As President-elect Donald Trump vows to impose tariffs on imports from China, Mexico and Canada, economists are warning that a retaliatory trade war could cause major financial damage for California’s agriculture industry. In an analysis published before the presidential election, researchers examined potential scenarios of tariffs and retaliatory measures, and estimated that if a significant trade war occurs, California could see the value of its agricultural exports reduced by up to one-fourth, bringing as much as $6 billion in losses annually. … “We have climate uncertainty already. We have water policy uncertainty,” [Sandro] Steinbach said. “And if you add now an additional layer of trade and tariff policy on top of it, why would I want to invest a large amount of money into producing agricultural commodities?” … Agriculture uses much of the water that is diverted and pumped in California. But Steinbach said the potential effects on farms’ water use, both regionally and statewide, are uncertain and will depend on a complex mix of factors.