MEGALOPOLISES

The fragility of gigantism

2007 brought an unexpected world record: according to the United Nations, for the first time ever the urban population (3.2 billion) exceeded the rural population (3.1 billion).
The margin may be narrow, but it is set to continue in line with the trend for migration from the countryside to the city that has increased fourfold over the past 50 years. It is a trend that will raise many questions of "sustainability".

Tokyo, 35 millions d’habitants avec sa banlieue. Au top ten des mégapoles. Pas pour longtemps… @ Shutterstock
Tokyo – a population of 35 million for the greater urban area. In the top ten megalopolises. But not for long…
@ Shutterstock

The "megalopolis" label is applied to cities with populations of 10 million or more. More populous than Canada, the Japanese capital (33 million, 35 including greater urban area) is considered to be the world's biggest city, with New York (22 million), Mexico City (22 million) and Djakarta (18 million) also clearly exceeding this threshold. This trend towards gigantism coupled with demographic growth and a globalisation that is redrawing the map of economic centres are resulting in a new urban geography. One example is the Chongqing "hyper-megalopolis" in central China that embraces four adjoining urban areas. Located on the Yangtze, close to the Three Gorges Dam, Chongqinq is home to 33 million inhabitants with 500 000 more arriving every year.

Zones of mega-poverty

The influx of new arrivals raises particularly dramatic issues for cities in the emerging developing countries. How will Dakar or Lagos manage their new arrivals when we know that their population will reach 9 or 10 million by 2015? What is the future for Africa's biggest shanty town, Kibera in Nairobi (Kenya), where a million people are crammed into 5% of the city area, over half of them without access to water?

In Asia, Africa and Latin America, sprawling urban areas are developing both chaotically and dangerously, sometimes on steep and unstable land and sometimes in areas close to the coast or encroaching on arid or semi-arid land. This raises serious questions regarding water supplies, stability and ground pollution due to the insufficient waste disposal - waste which is in fact often used to shore up land.

A number of natural disasters (hurricanes, floods, rising sea levels, earthquakes, landslides, etc.) show that only suitable geological approaches to these fragile areas - such as multi-risk mapping - can make it possible to evaluate and minimise these dangers.

Exportable models

A French consortium, headed by the company G2C Environment, the French National Institute for Agricultural Research (Institut national de recherche agronomique, Inra) and the consultancy firm M.E.E.D (1), is carrying out a very precise study to calculate the pressure of urban expansion on ecosystems. The chosen demonstration site lies in the port area of Marseille-Fos (FR). Modelling tools of the impact of port expansion and the city's waste on surrounding resources are currently being developed. "The case of Fos-sur-mer represents one of the typical situations found in developing countries, with considerable infrastructure and waste management programmes," notes Alain L. Dangeard, an economist and Chief Executive Officer of M.E.E.D. "The project also includes the development of decision-making tools for identifying and preserving ecological resources and the creation of a network of experts on urban models able to work on every continent. Taking the environmental dimension into account should be seen as an investment and way of combating poverty, while also taking the city-countryside interface into account."

Knowing the subsoil

A city is very dependent on its own subsoil and that of its hinterland in meeting a number of needs, such as the supply of (often underground) water, construction materials (largely of geological origin) and underground space capacity (foundations, canalisations, car parks, tunnels, storage areas). The risks linked to interaction with these subterranean areas mean that the geology must be taken into account for sustainable planning and development.

European research projects in the field of natural risks such as Armonia and LESSLOSS (6th Framework Programme), or the work of the Espon network (supported by the European Regional Development Fund), have developed innovative tools for integrating natural risks into urban planning and development.

Given that the transport of construction materials represents about one half of the tonnes/km carried by road in Europe, it is clearly important to bring the production centres for these construction materials close to the consumption centres so as to reduce CO2 emissions. This approach, which implies taking good account of knowledge of resources and protecting access to them, is an important element in a spatial planning policy that is essential to the sustainable city.

An opportunity or trap?

Anna Tibaijuka, Director of UN-Habitat,(2) believes the growth of cities to be inevitable - hence the need to "think in terms of sustainable urbanisation in the same way as one thinks of sustainable development. The city can be an opportunity for humanity or the very worst trap." If cities are indeed to prove an opportunity, they need efficient urban administrations that are ready and able to manage a number of crucial issues, such as waste, traffic, energy, access to water, construction materials, and socio-economic problems (unemployment, violence, health, drugs, ageing population, etc.).

Optimistic observers argue that cities have always been factors for growth and development - both material and cultural - offering ways out of poverty, schooling and access to health care, as well as favouring interaction and exchange. They argue that public transport can be developed (using non-polluting fuels), that energy consumption is 30 % less in grouped as opposed to isolated housing, and that solar power could be a boon to geographically favoured sites. Positive-minded sociologists point out that the inhabitants of shanty towns show "resourcefulness" and "imagination", creating sub-cultures that enable them to acquire a (relative) quality of life. Reassuring demographists also believe that the annual growth rate among the total population should end by 2010. (3)

Christine Rugemer

  1. Matières premières. Eau. Environnement. (Déchets). Développement. (Raw materials. Water. Environment.(Waste). Development.

  2. UN-Habitat, with its headquarters in Nairobi (Kenya), is the institution responsible for coordinating activities concerning human settlements within the United Nations.

  3. Reaching a fertility rate of 3.82 in Africa, 2.59 in Asia, 1.68 in Latin America, 1.06 in North America and 0.24 in Europe.

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Going underground

© Shutterstock
© Shutterstock

Montreal possesses the world's largest underground network for pedestrians (about 30 kilometres, carefully signposted), plus two metro lines. The city's universities, museums and public buildings are linked to this network (familiarly known as the Reso) which is full of shops (35 % of the city's shops), restaurants and service companies. Is this the solution of the future? Eduardo de Mulder, Executive Director of the International Year of the Planet Earth Secretariat and expert on the geosciences and urban development: "Under - ground development is a logical way to go in expanding urban centres, especially those where space is at a premium." Technically, anything seems possible underground. "Underground constructions are more durable in environmental terms and consume less energy for heating and air conditioning. They also need less maintenance, depreciate less quickly in financial terms and are safer in the event of an earthquake. On the other hand, they have to overcome problems of underground water at some sites, and special precautions must be taken for the foundations."

The vertical development of modern cities with the building of skyscrapers has its limits, while the creation of underground floors beneath the skyscrapers is justified for other reasons than stability alone. "There is a potential space for underground development, one that will be used over the coming decades. I believe that at least 25 % of the populations of megalopolises will work and travel underground. In China, about 30 million people live below ground. Human beings are able to adapt to all conditions."



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