Ecological connectivity in a protected area network under deep-sea mining

The Clarion Clipperton Zone (CCZ) is the focal region for imminent deep-sea nodule mining1, yet fundamental questions remain about ecosystem resilience2. To protect the marine environment in the CCZ, the International Seabed Authority (ISA) designated Areas of Particular Environmental Interest (APEIs)2,4. Connectivity was not a formal criterion in the original APEI design5,6, but has since gained prominence in ISA policy7. Use larval dispersal modelling and network analysis, we assess the connectivity of the APEI design. APEIs show internal cohesion and provide some larval input to areas of mining interest (AMIs), especially after 2021 additions4. However, the ‘network’ of APEIs is not functioning: APEIs are largely disconnected: fewer than 0.02% of simulated larvae disperse between protected areas, and most are functioning as isolated units. This weak connectivity limits the network’s effectiveness in a biologically variable region and undermines its capacity to sustain populations or support recovery following mining disturbance2. Most larval replenishment to AMIs originates outside both APEIs and AMIs, revealing opportunities to enhance APEI support for ecosystem resilience. Strategic expansion, totalling a 47% increase in protected area, could lead to full APEI connectivity, increasing inter-APEI connectivity 406-fold and nearly doubling larval input to AMIs8,9, strengthening conservation outcomes prior to mining.