Urban agriculture, the practice of growing food within cities, has been gaining popularity in recent years as a way to address food insecurity, promote biodiversity, and foster community engagement.
However, a new study by the University of Michigan reveals that urban agriculture may not be as green as it seems.
The study, published in the journal Nature Cities, found that fruits and vegetables grown in urban farms and gardens have a carbon footprint that is, on average, six times larger than conventionally grown produce.
This surprising finding challenges the assumption that urban agriculture is always beneficial for the environment and calls for more careful consideration of its climate impacts.
The Carbon Cost of Urban Farming
CHUTTERSNAP/ via Unsplash
The researchers analyzed data from 73 urban farms and gardens in five countries and compared the greenhouse gas emissions associated with their production to those of conventional agriculture.
They considered various factors such as the type of crop, the location, the size, and the management of the urban agriculture site, as well as the inputs and outputs of the farming process.
They found that urban agriculture sites emitted 0.42 kg of carbon dioxide equivalent (CO2e) per serving of food, while conventional agriculture sites emitted only 0.07 kg of CO2e per serving.
The main sources of emissions for urban agriculture were the materials and activities involved in establishing and maintaining the sites, such as the use of fertilizers, pesticides, irrigation, and machinery.
The researchers also noted that urban agriculture sites often had lower yields and higher land use intensity than conventional agriculture sites, which increased their carbon footprint per unit of food.
However, the study also identified some exceptions where urban agriculture performed better or equally to conventional agriculture in terms of emissions.
For example, tomatoes grown in open-air urban plots had a lower carbon intensity than tomatoes grown in conventional greenhouses, which require a lot of energy for heating and lighting.
Similarly, the emissions difference between conventional and urban agriculture disappeared for crops that are typically air-freighted, such as asparagus, since air transport has a very high carbon footprint.
The researchers recommend that urban farmers and gardeners focus on cultivating crops that are suitable for their local climate and soil conditions, that have high yields and low inputs, and that are typically greenhouse-grown or air-freighted.
They also suggest that urban agriculture practitioners adopt practices that enhance the carbon sequestration potential of their sites, such as using compost, mulch, and cover crops, and planting trees and shrubs.
Urban agriculture can still offer many benefits for the society and the environment, such as improving food security, nutrition, and health, enhancing biodiversity and ecosystem services, and strengthening social cohesion and resilience.
However, these benefits need to be balanced with the potential trade-offs and trade-offs of urban agriculture, especially its carbon footprint.
By adopting more sustainable and climate-smart practices, urban agriculture can become a more effective and efficient way to produce food in cities and contribute to the global fight against climate change.
