Originally Posted by
fixedmonkey
His view was that most abandoned urban areas can not sustain agriculture because the soil is corrupted by pollutants.
This is somewhat true, but not all unused urban space is
brownfield land. Rooftops, residential lots, backyards, and greenhouses are all good candidates for what you're talking about. I met a guy who grows 80% of what he eats on a 1/4 acre. This is in Utah where the growing season is shorter than other places. I'm not sure that it's possible to sustain a large population entirely with this type of agriculture, but it's a good start.