No sustainable development strategy can ignore cities: they are pivotal to all our current questions on political, economic, social, environmental, health-related and cultural fronts. Today, one in two people in the world lives in a city. Three billion others will likely have joined them by 2050, continuing a trend accelerating since the late 1980s. The major part of this growth takes place in the cities of Africa, Asia and Latin America, which welcome some five million new inhabitants every month, as compared to 500,000 in the cities of Europe and Northern America. Although urbanization is a phenomenon common to all five continents, the courses it follows bear a strong imprint of local cultures and social, economic and technical conditions. In Latin America, Northern America and Asia, large cities draw new residents. In Europe and Africa, however, urban growth mostly concentrates in the medium-sized cities and towns that have grown from the urbanization of rural areas. Other cities, especially in Eastern Europe, have seen their populations decline as a result of the economic crises affecting their regions.
The mainspring of urbanization is certainly economic. When cities position themselves as bridgeheads between territories and the globalized economy, they become the key drivers of growth. Global trade in goods, services and capital takes place primarily between cities interconnected by multiple networks, both material (communication, transport) and non-material (political, economic, cultural and scientific). And it is these opportunities for enrichment that attract a steady flow of new arrivals to urban centres.
The environmental impact of this ongoing urban transition is proportional to the scale of population shift. If cities now account for 75% of greenhouse gas emissions and consume 75% of the world's energy, it is mainly because they shelter half the planet's population and most of its economic activities. It is also because current urbanization replicates the growth model of cities in industrialized countries - greedy for resources, shaped by the development of the automobile and the low price of energy over the last half-century. Yet there are no longer sufficient natural and financial resources to support this pathway, and this calls for a profound and radical change in transport, investment, industrial and service-sector choices, habitat, and so on. This opens up an extraordinary window of opportunity for new avenues in urban development, as much for cities in the industrialized world as for those still largely under construction in emerging countries.
This global urban transition is also often marked by a growing social and spatial fragmentation. Most new city dwellers settle in informal districts that are badly serviced, underequipped and disproportionately poor. The share of urban populations living in precarious conditions already stands at 43% in South Asia and 62% in sub-Saharan Africa, yet policies to support these districts fail to measure up to their needs. Building an inclusive city consistent with socially sustainable development means guaranteeing access to basic services, providing decent and affordable housing, and ensuring free and easy circulation in a unified urban space.
The leaders and citizens of today thus have a major responsibility as trustees of the future. It is their task to influence the shape and structure of cities so that the generations to come can live healthy and contented lives. This collection of articles proposes ideas that may help formulate appropriate policies and plans to shape cities. Drawing on examples from some 80 cities across the five continents (see Figure 1), the authors identify, within their own fields, the contemporary trends, the mechanisms at play in city formation, and the tools that can influence current strategies and future action. There are no foregone conclusions in these approaches to present-day urbanization and its threefold relationship - environmental, economic and social - to sustainable development; they simply illustrate the diversity of manoeuvres open to all urban actors (local government, states, aid donors, companies, citizens) in the margins of urban complexity.
Steering the economic course
In today's world, cities are enmeshed in globalized economic flows. Connected to extensive commercial, financial, scientific, cultural and political networks, the largest urban centres play fully active roles in these flows, sometimes wielding even more influence than nation-states. The GDP of Tokyo, for example, is twice that of Brazil, and the number of inhabitants concentrated in the Japanese capital surpasses the populations of Sweden, Finland, Denmark and Norway combined. This situation is not essential to urbanization per se, but rather arises from successful economic strategies - grounded in investments targeting infrastructure and high-growth economic sectors, as well as the human capital (higher education, culture) that makes cities attractive, innovative and dynamic.
Pierre Veltz (Chapter 1) explores the prime movers of this globalized urban economy. Large well-integrated cities function as "powerful hubs that allow chains between producers, consumers and other social participants (such as universities) to be created and reconfigured constantly." As spaces of opportunity, they are proving powerful engines for growth. However, the lower communications costs underpinning this evolution over the past few decades have not produced a geographic homogenization. On the contrary, in a world where goods and information circulate ever more rapidly and freely, the polarization of wealth and power between and within cities has become more pronounced. Opportunities for social and economic advancement are not equally distributed, and tend to concentrate in certain city districts or networks. The challenge for local and central governments, and all the urban actors involved, therefore lies in organizing this growth and revenue-sharing to redistribute opportunities between and within territories.
