On scale and complexity in model design for marine reserve planning with Great Barrier Reef Marine Park and Philippines case studies

Implementing marine reserves that restrict harmful activities requires careful planning across multiple scales and analytical complexities to be effective. However, many processes, such as larval dispersal, and concepts, like trophic interactions, are encapsulated in models that influence reserve planning but are applicable only at limited scales and specific levels of complexity. A critical question arises: which design approach for model development should be chosen for the specific problem at hand? The design principles that define the boundaries of an individual reserve may not necessarily apply at regional scales. We believe that as the planning scale shifts from regional to local, the focus of design decisions transitions from strategy to tactics and then to detailed considerations. Similarly, designing a reserve for a local reef involves a lower level of analytical complexity than creating an interconnected regional reserve system. Process models, such as direct, thematic, vertical, horizontal, hierarchical, temporal, adaptive, and behavioral, inform the decision-making process at progressively higher levels of complexity. As the scale increases and the associated risk of failure grows, the analytical methods employed must incorporate more complex models. In this context, we present a conceptual framework for marine ecological modelers that acknowledges the roles of scale and complexity within the conservation planning process. The Great Barrier Reef Marine Park and the contrasting Philippines reserve network highlights the impact of scale and complexity on planning success.