Urban agriculture is an umbrella term that covers everything from allotments and community gardens, to more hightech solutions such as hydroponics or underground farming. The gap between the urban population and the food system has been growing. With the world facing a climate emergency, that gap is now being looked at seriously: it can reduce emissions, have huge benefits for urban environment, and provide social benefits, too.
Furthermore, it could add huge value to the rural sector. Climate change is going to have significant negative impacts on yields in the global south: urban agriculture can prop up that system. So I can see a lot of potential, and businesses are starting to get involved and looking to invest.
Michael Hardman is co-founder of the Food Geographies Research Group at the Royal Geographical Society, and a senior lecturer in geography at the University of Salford
By 2030, there will be 9 billion people on the planet, and researchers suggest we need to increase food production by 60% to feed them. Meanwhile, the number of pollinating insects is falling, 40% of insect species are in decline. So if the food system doesn't work, we need to find one that does.
One possibility is hydroponics: systems in which the roots are not in soil, and plants are watered with nutrients. Artificial light enables hydroponic farmers to grow crops indoors all year round, and you can also grow vertically, so you can get much higher yields per square metre.
There are downsides. Although they're space efficient, these systems may not be energy efficient. And to grow at the scale required to feed the population you would need an enormous amount of infrastructure.
I'm not saying cities will become self-sufficient. But plenty of urban agriculture is already happening in Africa, where rough estimates suggest that one-third of the food needed is produced in cities or on the urban fringe. And reducing the pressure we put on the environment is only good.
Silvio Caputo is a senior lecturer at Kent School of Architecture and Planning
My business partner and I realised there are huge problems with the way we currently produce food – so if we wanted to have a positive impact in the world, food was the place to do it. We decided aquaponics might be a sustainable way of growing in cities. It's a type of hydroponics, which uses fertiliser from fish, but it has the potential to grow food in cities, right next to where consumers live.
That would give people the freshest food possible, reducing the need for transport and packaging. Plus, growing indoors isolates agriculture from the effects of the climate. But there are open questions about energy requirements: you've got to ask where the power comes from.
There are three elements to what we do: we're an education company, teaching children about organic agriculture; we carry out research to explore the best way of using these systems in cities; and obviously we grow crops. This last element is the one we currently do the least, but we're ramping up to do small-scale commercial growing.
Jens Thomas is co-founder of Liverpool-based social enterprise Farm Urban
Greensgrow is a non-profit farm and garden centre, located in a very dense, depressed part of Philadelphia's urban core. It started in the late 1990s on a brownfield site, and today we have one full city block; part of the site is also set up for animals.
We grow about half of what we offer on the farm stand ourselves. The other half comes from regional farms. Urban farms won't be able to feed an entire city, but they can support a huge system of local farms, and help fill in the gaps. The limitations of the site include a lack of space and light, as well as just dealing with waste and pests.
One of the main purposes of urban agriculture is education: explaining the relationship between our food and the environment. The other big thing is wellness: farms attract birds, butterflies, caterpillars and more. There's a sense of smell and sensuality in that landscape that is hard to find in an urban park.
Meg DeBrito, executive director, Greensgrow, Philadelphia, US
Interviews by Jonn Elledge. Imagery by Almay