The number of people on our planet is growing rapidly. Food security is becoming increasingly difficult to achieve. The amount of arable land is limited, and increasingly threatened by climate change. Agronomists, engineers and architects are already working on ideas for the agriculture of tomorrow. Their scenarios show that agriculture is moving to the city - and going vertical.

Usually, it is people who live and work behind the walls of a high-rise building. Decorative houseplants are the only touch of green. In future, however, lettuces, tomatoes or rice plants will flourish behind the windows of skyscrapers. These city farms will reach for the sky as futuristic green high-rises alongside multi-story office buildings.

Architects are sketching visionary agricultural towers, with efficient greenhouses stacked up to a dizzying height, and have dubbed the system “vertical farming.”

The urban farms are equipped with environmentally friendly wind turbines and solar cells. The buildings are reminiscent of a sci-fi film: glass pyramids, towers flooded with light and the bulbous silhouettes of skyscrapers. The various floors have no internal partitions, but are entirely devoted to hydroculture: various types of fruit and vegetables will grow here, and rice and wheat seedlings will sprout.

There will even be room in these vertical farms for free-range hens and water tanks housing shrimp and fish. Some of them are designed to be installed on floating urban islands in coastal waters, which will be self-sufficient thanks to their integrated greenhouses.

Food for megacities

The city sketches and ideas for the agriculture of the future are merely imaginative designs at present. But if over 9 billion people are going to be living on the earth in 40 years’ time, we need innovative ideas today to ensure food security. The population of large cities, in particular, is growing rapidly: by 2025, the urban population, now standing at 3.5 billion, will grow to an estimated 4.5 billion, while the rural population will merely increase from 3.4 billion to around 3.5 billion.

The United Nations expects particularly strong growth in the megacities with over 10 million inhabitants. For example, 21 million people live in Delhi today, but in 2020 that figure is expected to grow by 5 million, according to the World Urbanization Prospects of the United Nations. Large cities such as Mumbai in India, Dhaka in Bangladesh, Kinshasa in the Democratic Republic of the Congo or Shanghai in China will also have considerably more people to feed.

More agricultural land is urgently needed. But there is hardly any more land on the planet to use. In fact, the available area of arable land per head has been shrinking for decades. According to United Nations figures, by 2050, there will be only around 0.19 hectares per head of suitable arable land – in 1950, the figure was almost three times as high at 0.52 hectares. More and more agricultural land is being lost owing to heat stress and drought.

“The losses in yield due to these abiotic stress factors are enormous, up to 80 percent in some cases,” says Dr. Alexander Klausener, head of research at Bayer CropScience. Current climate change trends could make the situation even worse, says the researcher. 

Urban agriculture could help to control the problems of the future.

Scientists like Professor Dickson Despommier see vertical farming approaches as the solution to a number of 21st century problems. The U.S. microbiologist from Columbia University in New York City is the original inventor of the high-rise farm. He sees the idea as much more than an important contribution to global food security.

Multi-story greenhouses could also save energy and transport costs. The expense currently involved in transporting our fruit and vegetables and emissions of environmentally damaging greenhouse gases could be considerably reduced, he says. Another advantage of the skyscraper farms is that land currently used for agriculture could be returned to nature - vital ecosystems such as forests, which store CO2, thereby removing it from the atmosphere, could be revived in this way.

Today, a city needs many times its own area in agricultural land if it is to feed its inhabitants. In future, says Professor Despommier, a 30-story building could supply around 50,000 people with fruit, vegetables, eggs, fish and chicken.