Logistical competition and risk in wheat trade and impacts of changes in Black Sea shipping

Abstract Geopolitical disruptions in the Black Sea have increased maritime shipping risks, constrained port capacity, and accelerated the development of alternative Russian grain-export routes through the Baltic and Caspian Seas. This study examines how these changes affect maritime logistics, port competition, and global wheat trade. We develop a monthly stochastic minimum-cost network-flow model using Optimized Monte Carlo Simulation (OMCS) that incorporates uncertainty in export prices, ocean freight rates, export supply, import demand, and port capacity. The results show that logistical constraints are strongly seasonal: Russian and Ukrainian port capacities become binding during peak export periods, diverting or deferring shipments. Expansion of Russian Baltic capacity reallocates exports away from traditional Black Sea and Sea of Azov routes and displaces shipments from competing exporters, particularly the United States. Relaxation of Russia’s export quota similarly increases Russian exports and alters their seasonal distribution. The results demonstrate that geopolitical disruptions and infrastructure diversification affect not only individual ports but also competitive trade flows throughout the maritime network. More broadly, the analysis shows how seasonality, uncertainty, and capacity constraints interact to determine maritime network resilience and route substitution.