It's the same situation as when you grow a pear in Argentina, send it to Malaysia and back to usa.

Boats are simply too big

A local farmer doing restocking trips, buying and transporting, you on trips buying the stuff needed to make those sweet iron and vitamin deficient mini tomatoes, soil, fertilizer, etc, consume lots of energy. Which might seem like a little but multiply that effort by the proposed method of "everyone planting and harvesting their own shit" and you soon see that it was kinder to mother earth and the climate to just transport shit over a cargo ship burning 400 trucks worth of fuel in one trip and transporting the equivalent of 9000 trucks, than you doing the 400 trucks worth of fuel trips and transporting, well 400 trucks worth of goods

It’s basically about scale. Shipping container ships run at low speed and maximize fuel efficiency.

When you drive, most of the fuel is used propelling the car forward, backwards, upwards and downwards. You make up a small amount of the stuff moved. You also change speeds. You come to full stops, take turns, maybe even go the wrong way. All of that is “wasted” energy that goes to the polluting impact of your vitamin deficient mini tomatoes.

However, a ships engine mostly works way more in per portion to move product across the oceans. Importantly once it maps out it’s routes and hits speed, it doesn’t deviate. Once the ship is up to speed getting it to keep going forward isn’t very hard.

It’s almost (because of need if preexisting infrastructure) the same with rail. The ability to carry a ton of stuff and maintain the same course and speed saves so much fuel, lowering the carbon footprint of any transported goods to your place to something miniscule you could never actually achieve by your own machinations

That's why they pollute more. That's right your homegrown tomatoes are more polluting than those of a mega corporation