Is it conceivable for a city to meet much of its own fruit and vegetable needs without depending on large international production networks? Yes, if there were enough urban allotments. So says a study by the Institute for Sustainable Food at the University of Sheffield, in the United Kingdom, published in Nature Food.

The hidden potential of urban allotments

Growing food in cities may seem paradoxical, yet urban areas have considerable potential for horticultural food production: the challenge lies in identifying spaces in which to practise it and in integrating it sustainably into the urban fabric. Starting from this premise, the study explored the subject through a case study and demonstrated that there is sufficient land available for horticulture in United Kingdom cities to meet the population's fruit and vegetable needs.

Growing from the ground to the rooftops

The researchers carried out their estimate using the city of Sheffield as a case study: they mapped existing urban allotments, but also green areas (parks, gardens, allotments, flowerbeds) with potential for cultivation, and calculated that the availability of space for urban allotments could increase from the 23 square metres per inhabitant currently used for commercial growing to 98 square metres — enough to provide five daily portions of fruit and vegetables to 709,000 inhabitants, more than Sheffield's entire population. More realistically, if horticulture were practised in at least 10 per cent of domestic gardens and on 10 per cent of the available land identified, it could feed 15 per cent of Sheffield's population for a year. The study also investigated the possibility of expanding the presence of urban allotments on the city's rooftops, estimating that if at least 10 per cent of the identified rooftops were used to host, for example, hydroponic tomato cultivation, the daily needs of 2 per cent of inhabitants could be met for a year.

A challenge for the future

Designing urban allotments capable of meeting a city's fruit and vegetable needs — as the scientists outline — requires agronomic, computing, engineering and architectural expertise: it means thinking about the sustainable and efficient operation of these systems, which should, for example, make use of renewable energy and be irrigated with rainwater, as well as being connected to one another to create a production network. This is a social and cultural challenge that concerns not only the United Kingdom but the whole world, and one that could fit within the Milan Urban Food Policy Pact, signed by 160 cities in October 2015 as a legacy of Expo Milano, which commits urban centres "to develop sustainable food systems that are inclusive, resilient, safe and diverse …" and to act to "promote and strengthen urban and peri-urban food production".

Urban allotments in Italy

The most recent available data on urban allotments in Italy date back to 2015: according to an analysis by Coldiretti, in that year Italy's regional capital cities counted 3.3 million square metres of municipally owned land divided into small plots and used for domestic cultivation, allotment gardening and recreational gardening. To these should be added further spaces forcibly occupied by spontaneous groups using guerrilla gardening techniques, alongside an increasingly widespread alternative use of private residential gardens and balconies converted into allotments for "do-it-yourself" food production.