It is well established that, starting from the period of urbanization induced in the nineteenth century by the birth of large-scale industry, cities can be considered responsible for producing as much as 75 percent of the CO2 in the earth’s atmosphere. The uncontrollable growth in CO2 is the root cause of global warming and its effects on our planet’s glaciers and oceans. Cities, where the majority of our species live, are also the main victims of the effects of global warming. Just think of the dramatic effects of flooding on the waterfronts of many coastal cities and the damage that a climate transfigured by warming oceans is causing to urban areas, which have become huge waterproof expanses, where water accumulates and flows without being absorbed by the soil. Think too of the worsening “heat island” effects that the increasing temperatures are creating in almost entirely mineral cities, let alone the shocking number of deaths that higher temperatures combined with air pollution are causing among the inhabitants of urbanized areas. Cities, however, currently have the resources and the potential to become the main players of a radical reversal in this trend, aimed at countering the dramatic effects of the climate emergency.
The magnitude and intensity of the climate emergency are such that the British environmentalist philosopher Timothy Morton classifies it as a hyper-object, i.e., an object that is so massively distributed in time and space as to transcend location itself. We are in fact faced with a multiplicity of effects that are often barely visible or only perceptible in the long term. Or to effects, such as the melting of permafrost in Siberia and rising sea levels in the Fiji islands, which may be geographically distant but are in reality closely connected, although at first sight they might be deceiving.
Unsurprisingly, an authoritative newspaper like The Guardian recently proposed a substantial change in the terminology related to climate change, which is named and defined as a crisis or climate emergency. It is precisely the incredible acceleration in the evolution of this phenomenon in recent years, and its increasingly intense and devastating repercussions on the urban environment, that prompt the change of terminology and give us the measure of the gravity of a situation which, generally speaking, has already defeated us.
Cities and climate emergencies are also mutually intertwined with the growth of migratory flows which, due to the increasing uninhabitability of various areas of the planet, flow into urban areas, generating a real chain effect. In 2012 alone, as a result of around 300 environmental disasters (including hurricanes, floods and earthquakes) which hit China, the United States, the Philippines, Indonesia and Afghanistan in particular, there were more than 32 million climate refugees. adding to all those who are leaving their homelands due to creeping desertification and continuous famines, wars and relgious or gender-based persecutions or those linked to sexual orientation that increasingly characterize some African and Middle Eastern countries. According to the most recent estimates, between 200 and 250 million human beings will be forced to abandon their homes and move to cities by 2050, thus further increasing the factors that are the primary cause of the climate emergency itself.
From the perpetrators of the crisis to the protagonists of change
The big challenge in the coming years will be to alter the planet’s cities’ role, so they are no longer just contributors to and victims of our climate emergency, but also the protagonists of a global campaign to reduce and slow down its triggers. Urban forestation is one of the most effective tools for making this happen. The aim is not only to reduce the production of greenhouse gases to a minimum but also to absorb significant amounts of those already produced, and today the cheapest and most effective technology in nature to absorb CO2 is photosynthesis by plants. Forests already absorb about 40 percent of the CO2 produced by 76 percent of the cities. Significantly increasing forest areas in and around urban areas means bringing the most effective tool to absorb greenhouse gas to the place where it is produced. But the positive effects of forestation do not end there. Trees are also able to absorb pollutants such as fine dust and, thanks to the shade they provide, they attenuate the “heat island” effect of dense and congested urban centers, cooling the air temperature by 2-3 degrees centigrade and allowing the electricity used for air conditioning in urban interiors to be significantly reduced. In summary, Urban forestation helps to counteract the effects of climate change, reduce energy requirements and positively affect the urban microclimate and the physical and psychological well-being of the world's citizens.
The focus on Urban forestry policies is therefore particularly strong at this time in history. The awareness-raising work started last year, with the first World Forum on Urban Forests in Mantua, continued with the second forum held at the Milan Triennale and organized jointly with FAO, SISEF and the Milan Polytechnic. Both provided important opportunities to compare urban forestation policies on a global scale, thanks to the contribution of professionals from different disciplines and meetings with representatives of the world of politics and institutions, without neglecting the important dialog with citizens.
Re-establishing a new alliance between Forests and Cities is today a global challenge that requires joint action between networks of cities and multiple countries, collaboration between different disciplines and coordination between various decision-making, political or institutional areas. As in the case of “ForestaMI,” a project implemented thanks to a memorandum of understanding between the Municipality of Milan, Città Metropolitana di Milano, Parco Nord Milano and Parco agricolo sud Milano to build a strategic vision of the role of green areas in the Milanese metropolitan area, with the aim of bringing together, developing and enhancing the main green, permeable and tree-lined systems, and the life around them, within the perimeter of the Greater Metropolitan Park by 2030. This ambitious project provides for three million trees to be planted by 2030 and is already achieving remarkable success among business owners, institutions and individual citizens ready to take action to plant the greatest possible number of trees in the city. Milan is therefore doing a great deal to enhance its green infrastructure, which is very significant now that three years have passed since the “Un Fiume Verde per Milano” (a green river for Milan) project was launched, when we were already planning to recover the city’s disused freight railroad stations by constructing a continuous linear park across the city, limiting land use and promoting the expansion of green wooded areas.
Grafting green buildings into an established fabric
In our work as an architecture and urban planning firm focused on urban forestry, we are involved in a variety of projects, from developing global visions and master plans, to purely architectural work, including interior and product design.
In urban areas, one of the ways of creating a forestry project is to graft green buildings into the heart of the consolidated urban fabric. This is precise work and reflects the scale of the building of which the planting integrated into the architecture becomes its main feature. The forefather of this approach is the Vertical Forest of Milan, a building designed to be inhabited by trees as much as by human beings that becomes an ecological device to counteract the effects of climate change. This is a new type of urban ecosystem which we are studying, developing and building in different countries, adjusting it to reflect the features of the climate where we find ourselves operating. The projects currently under way, from Nanjing to Utrecht, Cairo, Shanghai, Tirana and Lausanne, are experimenting with different construction technologies, architectural structures and plant selections depending on the project requirements and local environmental characteristics. This multidisciplinary work is made possible by the important collaboration between architects, landscapers, ethologists, agronomists and structural engineers.
Eindhoven in the Netherlands, for example, is building the “Trudo Vertical Forest,” a vertical social housing forest providing low cost accommodation for young professionals and new families. The building is located in a formerly redeveloped industrial area and, by optimizing the materials and technologies used, as well as using prefabricated elements, it offers homes at controlled prices and a democratic distribution of green areas, meaning that each terrace contains a natural micro environment consisting of a tree and around 20 bushes.
Another example is the “Forêt Blanche” designed for Paris, which consists of a vertical forest made with a wooden structure. Wood is a material that allows us to continue our research into an increasingly sustainable form of architecture, particularly in terms of the materials used to ensure the least possible environmental impact.
In addition to the Vertical Woods in various cities of the world, we are currently working on various solutions that integrate nature in urban contexts, from the creation of green infrastructure systems to the establishment of real “forest cities.”
In general, the challenge to which cities are called to respond is to exponentially multiply their number of trees, improving air quality and, consequently, the quality of life of their inhabitants: a challenge we must face immediately and all together.
Stefano Boeri is an architect, urban planner, professor at the Polytechnic of Milan and a visiting professor at several international universities. Directs the “Future City Lab” at Tongji University in Shanghai: a post-doctoral research program that explores the future of contemporary cities in terms of biodiversity and urban forestry.