A Multiperiod, Multicommodity, Capacitated International Agricultural Trade Network Equilibrium Model with Applications to Ukraine in Wartime.

This article focuses on the development and application of a multiperiod, multicommodity, international agricultural trade network equilibrium model with capacity constraints on production, transportation, and storage of agricultural commodities. The model incorporates multiple routes, transport modes, and storage options across producing, consuming, and intermediate countries, allowing for nonlinear and asymmetric cost and price functions and competition among commodities for limited resources. Using variational inequality theory, the paper establishes equilibrium conditions, proves existence and uniqueness results under monotonicity assumptions, and presents an algorithmic solution method. Numerical examples inspired by disruptions caused by Russia's full-scale invasion of Ukraine illustrate the model's ability to quantify impacts on commodity flows, prices, and food security, highlighting the critical role of Black Sea ports, alternative transport routes, and storage capacities in Ukraine's grain exports to Middle East and North Africa countries such as Lebanon and Egypt. The study underscores the consequences of war and related disruptions on global food security and farmers' earnings, offering insights relevant to policymakers and stakeholders in affected regions.