رابطه بین انعطاف پذیری و پایداری سیستم های اقتصادی زیست محیطی

Resilience as a descriptive concept gives insight into the dynamic properties of an ecological-economic system. Sustainability as a normative concept captures basic ideas of intergenerational justice when human well-being depends on natural capital and services. Thus, resilience and sustainability are independent concepts. In this paper, we discuss the relationship between resilience and sustainability of ecological-economic systems. We use a simple dynamic model where two natural capital stocks provide ecosystem services that are complements for human well-being, to illustrate different possible cases of the relationship between resilience and sustainability, and to identify the conditions under which each of those will hold: a) resilience of the system is necessary, but not sufficient, for sustainability; b) resilience of the system is sufficient, but not necessary, for sustainability; c) resilience of the system is neither necessary nor sufficient for sustainability; and d) resilience is both necessary and sufficient for sustainability. We conclude that more criteria than just resilience have to be taken into account when designing policies for the sustainable development of ecological-economic systems, and, vice versa, the property of resilience should not be confused with the positive normative connotations of sustainability.

Speaking about resilience and sustainability is speaking about two highly abstract and multi-farious concepts, each of which has a great variety of interpretations and definitions. Here we adopt what seems to be the most general and at the same time most widely accepted definitions of resilience and sustainability.1 We understand sustainable development as the Brundtland Commission defines it as “development that meets the needs of the present without compromising the ability of future generations to meet their own needs” (WCED, 1987). In this definition, sustainability is a normative concept capturing basic ideas of intra- and intergenerational justice.2 Concerning obligations towards future generations, the primary question of sustainability then is to what extent do natural capital stocks have to be maintained to enable future generations to meet their needs.3 In contrast, resilience is a descriptive concept. In a most common definition that goes back to Holling (1973), resilience is thought of as “[…] the magnitude of disturbance that can be absorbed before the system changes its structure by changing the variables and processes that control behavior” (Holling and Gunderson, 2002: 4). The underlying idea is that a system may flip from one domain of attraction into another one as a result of exogenous disturbance. If the system will not flip due to exogenous disturbance, the system in its initial state is called resilient. Although Holling-resilience can be quantitatively measured (Holling, 1973), we focus on the qualitative classification, where a system in a given state is either resilient, or it is not.4 In the literature, many connections have been drawn between resilience and sustainability (e.g. Folke et al., 2004, Walker and Salt, 2006 and Mäler, 2008). In some contributions, resilience is seen as a necessary precondition for sustainability. For example, Lebel et al. (2006: 2) point out that “[s]trengthening the capacity of societies to manage resilience is critical to effectively pursuing sustainable development”. Similarly, Arrow et al. (1995: 93) conclude that “economic activities are sustainable only if the life-support ecosystems upon which they depend are resilient”, and Perrings (2006: 418) states that “[a] development strategy is not sustainable if it is not resilient”. Some authors explicitly define or implicitly understand the notions of resilience and sustainability such that they are essentially equivalent: “A system may be said to be Holling-sustainable, if and only if it is Holling-resilient” (Common and Perrings, 1992: 28), or similarly: “A resilient socio-ecological system is synonymous with a region that is ecologically, economically, and socially sustainable” (Holling and Walker, 2003: 1). Levin et al. (1998) claim in general that “[r]esilience is the preferred way to think about sustainability in social as well as natural systems”, thus also suggesting an equivalence of resilience and sustainability. In contrast to this view, it has been noted that “[r]esilience, per se, is not necessarily a good thing. Undesirable system configurations (e.g. Stalin's regime, collapsed fish stocks) can be very resilient, and they can have high adaptive capacity in the sense of re-configuring to retain the same controls on function” (Holling and Walker, 2003: 1). In other words, resilience is not sufficient for sustainability, and it can therefore not be taken as an objective of its own. While systems with multiple stable states are widely discussed, a systematic analysis of the relationship between the concepts of resilience and sustainability in a system with multiple stable states has not yet been conducted. To illustrate this research gap, the statements quoted above do not take into account the following possibilities: if some particular management does not conserve a system's resilience, such that under exogenous disturbance the system may flip from an undesirable state into a desirable one, or from a desirable state into another desirable state, the system management might still achieve sustainable development of the system, even though it is not resilient. As a consequence, one may conclude that resilience is neither desirable in itself nor is it in general a necessary or sufficient condition for sustainable development. In general, four relationships between resilience and sustainability are logically possible, and any of those may hold in a given system: a) resilience of the system is necessary, but not sufficient, for sustainability; b) resilience of the system is sufficient, but not necessary, for sustainability; c) resilience of the system is neither necessary nor sufficient for sustainability; and d) resilience of the system is both necessary and sufficient for sustainability. In order to clarify and illustrate the different possibilities, and to identify the conditions under which each of those will hold, we use a simple dynamic ecological-economic model where two natural capital stocks provide ecosystem services that are complementary in the satisfaction of human needs. This model is not meant to represent a real ecological-economic system, or to give a fully general representation of ecological-economic systems. Rather, it is meant to illustrate the complexity of relationships between resilience and sustainability even in a simple dynamic model. In contrast to other models used to study resilience of ecological-economic systems, such as the shallow lake model (e.g. Scheffer, 1997 and Mäler et al., 2003) or rangeland models (e.g. Perrings and Stern, 2000, Anderies et al., 2002 and Janssen et al., 2004), it features more than two domains of attraction and the possibility of more than one desirable state. In traditional models of bistable systems only two relationships of resilience and sustainability are possible: (i) the system is resilient in a desired state, such that the system's resilience has to be maintained for sustainability; and (ii) the system is resilient in its current state which is, however, not a desired one, such that resilience prevents sustainability. A situation in which the system is not resilient in a desired state but nevertheless on a path of sustainability cannot – by construction of these traditional models – possibly occur. Our dynamic model, as simple as it is, overcomes this shortcoming and may therefore add another valuable dimension to the model-based study of resilience and sustainability. The outline of the paper is as follows. In the following section, we present the model (Section 2.1), analyze its basic dynamics (Section 2.2), introduce formal definitions of resilience and sustainability (Section 2.3), and discuss the possible relationships between resilience and sustainability (Section 2.4). In Section 3, we discuss our findings and draw conclusions concerning the sustainable management of ecological-economic systems.

