Exploring the potential of theory-based evaluation to strengthen marine spatial planning practice

Marine spatial planning (MSP) is an approach to ocean management with an increasingly global reach. However, existing evaluation strategies have yet to ascertain the extent to which MSP achieves social, ecological, and economic goals to benefit coastal environments and human communities. Here, we experiment with a theory-based approach as a means of overcoming long-standing obstacles to MSP evaluation. We developed and applied an eight-step evaluation protocol to five diverse cases of MSP, focusing on the evaluative feasibility of the protocol as we moved from identifying objectives to assessing the sustainability of outcomes. We found evidence that theory-based evaluation (operationalized via theories of change) can bridge quantitative outcome and qualitative process evaluations, two essential approaches that on their own produce incomplete pictures of MSP. Our work suggests that a theory-based approach can enhance opportunities to incorporate diverse knowledge sources and data types into outcome evaluations and thus better capture complex social, political, and historical dimensions that are difficult to quantify but critical to MSP success. We also uncovered likely challenges to implementing theory-based evaluation for MSP, including the apparent data- and time-intensive nature of the approach. We found that applying theory-based evaluation is difficult for plans lacking well-defined goals, objectives, and intended outcomes and that increased documentation of planning motivations and the planning process are needed to rigorously evaluate MSP. Ultimately, we join others in the marine conservation and management fields who are optimistic about theory-based evaluation. Our evaluation protocol provides a first step towards a practical guide to accelerate the use of this assessment approach. •Marine spatial planning (MSP) is expanding despite unknowns about its effectiveness.•Common evaluation approaches are less suited to the complexity and diversity of MSP.•The adaptation of theory-based evaluation to MSP shows promise and feasibility.•Theory-based evaluation can holistically integrate process and outcome evaluations.•Theory-based evaluation can provide insight into MSP attribution.