RIO DE JANEIRO, Brazil — High on a hillside west of Rio, workers in the Tijuacu favela smooth mortar on bricks near shiny sewage treatment tanks, and carry bags of concrete on their shoulders to a new gravity-fed water system at the edge of the forest. Soccer fields punctuate the base of the steep slope, cluttered with makeshift homes.

NEW YORK — Growing food in cities isn’t a new concept for the poor. Rural farmers forced to migrate to urban areas in the developing world in search of work have long turned to their agricultural skills as a way of feeding themselves and their families when all else fails. It is only recently that urban agriculture has garnered attention in the first world, something many attribute to the growing popularity and romanticizing of small-scale organic farming.