Modelling urban networks at mega-regional scale: Are increasingly complex urban systems sustainable?

Are the dynamics of mega-regions sustainable or not? We explore the hypothesis that increasing complexity in mega-regions implies less demands on resources needed to generate organized information, thereby making the systems more efficient and stable. This article aims to identify structural indicators for measuring urban networks at the mega-regional scale. We use night-time light data from the broad band near-visible infrared channel of the DMSP-OLS to monitor the dynamics of urbanization. We study the urban networks as graphs, where nodes are cities, and the main road and railway infrastructures represent the edges. We propose four indicators for measuring the complexity, polycentricity, efficiency and stability of networks of cities. These indicators are derived from studies and approaches such as the use of graphs and small-world networks that other authors have carried out to explain similar structures. In the article we apply the structural indicators to 12 European mega-regions. The main conclusion is that mega-regional urban systems respond to increasing complexity by adapting their relational structures to become more efficient and stable, and become more sustainable forms of organization. Consequently, it could be necessary to re-direct land use policies towards improving sustainability at the level of the mega-region.