Barcelona Metropolis

Green infrastructure[2] includes things from plant-covered roofs to river corridors, and in between gardens, squares, city parks, avenues and a whole host of open spaces that allow us to understand the relationship of the urban habitat with the rest of the land as an eco-region with trans-scalar dynamics. These elements have structured cities in all civilisations, since the management and the supply of water, food production, air regeneration, as well as recreation in contact with nature have facilitated urban life in them. Climate change and the environmental crisis pose a structural challenge today, which inevitably brings a paradigm shift in the human interface with natural systems, i.e. in social metabolism – the resource management model that human society establishes with the environment –, highlighting the need to critically review the current role of this green infrastructure in order to develop proposals that will allow its decisive role to be reasserted.

The paradigm shift poses a major challenge that calls for benchmark models, and heritage plays a key role in this regard. The historic city ensured the habitability of traditional societies supported by an organic-based[3] production system and that based its activity on maintaining the environment’s productive capacity in equilibrium with it. Through physical work and thanks to solar energy and water management by gravity, they grew food, processed products and reused waste to maintain soil productivity, as they were organic – assimilable by the environment – according to a functional model of symbiotic relationships with the environment, the mimesis of natural ecosystems. This holistic understanding of habitat was linked to a set of social and cultural knowledge and practices related to land management.

The crisis of the current model

This model was overhauled with the industrial revolution, which allowed the systematic extraction of material and energy resources from the lithosphere. Today’s capitalist industrial society generates serious consequences for the environment, both on account of on-going resource extraction and the persistent spread of polluting waste, establishing a linear social metabolism with adverse and alarming impacts, both locally and globally. The growth of production has also led to the explosion of cities since the 20^th century, in which the role of urban green areas has been heavily transformed, relegated to a consumptive second place and suffering the considerable physical and environmental degradation resulting from the imbalance caused by urban growth and its polluting processes.

Urban planning as an institutional practice and body of laws is based on organising and regulating urban growth from an urban-centric perspective, but it is not equipped to tackle the current metabolic challenges through urban regeneration. The environmental crisis, manifested in its starkest terms in global warming, but also in its manifold consequences or parallel processes, mainly affects the metabolic vectors that are decisive for life: the water cycle, food with the organic matter cycle and air quality. These facts highlight the need to critically review the current role of green infrastructure to develop proposals that allow its structural role in the city to be reasserted.

Changes in climate variables in relation to the water cycle, such as the fall in precipitation and alterations in rainfall regimes, generate impacts such as erosive processes or the higher frequency of floods,[4] which calls for rethinking management of the water cycle in its entirety, both from the systems of capture and supply and management of runoff and infiltration to treatment at the river basin scale. Climate variables also result in biophysical variables that decrease water availability, increase water needs for irrigation, reduce river and stream flows and the length of snowfall periods. All of this adds to the deterioration of river systems triggered by urban growth, soil sealing that alters the natural water cycle or the vulnerability of coastal systems.

In terms of organic matter, a rise in the loss of biodiversity, a fall in the production of wood and other forest products, as well as an increase in the risk of fires are expected. As regards food, the agricultural land that occupied almost 30% of the surface of the Metropolitan Area of Barcelona in the mid-20^th century dropped to 8% in 2015,[5] a situation of tremendous concern due to the loss of sovereignty and food traceability, as food is already responsible for 37% of global greenhouse gas emissions.[6] Just as we talk about energy poverty to explain the phenomenon of households in poverty and with difficulties in affording the cost of energy,[7] we can also talk about food poverty when vulnerable households cannot source quality fresh food, which is paradoxical since they mostly occupy city outskirts with a high potential for production.

Towards a new paradigm

These peri-urban areas, with the rest of green infrastructure, are precisely areas of opportunity to meet the needs for adaptation to climate change and the current crisis due to their potential for self-sufficiency. This change must be accompanied by a new story, a new perspective on the so-called undevelopable land and the green infrastructure that connects it to the city. It is imperative to understand the biosphere processes of natural ecosystems that, like waterways, can promote the necessary metabolic, social and cultural reconnection of the city with its land.[8] There are already models of cities that in crisis situations have prioritised the food vector within urban planning, from the models of closing the cycle of organic matter put forward by Leberecht Migge for the city of Frankfurt[9] in the interwar period, to the well-known urban vegetable gardens in Havana, to the replanning of Detroit to revive the economy in the wake of the post-industrial crisis and to solve the resulting social and food desert problems. Meanwhile, cities such as Vitoria and Portland are examples of cities that integrated the water vector in their comprehensive planning at the river basin scale and in urban soil sealing to facilitate water management.

Disasters like the current pandemic do not bring about urban change in themselves, but they can speed up the envisioned transformations, becoming opportunities for evolution towards this necessary new paradigm. Now we need to transform this model of coexistence and culture of relations between the city and the land, orienting the demand for resources to the limited supply offered to us, understanding the positive role that human action can also play if it can read its dynamics. The city is the artefact of the highest metabolic concentration, where more people live, and it is them and their culture that generate certain living conditions. It is time to provide methodological tools and to build the story of urban regeneration necessary to enable a city that cares, both for the environment that gives life to us, and for us, the people that inhabit it.