Reading passage
On a rooftop in Singapore, rows of lettuce grow in shallow channels of nutrient-rich water, forty storeys above the street. Similar scenes can now be found in warehouses in Detroit, on car parks in Paris and beside railway lines in Tokyo. Urban farming, the practice of growing food within and around cities, has moved from the margins to the mainstream over the past two decades, driven by concerns about food security, climate change and the distance that produce travels before it reaches the plate.
The idea is older than it appears. During the Second World War, victory gardens in Britain and the United States produced, by some estimates, around 40 percent of the fresh vegetables consumed in America by 1944. In Cuba, the collapse of the Soviet Union cut off supplies of fuel and fertiliser in the early 1990s, and Havana responded by creating thousands of small organic market gardens that still supply much of the city's fresh produce. These historical examples show that cities can grow far more food than is commonly assumed.
Modern urban agriculture takes several distinct forms. Community gardens divide public land into small plots rented by residents. Rooftop farms exploit space that would otherwise be wasted, while also insulating the buildings beneath them. The most technologically ambitious operations are vertical farms, in which crops are stacked in layers inside warehouses and grown under LED lighting with precisely controlled temperature, humidity and nutrients. Advocates claim that a vertical farm can produce ten times more lettuce per square metre of floor space than a conventional field.
The environmental case for city farming rests partly on transport. Much of the salad eaten in northern cities travels thousands of kilometres by lorry or aircraft, and some studies attribute a significant share of food-related emissions to this food mileage. Growing lettuce a few streets away from the consumer eliminates most of that journey, and because urban crops are typically sold within hours of harvest, they need less packaging and refrigeration. Surveys also suggest that fresher produce retains more vitamins, although the evidence on this point is mixed.
There are social benefits as well. Community gardens have been shown to encourage neighbours to cooperate, and several studies link participation in gardening with improved diet and reduced stress. In Detroit, where the decline of the car industry left tens of thousands of vacant lots, urban farms have turned derelict land into productive space and created jobs in districts with few other employers. City governments increasingly see farming as a tool of urban renewal rather than a relic of rural life.
Critics, however, point to serious limitations. Vertical farms consume large amounts of electricity for lighting and climate control; one widely cited analysis found that lettuce grown indoors under artificial light can generate several times the carbon emissions of field-grown salad shipped from abroad, unless the electricity comes from renewable sources. Urban soils may be contaminated with lead and other heavy metals, requiring raised beds or hydroponics. And most city farms supply high-value salad crops and herbs, not the staple grains and potatoes that provide the bulk of calories.
Economists add that few vertical farms have yet made a profit. The capital cost of buildings, racks and lighting is high, and the wages of technicians exceed those of field workers. Several high-profile companies expanded rapidly on venture capital and then collapsed when energy prices rose in 2022. Supporters reply that costs will fall as LED efficiency improves and as farms learn to automate seeding, harvesting and packaging, but for now the industry feeds investors' expectations more reliably than it feeds cities.
The most realistic vision, many researchers argue, is a mixed one. Rooftop gardens, allotments and peri-urban market gardens can supply a meaningful share of a city's fresh vegetables, shorten supply chains and reconnect urban dwellers with how food is produced, while energy-intensive vertical farms focus on seedlings and high-value greens where their advantages are greatest. Urban farming will not replace the countryside, but it is already changing what cities are for.