The idea of growing fruit trees on the top of buildings, or producing fruit and vegetables inside multi-storey buildings using artificial light, might have been viewed as a fanciful idea once, but not any more.
From Beijing to Sydney and Tokyo to Singapore, urban farming is becoming an integral part of the city landscape, not only in Asia but throughout the world.
Chris Williams, lecturer in urban horticulture at the University of Melbourne’s Burnley campus, said urban farming, in all its forms, was the new reality in a world where more than half the population is now urbanised.
That figure is expected to rise to 70 per cent by the middle of this century, according to United Nations data.
Williams said rapid urbanisation had pushed market gardens that once surrounded our cities and towns further out or simply covered them under concrete and asphalt.
Today, urban farming is the buzzword for urban planners, whether it is in the industrialised or developing world.
In such cities as Manila, Bangkok and Jakarta, people grow vegetables on any land they can find for day-to-day survival. Meanwhile, in Tokyo it is high-tech vertical farming on a massive commercial scale.
Williams said urban farming, however, should be put into perspective.
"There is a huge difference between urban agriculture in developing countries and what industrialised countries are doing," he said.
He said that in such cities as Phnom Penh and Ho Chi Minh City, urban agriculture was a question of survival for the poor. "In Singapore, it is a question of national food security."
He said the cities of the future would be a "patchwork" incorporating urban farming "and all the new technology that comes with it".
In Milan, Italy, last October 20, mayors from more than 100 cities around the world, among them many from Asia, met to sign a pact on urban food policy to coordinate their food systems and urban agriculture better.
Tim Lang, professor of food policy at City University London and one of the world’s leading experts on the subject, said the Milan Urban Food Policy Pact "signals the return of city regions as powerful voices in modern food policy".
"Many have been auditing how they are fed," he wrote in a recent research paper. "They now recognise their food systems are in a delicate state even when the surface looks fine.
"Health and environmental impacts are high. Geopolitics are tricky. Aspirations for cheap food have become hard-wired into consumer expectations. Waste is rampant and governments bow too much to giant food companies selling sugary, fatty, ultra-processed food."
Almost one-third of all agricultural output in Japan is generated by urban agriculture, and urban farmers account for 25 per cent of the country’s farming households, according to a report by Japan-based United Nations University.
In Tokyo, one of the largest and most congested cities in the world, among the intricate networks of railways, roads, buildings and power wires, local agriculture produces enough vegetables potentially to feed almost 700,000 city dwellers.
It is also home to the world’s biggest indoor farm, which covers 2,300 square metres. The farm produces 10,000 heads of lettuce a day – 100 times more per square metre than traditional methods. It uses 40 per cent less power and 99 per cent less water than outside fields, according to WebUrbanist, an online magazine featuring urban architecture.
Similar vertical farms are being developed for Hong Kong, Russia and the Chinese mainland.
With 70 per cent of China expected to become urbanised by 2030, according to UN data, farmland is fast disappearing to the developers.
Throughout China, cities have been encouraging the development of urban farming as a way of bringing food production closer to consumers and reducing its environmental footprint.
Beijing was one of the early pioneers for integrating urban agriculture into its strategic development plans.
Recognising the importance of urban agriculture to sustainable urban development, Beijing’s municipal government has supported the development of "agro-parks", which not only produce food but also attract tourism and are used as educational tools, according to Chinadialogue, a website devoted to climate change and the environment.
"Beijing has created five zones that govern the type of agro-parks in the city," the site said.
The "inner urban core" focuses on gardening, landscaping, and exhibition. The "inner suburban plain" specialises in recreational agriculture, which attracts tourism, and precision agriculture, which utilises smart technologies such as moisture monitoring for automatic irrigation.
The "outer suburban plain" emphasises large-scale, modern agricultural production and processing. The "mountainous" zone is devoted to special fruit and ecological protection.
And finally, the "regional cooperation" zone helps to bolster food security by facilitating relationships with nearby cooperatives and assists to ensure the quality of imports, according to the website.
In South Korea, interest in city farming has increased in Seoul after the incumbent mayor, Park Won-soon, came to power in 2011. Park declared 2012 as the start of an urban farming era and unveiled a plan to secure enough farming space in the congested capital.
According to the local government, the number of city farmers in Seoul surged from 287,000 in 2011 to 440,000 in 2012. The total area of land for urban farms in the city grew from 29.1 hectares in 2011 to 84.2 hectares in 2012.
In Singapore, urban farming has become an issue of national security, while in Bangkok, it is a cheap, convenient way to help feed the poor.
The challenge facing governments will be to find sustainable ways of providing enough food to feed the urban masses.
The situation is particularly acute in Asia, where cities have grown at a faster rate than any other region in the world, according to the Food and Agriculture Organisation (FAO).
The UN body says Asia has urbanised at unprecedented speed during the past 20 years and feeding its mushrooming urban population will be one of the biggest challenges facing urban planners in the 21st century.
According to Hiroyuki Konuma, the FAO’s assistant director-general and regional representative for Asia and the Pacific, 13 of the 20 most populated urban areas in the world are now in Asia.
"Asia is urbanising at unprecedented speed," he told a conference on urban farming in Bangkok in 2013.
Though still predominantly rural, this upward trend is expected to continue for many years to come. In this decade alone, it is anticipated that two-thirds of the growth in the world’s cities will occur in Asia, raising its urban population by another 411 million, Konuma said.
"Migration, primarily rural to urban, is a key driver of this growth. However, together with natural growth, reclassification of rural areas is also an important contributor: Every year millions of people become city dwellers by this way even without movement, as their communities are transformed into cities because of rapid urbanisation."
Nicholas Williams, urban ecologist and associate professor at the University of Melbourne, said: "It is the story of urbanisation."
Throughout history, market gardens existed around towns and cities to feed the urban population, he noted. "What we are seeing today, however, is rapid urban growth on a scale not seen before and all that productive land disappearing to roads, rail and housing."
Urban farming is not a new concept, he said. But it has taken off in many cities on a larger scale in recent years.
Williams cited Singapore as an example where food security and water are seen as national priorities. South Korea is also a supporter of the concept.
"In the South Korean city of Incheon, entire urban blocks have been given over to urban farming. Not only do they provide food but a meeting place, especially for older Koreans."
On the fringes of the global climate change summit in Paris in December, many of the world’s city mayors met on the sidelines to promote the Milan Urban Food Policy Pact.
The global food system is both victim and perpetrator of climate change. Food production and consumption contribute up to 30 per cent of the total greenhouse gas (GHG) emissions and the impact of climate change on food security could be dramatic.
In a statement, the mayors said many cities are already adopting climate-smart strategies.
However, the large-scale shift of the global food system towards more sustainable production and consumption patterns has yet to begin.