Contenu du sommaire : Quel periurbain aujourd'hui

Périurbanisation is a particular feature of urban development in the coastal regions of Provence. The process has been strongly encouraged by the elected representatives of rural communities and has spread vigorously throughout the coastal hinterland. It became an important force in local development and a major election issue, leading to increasing and often incontrolled urban sprawl. In the 1990s a pro-environmental reaction stopped this "periurban slide". Today there is still strong antagonism between the protection and development lobbies.

This article presents a critical view of the city planning phases that have patterned the Montréal metropolitan area from the 19th century up until today, by focusing on the social relations with the natural environment. Montréal has manufactured an image of itself akin to other great cities, which emphasizes natural landmarks and features, agricultural activities located on its outskirts and a physical proximity to nature. Efforts to plan the development of a metropolis embedded in nature have had a slight impact. Nevertheless, a large area of the land included in the metropolitan region remains today green but under constant pressure to be urbanised. In fact, close to 60% of the Montréal metropolitan area is made up of natural or agricultural domains. However, analysis of current data seems to indicate that the distribution of such areas throughout the area reflects social and economic differences. Well- off suburbs are greener and suffer less the loss of their wooded areas.

Urban expansion is currently a major trend in most European countries and is accompanyied by the outward spread of the urban area, a process referred to in France as périurbanisation. This phenomenon questions the dynamics of these periurban territories and especially their autonomy with respect to neighbouring urban centres. We suggest that these periurban areas, through their diversity, can become independent in the face of a strong movement of unban expansion. This autonomy is expressed through development projects conceived and put in to practice locally. The environmental factor is crucial in these projects and reflects a consensual desire to enhance the quality of life. There is also a local expectation to create networks of environmental technical services. Depending on the conception of the environment, co-operation between communes ca be initiated, leading to the emergence of political leader's from certain categories of politicians.

Troughout the twentieth century, there has been a strong movement favouring urban sprawl. In France over a period of fifty years, urban development has transformed an area the equivalent of five departments. Périurbanisation, which has been encouraged by housing policies, leads to the resulting neo-rural population being highly dependent on the car. However, the dream of the detached house, with its heafthy connotations, paradoxically produces major environmental problems. Thus, photochemical pollution affects preferentially periurban zones. This is shown by the spatial analysis of the distribution of ozone during the summer in the urban areas of Lille and Lyon.

Over the last fifty years the growth of towns and cities has been characterised by the outward extension of the urban area and by its increased fragmentation and lower densities. These features are largely explained by the fact that as the distance of journeys has increased so too have travel speeds. However, if land prices represent a major factor of social différenciation in high- density urban areas, and if in periurban zones, even if land is abundant, segregation is still a feature, it is not possible to claim that access to rapid transit systems in the Ile-de-France region is a discriminatory factor. It cannot be shown either that faster journey times benefit only the more affluent members of society. From a social perspective, transport systems, through the density of their networks, have been able to compensate part of the discrimination induced by land prices. Geographically, due to shorter journey times, they hace helped to neutralise part of the "distance effect" related to périurbanisation.

The rapid transformation of metropolitan areas involves the development of new employment patterns which are modifying the traditional relations between the downtown and the suburbs. The spatial concentration of high-order economic activities in suburban centres is creating a structure and a dynamic that are very different from those of the past. Recent evidence of the generalized dispersion of employment has lead researchers to question the relevance of the polycentric model of metropolitan form that had been seen as the replacement of the monocentric model. Is polycerrtricity simply a transitory phase on the way to dispersion ? An analysis of the spatial distribution of employment in the four largest Canadian metropolitan areas, and its changes over the period 1981-1996, enables us to examine these issues, and to consider the extent to which political and cultural factors play a role in the emergence of these new models of metropolitan organisation.

The diffusion of périurbanisation in the urban areas of Dijon has varied in both space and time. This has resulted in important spatial contrasts which in part can be related to general models of urban development. Thus, the aureoled structure displayed by demographic trends is largely explained by access times to the centre. Other disparities relate more to local factors : the diversity of physical environments, the differential way in which agriculture has resisted the pressures of urban development and the proximity to secondary centres which act as ancorage points for periurban growth. These centres, however, given the attraction exerted by Dijon and irrespective of their situation, experience different pressures linked to the forces of polarisation and to the extension of the urban area.

In the Greater Lyon region, forty years of urban sprawl have not led to the decline, disappearance or weakening of the surrounding secondary urban centres. These small, peripheral towns have not lost their identity as they have been absorbed by the outward growth of the neighbouring metropolis. They still stand out in the landscape and in the minds of the population. Certain of their traditional functions have even been reinforced. Périurbanisation and the creation of new peripheral industrial and commercial poles have accompanied the strengthening of these towns as centres for the provision of household services. Thus, against expectations, these secondary centres have reinforced their role as central places, polarising to a lesser or greater extent the surrounding space.