But according to a study published in the journal Nature Cities, urban agriculture may not be as eco-friendly as it was originally made out to be.
The authors estimate that the carbon footprint of food that comes from urban agriculture is six times greater than that of conventional agriculture (420 gCO2e versus 70 gCO2e per serving).
This sizeable difference is mainly due to the energy expended in building infrastructure (such as raised cultivation beds or pathways between plots), as well as for materials (notably compost, fertilisers, garden fabric to protect against weeds and fuel for equipment). Of course, water consumption for irrigation of crops is also a factor in the footprint.
The researchers looked at data from 73 urban agriculture sites (community gardens, individual gardens and urban farms) in Germany, France, Poland, the UK and the USA.
The research did, however, find that in a few cases urban agriculture was less energy-intensive than conventional farming, such as for tomatoes grown in the soil of open-air urban plots compared to those grown in conventional greenhouses, or for air-freighted crops such as asparagus.
Such exceptions were observed at 25% of the individually managed gardens included in the research.
“The exceptions revealed by our study suggest that urban agriculture practitioners can reduce their climate impacts by cultivating crops that are typically greenhouse-grown or air-freighted, in addition to making changes in site design and management,” pointed out Jason Hawes, study co-lead author and doctoral student at the School for Environment and Sustainability at the University of Michigan in a press release.
Reusing urban waste and recycling rainwater
Moreover, the carbon impact of urban agriculture can be considerably reduced, in particular by extending the lifespan of materials and structures that are used, reusing urban waste and recycling rainwater and greywater for crop irrigation.
“A raised bed used for five years will have approximately four times the environmental impact, per serving of food, as a raised bed used for 20 years,” outlines the press release.
“Urban agriculture offers a variety of social, nutritional and place-based environmental benefits, which make it an appealing feature of future sustainable cities. This work shines light on ways to ensure that urban agriculture benefits the climate, as well as the people and places it serves.”
According to a large-scale meta-analysis recently published in Earth’s Future magazine and carried out in over 50 countries, certain foods grow faster when cultivated in cities.
This is particularly true of cucumbers and gherkins, which are four times more likely to flourish in urban areas, while tomatoes, fresh vegetables, chillies and peppers have yield rates between 2.4 and 3.1 times higher than those grown in rural areas.