The City Network Is Not a Tree
Forms and typologies of the global city
Céline Rozenblat
“From this network, Christaller (1933) has defined a regularity founded on a hierarchy of the central locations…” image courtesy Céline Rozenblat
Christopher Alexander entitled one of his best-known articles A City is not a Tree (1965). He employed the metaphor to criticize the poverty of representation that stems from the human mind’s inability to comprehend and represent the complexity of the city. Urban theorists often simplify complex urban structures with tree diagrams that tend to separate elements rather than link them. In contrast, the social networks within the city interweave and overlap with no shortage of intersecting and redundant branches. It is in fact this complexity that gives rise to the richness of the city. It is composed of people and their interactions, of a combination of resources and the exercise of power (Allen, 1999).
The relationships between distant cities are fundamental in order to understand the challenge posed by economic globalization
This constituent richness of all cities can only be developed, maintained and transformed through relations with other cities. Unlike the village which capitalizes on essentially local resources (its location), the city owes its existence to the networking of distant locations, based on its geographical situation. Thus, at the core of each city, tension is generated between on one side the interactions of its inhabitants and on the other the relationships and exchanges maintained with the surrounding countryside and other cities.
Centrality: “…Paris is surely more central than London, even if the latter is the more cosmopolitan European city…” image courtesy Céline Rozenblat
Today long-distance relations between cities are of fundamental importance in understanding our cities’ role in the globalization of the economy. Cities form complex networks of social, economic, cultural and political relations. The representations that are made of them are often simplified and only show the high peaks of the “global city”, composed of New York, London and Tokyo (Sassen, 1991), which constitute a horizontal network of multiple, intense relations. In opposition to this horizontal network, the other cities of the world integrate around this system in a tree-like vertical network composed of consecutive peripheries. This opposition between a horizontal network and a vertical network corresponds more to an ideological stance that stresses the symbolic weight of the three core cities in relation to a peripheral world, than an objective representation of the world (Musso, 2003). That is why other accounts must be represented in order to supplement this simplistic view. On one hand, the centre-periphery framework outlined by Wallerstein (1980) includes multiple poles and power relations that intersect and do not define a unique hierarchy. On the other, if a hierarchy of economic power exists, this is broken down into multiple systems operating at different spatial-scale levels. In particular, continental spaces, composed of free-trade areas, determine systems that are much more integrated than the global system (Rozenblat, 2004). Some cities relay these continental systems at global level, but are not necessarily central to those systems.
“…the various relational levels are completed reciprocally and their spatial capacity may be defined as a vertical arrangement of graduated levels” image courtesy Céline Rozenblat
Thus it is no contradiction to say that, in Europe, Paris is undeniably more central than London, even though London remains the most global of European cities. The spatial integration of an archipelago of cities is implemented by relay-cities, generally from global level to local level. The large number and the overlap of these levels often justifies isolating each level.
Inter-city relations over greater or lesser distances have always existed. In the past, relations with the surrounding region or nation prevailed. Of this there remains a legacy of interrelated city distribution formed through periods of displacement, but also of local competition and complementarity. Examining this distribution, Christaller (1933) determined an ordering principle based on a hierarchical arrangement of central places. This hierarchy, based on a vertical networking of city function levels, has been the object of extensive research both in theory and in practice. However, since the 1980s this view has been largely criticized because of its simplification of city-to-city proximity relations. These days, images that pay more attention to local egalitarian initiative in the playing out of local proximities are preferred. Non-hierarchical urban groups enable local, regional and cross-border cooperative relations to be to suggested that become part of a polycentric network. Behind this polycentric vision of the system are concealed the increasingly political roles of local and regional authorities, which rebel against all-encompassing globalization.
The pattern of the european cities: “Non-heirarchized urban networks suggest cooperative relationships on the local, regional and cross-border levels, which are inscribed in a polycentric network” image courtesy Céline Rozenblat
The real test now, it seems to me, is to succeed in demonstrating that long- and short-range city networks are not in opposition. On the contrary, they develop fully at relational levels where the spatial range can provide a verticality of scalar levels. City systems effectively form complex multi-scalar networks. Their richness is to be found in their diversity of size, type and history but also, and especially, in the communication across the spatial-range levels of relations that each city makes possible. Cities are, in effect, the common nodes that bind these scales.
“Local to global” integration in large part depends on their ability to perform this role of interface and communicator between levels. Our cities should therefore encourage the flow of exchange in both directions in this local-global verticality. True urban equity lies in rendering accessible to all citizens not only the social space of the city but, more than anything else, this verticality of aperture to the world.
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Bibliography:
Alexander, C. (1966), “A city is not a tree”, in “Design”, 206, febbraio february, pp. 46-55 (già in already in “Architectural Forum”, 122/1, aprile April 1965, pp. 58-62 (I); ivi, 122/2, maggio May 1965, pp. 58-62 (II)).
Allen, J. (1999), “Cities of power and influence: settled formations”, in Allen J., Massey D., Pryke M. (eds.), “Unsettling cities”, Routledge, London-New York.
Beaverstock, J.V., Smith, R.G., Taylor P.J. (2000), “World City Network: A New Metageography?”, in “Annals of the Association of American Geographers”, 90/1, pp. 123-134.
Musso, P. (2003), “Critique des réseaux”, P.U.F., Paris.
Rozenblat, C. (2004), “Intégration dans le commerce international: l’évidence du graphique triangulaire”, in Mappemonde, 3, settembre, http://mgm.mappemonde.fr
Sassen, S. (1991), “The Global City”, New-York, London, Tokyo, Princeton University Press, Princeton [trad. it. “Città globali”, New York, Londra, Tokyo, UTET, Torino 1997]
Wallerstein, I. (1980), “Le système monde du XVe siècle à nos jours”, Flammarion, Paris [ed. or. 1974 ; trad. it. “Il sistema mondiale dell’economia moderna”, Il Mulino, Bologna 1978]
