Sustainable Marine Structures

Designing Sustainable Marine Protected Area Networks: A Graph-Based Optimization Approach for Mediterranean Conservation

Khaled Mili

Department of Quantitative Methods, College of Business Administration, King Faisal University, Al-Ahsa 31982, Saudi Arabia

Majdi Argoubi

Department of Quantitative Methods, University of Sousse, Rue Khalifa Karoui, Sahloul, Sousse BP 526, Tunisia

DOI: https://doi.org/10.36956/sms.v8i2.3143

Received: 12 February 2026 | Revised: 12 March 2026 | Accepted: 17 March 2026 | Published Online: 7 April 2026

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Abstract

Marine Protected Area (MPA) networks face a persistent challenge: protecting biodiversity while maintaining ecological connectivity and minimizing economic costs. Traditional planning methods optimize single objectives or face computational barriers when scaling thousands of potential sites. We developed a computational framework combining graph-based site embeddings with constraint-driven optimization to identify cost-effective MPA networks at the basin scale. We analyzed 10,741 candidate sites across the Mediterranean Sea (30 km resolution) using 84,721 species observations, bathymetric data, and spatially explicit opportunity costs. The optimized 15% coverage network (1,611 sites, 1.45 million km²) protects 99.2% of 120 target species including all threatened Mediterranean resident taxa, achieves network connectivity 4.4 times higher than random selection, and reduces costs 42% below random approaches (€1.69 billion versus €2.94 billion). The framework enforces ecological constraints—threatened species protection, shallow habitat representation, and regional balance—while completing each optimization scenario in 8–15 min. Network connectivity scales super linearly with coverage (power law exponent 1.17), indicating that well-connected networks deliver disproportionate conservation value. Results remain robust across 10–30% coverage targets, with consistent species representation and spatial patterns. The modular framework transfers to other marine regions through the substitution of region-specific data and enables rapid scenario testing for stakeholder negotiation. Systematic optimization identifies MPA configurations delivering superior conservation outcomes at substantially lower cost than alternative strategies, supporting evidence-based pathways toward international marine protection targets.

Keywords: Marine Protected Areas; Conservation Planning; Network Optimization; Biodiversity Conservation; Mediterranean Sea; Cost-Effectiveness; Ecological Connectivity

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