US Tariffs and Trade Tensions Threaten Great Lakes Shipping and Canada-US Supply Chains US tariffs and a growing political rift between Washington and Ottawa are threatening the deeply integrated $6 trillion regional economy of the Great Lakes and the St. Lawrence Seaway. Cargo traffic at key ports like Duluth-Superior has seen sharp declines—plunging 23% through August compared to the previous year—as reduced coal volumes and tariffs on steel and iron ore strain binational trade and disrupt traditional supply chains. While politicians and trade officials signal potential willingness to negotiate, industry stakeholders warn that prolonged friction risks permanent damage to maritime commerce. US shipping groups point to regulatory disparities and fleet competition, whereas Canadian operators highlight structural shortages in shipyard capacity, leaving local businesses caught in the middle of broader geopolitical trade disputes.