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

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.