We called it the “asphalt jungle”. Today, on the contrary, we want it greener and greener. Compounded by the worsening of air quality and, more recently, the development of strategies for adapting to ongoing climate change, the city has stopped conceiving of itself as antithetical to the natural world. Increasingly dense and more and more pushed to the limits in the use of resources, the city rejects, at all latitudes, the opposition nature-artifice to become a hybrid ecosystem, where flora and fauna coexist with our built world.
The impetus generated by the need to increase the resilience of cities in the face of an increasingly hot climate, also ratified by the Paris Agreements, has certainly amplified the awareness of the role played by nature in our urban spaces which, it is often remembered, will continue to attract more and more inhabitants (they will be home to 70% of the world’s population in 2030 according to the World Urbanization Prospects 2018, compared to today’s 54%). The pandemic, so far, doesn't seem to have bucked the trend.
This concentration, many experts argue, does not diminish the pressure on the ecosystem, nor does it allow us to consider separatism between humans and nature as an environmental protection strategy. The extension of cities now accounts for only 2% of all dry land; however, 70% of the world’s CO₂ emissions come from cities. Restoring the planet’s resources, then, means improving the way cities are able to manage, dispose of and offset their emissions. In a world where carbon capture technologies are still in their infancy and there is a lack of reliable forecasts on their effectiveness, one of the most sophisticated technologies we can count on is already made available by nature: it is called a “tree”, and it is capable of playing a fundamental role in the absorption of urban gases.
Through the process of photosynthesis that regulates their growth, trees are our best allies in “purifying” the air of gases such as carbon dioxide and fine dust. Yet, the role played by shrubs and high trees within the city is not limited to this. We know that in the summer, and even more so during extreme heat waves, the shade offered by tree canopies in the streets can reduce the perceived temperature by up to 10 °C, helping to naturally dampen the many heat islands that, especially in large paved squares, are responsible for the harmful heat peaks. Not to be disdained, moreover, the effect of mental well-being exerted by the greenery on the inhabitants of the city. An antidote to aggression, urban greenery, as if that were not enough, has proven to be an adjuvant to a better quality of life thanks to its noise mitigation effects.
A national strategy
New “catalysts of green”, to use an expression of Stefano Boeri published in the recent publication Green Obsession, Trees toward Cities, Humans toward forests, cities have recently become the subject of a vast plan coordinated by the newly founded Ministry of Ecological Transition, which has allocated funds equal to 330 million euro dedicated to the increase of urban forests in Italian cities.
The invitation to tender for the “Protection and enhancement of urban and suburban green areas”, part of the broader National Recovery and Resilience Plan prepared by the Draghi government, has a goal of planting 6.6 million trees in 14 metropolitan cities. These new green areas will be able to offer, in the vision of the promoters, a significant contribution to the reduction of air pollution, contributing to the enhancement of widespread biodiversity, to a reorganisation of the landscape, to the limitation of land consumption for industrial activities or for new residential complexes.
The outcome of the identification of sites has been announced by the Ministry led by Roberto Cingolani: Bari, Bologna, Cagliari, Catania, Genoa, Florence, Messina, Milan, Naples, Palermo, Reggio Calabria, Rome, Turin and Venice will be the cities where the 6,600 new hectares will take root. Depending on the individual projects, the new areas will extend existing woods in urban or areas of the urban belt, create connections between city parks and in some cases will be equipped with infrastructure for educational activities and tourist use.
The new brand of a city
The great Italian plan surely represents a vanguard in Europe, but it is certainly not the only one to mark the green renewal of our urban fabric. In France, the sustainable development plan launched by Nice is already a case in point. The coastal city, emblem of the “dolce vita” of the French Midi and traditionally conservative in political outlook, has surprisingly played the card of ecological resilience as early as 2008. Urban planning and transport interventions, managed by the Municipality through participatory processes and citizen consultations, have gone hand in hand with an intended reforestation of urban spaces. The results are already starting to be seen: the Promenade du Paillon, the new city park erected where an old bus station and its interchange parking lot once stood, is now a landmark on the same level as the historic Promenade des Anglais. But that’s not all: under the slogan “1 tree for every 5 inhabitants”, urban planting has managed to contain the emission of particulate matter.
In the case of the Promenade des Anglais, where the new trees have been accompanied by the electrification of the streetcar line and the reduction of the lanes reserved for cars, the reduction in particulate matter has stabilised at an impressive -65%. But that’s not all: at the rate of 130 trees planted every day - that’s the average under the tenure of Mayor Christian Estrosi, in office since 2017 - the city of 360,000 residents has updated its goal to “one tree per inhabitant”. Beyond the bet on climate security, the challenge also lies in the repositioning of the city’s brand: the new “ville verte” will be able to strengthen its attractiveness and its positioning in the field of luxury tourism through its new sustainable identity.
A continent put to the test
However, sensitivity to reforestation of urban spaces is certainly not an exclusive of developed countries. In Africa, where the effects of climate change are expected to be much more accentuated than in the West despite low CO₂ emissions, the United Nations has drawn up dedicated programmes for the reforestation of urban areas. Launched in 2019, the “Great Green Wall for Cities” plan, ancillary to the African Great Green Wall project launched in the early 21st century by the African Union, aims at reforesting 500,000 hectares of new urban forests by 2030. Focusing on 30 countries, including some Asian cities, the plan aims at creating three urban forests per country so as to impose a virtuous model to be scaled up later in a growing number of residential areas.
FAO Director Qu Dongyu said the plan “can help reduce air temperature by 8°C, reduce costs associated with air conditioning by 40% and improve water quality”. The cost? The estimated budget by the international organisation is $1.5 billion for 800,000 hectares. The reforestation activity, the United Nations reminds us, will be married with activities aimed at the protection of existing forests, including the 300,000 hectares of areas already present in these urban spaces.