>It's much more efficient to grow food where it grows best
Food grows best (when measured in both biomass-per-acre and biomass-per-man-hour) in forests, not monoculture fields. This becomes pretty obvious when you compare the percentage of sunlight that hits bare soil.
The only trick is to figure out how to design a forest (a non-trivial task by itself) using species that produces edible biomass, and arrange everything such that it's easy to harvest.
which also explains why both old (reliant on intensive manual labour) and modern farming methods (almost entirely reliant on oil) are unsustainable in the long term.
Food grows best (when measured in both biomass-per-acre and biomass-per-man-hour) in forests, not monoculture fields. This becomes pretty obvious when you compare the percentage of sunlight that hits bare soil.
The only trick is to figure out how to design a forest (a non-trivial task by itself) using species that produces edible biomass, and arrange everything such that it's easy to harvest.
One example of forest gardening: https://www.youtube.com/watch?v=GFbcn06h8w4