So what does this have to do with Southern California? Think Inland Empire housing bust. The "roof farm" housing tracts for the LA urban centers are no longer viable, not that they ever really were before the "growth vision" bubble popped.
Detroit has been depopulating because the old single-sector company industrial production model no longer exists, hence large swaths of the city are abandoned and decaying. This presents one of the best opportunities for sustainable redevelopment in the country. Here are the opportunities for restoration of natural processes, linked public transit, clean utilities, multiple land uses (including "local food") and myriad commercial and "new industry" centers. This more closely mimics the natural structure of complex ecosystems and biodiversity necessary to sustain living systems. An article discussing the "shrinking city" is here in new geography.
The concept being put forward per the image above (click to enlarge) is discussed in the local Detroit free press (FREEP) involving a complete redevelopment of the old industrial areas, using "smart growth" to establish infrastructure that can replace the old, useless industrial infrastructure and connections. Coal usage was the base source of energy from the early industrial age, and now this is an opportunity to restructure the city with many strategies for clean energy generation that fits the new scale of habitation. Technology can be implemented to vastly reduce consumption and waste, given the opportunity for developers to install these systems and attract diverse businesses that employ people locally and develop a new financial base and appeal to a better quality of life.