Phys.org [phys.org]:
Urban farming has grown by more than 30 percent [doi.org] in the United States in the past 30 years. Although it has been estimated that urban agriculture can meet 15 to 20 percent of global food demand [jacsmit.com], it remains to be seen what level of food self-sufficiency it can realistically ensure for cities.
One recent survey found that 51 countries do not have enough urban area to meet a recommended nutritional target of 300 grams per person per day of fresh vegetables. Moreover, it estimated, urban agriculture would require 30 percent of the total urban area [doi.org] of those countries to meet global demand for vegetables. Land tenure issues and urban sprawl could make it hard to free up this much land for food production.
Is urban farming a pipe dream, or can appropriating vacant lots for traditional farming or employing hydroponics make it work?