Scenario-dependent functional connectivity in a crowded seascape: habitat suitability, shipping pressure and marine infrastructure in the North Sea

Catia Matos

Marine spatial planning increasingly needs seascape connectivity evidence to balance biodiversity conservation, offshore energy development and shipping. However, predicted functional connectivity depends strongly on how habitat suitability and human-use pressures are translated into resistance surfaces. This study tested how shipping and marine infrastructure alter HSM-derived connectivity metrics for four North Sea species: Atlantic cod, European plaice, harbour porpoise and grey seal. Species-specific habitat suitability models were developed using broad oceanographic predictors and local habitat/productivity predictors. Core habitat was then overlapped with shipping density, offshore wind infrastructure and oil/gas infrastructure. Functional connectivity was compared between habitat-only and infrastructure-weighted resistance scenarios using Circuitscape. Movement-threshold analyses tested whether connectivity conclusions were robust to literature-informed species movement limits. Cumulative current, core habitat and pressure layers were then combined into connectivity-pressure priority categories. Habitat suitability was structured by species-specific environmental drivers. Combined environmental models performed best for Atlantic cod, harbour porpoise and grey seal, while local habitat/productivity predictors performed best for European plaice. Core habitats were substantially exposed to human use: 31.2–65.8% occurred in high-shipping areas, 62.0–81.8% occurred within 25 km of offshore wind infrastructure, and 58.9–76.0% occurred within 25 km of oil/gas infrastructure. The infrastructure-weighted scenario produced lower median effective resistance and higher conductance across all species, with resistance decreases of 9.4–18.2% and conductance increases of 10.3–22.2%. Movement-threshold analyses showed that demersal fish had stronger changes in resistance magnitude, while harbour porpoise showed greater sensitivity in the identity of strongest links. High-connectivity/high-pressure areas were spatially restricted. These results show that suitable habitat in the North Sea is embedded within shipping and infrastructure pressure, and that including these pressure metrics can change predicted connectivity outcomes. Scenario-based connectivity modelling can support marine spatial planning by making resistance assumptions transparent and identifying where empirical validation is needed.