The two contrasting aspects of stability—essentially one that focuses on maintaining efficiency of function (engineering resilience) and one that focuses on maintaining existence of function (ecological resilience)—are so fundamental that they can become alternative paradigms whose devotees reflect traditions of a discipline or of an attitude more than of a reality of nature. As mentioned in the first post in this series, system resilience can be decomposed into two subtypes: active resilience and passive resilience. Annual Review of Ecology and Systematics 4:1-23. Two of the original examples continue to provide insights. 1992. 1984) where simplified, untouched ecological systems are imagined, or from traditions of engineering, where the motive is to design sys-. Proceedings of 1987 Crafoord Symposium. 1991. For example, is the following a resilience requirement or a robustness (fault tolerance) requirement: The system shall continue to provide service X, possibly in degraded mode, when a fault occurs in subsystem Y (adverse event). In this example, as time progresses,  a progressively smaller perturbation is needed to change the equilibrium state of the system  from one domain to the other, until the system spontaneously changes state. The second is that there is, in principle, no different way for agencies and people to manage and benefit from resource development. Energy flow, nutrient cycling and ecosystem resilience. Endothermy is a true innovation that explosively released opportunity for the organisms that evolved the ability to regulate their body temperature. maintain its functions when an attack occurs. 1. PA 15213-2612 412-268-5800, system resilience is closely related to other quality attributes, System Resilience Part 3: Engineering System Resilience Requirements, maximum acceptable level of degradation of services/capabilities, minimum acceptable availability of service/capability during adversity and prior to recovery, minimum acceptable reliability of service/capability during adversity and prior to recovery, maximum acceptable harm to asset required for delivery of service/capability, maximum acceptable adverse condition/event detection time (required to detect adversity), maximum acceptable reaction start time (time between detection and reaction to prevent further harm), maximum acceptable reaction duration time (time required to complete reaction to stop further harm), maximum acceptable recovery duration time (time between completion of reaction to completion of recovery), maximum acceptable duration of loss/degradation of services/capabilities. Chaos engineering results in more peace of mind, more resilient systems and processes, and accelerates the production use of Kubernetes for data. The recent application of “resilience” to engineered systems has led to confusion over its meaning and a proliferation of alternative definitions. System resilience requirements do not include requirements for subordinate quality attributes unrelated to maintaining specific capabilities in the face of adversities (i.e., the bottom row of the following figure). Can predators regulate small mammal populations? B. Waide, and T. F. H. Allen. On the other hand, passive system resilience can be achieved if the system is overengineered to passively avoid disruption (e.g., by having sufficient capacity that excessive loads do not result in lost or degraded capabilities). This encouraged expansion of pulp mills but left the forest, and hence the economy, more vulnerable to an outbreak that would cause more intense and more extensive tree mortality than had ever been experienced before. These differences in definition reflect which of two different aspects of stability are emphasized. 5. Topographic analogy and state space views of evolving nature. A Hierarchical Concept of Ecosystems. Droughts can no longer be sustained and the system can suddenly flip to become dominated and controlled by woody shrubs. If there is more than one objective function, where does the engineer search for optimal designs? Laxenburg, Austria. 1979. The idea behind Reliability Engineering and Resilience is to answer the safety problems concerns which may refer to a … Each mechanism is not notably efficient by itself. All rights reserved. This separation of requirements keeps the system resilience requirements at such a very high level of abstraction that they ignore quality-attribute-specific adversities. Of the cases I know well, management of the forests of New Brunswick seems most clearly to demonstrate the cycles of crisis and learning and the hesitant emergence of a more sustainable path. Walker, B. H., D. Ludwig, C. S. Holling, and R. M. Peterman. 1986. While this wa… A second approach is to have requirements that are simultaneously both resilience requirements and subordinate quality attribute requirements. Oddly, nature itself provides such counterexamples of tightly regulated yet sustainable systems in the many examples of physiological homeostasis. That surely is at the heart of sustainable development—the release of human opportunity. Similar requirements can be specified concerning adversities related to anti-tamper (e.g., attempts to remotely access critical program information), survivability (e.g., detection of threats such as enemy radar or missile lock), capacity (e.g., system approaching or exceeding its maximum capacity), and longevity (e.g., system component approaching or exceeding its design life). Holling, C.S. (1) where Po ( to) is the initial performance function before a disruptive event at time ( td ), and P ( t) is the performance quality of a system which varies with time. Alternative indices of resilience. (b) Provides an abstract state space view of a point's movement toward the stable equilibrium, with x1 and x2 defining, for example, population densities of predator and prey, or of two competitors. Successful suppression of spruce budworm populations during the 1950s and 1960s in eastern Canada, using insecticide, certainly preserved the pulp and paper industry in the short-term by significantly reducing defoliation by the insect so that tree mortality was delayed. Those are the features of adaptive environmental and resource management. Rather, destabilizing forces far from equilibria, multiple equilibria, and disappearance of equilibria define functionally different states, and movement between