I have always admired those people referred to as Futurists. Thinkers and philosophers who see what is now and compare that to future needs, and suggest what the future may be like. Although ill equipped, I am about to take a shot at being a Futurist.
The third world is pockmarked with small farms barely feeding families or villages. Some of the more prosperous countries grow large quantities of a single crop or two, like rice or wheat. The land area of Europe is insufficient to have farms that can feed the world.
Canada has a short growing season. Mexico contributes, but not enough. The United States has the land area, the technology, and the massive agri-business to handle the load today. But not into the future with today's efforts.
There are cities, like Detroit, where large areas have fallen into ruin. Right now they give no value back to their city. I can see these blighted areas being plowed under and huge, warehouse like, structures being built. Multi-story buildings where one acre of building would yield five or more acres of productive space.
I picture fish tanks on the top floor where talapia, salmon, trout, and other species of food fish could be grown and harvested. Underneath there could be floors of twelve foot tall tomato plants in a constant production cycle. Below that floors of various greens. The waste from the fish could fertilize the plants. One end of such a building could be dedicated to harvesting, processing, and shipping their product.
A program like this would clean up destroyed neighborhoods, provide jobs, and enhance tax revenue for the cities. I think that it would even be feasible to provide free public transportation to bring workers in without wasting space on parking lots.
I have seen fish raised indoors and plants raised indoors. It is just a matter of uniting the systems and increasing the scale. All we need is leadership.