Rome declined, we all know that. From a million people at the beginning of the Common Era, its population was down to five percent of that in the Middle Ages. Now Detroit--once the capital of the Auto Empire--is up against a similar challenge: how to adjust to a loss of a quarter of its population.
Part of the plan, according to the New York Times, is guiding people to leave declining neigborhoods and concentrate in more stable ones, where it will be easier to deliver services. Some see this as a new form of "urban renewal" which, like the old one, requires the poor to do the moving and provides the better off with a better functioning city.
Others see it as a chance to homestead the city, to reclaim disused land for agriculture, to create new jobs and provide better, cheaper, local food.
Sounds interesting, particularly if you've been browsing books like a new one recommended by a friend: Urban Homesteading. Other urban homesteaders like ones in Pasadena have been trying this kind of thing for a couple of decades.
But I don't think anybody has taken a big, formerly industrial city, and tried to turn it into an agricultural community. Will it work? Probably not on the scale that some would like. There are so many things that could go wrong. Remember that when Rome began to grow again in the Renaissance, much of the marble used to construct those grand ruins of the Empire were taken out and burned to make lime for new construction.