By way of the networks that develop among them and are driven by them, cities contribute to organising space across the world. This is true on all scales, whether with respect to the lives of the inhabitants, the outcomes of the regional or national territories, or the political and economics systems of organisation arising from financial, cultural or information flows. Cities are never in a state of isolation, they evolve in interdependent manner. These complex systems are largely self-organising, but they are also oriented in their evolution by the dynamics of path-dependency (the historical chain of events). In this area of research, the PARIS team is working on an evolutive theory of the city system making it possible to explain the differences that are observed between the different city systems across the world, and also to suggest possible scenarios for future developments, to provide better understanding, and to anticipate trajectories for given cities.
The theoretical construction of this project is grounded in the observation and modelling of the dynamics of city systems in a “complex system” perspective by way of epistemological consideration of the different models, and interdisciplinary collaboration. This involves considerable work on spatial and temporal harmonisation of databases on cities, with a view to effecting historical comparisons across the globe. Interdependencies among cities arise from social interactions, in particular those that accompany changes in mobility patterns, and to study them enables better apprehension of the dynamics of flows, networks and hierarchical re-organisation. Using concrete examples, this approach thus casts light on the shift from the intra and extra-urban sphere towards interconnection between cities and city networks.
The dynamics of city systems, in a “complex system” perspective
The theory is constructed by confronting observations derived from comparative analyses with concepts and models brought in from more formalised sciences (mathematics, physics, computer sciences) and this in turn enriches a scientific approach to complex systems that also includes historical, social and spatial processes. This work leads on from work already conducted on simulating the evolution of city systems using multi-agent systems via the Eurosim and Simpop2 models, on scaling laws and their relationship with cycles of urban economy, and on models for urban growth that integrate spatial interactions, and models for analysing complex networks.
The spatial and temporal harmonisation of city databases with a view to historical comparisons across the world
The development of evolutionary urban theories requires definition of relevant and coherent urban entities to enable comparative analyses in time and space. Thus the construction of spatio-temporal urban databases is essential. Regions that are representative of the diversity of urban typologies across the world have been selected: Europe, South Africa, India and the USA. Data models are being constructed to develop and manage these databases that are multi-level, dynamic, and multi-sourced. A more specific aim is to explore recent urban data for Europe, in interaction with comparative analysis research and modelling.
Flows, networks and hierarchical reorganisation
To compensate for the scarcity of empirical data on the interactions that reorganise city systems, surveys have been conducted on mobility patterns, and on the contribution of new mobility patterns to the networking of cities in Europe. In addition, work is ongoing on student mobility, and the research networks implicated in converging technologies (NBIC). The results should enable better interpretation of these phenomena in the framework of polycentric theory, already widely explored in earlier research.
The articulation between cities and city networks
A first image of the situation of a given city in an overall structure of urban hierarchies and specialisation is classically provided by multivariate analysis of numerous attributes of cities. The evolutionary theory sets out to complete this description by the description of spatio-temporal interactions between the outcome of a city and that of other cities, in the form of exchanges and flows within an integrated territory. The research concerns the relative position of French cities according to indicators for pollution and health. It also aims to capture functional reorganisation occurring in relation to changes in capital city in certain European countries, and more generally the way in which the internal morphology of cities articulates with the shape of the city system.