The cities' integration into international trade is a decisive factor for foreign private investment. This linkage provides the basis for the rating agency rankings that guide the decisions of most real estate investment funds. As a result, investments by multinationals, drawn by the promise of high short-term returns, further enhance the attractiveness of these cities and foster a seemingly virtuous circle of economic growth. Taking Bangalore (India) and Greater Mexico City (Mexico) as examples, Louise David and Ludovic Halbert (Chapter 2) show how investors steer these financial flows towards specific sites within the city - not only because of investment logic, but via collaboration with the local facilitators who make these operations possible. Working at the crossroads between the worlds of finance, the city's concrete production, industry and political decision-making, these facilitators act as craftsmen of the globalized city, not simply in its economic flows but also its urban fabrication. No sustainable urban policy design should overlook these conditions, or fail to influence them in seeking to redeploy investment across the whole territory.
The logic of global economic relations funnels the effects of this economic growth into certain districts and specific urban areas, widening inequalities even within territories. Tracing the urban history of São Paulo (Brazil), Sergio Moraes (Chapter 3) shows not only how industrial activities and residential zones developed contingent on transport networks and roads, but also how the urban fabric itself concretizes the social inequalities underpinning the city's economic growth. In Bangalore and Greater Mexico City alike, economic development marks out the boundaries of a "useful city," to the detriment of other, declining city districts. This calls for greater attention to municipalities now seeking to rebuild socio-economic cohesion by involving the most marginalized populations in urban planning.
Steering the environmental course
Urbanism is often presented as synonymous with pollution and predatory environmental behaviour. Certainly, the high concentration of people, industries and vehicles in urban areas explains the massive consumption of natural resources and the high levels of water, air and soil pollution. Yet territorial dynamics go beyond pollution: city dwellers may be the main producers but they are also the main victims of environmental degradation. At the interface between a territory and its population, the city offers a privileged intervention framework for influencing the causes and effects of these issues.
Today's broad public focus on climate change and energy consumption raises questions about the city, its housing and transport. Urban formations are not powerless in the face of these challenges, because the higher their population density, the greater their hope of achieving economies of scale and intensifying their energy use. A very substantial share of the current increase in CO2 emissions reflects the growth of emerging countries, caught between their energy needs and the scarcity and cost of supplies. Faced with rising sea levels, heat waves, flooding, storms, and the arrival of "climate migrants" driven from the countryside by drought, cities will have to adapt to the expected impact of climate change. Partha Mukhopadhyay (Chapter 4) looks at how Indian cities can adequately address these challenges. In a still largely rural India, building carbon-light cities resistant to climate change remains a viable choice. While technological progress helps further this objective, it will not suffice in itself to change the present course of development. Only by integrating climate and energy objectives across the whole urban policy spectrum is there a hope of reshaping representations of the optimal city and influencing its development.
The fight against urban sprawl is one of the keystones of integrated environmental and urban policies. In the cities of the industrialized world, it is imperative to break with a development path linked to easy motorized transport and fuelled by land and property prices that decrease relative to the distance from the urban core. Developing and emerging countries must avoid such mistakes, and counter trends towards urban sprawl fed by proliferating informal districts. This means that cities everywhere must restructure themselves to foster new lifestyles. Serge Salat and Caroline Nowacki (Chapter 5) propose a return to ambitious policies shaping urban morphology, to encourage city dwellers to change their transport habits and consumer behaviour. Again, technology can ease this changeover, provided that it forms part of an integrated approach to urban development. A city-scale logic will address social, environmental and economic needs and also facilitate the design of integrated projects that promote all three in parallel, rather than favouring one at the expense of the others.
