I remember reading a few years ago, that Detroit in fact wanted to bull doze large sections of the city and return them to farming or natural habitat but didn’t because Detroit could not afford the cost.
Read more: http://articles.businessinsider.com/2010-03-10/news/29955619_1_detroit-mayor-dave-bing-entire-city-dan-kildee#ixzz1qQEfM4Oq