MPA networks as learning systems: governance interactions and shared challenges in Southeast Brazil

Marine Protected Area (MPA) networks are increasingly recognized as essential for conservation at scale, yet the gap between formal designation and operational reality remains a persistent governance challenge. This study examines MIAMP (São Paulo State MPA Network) in Southeast Brazil to understand how institutional and territorial challenges shape network governance, and what informal integration emerging in the formal network’s absence reveals about MPA governance more broadly. Through participatory workshops, questionnaires, and Social Network Analysis (SNA) with managers across 26 MPAs spanning the São Paulo coastline, we mapped institutional problems, territorial pressures, and informal governance connections structuring the network. Findings reveal that MIAMP, despite existing in legislation since 2008, has never been operationalized, functioning instead as a “paper network” whose primary barrier is not design but chronic institutional underfunding and understaffing at the unit level. Yet in the formal network’s absence, an informal learning network has self-organized: managers connect through shared management demands, territorial proximity, and the practical necessity of addressing problems individual units cannot solve alone. SNA identifies two regional clusters — South/Central and North — connected primarily through the Marine Environmental Protection Areas, which function as structural hubs of this emergent governance system, performing coordination functions the formal MIAMP has not. Seventeen management themes led by Tourism, Public Use, Climate Change, and Environmental Licensing are shared network-wide, constituting the empirical foundation for integration. The informal network’s operational geography extends significantly beyond the 2008 decree, incorporating MPAs established after its baseline, leading us to propose an evidence-based redesign expanding the network from 15 to 29 units. This redesign formalizes what already exists informally rather than imposing new top-down structures. These findings contribute to the international MPA governance literature by demonstrating that informal integration can constitute a functional governance mode, not merely a transitional phase, and that effective network design should be grounded in demonstrated relationships rather than administrative boundaries. As the global community pursues the 30x30 target, MIAMP offers an empirically grounded argument that designation without institutional support produces paper networks, while informal connectivity, properly recognized and resourced, can bridge conservation ambition and governance reality.