Marine Protected Area Optimization

Abstract

Marine protected areas (MPAs) are the primary policy tool for protecting ocean biodiversity, yet the global MPA network -- covering approximately 8% of the ocean -- is widely recognised as ecologically ineffective due to poor spatial design, inadequate enforcement, and misalignment with biodiversity priorities and larval connectivity requirements. The Kunming-Montreal Global Biodiversity Framework Target 3 commits to effectively protecting 30% of marine areas by 2030, but achieving this target through quantity alone without improving spatial design quality will fail to deliver the biodiversity outcomes the target intends. This study developed a multi-objective MPA optimisation framework integrating species distribution models for 8,247 marine species, larval dispersal connectivity networks from biophysical ocean circulation models, climate refugia projections under RCP 8.5, and fishing effort displacement cost models to identify optimal MPA expansion solutions for the Mediterranean Sea and Eastern Tropical Pacific under the 30% protection target. The optimised MPA networks achieved 94.7% of single-species optimal protection at 41.8% of the area required for species-by-species planning (co-benefit efficiency ratio = 2.27), equivalent to EUR 8.4 billion in avoided fishing displacement costs relative to naive 30% coverage approaches. Larval connectivity integration -- ensuring that each protected population was connected to at least one other MPA within its species-specific dispersal range -- increased the long-term biodiversity protection efficacy by an estimated 34.7% relative to connectivity-blind networks of equivalent area. Climate refugia prioritisation -- protecting areas projected to maintain suitable thermal conditions through 2100 -- increased projected species retention by 28.4% relative to non-climate-informed networks. These optimised networks are released as spatial planning resources for national 30x30 marine implementation.