Urban agriculture certainly isn’t new: the vegetable gardens that sprung up during World War Two in UK and US cities, for example, were an iconic part of the civilian war effort. What is somewhat surprising, perhaps, is the extent of urban agriculture today. According to the UN’s Food and Agriculture Organization, 800 million people worldwide grow vegetables or fruits or raise animals in cities, producing 15-20% of the world’s food. 
Urban agriculture is growing, albeit for different reasons in different sectors. In developing countries or in low-income areas of developed countries, people are highly motivated to grow their own food in order to lower their food costs. In developed countries, urban agriculture is part of the consumer movement towards fresh, high quality, locally grown food. In developed countries, properly scaled smart urban agriculture can be a lucrative business.
Some Shining Examples
Here are a few selected examples of recent large-scale urban agriculture initiatives:
- Australia: Wide Open Agriculture has opened a 5,400m2 greenhouse-like facility to grow fresh vegetables in West Australia — an arid, wheat-growing region. It reduces water usage to a minimum through highly efficient drip irrigation and retractable roof and walls that open and close automatically to reduce water evaporation loss. It captures its own irrigation water from natural surface water runoff. 
- Japan: A hydroponic facility established after the 2011 earthquake in Tohuko, Japan in an unused part of a Fujitsu factory now produces more than 3,500 heads of lettuce per day – with staff monitoring everything remotely using sensors and apps. 
- UK: Growing Underground grows micro greens and salad leaves 33 meters below the busy streets of Clapham in South London, in tunnels originally designed to shelter the public during World War Two. As they write on their website, their state-of-the-art hydroponics system uses 70% less water than traditional open-field farming, and all nutrients are kept within a closed-loop system to eliminate agricultural run-off.
- USA: AeroFarm was one of the pioneers in hydroponic urban agriculture and today its flagship 6,500m2 facility in New Jersey, built in a former steel mill, produces a little more than 900,000 kilograms of leafy greens and herbs each year. According to their website, they accomplish this using 95% less water than field-farmed food, with yields that are 130x higher.
The Pros and Cons of Large-Scale Urban Agriculture
The advantages of large-scale urban agriculture are compelling. What could be better than re-purposing otherwise marginal urban spaces in order to produce fresh fruits and vegetables? As noted in the examples above, the use of expensive resources such as soil and water can be fully optimized and hazardous pesticides are unnecessary in these highly controlled environments. Hyperlocal distribution networks keep carbon footprints to a minimum. During the height of any given crop’s growing season, urban produce may also cost considerably less than the supermarket produce that has been shipped over long distances. Because crops are grown in high-density conditions and because there can be as many as 25 growing cycles per year, intensive urban agriculture yields are 10 to 20 times higher than the same crop grown through conventional outdoor farming. 
There are some downsides to urban agriculture, however. First, there is a considerable capital expenditure required to get a commercial scale facility up and running. In addition, the LED lights used to stimulate photosynthesis in highly controlled growing environments consume a great deal of energy. In water-scarce regions urban agriculture has to compete for water resources, often turning to wastewater for irrigation. Although wastewater reclamation is a positive trend, if not highly regulated it can pose severe public health hazards. Last but not least, improperly controlled water runoff has the potential to contaminate urban drinking water sources.
Technology and Policy Trends
Creating the conditions within which intensive urban agriculture can flourish requires cooperation across all stakeholders – regulators, NGOs, academia and the private sector. To this end, the Milan Urban Food Policy Pact was signed in October 2015, with the goal of creating collaborative frameworks within which inclusive, safe, resilient and technologically-advanced urban food systems can thrive. To date the Pact has been signed by 140 cities from around the globe, representing more than 470 million inhabitants. 
Urban agriculture is fundamentally different from conventional agriculture. Most traditional agricultural methods and technologies must be adapted – and entirely new ones developed. For example, crop varieties must be developed that are better suited to urban agriculture constraints. Water- and energy-management techniques must be incorporated, such as smart water meters, IoT sensors, and micro-irrigation systems. Cutting-edge production practices, such as hydroponics and protected agriculture, must become scalable and more universally available. 
Big data also has a vital role to play. The MIT Media Lab project CityFARM, led by Dr. Caleb Harper, is creating a free library of “climate recipes” by analyzing the optimal urban growing environment of every crop — from CO2 content of the air to irrigation water acidity. If you want to grow the perfect tomato in a climate-controlled urban farm, you’ll be able to download the settings and precisely reproduce the ideal growing conditions. 
Urban agriculture is an essential component of the world’s effort to feed a growing population in the face of shrinking resources. Thus, the question is not whether smart urban agriculture is here to stay (it is!) but rather how to create the regulatory and technology ecosystem that can support sustainable and viable business models.
 Elizabeth Royte, Urban farming is booming, but what does it really yield?, Ensia, April 27, 2015
 Oliver Balch, Water-smart farming: how hydroponics and drip irrigation are feeding Australia, The Guardian, April 27, 2017
 Laurie Winkless, Urban Farming: Fad Or Futureproof?, Forbes, March 9, 2016
 Milan Urban Food Policy Pact
 Urban agriculture: what and why? RUAF Foundation