Using 10% of a city's green spaces such as gardens and urban parks could provide the fruit and vegetables to feed 15% of the local population, according to a new study.
Researchers at the Institute for Sustainable Food at the University of Sheffield analyzed the potential of urban horticulture in feeding Sheffield citizens by mapping its green and grey spaces.
Domestic gardens, allotments, and suitable public green spaces put together would correspond to 98 square meters per person in Sheffield for growing food. Commercial horticulture across the UK currently uses around 23 square meters per person, the paper adds.
Green spaces cover around 45% of the city, which is similar to other cities in the UK. Allotments represent 1.3% of this surface, with domestic gardens, which have immediate potential to start growing food, making up 38%.
Using data from Ordnance Survey and Google Earth, the team showed that a further 15% of the city's green space (such as parks and roadside verges) could also be converted into community gardens relatively easily.
If all the green areas in Sheffield were to be turned over for food production, the team estimates it could provide fruits and vegetables for approximately 709,000 people per year (that number is, currently, 122% of the city's population). But even if only 10% of available green space is used to grow food, it could provide for 87,375 people, or 15% of the city's population. The team explains that this would greatly improve the UK's food security, by increasing the share of locally-grown food in the economy.
The team also analyzed soil-free farming on flat roofs through means such as hydroponics (plants grown in a nutrient solution), and aquaponics (a system combining fish and plants). Such farms would allow year-round growing of food with minimal lighting requirements, and virtually no ecological impact -- the greenhouses would be powered by renewable energy and heat captured from buildings, with rainwater harvesting for irrigation. The 32 hectares of flat roof cover in Sheffield would translate to only half a square meter per local, but the team says it could have a significant impact on local food security.
"At the moment, the UK is utterly dependent on complex international supply chains for the vast majority of our fruit and half of our veg -- but our research suggests there is more than enough space to grow what we need on our doorsteps," says Dr. Jill Edmondson, Environmental Scientist at the University of Sheffield and lead author of the study.
"Even farming a small percentage of available land could transform the health of urban populations, enhance a city's environment and help build a more resilient food system."
The paper "The hidden potential of urban horticulture" has been published in the journal Nature Food.