Community Resilience to Climate Change: Theory, Research and Practice

64 1.1. Understanding Resilience: Four Academic Domains The word resilience originates from the Latin word “resiliō” meaning to “spring back.” Resilience generally refers to the ability of a system to withstand an array of shocks and stresses. Within the literature, resilience has overlapped with concepts such as stability and robustness [6] and is considered a complementary approach to sustainability [7,8]. Definitions of resilience are grounded in a diverse array of disciplinary perspectives. While the definitions of resilience across domains overlap, it is important to explore the differences in how resilience is framed in each individual domain. This allows one to grasp how resilience definitions may shape policy and professional efforts to adapt the building stock to climate change. A review of the literature has identified four main academic domains of resilience: ecology, engineering, disaster risk reduction, and the social sciences. 1.1.1. Ecology Perhaps the most prominent researcher on resilience is Holling, who introduced the concept of resilience to the field of ecology in 1973. Holling defines resilience as a, “measure of the persistence of systems and of their ability to absorb change and disturbance and still maintain the same relationships between populations or state variables” [9]. In this definition, ecological systems are viewed as having multiple equilibrium or stable states; ecological resilience examines the threshold required to move a system from one equilibrium state to another [10,11]. In recent years, literature on ecological resilience has explored notions of constantly changing systems, or nonequilibrium systems. As such, resilience reflects a process of continuous adaptation to stresses and disturbances rather than an attribute or outcome. Nonequilibriumnotions of resilience shift from reinforcing the ability to bounce-back towards exploring opportunities for transformation and change or “bouncing forward.” This literature also acknowledges interactions between social and ecological systems. This conception of resilience in the ecological domain was essential to understanding change in social-ecological systems (SES). Resilience in SES is defined as, “the capacity of linked social-ecological systems to absorb recurrent disturbances such as hurricanes or floods so as to retain essential structures, processes, and feedback … the degree to which a complex adaptive system is capable of self-organization (versus lack of organization or organization forced by external factors) and the degree to which the system can build capacity for learning and adaptation” [12]. In this way, resilience in the ecological domain also embraces a potential for change and highlights the capacity of systems to reorganize. Disturbances can create (or force) opportunities for decision-makers and stakeholders to innovate and adapt [13]. Ecological resilience addresses both acute and chronic stresses, meaning it does not focus primarily on temporary disturbances, but requires a shift in practices that respond to long term impacts and chronic vulnerabilities within a system. 1.1.2. Engineering Engineering resilience describes the capacity of a system to withstand disturbances and return to a steady state. To engineers, systems have only one equilibrium state that they return to after a shock or disturbance. Engineering resilience thus emphasizes a system’s resistance to disturbances, the speed of return to a resilient state, and its overall ability to bounce back [4,11]. This contrasts with the concept of ecological resilience which recognizes systems as having multiple states of equilibrium. Generally, engineering resilience is appropriate when a stable state is desired; the bearing capacity of building foundations and the robustness of a building’s structure are examples. While engineering resilience has limitations in capturing the dynamics of a system under stress, because the desired state is defined, the operationalization of resilience may be easier to attain [14]. In the built environment, the idea of recovery and bouncing back, or engineering resilience, underpins many resilience efforts and is well-represented in government documents [2]. For example, the Department of Homeland Security defined resilience as, “the ability to adapt to changing conditions and withstand and rapidly recover from disruption due to emergencies” [15]. However, recovery to the norm and speed of return alone are not sufficient measures of resilience [16]. Generally, single-equilibrium viewpoints do not adequately account for multiple pathways that retain essential structures within a system [16]. These other resilience strategies may be better explored under a disaster risk reduction or social science-based approach. 1.1.3. Disaster Risk Reduction While engineering and ecological resilience are dominant domains of resilience [11,13], resilience has been growing in other fields, notably disaster risk management/reduction and the social sciences. A disaster-risk reduction approach, like engineering, generally adopts a single-state equilibrium viewpoint of resilience [10]. Resilience in the disaster risk reduction domain attempts to quantify the probability of a hazardous event and understand internal and external vulnerabilities of cities/communities/buildings, and measures