Steps in Understanding the Role of Instability upon Urban Territorial Systems

IntroductionSystemic instability relates to the dynamic interaction of the system variables that are under the influence of an unequal cause-effect relation that results into feedbacks and amplifications that change the structure and behaviour of the system. Such systems are defined as non-linear systems (Kiel 1991) that, under the impact of instability, continue to exist in a new form of equilibrium and a superior state of organization or, on the contrary, they may face chaos and a falling state of organization. But chaos generally represents only a stage in the entire existence of a system while instability transforms it after that into a new system with a different structure and functionalities grounded on its former identity and functions.Non-linear processes represent the main drivers of territorial systems' dynamics and their analysis faces problems related to predictability, reproducibility, testability, and explainability. All these analysis prerequisites have one feature in common - instability, which is seen as the source of complexity, self-organization, and pattern formation (Langer 1980). In this way, measuring instability can represent a starting point for assessing a territorial system 's complexity, self-organization, or determination of a specific pattern (system's identity). The evaluation of specific processes in non-linear territorial systems in relation to systemic instability should be done by rather more qualitative approaches than by 'pure' quantitative ones dedicated to classical technical and exact systems (Schmidt 2011, Hellesland 2012, Chesi 2015).In order to reveal such structural changes and non-linear processes inside a territorial system, a specific theoretical framework is also needed to create the necessary conceptualizations. In this sense, the theory of dissipative structures (Prigogine and Stengers 1984, Prigogine 1997) and the theory of complexity are best suited to conceptualize such types of phenomena (Allen 1982, Arthur et al. 1997, Krugman 1997, Ciliers 1998, Martin and Sunley 2006).The theory of dissipative structures is currently part of the complexity theory while dissipative systems evolved to the complex adaptive systems that enter reconfiguration and restructuring processes as effect of the instability of systemic fluxes and relations. Dissipative structures (Prigogine and Stengers 1984, Prigogine 1997) represent open systems that exist based on the import and export of energy within the external environment (Ianos et al. 2011). So that, the system requires the entropy that is dissipated or exported back to the external environment in order to maintain its structure and functions. Dissipative structures have a strong dynamics built on vulnerability and non-linear (unstable) relations among the system components, resulting in minor changes with major impact within the system (Prigogine and Stengers 1984, Prigogine 1997).The complexity theory relates also to the non-linear dynamics of the system's components. So that the system dynamics determined by instability faces different points of equilibrium, non - predictability, inefficiency, asymmetry, lock-in situations and path dependence (Arthur et al. 1997). But the system dynamics is difficult to predict on long term as complexity involves the emergence of order as a result of auto-organization. These emergence and auto-organization processes conduct to (inconstant) resilience and adaptation along the dynamics of the system (Martin and Sunley 2010, Walker and Cooper 2011).Urban territorial systems function closely to socio-ecological systems that are founded also on an identity of their own (Cumming and Collier 2005) and their internal structure relates to the external environment while they are also vulnerable to disturbances so that they require increased adaptability and resilience (Gallopin 2006, Young et al. 2006, Zurlini et al. 2006, Stokols et al. 2013, Garmestani 2014, Sikula et al. …