From system ecology to urban morphology : towards a theory of urban form resilience

As cities grow in scale and complexity, the extent to which their urban forms will be able resist, adapt to or co-evolve under unpredictable circumstances and fulfil needs different from those they were originally designed for, may be crucial for the very survival of cities. In this context, the concept of resilience, originated in ecology as a way to deal with change and uncertainty in ecological systems, particularly in its ‘evolutionary’ interpretation, has gained salience in relation to urban systems where, not unlike in other kinds of complex adaptive systems, change can both be triggered by external idiosyncratic shocks and emerge gradually from internal processes of self-organisation, and is now considered as pivotal for the design and management of the built environment. Whilst several authors have tried to build a bridge between resilience thinking and urban design, the role of the morphological structure of cities in enabling or constraining resilient responses has never been addressed systematically and, indeed, evidence that the framework of evolutionary resilience can be extended to the urban form is hardly systematic. To overcome this gap, this article seeks to evidence the link between urban form and resilience theory. This is done by building a parallel between concepts, models and organisational principles developed in system ecology to explain dynamics of change in ecosystems (i.e. Adaptive Cycles, Panarchy), to analogous models developed independently in the discipline of urban morphology to describe dynamics of change in urban form (i.e. Burgage Cycle, Territorial Development Cycle, Urban Form Compositional Hierarchy). On this basis, a new theoretical model of urban form change grounded on an understanding of urban form as complex system, is formalised, substantiating the application of evolutionary resilience urban form