Community Resilience to Climate Change: Theory, Research and Practice

51 steady state and is defined as the amount of disturbance that a system can absorb before changing to another stable regime, which is controlled by a different set of variables and characterized by a different structure. It has been termed ecosystem resilience (Gunderson and Holling 2002) and it is applied almost interchangeable with the words ecological resilience (e.g., Holling 1996, Holling et al. 1997, Gunderson 2000, Gunderson and Pritchard 2002, Anderies et al. 2006) or resilience (e.g., Holling 1973, 1986, Arrow et al. 1995, Perrings et al. 1995, Carpenter and Cottingham 1997, Carpenter et al. 2001, Walker et al. 2002, 2004, Bellwood et al. 2004, Folke et al. 2004, Carpenter and Folke 2006). It is this second kind of resilience to which we refer in this text. The result of our analysis is displayed in Table 1. It shows 3 categories, 10 classes, and correspondingly 10 definitions of resilience. The three categories reflect whether the definition is in accordance with either a genuinely descriptive concept (Category I), a hybrid concept, in which descriptive and normative connotations are intermingled (Category II), or a genuinely normative concept (Category III). Thus, our scheme in the first place emphasizes the degree of normativity included in the different definitions that fit under the overall category of resilience as characterized above. However, we also found it useful and necessary to distinguish between purely ecological definitions, i.e., Class 1–4, and those which are also used in the context of other fields such as economy and sociology, i.e., Class 5–10. In the following, each definition of resilience is explained in more detail with respect to its category and class, respectively. Note that the proclaimed titles do not correspond to the particular references. Category I: Descriptive concept Sub-category Ia: Ecological science Class 1: Original ecological definition In his seminal paper, Holling (1973) 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” (Holling 1973:14). In this original- ecological meaning, resilience focuses on the persistence of populations or communities at the ecosystem level and corresponds to both the overall area and the height of the lowest point of a population’s domain of attraction. A relative measure is a population’s probability of extinction. Class 2: Extended ecological definition Subsequent work published from the late 1980s (Holling 1986, 1996, Walker 1999, Gunderson 2000, Gunderson and Holling 2002, Gunderson and Pritchard 2002, Walker et al. 2002, 2004) is strongly influenced by theory on complex adaptive systems (e.g., Levin 1998) including the cross-scale morphology of ecosystems (Holling 1992). According to the extended keystone hypothesis originally proposed by Holling (1992), the hierarchical structure of ecosystems is primarily regulated by a small set of plant, animal, and abiotic processes each operating over different scale ranges. Important changes in ecosystem dynamics can be understood by analyzing a few, typically no more than five, key variables (Walker et al. 2006). In this interpretation, the scientific focus is on the critical structure and processes of an ecosystem. Individual species can be replaced if the critical structure and key processes persist (Walker et al. 1999, Elmqvist et al. 2003, Nyström 2006). In this extended-ecological meaning, resilience is defined as “the magnitude of disturbance that can be absorbed before the system changes its structure by changing the variables and processes that control behaviour” (Gunderson and Holling 2002:4) or “the capacity of a system to experience shocks while retaining essentially the same function, structure, feedbacks, and therefore identity” (Walker et al. 2006:2). Class 2a: Three characteristics Some authors interpret the extended-ecological meaning as comprising three characteristics. Those are: (1) the amount of change a system can undergo and still remain within the same domain of attraction, i.e., to retain the same controls on structure and processes; (2) the degree to which the system is capable of self-organization; and (3) the degree to which the system expresses capacity for learning and adaptation (Carpenter et al. 2001, Walker et al. 2002, Folke 2006). Class 2b: Four aspects One line of research emphasizes the concept of alternative stable regimes (Scheffer and Carpenter 2003, Folke et al. 2004, Walker and Meyers 2004). Note that the term “regime” is preferred to avoid the static connotations of the term “state” and to describe the actual dynamic situation of a specified ecosystem (Scheffer and Carpenter 2003). Formally, alternative stable regimes exist within alternative basins of attraction (Walker et al. 2004). Four aspects of a basin of attraction are crucial. Those are: (1) latitude or the maximum amount the system can be changed before losing its ability to recover, e.g., the width of the basin; (2) resistance, which matches the ease or difficulty of changing the system, e.g., the topology of the basin; (3) precariousness, i.e., the current trajectory of the system and proximity to a limit or threshold; and (4) cross-scale relations, or how the above three aspects are influenced by the dynamics of the systems at scales above and below the scale of interest (Folke et al. 2004, Walker et al. 2004).