Long-term processes of global change are altering biogeochemical cycles, climate, and land use, and thus the composition, structure, and function of the world's ecosystems. Ecosystem studies have aimed to understand the processes that mediate the flow of energy and materials through ecosystems to better understand patterns and processes that may be important in the future. Observational and experimental approaches are useful for studying ecosystem processes on relatively short time-scales (i.e., years to decades). But ecosystem processes that operate over hundreds to millions of years are difficult to document, although they are likely essential for understanding future ecosystem changes. Ecologists have traditionally studied these long-term ecosystem variations using the chronosequence approach, which adopts a “space-for-time” substitution. Additionally, over the past decade innovative paleoecological techniques have been applied to lake sediment (lacustrine) records to enable information about these slow ecosystem processes to be directly, albeit retrospectively, studied through time. We aim to synthesize information derived from the complimentary, yet unique, chronosequence and paleoecological approaches that form the emerging field of paleoecosystem ecology. The purpose of this symposium is to highlight recent and exciting examples of how paleoecosysem ecology studies have informed theories of ecosystem change over time and to address the challenges that lie ahead. For example, do lacustrine records support a “space-for-time” assumption? How can paleoecosystem studies best inform conservation and management decisions during periods of rapid climate change? How do nutrient cycling and the fate of primary productivity change during ecosystem development? The topics addressed by speakers will include comparisons of chronosequence studies and sediment records, evaluations of the role of vegetation and climate in influencing terrestrial nutrient cycles, and investigations that utilize geochemical techniques to advance our understanding of tempo and time in ecosystem ecology. This synthesis will help pave the way for discussion and collaboration among ecosystem ecologists, paleoecologists, biogeochemists, pedologists, and global-change scientists.