byGreta Fear
A recent study analyzed the carbon footprint of urban agricultural sites in comparison to their more conventional agricultural counterparts. The study found that while 43% of urban farms have a smaller carbon footprint than conventional farms, food from the remaining 57% of urban farms and gardens leaves a significantly greater carbon footprint — up to six times greater than conventional farms. The study was organized by researchers at universities around the world — including the University of Michigan School for Environment and Sustainability, University Paris-Saclay and University of Kent School of Architecture and Planning — and the Research Institute for Regional and Urban Development.
The data used in the study was collected by citizen scientists, or members of the general public trained in the methods required for the city, from 73 urban-agricultural sites across France, Poland, Germany, the United Kingdom and the United States. The researchers studied the environmental impacts of three kinds of urban farms: high-production urban farms, volunteer-led community gardens, which have a social-impact orientation, and individual gardens.
In an interview with The Michigan Daily, Rackham student Jason Hawes, a co-lead author of the study, said the infrastructure of certain urban agriculture sites influenced how carbon-intensive they were, even more so than conventional agriculture.
“The primary contributor to environmental impact was infrastructure on the sites, the things that people built in order to enable food growing, so that could be raised beds, pathways or garden sheds,” Hawes said.
Hawes also said there are lesser, but still substantial, negative environmental effects from certain supplies such as compost and water irrigation. He identified three practices that can make an urban agricultural site more carbon-friendly, including treating sites as permanent rather than temporary and reusing urban waste. Hawes also said though it seems counterintuitive to grow relatively carbon-intensive foods on-site, it can also reduce the carbon footprint of urban farms because there is no need to transport foods with a high carbon footprint to a secondary location.
“If you look for examples of food products that are grown in a relatively carbon-intensive way in conventional settings, and you can actually grow those things in cities, then your net carbon impact is less,” Hawes said. “Our examples were tomatoes, that are often grown in greenhouses for northern cities, or asparagus, which (are) often air-freighted, are kind of shipped in by airplane because it’s highly perishable and spoils quickly so it can’t (be transported) on a boat or on a train.”
According to Hawes, the findings of this research do not mean that the benefits of urban agriculture should be downplayed. Hawes said urban farms can sometimes outperform conventional farms and positively impact the community.
“There’s a lot of nuance in how we understand the impacts of urban agriculture, not just on the climate, but kind of on the communities that it’s embedded in,” Hawes said. “(Urban agriculture) is a rising trend among cities in terms of planning for a more sustainable, resilient and just future. What we set out to do in this work was to identify the major contributors to the carbon footprint in order to better understand how urban (agriculture) can be designed better for a more climate-friendly future.”
Jennifer Blesh, associate professor in agroecology for the School for Environment and Sustainability, told The Daily the paper explored ways to mitigate current flaws in urban agriculture and maximize its positive environmental and community effects.
“The paper goes into how the social benefits can help counter (the carbon footprint) — they are thinking about the trade-offs,” Blesh said. “Many urban farms and gardens are working to improve access to healthy diverse diets for people in urban settings. They mentioned that if this approach succeeds in getting people to eat more vegetables and fruits and less of carbon-intensive foods like meat, then that could really counteract some of the carbon footprint.”
In an email to The Daily, Jeremy Moghtader, U-M Campus Farm program manager, said he believes urban farms must be analyzed with a holistic approach. Moghtader said he has seen firsthand the impact of urban farms in Detroit.
“The work of these organizations and the impacts of urban agriculture extend well beyond the importance of the nutritional or caloric value of the food they produce, acting as a critical catalyst for health, well-being, economic opportunity and justice led by communities,” Moghtader wrote. “Meaningful measures of sustainability must include these elements of justice and community self-determination that inherently extend beyond any single metric. As such, any cost-benefit analysis or conclusions one might wish to draw about the utility or impact of urban agriculture must weigh all its benefits against the costs whether the cost accounting is in dollars or greenhouse gas emissions.”
Blesh said she believes this study filled a need in the sustainable agriculture community by collecting necessary data to work toward collective sustainability goals.
“I think we need really detailed data to understand what different management systems look like on the ground and to link that to a range of outcomes so that we can figure out more strategic policies that support sustainable agriculture,” Blesh said.
Daily Staff Reporter Greta Fear can be reached at gcfear@umich.edu.
