruit, resulting in bursts of progress on topics such as the general relationship between biodiversity and productivity, the nature of ecological connectivity, and approaches to predicting ecological vulnerability and resilience. LTER’s strength -- mechanistic understanding of ecosystem dynamics -- has a pivotal role in the field of ecology as the program moves into its 5th decade. Long term question-driven science provides a critically important bridge between individual short-term projects and observatory infrastructure such as NEON. Nowhere is this more clear than in the study of evolution in the wild. Consistent long term records and ecosystem manipulations provide controlled tests of how populations and communities change in response to drivers and combinations of drivers. Understanding potential responses and the conditions under which they can be expected is a powerful tool for choosing where to invest observation resources, where to focus attention, and how to respond in the era of big data ecology. The goal of this session is to feature several important research themes that have emerged across LTER sites during the first 40 years of the program: biodiversity and ecosystem function; landscape transport processes, controls on ecosystem resilience, and rapid ecological evolution. The four speakers have been selected for their diverse expertise and deep involvement with site-based and cross-site LTER research.