Study: Published in Nature Food
Source: University of Sheffield (Great Britain)
Summary of ScienceDaily: „Growing fruit and vegetables in just 10 per cent of a city’s gardens and other urban green spaces could provide 15 per cent of the local population with their ‚five a day‘, according to new research.“
Method of Research
The interdisciplinary team used data from Ordnance Survey (national mapping agency for Britain, founded in 1791) and Google Earth.
- 45% of Sheffield is covered by allotments, parks, gardens and woodland
- Allotments cover 1.3% while 38% are comprised of domestic gardens
- An extra potential of 15% of Sheffield’s greenspace has the potential to be converted into garden communities
- Allotments and suitable green spaces, if put together, would open up 98m² per person in Sheffield for growing food, that’s four times more per person than currently used
Hypothetical and Realistic Scenario
Hyptothetical 100%: approximately 709,000 people could be fed (per year their „five a day*„), or in other words: 122 per cent of Sheffield’s population
Realistic 10%: 15 per cent of the population (87,375 people) of the city could be provided with a sufficient amount of fruits and vegetables
The potential for soil-free farming on flat roofs, using methods such as hydroponics, was also investigated by the study. Hereby, plants are grown in a nutrient solution. Another option is aquaponics, a system combining fish and plants.
Meaning for the UK…
As the article puts it: „The UK currently imports 86 per cent of its total tomato supply — but if just 10 per cent of the flat roofs identified within the centre of Sheffield became soil-free tomato farms, it would be possible to grow enough to feed more than eight per cent of the population one of their ‚five a day‘. This increases to more than 60 per cent of people if three quarters of the flat roof area is utilised.“
This, in turn, is also environmentally friendly since less transportation is needed. To some extent, the UK would also become more independent from the complex international supply chain. However, Professor Duncan Cameron, the co-Author and Director of the Institute for Sustainable Food at the University of Sheffield, said:
„It will take significant cultural and social change to achieve the enormous growing potential of our cities — and it’s crucial that authorities work closely with communities to find the right balance between green space and horticulture.
„But with careful management of green spaces and the use of technology to create distribution networks, we could see the rise of ’smart food cities‘, where local growers can support their communities with fresh, sustainable food.“
…Meaning for the Rest of the World
These findings, although very specific for the UK, highlight the potential of urban farming. Next to the farming on flat roofs, allotments, parks, or other green spaces, vertical farming could be an option for highly populated cities – even in regions which are dry and not suitable for conventional farming. Thus, a similar percentage could be provided with food as well. Since vertical farming takes place inside, it isn’t susceptible to weather and other environmental factors. Thus, an all-year supply is possible.
However, these changes, as Professor Duncan Cameron pointed out, need significant cultural and social change in order to reach their potential.
Addendum *: For those unfamiliar with the term 5 A Day and what it means.
5 A Day is one of many national campaigns of developed countries such as the UK and Germany. The goal is to encourage the people to consume at least five portions of fruits and vegetables each day, following an recommendation of the WHO that individuals should consume „a minimum of 400g of fruit and vegetables per day (excluding potatoes and other starchy tubers)“. A study in 2017 found that the double of the minimum recommendation (800 g or 10 a day) provided an increased protection against all forms of mortality.