How can a city in a developing country initiate an environmental protection policy? How can it fully engage an agenda that may seem less urgent than (for instance) the fight against poverty? Taking the example of two African capitals, Yaoundé in Cameroon and Ouagadougou in Burkina Faso, Florence Fournet, Aude Nikiema, Blaise Nguendo-Yongsi and Gérard Salem (Chapter 6) show that the way forward often proves roundabout. The impact of pollutants on health generally forces municipal action on this issue. However, the technical means of intervention remain very limited in urban spaces with a high rate of informal settlements that maintain close ties with rural areas. Such settlements often bypass centralized solid waste disposal, for example, as alternative rural outlets are found for part of the waste, a practice that may run counter to the interests of health and environment. To surmount these obstacles, the most promising courses of action will elaborate solutions in collaboration with the urban populations concerned, so that they become aware of the stakes and adopt the technologies required.
To grow and function, cities draw on resources from increasingly remote hinterlands, and their polluted emissions do not stop at the city limits. Reducing or controlling a city's environmental footprint in line with a course towards sustainable development requires action in all of these interrelationships. The underlying rationale is as much environmental as economic, as Bernard Barraqué (Chapter 7) shows with respect to municipal water suppliers in European cities. Although technical improvements such as water treatment have temporarily given municipalities greater autonomy, present-day demand for better quality water and the resulting higher costs now favour territorial partnerships to prevent the pollution of catchment areas. Protecting water catchments located upstream from cities increasingly entails co-operation with farmers, and the non-pollution of ecosystems appears to be the less costly solution.
Steering the social course
Today's urbanization involves a proliferation of informal districts with poor public provisions of water, sanitation and energy. With no security of land tenure, no decent housing, and no basic services, these city dwellers are not really citizens in the full sense. However, Sylvy Jaglin (Chapter 8) shows us that connections to the main public water utility networks - a marker epitomizing urbanity - are being outstripped by "uncontrolled - and most often illegal - commercial modes of water supply" more suited to the income status of different populations. This resourcefulness is not simply technological but also institutional. Everywhere in Asia, Africa or Latin America, we see the emergence of composite systems that integrate private informal suppliers into overall service provision, alongside connection to the urban utilities' distribution systems. Although these developments improve the quality of life for the poorer city dwellers, questions of rates, intra-city solidarity and cost-sharing mechanisms remain unresolved. The situation calls for a strengthening of governance mechanisms capable of establishing common norms and redistribution schemes.
If local authorities require tools in order to integrate informal districts, they also need the will to do so. Marie Huchzermeyer (Chapter 9) takes the example of South Africa, where cities have opposed the influx of poor migrants to heighten their national and international appeal. Providing housing for these migrants is considered not only a burden but also an obstacle to economic prosperity. The rare extant social housing programmes relegate them to the city outskirts, necessarily raising their transport costs and depriving them of opportunities offered by central city districts. The author examines the case of Nairobi (Kenya) to show how a regulated private market can deliver affordable rental accommodation at lower cost and in better locations, by favouring a compact and densely populated city over a sprawling and socially segregated one.
Yet all the efforts to promote social cohesion, in developed and developing countries alike, are jeopardized by "security discourses" - policies and practices that advocate distrust and control of the city's younger and poorer residents, rather than addressing their needs. Luca Pattaroni and Yves Pedrazzini (Chapter 10) analyze the effects of this discourse on the urban fabric, coining the term "urbanism of fear" to describe the fragmentation it generates. The number of control points, barriers, and gated communities continues to rise in cities around the world - all signs of daily humiliations, and conducive to explosions of violence. Political will alone can counter this oppressive trend, by asserting an "urbanism of recognition" that assures each resident a place and a means of urban livelihood.
Steering governance for a new course of urban planning
Whether they explore the economic, environmental or social dimensions of a sustainable city, all these chapters emphasize the importance of political decision-making and the need for tools to manage urban services and planning. In the same vein, Thierry Paulais (Chapter 11) notes that addressing the global financial crisis requires that governance systems incorporate room to manoeuvre between their echelons - territorial administration, private and public actors, and even international aid entities. The global financial crisis that began in the United States in 2007 has not spared local governments and continues to weaken their urban investment finance systems. With economic activity on the decline, municipal budgets dwindle and access to loans becomes difficult. Paulais outlines this situation to propose some key reforms in the urban finance sector, as well as in urban planning and housing, now needed to guarantee the continuity of urban development. Above all, restoring municipal finance capabilities means overhauling relations between the state and local governments.
