Anastasia Touati: The political economy of densification in predominantly suburban areas: the emergence of differentiated post-suburban strategies

The aim of this thesis is to examine the processes of densification in predominantly detached-house neighbourhoods within suburban and peri-urban areas, which have so far received little attention in terms of their morphological transformations. To this end, we adopt an approach rooted in the political economy of urban production, which seeks to examine jointly the political, economic and social aspects, as well as the regulatory and technical factors, that may explain the material reality of the urban transformations observed. In this regard, we bring together two strands of research: work on territorial political economy and work on the economics of spatial planning. More specifically, the concept of post-suburbanisation—understood as a widespread process of intensive development that affects suburban areas in different ways and leads to the gradual autonomy of these suburbs from the central city of the conurbation—is at the heart of our approach.

Post-suburbanisation differs from suburbanisation, which was based primarily on extensive urban development. It therefore raises the question of densifying the low-density residential areas inherited from the suburban era. However, not all local authorities are seeking to densify; some deliberately prevent densification, whilst others, on the contrary, seek to encourage it. This leads us to formulate the central hypothesis of our work, namely that there is a link between a local authority’s post-suburban strategy and the preferred form of densification.
We have studied densification processes in predominantly detached-house neighbourhoods, in contexts characterised, amongst other things, by the existence of explicit local densification policies, in two municipalities in the Toronto metropolitan area in Canada (Guelph and Markham) and in two municipalities in the Paris region in France (Magny-les-Hameaux and Noisy-le-Grand). A comparison of the four case studies reveals two main types of densification processes: soft densification processes (Guelph and Magny-les-Hameaux), characterised by densification without a change in urban form; and strong densification processes (Markham and Noisy-le-Grand), characterised by a significant alteration of the urban form that may lead to the replacement of all or part of the pre-existing detached housing stock with apartment blocks. This is our first finding.

A detailed analysis of contextual processes and the various policies specifically aimed at densification reveals a second finding: in all four municipalities, the stated densification policies are explicitly linked to a pursuit of relative centrality. The form of densification observed within predominantly suburban areas thus appears both as a means and as a result of the degree of centrality sought by a given municipality within the post-suburban hierarchy. More specifically, in the cases studied, incentive-based policies for gentle densification are implemented in municipalities adopting a strategy of centrality with a largely local scope, which translates into a policy of moderate, mainly residential growth. Whereas strong densification policies (whether incentive-based or interventionist) are the preserve of municipalities adopting a sub-regional centrality strategy, which translates into entrepreneurial-style policies aimed at attracting households and jobs to their territory. This research also shows that whilst densification processes result mainly from market mechanisms that manifest themselves differently depending on the national urban and cultural context, the policies implemented play an important role in the creation of these land and property markets.

Finally, we identify four types of local policies aimed at increasing the density of predominantly suburban areas: incentive-based policies for gentle densification, incentive-based policies for intensive densification, interventionist policies for intensive densification, and interventionist policies for gentle densification. These different types of policies influence, in distinct ways, the form (resulting urban forms) and configuration (stakeholders involved, stakeholders affected, distribution of capital gains) of densification processes.