Under a little-known international treaty... fuel for international travel and transport of goods, including food, is exempt from taxes, unlike trucks, cars and buses. There is also no tax on fuel used by ocean freighters.
So in essence there's a tariff on domestically grown foods -- artificially biasing the market against home-grown. It would be hard to imagine a more toxic arrangement.
And remember, foods transported long distances by freighter are also refrigerated, meaning they're burning up way more fuel (and generating way more heat and greenhouse gases) than would be needed for transport alone.
See the full article here.