states maintains structure and diversity. It is those ecosystem functions and ecological resilience that provide the ecological ''services'' that invisibly provide the foundations for sustaining economic activity. The other focuses on persistence, change, and unpredictability—all attributes embraced and celebrated by biologists with an evolutionary perspective and by those who search for safe-fail designs. It is measured by the resistance of the ball to disturbances away from the equilibrium point and the speed of return to it. Within Resilience Engineering, resilience is more precisely defined as “the intrinsic ability of a system or organization to adjust its functioning prior to, during, or following changes, disturbances, and opportunities so that it can sustain required operations under both expected and unexpected conditions” (Hollnagel, 2014). Sign up for email notifications and we'll let you know about new publications in your areas of interest when they're released. The result is that the ecosystem evolves to become more spatially uniform, less functionally diverse, and more sensitive to disturbances that otherwise could have been ab-. Therefore resilience, in this case the range of internal temperatures that separates life from death, clearly does contract as variability in internal temperature is reduced, just as in the resource management cases. regulation by management where goals of operational efficiency gradually isolated the regulating agency from the things it was regulating. Ready to take your reading offline? That is, ecological resilience is reduced. This seems to define an ultimate pathology that typically can lead to a crisis triggered by unexpected external events, sometimes followed by a reformation of policy. Hence the price of reducing internal resilience, maintaining high metabolic levels, and operating. But that seems to leave an even starker paradox for management; seemingly successful control inevitably leads to collapse. That is at the heart of the role of functional diversity in maintaining the resilience of ecosystem structure and function. Ecological policy design: A case study of forest and pest management. Journal of Animal Ecology 59:1147-1164. Prod that is certainly consistent with the engineer's desire to make things work, not to make things that break down or suddenly shift their behavior. A requirement is a system resilience requirement (indicated by a gray box) if it specifies that a system shall maintain a specific level of a specific capability when faced with a specific adversity. The puzzle needs to be clarified to test its significance and generality. That would seem to be a recipe for not only disaster but a very inefficient one at that. There are indeed strong suggestions that management and institutional regimes can be designed to preserve or expand resilience of systems as well as provide developmental opportunity. For example, an employee who can maintain business as usual during a period of turbulent change such as a takeover. Those cases and their diagnoses were summarized in Holling (1986). 1994. Rare events, such as hurricanes, or the arrival of invading species, can unpredictably shape structure at critical times or at locations of increased vulnerability. Effective protection and enhancement of salmon spawning through use of fish hatcheries on the west coast of North America quickly led to more predictable and larger catches by both sport and commercial fishermen. But ascribing that designation to engineering is to stereotype the field with only one face of its activities, just as ecological resilience represents only one face of ecology. 8. Do you enjoy reading reports from the Academies online for free? Two views of a single, globally stable equilibrium. At its most basic level, system resilience is the degree to which a system continues to perform its mission in the face of adversity. The shaded area of concern in Fig. In the 1990s, James Reason moved beyond this active description to a more passive model, one that describes the evolution of failure in a system as the unanticipated alignment of weaknesses across the organisation (Figure 2). On the other hand, it is possible for other adversities to have a common cause or to have a sufficiently high probability that simultaneous occurrences must be considered. In the practice of resilience engineering, a method known as chaos engineering is one way to test resiliency: The goal of resilience engineering is to design systems to adapt in the event of failure. Oddly, the result is opportunity. 1986. bridges to ecosystem and institutional renewal (Gunderson et al., 1995), so here I will deal only with highlights. Spatial attributes are not uniform or scale invariant. Rather, productivity and textures are patchy and discontinuous at all scales from the leaf to the individual, the vegetation patch, the landscape, and the planet. Cambridge, England: Cambridge University Press. Water Resources Research 18:33-39. For each subordinate quality attribute, consider the associated types of adverse events and conditions that can harm resiliency-related critical assets. Patten, ed. (10,11) However, the majority of resilience engineering research has focused on identifying how resilience manifests in different work systems rather than on building a comprehensive readily usable toolkit for application. For example, is the following a resilience requirement or a robustness (fault tolerance) requirement: The system shall continue to provide service X, possibly in degraded mode, when a fault occurs in subsystem Y (adverse event). 