The Nature of Cities (TNOC) is a blog-style international platform to share ideas and discuss about cities and nature. Last 30th June, a global roundtable on sustainability and urban agriculture was published with the aim of answering the following question: Urban agriculture has many benefits. Is one of them a contribution to urban sustainability?
The roundtable compiles the ideas and opinions from 20 researchers from around the world. Together with Kathrin Specht from the Leibniz-Zentrum für Agrarlandschaftsforschung (ZALF) (Berlin, Germany), we have contributed to the discussion with our thougths regarding rooftop agriculture in Europe.
<<What can we expect from urban rooftop agriculture in terms of sustainability?
It is a common phenomenon that people consider food production and consumption as a one-way road, whereby food products are transported from rural areas to the cities. But there are broader visions for food production in the future. Urban agriculture is taking up the idea that the city itself can be productive, too, while so-called waste products (like organic “waste”, “waste” water, or “waste” heat can be used or re-used for food production.
We follow the understanding that sustainability has three different dimensions (environment, society, and economy) which need to co-exist in a balanced manner. All three dimensions must be considered in order to avoid the generation of negative environmental or social impacts when exclusively promoting economic development, for example.
Depending on their geographical context and goals, urban agriculture can have very diverse effects. Recently, we investigated the effects of rooftop agriculture in different European cities. One of our studies demonstrates that rooftop agriculture could increase the current production of local food in cities by using those roofs that are currently without a function. Such production would signify food production at “kilometer 0”, since production and consumption are co-located. In the city of Barcelona, local tomatoes produced in a rooftop greenhouse could substitute the demand for imported tomatoes from Southern Spain. This effect generates the reduction of environmental impacts (such as greenhouse gas emissions or energy consumption) compared to the imported tomatoes.
The different initiatives of rooftop agriculture can be differentiated in four main groups.
- Rooftop gardens. Here the food production is not the unique aim of the system. These initiatives are devoted to address social gaps and educational needs.
- Rooftop farms are business-oriented projects, where food production is the main goal, although it can be combined with other activities.
- Rooftop engineering initiatives are research- and business-oriented types, where technology development is the major aim (e.g. research projects, start-ups).
- Landscape rooftop projects are initiatives where, similar to green roof systems, the greening of the space is the main function.
These four groups contribute differently to urban sustainability. While rooftop farms have a large contribution to food security, rooftop gardens focus more on community development at the social level.
At the moment, rooftop agriculture initiatives in Europe are limited in number and area. This means that rooftop agriculture is not a main source of urban food products, particularly considering the large urban population. However, recent trends in food consumption indicate that the demand for local and ecologically-friendly food is growing and urban agriculture could be a source to feed these types of consumers.
Similar to rural agriculture, the environmental sustainability of urban rooftop farming depends on the applied farming practices (use of energy, input of fertilizers, etc.). Therefore, urban rooftop agriculture is not sustainable per se, and the production can be as unsustainable as in conventional agriculture, depending on management techniques. However, urban agriculture covers many particular urban needs beyond producing food, such as education and social inclusion.
If we are asked to answer if urban rooftop agriculture can make a substantial contribution to food security in Europe, we can answer: not in its current state. Even though it has high potential to increase production quantities in the future, it can only be considered a part of the whole food system at the moment and a “plus” to rural production.
by Kathrin Specht (ZALF) and Esther Sanyé-Mengual (RESCUEE-AB)>>