Almost all ecological research stems from some aspect of ecological theory. An underlying theoretical construct guides research on what to observe or measure, on experimental approaches, and on interpretation of results; in short, theory drives innovation in both basic and applied ecology. Theory, both mathematical and conceptual, has complemented observation to advance ecological understanding for decades, but as global change and unprecedented events increase in frequency and intensity, new approaches are needed to reinvigorate ecological theory to guide future research. “A Change is Gonna Come”; we cannot take each new problem in isolation. If we are forced to reinvent the wheel each time a new problem arises, it will not be possible to address everything that requires our attention. For this reason, we need theory that can flexibly address the multiple challenges arising in an ever-changing world. Such challenges, posed by complex, adaptive systems and by rapidly increasing data streams, argue for new coordination and integration across families of ecological theories and perspectives. We need guidance from a predictive science that focuses on the real world and identifies key commonalities across systems despite the many complexities that exist and will arise. New theory is therefore needed to extract deeper understanding, develop models, formulate testable hypotheses, identify general principles, and test intuition from a burgeoning flow of empirical data. Our symposium focuses on four key topics/themes, each with broad implications for multiple ecological systems. Specifically, we address how theory should most usefully be integrated across organizational levels, the shifting and interacting role of internal and external forces in ecological systems, the role of transient dynamics and non-stationarity in a changing world, and the challenges and opportunities posed by uncertainty in the age of Big Data.