292-317 in Sustainable Development of the Biosphere, W. C. Clark and R. E. Munn, eds. Figure 1. Holling, C. S. 1986. ...or use these buttons to go back to the previous chapter or skip to the next one. This led to a new law that restructured the licensing and forest management policies and freed the innovative capacity of local industries within a regional set of goals and constraints. Resilience is here the ability to return to the steady-state following a perturbation. This metaphor contains two features that were not evident in my earlier descriptions of examples of resource management. If it is assumed that only one stable state exists or can be designed to so exist, then the only possible definitions for, and measures of, resilience are near-equilibrium ones—such as characteristic return time. Approach 2 - Simultaneously Resilience and Subordinate-Quality-Attribute Requirements. System resilience requirements specify the degree to which the system shall continue to provide system capabilities in the face of adversities by detecting, reacting to, and responding to adverse events and conditions. Engineering resilience considers ecological systems to exist close to a stable steady-state. These two aspects of a system's stability have very different consequences for evaluating, understanding, and managing complexity and change. Such diversity provides great robustness to the process and, as a consequence, great resilience to the system behavior. System resilience requirements include requirements that prevent (a.k.a., avoid) adversities, passively resist adversities as well as actively detect the existence of adversities, react to detected adversities, and recovery from harm caused by adversities. Engineering resilience considers ecological systems to exist close to a stable steady-state. First, the kind of regulation is different. Ecology 61:764-771. 1995. agency staffs that budworm damage was controlled in an efficient and cost-effective manner and that there was plenty of wood available for harvest. Are there any system-external assets on which the system services depend and for which the system is responsible? Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text. Moreover, the cost of achieving that regulation requires ten times the energy for metabolism that is required by ectotherms (cold-blooded animals). Risk is the intentional interaction with uncertainty. That is quite unlike the examples of rigid. The above conclusion is based on two critical points. It also has the problem of redundant specification making it more difficult to ensure that requirements have unique requirement IDs and to trace requirements to tests (e.g., capacity, robustness, safety, security, and interoperability tests). Volume IV, pp. But there seems to be something inherently wrong with that conclusion, implying, as it does, that the only solution is humanity's radical return to being "children of nature." (One expert claims that well over 100 unique definitions of resilience have appeared.) Linking species and communities to ecosystem management. engineering resilience into such systems (Hutchison, 2018). Click here to buy this book in print or download it as a free PDF, if available. Determining the Balance Between Technological and Ecosystem Services, A Scalar Approach to Ecological Constraints, The National Academies of Sciences, Engineering, and Medicine, Engineering Within Ecological Constraints, Engineering Resilience versus Ecological Resilience, A Perspective on the Relationship Between Engineering and Ecology, Designing Sustainable Ecological Economic Systems, Ecological Integrity and Ecological Health Are Not the Same, Ecological Engineering: A New Paradigm for Engineers and Ecologists, Engineering for Development in Environmentally Sensitive Areas: Oil Operations in a Rain Forest, Lessons in Water Resource and Ecosystem Regulation from Florida's Everglades and California's Bay/Delta Estuary, Engineering Studies Based on Ecological Criteria, 'Do No Harm': A New Philosophy for Reconciling Engineering and Ecology, Ecological change is not continuous and gradual; Rather it is episodic, with slow accumulation of natural capital such as biomass or nutrients, punctuated by sudden releases and reorganization of that capital as the result of internal or external natural processes or of man-imposed catastrophes. Waide, J. 7. As Figure 1 shows, the costs of some of these disasters in the United States alone can be staggering. Cambridge, England: Cambridge University Press. Similarly, what critical system data must be protected in terms of availability, confidentiality, and integrity? What are the maximum acceptable amounts of harm that adversities can cause to assets needed for maintaining critical capabilities and services? Those are the features missing in the descriptions I presented of traditional, piecemeal, exploitive resource management and its ultimate pathology. Freshwater acidification, reversibility and recovery: Comparisons of experimental and atmospherically-acidified lakes. There are three schools of thought regarding the overlapping of resilience requirements with requirements of other quality attributes: The figure below illustrates the MITRE approach to system resilience requirements [MITRE 2019]. Once requirements engineers specify the high-level resilience requirements, they derive multiple subordinate-quality-attribute requirements from these resilience requirements. System resilience at a deeper level is therefore the degree to which a system rapidly and effectively protects itself and its continuity-related assets from harm caused by adverse events and conditions. At least some aspects of ecologically resilient control are equally familiar to the control engineer, for operation at the edge of instability is characteristic of designs for high-performance aircraft. Jump up to the previous page or down to the next one. Schindler, D.W. 1993. From its conceptual discussions to the practical experience reflected in case studies, this volume will be important to policymakers, practitioners, researchers, educators, and students in the fields of engineering, environmental science, and environmental policy. Reputational risk, risk of financial losses, business continuity, and failure to evolve are all types of risk which impact organisations today. How can we transfer ecological principles to economic systems? New York: Columbia University Press. 1977. Having built the foundations of chaos engineering into individual businesses, Andrus has brought resilience-focused engineers from firms including Amazon, Netflix, Google, and Dropbox to make building resilience a software development industry best practice. What types of adverse conditions and events can cause unacceptable critical services and capabilities to be lost or significantly degraded? Based on the maximum acceptable harm to critical assets, develop high-level system resilience requirements. Railway system can seemingly successful control inevitably leads to long-term edge of instability is more than one equilibrium in. Munn, eds dublin, H. H. Shugart, and J. Roughgarden ( Pimm.! 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