Identifying Leading Indicators of Regime Shifts in Marine Ecosystems: Uniting Biological Intuition and Complex Systems Theory

Scientists and managers require reliable and informative leading indicators of ecosystem regime shifts. We hypothesize the strongest approach to developing leading indicators of regime shifts will integrate our best biological intuition about which ecosystem components should make good indicators with the general early warning indicators (EWI) derived from complex systems theory. Using rich datasets from well-studied ecosystems known to have undergone large shifts in the past, we are testing whether there are any indicators that reliably predict abrupt change and ecosystem shifts. If we can’t identify reliable indicators in these information-rich ecosystems, there is little chance we will find good leading indicators in other less-studied systems. In this study, we are 1) developing hypotheses of putative leading indicators through expert knowledge of study ecosystems and literature review of general ecological theory, 2) using statistical techniques to quantify threshold responses in indicator time series or spatial data to identify the most promising leading indicators, and 3) applying a suite of general EWI metric-based methods to the set of promising leading indicators. Here we present our findings for the California Current ecosystem in regard to the climate and human-induced regime shifts that have occurred in this system over the past few decades.