Research and practice during the last 20 years has shown that urban agriculture can contribute to minimising the effects of climate change by, at the same time, improving quality of life in urban areas. In order to do so most effectively, land use and spatial planning are crucial so as to obtain and maintain a supportive green infrastructure and to secure citizens' healthy living conditions. As people today trend more towards living in green and sustainable city centres that can offer fresh and locally produced food, cities become again places for growing food. The scope of urban agriculture thereby is to establish food production sites within the city's sphere; for example, through building-integrated agriculture including concepts such as aquaponics, indoor agriculture, vertical farming, rooftop production, edible walls, as well as through urban farms, edible landscapes, school gardens and community gardens. Embedded in changing urban food systems, the contribution of urban agriculture to creating sustainable and climate-friendly cities is pivotal as it has the capacity to integrate other resource streams such as water, waste and energy. This article describes some of the current aspects of the circular city debate where urban agriculture is pushing forward the development of material and resource cycling in cities.

Urban agriculture (UA) plays a key role in the circular metabolism of cities, as it can use water resources, nutrients, and other materials recovered from streams that currently leave the city as solid waste or as wastewater to produce new food and biomass. The ecosystem services of urban green spaces and infrastructures and the productivity of specific urban agricultural technologies have been discussed in literature. However, the understanding of input and output (I/O) streams of different nature-based solutions (NBS) is not yet sufficient to identify the challenges and opportunities they offer for strengthening circularity in UA. We propose a series of agriculture NBS, which, implemented in cities, would address circularity challenges in different urban spaces. To identify the challenges, gaps, and opportunities related to the enhancement of resources management of agriculture NBS, we evaluated NBS units, interventions, and supporting units, and analyzed I/O streams as links of urban circularity. A broader understanding of the food-related urban streams is important to recover resources and adapt the distribution system accordingly. As a result, we pinpointed the gaps that hinder the development of UA as a potential opportunity within the framework of the Circular City.

A significant sample of twenty-nine Portuguese urban agriculture (UA) initiatives is analysed in this article. It argues that emerging initiatives are relevant for shifting from a post-crisis approach to one that is more developmental. This multi-level analysis finds that UA in Portugal: embraces allotment gardens, urban farms and short food chains; deals primarily with vegetables and fruit; takes place predominantly on public and institutional land; and is championed by municipalities and to a lesser extent by civil society initiatives. UA is predominantly a metropolitan phenomenon. Furthermore, activities are organised around three pillars: production of food; simple processing and distribution; and a significant set of capacity building and training activities. UA is recent phenomena in Portugal, and it has expanded quickly since the 2008 economic crisis. The paper explores in-depth four innovative short food chains from the sample of initiatives. They are led by young entrepreneurs, make positive use of social networks, are committed to social and economic values, and expanded successfully in generating jobs at the time of the crisis. These examples strongly suggest that UA social economy enterprises are a driving force behind integrated sustainable development approaches in European cities, if and when supported by public policies.

This paper presents a conceptual exploration of Urban Agriculture in Portugal. We argue that Portuguese Urban Agriculture primarily focuses on food production for self-consumption and that its links with the other components of urban as a system are quite limited. To substantiate our argument several Urban Agriculture international definitions are presented and critically analysed along with: 1) interviews of relevant key actors; and, 2) a web search based on key words. We conclude that there is a need to clarify the very concept of Urban Agriculture among actors involved. This could be achieved through a national network able to raise a must needed debate about this promising sector. Political decision makers, civil society, and planners, among others should be involved in this collaborative process. Finally, the paper brings some reflections on what the Portuguese experience contributes to the broader debate and definitions of Urban Agriculture.

Two interconnected questions are addressed in this paper: (i) why urban agriculture (UA) and food-related initiatives take usually years to materialise in Portugal; and (ii) why resilient initiatives do not scale up and shift from practices to local food policies. We argue that existing initiatives are viewed as single events and therefore garner quite limited long-term political commitment and support. Based on interviews with food champions and a literature review, four Portuguese UA initiatives are analysed and these highlight the constraints that hinder their scaling-up. We conclude that drivers to lead to scaling-up are a combination of factors, with an enabling environment the most relevant one. On the other hand, constraints are related to limited democratic governance and poor policies, insufficient funding and weak participatory processes. Such findings are quite in line with existing literature. The limited integration of Portugal within the international UA and food debates might partially explain why UA is still struggling to find its proper place in Portuguese cities and their peripheries. Raising awareness among decision makers is critical to scaling-up UA initiatives and turning them an integral component of local food systems. A national observatory able to gather relevant data and produce knowledge, assess and monitor on-going initiatives may be the key step to gather different stakeholders together, that can then better advocate and then lead to higher political support, not only in Portugal but in any country where UA and food issues are emerging.