Likewise, according to Saskia Sassen (Chapter 12), only by rethinking decision-making from the local up to the global level can we reduce the environmental degradation associated with a resource-hungry, governance-deficient urban development model. Cities should be seen "as structural platforms for acting on and contesting irresponsible and powerful corporate actors." Their geographical base can indeed unite actors within various legislative measures and behaviours and make them accountable. To achieve this, we need to espouse a vision of cities as complex systems, active at multiple levels of scale and time, and thus able to create links among a diversity of actors. Analysing these interactions may identify the mechanisms needed to design environment-friendly urban policies.
The geographical encounter between diverse actors and rationales prompts a wealth of alternative strategies. Jérémie Cavé and Joël Ruet (Chapter 13) examine institutional innovations tested in emerging countries as a blueprint for new norms of urban planning and governance. Using examples drawn from the water and energy sectors in India and Brazil, the authors show how new alliances of actors, such as national enterprises, globalized firms, NGOs, international development agencies, and so on, have emerged in these cities, proposing new technical systems for providing essential services. In the long run, this inventiveness reveals the "power of norms," whose first signs have already become visible. This potential spurs new thinking on the role of public authorities' power, and promotes adaptation of analytical tools for urban development policies. This analysis shows, in fact, that the decentralized approach underpinning these policies, reinterpreted in the light of sustainable development, can also inspire developed countries facing renewal of all of their urban utilities networks.
Finally, all cities currently in search of sustainable development share a dual need: they must adopt the constraints and opportunities of a globalized world while grounding policy in local specifics, in the strategies of local actors and the potential of local government. And many cities need support in this complex process. Elisabeth Gateau (Chapter 14) observes how decentralization has generally moved forward, transferring more authority to the cities without always giving them adequate means to cope. The strengthening of city networks since the second half of the twentieth century shows their will to exchange information and experiences, aiding them to play their role more effectively and to make their voices heard at national and international level - without competing with state prerogatives of international representation and territorial solidarity.
Integrate for sustainability
The very diverse pathways that cities follow require evaluation over the long term. Although cities now assemble half of the world's population, other slower-changing factors also determine their structures: their built environments, transport infrastructures, diverse networks, and massive investments locked up for several decades. Changing their economic, environmental and social policies - and the course of cities' development - necessarily means identifying long-term objectives and planning how to achieve them. Today's decisions shape the urban environment that the next few generations of citizens will inherit.
This means that investment choices are vital. Rather than simply relying on outside support and seeking to attract international investment, cities also need to promote the development of local businesses. In an economy where innovation proves the wellspring of added value and where - as Pierre Veltz (Chapter 1) points out - it has become "more strategic for cities to attract talent than to attract capital," the needs of their inhabitants must not be neglected. Education, health, environment and culture are all long-term investments.
This need to anticipate justifies a critique of the currently over-compartmentalized management of economic, environmental and social problems. Changing the course of urbanism requires more than marginally correcting the more troublesome effects of uncontrolled development. Everything argues for ambitious policies that integrate as many different dimensions of sustainable development as possible: weighing up the environmental and social consequences of investments, safeguarding the environment for reasons of economic good sense and social wellbeing, and - given the tight interconnection of all three dimensions - treating the economy and the environment as agents of social integration.
Adopting these challenges requires technical innovation, investments and institutional know-how. It also depends on seeing decentralization processes through to completion, and firmly establishing local governments as the lead actors in sustainable development. Yet this strengthening will have little reason or effect until states safeguard the balance between local governments and financial solidarity, and ensure that their populations are truly represented in globalized economic and political processes. Finally, to guarantee that local specifics receive their due, urban development must find ways of effectively involving citizens in defining the directions of public policy. It is only through efforts such as these that cities will become cities in the true sense of the word.
THE 80 CITIES COVERED IN THIS BOOK