More than 1300 cities have already signed

In Copenhagen, in December, the optimism of the local elected officials contrast with the clashes of their national representatives on the future of the fight against climate change. The Governor of California, Arnold Schwarzenegger, to the mayors of Paris, Mexico City, São Paulo, Toronto, London and New York, each aedile promised to hire ambitious territorial policies to reduce greenhouse gas emissions. Half of the world's population lives in the city and the pace of urbanization in Asia, Africa and Latin America is equivalent to the construction of a city of 1 million people a week... Also, the reflection on the "sustainable" development becomes critical. As urban growth is more drawn by the multiplication of slums that by planning, which leads to enhance segregation social and space, while the cities already consume more than three quarters of resources of the planet and reject 75 of the emissions of carbon dioxide (CO2).

However, the fight against greenhouse gas emissions has a common enemy with policies to fight against inequalities: urban sprawl! The poor live far from the centre, less their chances for employment, health and education d'accéder is great, at least for the municipality put in place of collective transport efficient and far from le de le,, à moins que la municipalité ne mette en place des transports collectifs efficaces et loin de le, plus les pauvres habitent loin de le centre, moins leur chance d'accéder à l' emploi, à la santé et à l' éducation est grande, à moins que la municipalité ne mette en place des transports collectifs efficaces et loin de le, que municipalité en place que municipalité que municipalité in place The city lies, more carbon footprint increases. As China and the India will develop a model urban European type (compact, sobre energy) or American (spread, energy-intensive), global emissions of CO2 will be more or less mastered.

In France, a household that resides on the outskirts consumes three times more energy to move only one household in dense zone. "He must leave the urban extension to go towards a recycling planning," advocates Vincent Fox, who denounced the urban sprawl. Densify the city, the issue is critical, because technical solutions such as the insulation of buildings or the development of clean urban transport are expensive and not enough to catch up with a poor urban form. But the density is not synonymous with the construction of towers or large sets, which claim of extensive access infrastructure.

Exchanging experiences

The laboratory of urban morphologies of the CSTB so calculated that, despite their 40-storey towers, many neighbourhoods of Hong Kong are finally less dense than the haussmannian Paris. Among the various forms of habitat, the European model with islands of 3 to 6 floors in a continuous urban fabric around streets of average size shows less greedy energy. Indeed, the capitals display balance of CO2 emissions per capita (see table below) average European General. In recent years, local authorities have become aware of their carbon footprint and organize network to exchange experiences. "Without the mobilization of the territories, which can give a decisive boost on at least 50 of the energy consumption of a city, States fail to achieve their goals of reducing gases greenhouse", says Ronan Dantec, Deputy Mayor of Nantes and co-Chair of the climate of Eurocities. The Convention of mayors launched in February 2009 by the European Commission calls local to submit climate action plans which aim in 2020 than the 20 emissions reductions promised by the European Union. More than 1,300 cities have already signed. However, they claim financial assistance as a bonus to the interest rate of the European Investment Bank for their projects or to amounts that will be thrown by the future auction of permits for the emissions of industry in Europe.