Managing estuaries for ecosystem function

Estuary management is limited by lack of consensus on operational tools for handling multiple conflicting management objectives. One critical step to this goal is a shift from individual problems to a focus on maintaining ecosystem functions that benefit humans. If function is maintained, then the ecosystem is said to be functionally equivalent to its unimpacted state, which is sufficient for management. We propose an adaptation of a functional equivalency (FE) assessment approach from marine fishery management and use a case study demonstration to address how this approach can be integrated into existing ecosystem assessment tools. The functional equivalency framework has three components for implementation: definition of target ecosystem functions, measurable metrics of ecosystem functions, and policy-based thresholds for each metric that indicate when functional equivalency is lost and must be restored. Each case study is an application of available data, models, and management policy to define these ecosystem function components. We intend to foster discussion and future work on integrating the FE approach into existing ecosystem assessment tools. Data requirements are high, as is the necessary integration between science and policy. The results can be a more integrated management approach focused on maintenance of ecosystem functions most beneficial to humans. (C) 2019 Published by Elsevier B.V.