Vacant land doesn't have to be non-producing real estate.
Under supervision of citizens who like to garden, there has been a big upswing in food and flower cultivation on unused urban land. In San Francisco, for example, there are now about 55 community gardens (with plots of various sizes) on vacant property, and more to come.
Formed loosely into the San Francisco League of Urban Gardeners (SLUG), growers are expected to farm these unused city plots (some are private) with effective productivity and attentive responsibility.
Those chosen to work this soil--and there is a two-year waiting list--can grow whatever they like in the designated areas. But they must abide by the league rules: no dangerous chemicals, use of staggered rows for crops and cultivation methods embracing good organic farming practices, plus the constant elimination of weeds.