Then also make the airlines price seats to pay for externalities. I bet people won't be flying as much if the seat cost $5000 instead of $500 to pay for damage to environment. Don't single out ag. Tech and transportation are just as bad. At least with agriculture, it produces food.

So, I agree with this in theory, but how does this work in practice? To stick with the topic of seafood, it's just out there in the ocean; as long as it exists in fish-able quantities, people will fish and fish until there's none left. Pricing in externalities would be huge for the US, but it would need to happen on a global scale to make a difference.

No, it is not. People just choose not to see the facts. People do not want to know where their food comes from as they suspect it would be not good to know as changing habits is hard and they have lots of other stuff going on to take care of.

But once they have seen movies like "we feed the world" they do care at least a bit.