They are working on that...
Deep in financial crisis, Detroit wants to save itself by turning urban areas back to farmland
http://www.oregonlive.com/news/index.ssf/2010/03/deep_in_financial_crisis_detro.html
Plowing Detroit Into Farmland
http://ideas.blogs.nytimes.com/2009/11/09/plowing-detroit-into-farmland/
The only problem with this is that the people living in that slum will move to other cities and destroy them also. The country needs to come down on these people and come down hard on them.