Growing populations, urban heat islands, buildings and street furniture in need of reinvention: this is how (resilient) cities are rising to the challenge of a changing climate.
L'urbanizzazione and the consequent depopulation of rural areas is a phenomenon that has spread across the world in recent decades. Driven by a shift in economic and productive models, more than half of the world's population now lives in cities. And it is for this reason that urban centres, starting with major cities, represent the front line in the fight against climate change.
"Climate change," explained Holger Robrecht, deputy regional director of ICLEI (the International Council for Local Environmental Initiatives), on the website of the European Environment Agency (EEA) "will have numerous consequences for cities: in Europe, for example, there will likely be an increase in extreme weather events such as floods, storms and heatwaves. This poses a threat to urban infrastructure such as transport systems, sewage networks and even food distribution systems".
All of this is compounded by the particular conditions that characterise urban centres. During heatwaves, cities face the risk that rising temperatures will be amplified by so-called "heat islands", which can prove fatal for the most vulnerable. The physical phenomenon is a simple one: during the day, cities absorb heat from solar radiation and traffic, releasing it at night. When heatwaves are extreme, the night is not long enough to dissipate all the accumulated heat, and the following day begins with temperatures that are already scorching, triggering a vicious cycle.
Many people remember the terrible summer of 2003, during which an exceptional heatwave struck Europe, causing more than 70,000 deaths, according to various studies conducted by the World Health Organization. These are "exceptions" that we will need to get used to: in a metropolis like Los Angeles — which has few parks, a great many cars and four million inhabitants — according to Michael Boswell, a lecturer at California Polytechnic State University, "today temperatures exceed 35 degrees Celsius for six days a year. By 2050 that will rise to 22, and in 2100 it will be 54".
The hope is that climate change can be halted, or at least limited, by global policies whose objectives were set out in the Paris Agreement signed at the end of COP 21 in 2015. But if that is not the case, how can we "adapt" our cities to rising temperatures — that is, become "resilient"? "The first thing to do is to plant trees for shade. But it must be done correctly, otherwise you risk trapping even more heat and pollution at ground level," Ingrid Coninx, from Wageningen University in the Netherlands, explained to the French Huffington Post.
Another useful approach is to make more effective use of waterways, or to plant shrubs on the roofs of buildings. Or, indeed, to completely rethink the latter, in favour of sustainable architecture, as in the case of the city of Masdar, in the United Arab Emirates, which has constructed buildings capable of "capturing" wind above their roofs and channelling it downwards to circulate the air.
"Many European cities," Robrecht continues, "have adopted cutting-edge adaptation plans, as in the cases of London, Copenhagen, Bratislava and Almada, in Portugal." The official cites among others the cases of Rotterdam and Ghent, "whose municipalities have formed partnerships with research centres, asking them to identify the hottest spots in the city during heatwaves. Fixed and mobile thermometers were installed in various urban areas and on trams: in this way, it was possible to pinpoint the parts of the city where the heat island effect was most pronounced and to implement mitigation measures. For example, trees were planted in some of these areas".
In Amsterdam, meanwhile, considered one of the European cities that will suffer most from climate change, an institute dedicated to finding solutions has been established: Amsterdam Metropolitan Solutions, in collaboration with Delft University of Technology. The Dutch capital sits on average just six metres above sea level, and one of the projects (called Rain Sense) aims to create an early-warning device in the event of torrential rainfall — a phenomenon that is becoming increasingly frequent — and the resulting flooding.
Also in the Netherlands, the "Room for the River" programme has been launched to restore to riverbeds the width they need to be able to drain any excess water adequately. Work has begun in more than 30 locations. A very similar initiative is the one launched by Munich to drain flows descending from the Alps, through a modernisation programme called "Isar-Plan".
In Hamburg, architect Philippe Rahm has designed "convective apartments", in which the layout of the rooms is conceived according to the movement of air masses: the bathroom is thus the highest room, followed by the living room, the kitchens and, at the bottom, the bedrooms. Paris, on the other hand, has decided to rely on two Green Bonds worth half a billion euros each — the first of which has already been issued — to finance the renewal of its infrastructure, making it green and sustainable and, in future, replace its entire fleet of city buses — around 4,600 — with clean vehicles.
The commitment of cities in the fight against climate change is therefore increasingly serious and decisive for the fate of the planet. This is why coordinating bodies such as "World Urban Parks" have been established, aiming to rationalise, enhance and expand parks in urban areas. And for the same reason, in the United States, local administrations immediately responded to President Donald Trump's decision to withdraw from the Paris Agreement. Almost immediately after the American billionaire's announcement, the initiative "We are still in" was launched, with 125 cities, 9 federal states, 902 businesses and 183 universities signing up. Together, they are saying that they will continue to do their part to meet the goal of limiting the rise in average global temperature to two degrees Celsius by the end of the century, relative to pre-industrial levels. In doing so, they are echoing the dozens of mayors gathered in the C40, a working group that has been active for years and is made up of leaders of major cities who have decided to defend the climate.
In an interview given to the New York Times, former New York City mayor Michael Bloomberg, who coordinates the rebellious local authorities and businesses of "We are still in", explained: "We will act as if the United States had remained in the Agreement." Without losing any time, California Governor Jerry Brown, during a tour of China, signed a cooperation agreement with President Xi Jinping to reduce greenhouse gas emissions, based on the development of renewable energy sources, zero-emission transport and energy efficiency. "We cannot tolerate obstacles being thrown in our path," the American official declared, "in this immense challenge of steering the planet towards a sustainable future."