"Food grows where water flows" in that image you used is the key. Allow people to migrate freely as long as they are peaceful. Born in a place that does not support agriculture? Move. It really is that simple.

There is abundance from nature as long as you have humans willing to work for the food. It is not even a lot of work either. I'll never live far from mountains for spring water and forest for sustained life.

You cannot force anyone to do anything. The right incentives need to be provided. They never will be with governments controlling people's migration and practically every other choice.

Heck, in many places of the world, the government suggests it owns all water ways. They also buy up and own the most fertile lands. Coincidence? I don't think it is.