> If you have the money, the equipment, and the climate, what's stopping you from shifting agricultural production from one good to another on any scale you like?
Then we will lack whatever was produced on the place where you those new ponds with huge amount of fish.
Fish don't care about soil quality or level ground. If anything fish ponds can benefit from height differences because that allows you to flow water through multiple ponds before pumping it back up
Obviously nations do have limited surface area and creating new agricultural areas for them would be to the detriment of forests and "nature"
This argument does not work, because we are not limited by available space in total agricultural output. Just consider the Netherlands: Second largest food exporter despite the US being >200 times larger.
Most of the richer countries/trade unions have a large meat surplus that could be easily shifted to something else, too.