In this paper, we have studied how, in general, resilience is related to sustainability in the development of an ecological-economic system. Resilience is in the first place a purely descriptive concept of system dynamics. In contrast, sustainability is a normative concept capturing basic ideas of intergenerational justice when human well-being depends on natural capital and services. Thus, resilience and sustainability are independent concepts characterizing the dynamics of ecological-economics systems. We have distinguished and specified four possible relationships between resilience and sustainability: a) resilience of the system is necessary, but not sufficient, for sustainability; b) resilience of the system is sufficient, but not necessary, for sustainability; c) resilience of the system is neither necessary nor sufficient for sustainability; and d) resilience of the system is both necessary and sufficient for sustainability. All of those are logically possible, and any may hold in the simple dynamic ecological-economic model that we have presented here, depending on the initial state of the system, the normative sustainability threshold, and the uncertain disturbance to the system. The result that there are four potential relationships between resilience and sustainability has a much broader validity and generally holds for all systems with more than two domains of attraction. Generalizing from our particular model, we conjecture that the following holds. If the sustainability set is a subset of the domain of attraction and the system initially is in the sustainability set, resilience of the system is necessary for sustainability. Resilience is sufficient for sustainability, on the other hand, if the entire domain of attraction in which the system initially is, is contained in the sustainability set. Finally, resilience and sustainability are equivalent if the domain of attraction in which the system initially is coincides with the sustainability set. All taken together, in general the deduction from sustainability to resilience, or vice versa, is not possible. This has implications for the sustainable management of ecological-economic systems. In particular, the property of resilience should not be confused with the positive normative connotations of sustainability, and, vice versa, more criteria than just resilience have to be taken into account when designing policies for the sustainable development of ecological-economic systems. Rather, for the sustainable management of an ecological-economic system it is decisive to know (1) the current state of the system, (2) the domains of attraction of the system, (3) the sustainability norm and the associated sustainability set in state space, and (4) the potential extent of disturbance.