What is Resilience?

Excerpts from the book

Confronting Complexity

X-Events, Resilience, and Human Progress


John L. Casti

Roger D. Jones

Michael J. Pennock



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In the summer of 1973, one of us (JC) took a position as one of the first scientists at the International Institute for Applied Systems Analysis (IIASA), located at a former hunting palace of the Austrian Empress Maria Theresa, just a few miles south of Vienna in the village of Laxenburg, Austria. IIASA was a joint venture of the US National Academy of Sciences and the Soviet Academy of Sciences, with several junior partners, the countries of eastern and western Europe, along with Canada and Japan. The research structure of the Institute was set up along the lines you’d find in a university, except that the “depart- ments” had names like Energy, Urban Studies, Water Resources, Methodology, and so forth, reflecting the fact that IIASA was set up to study questions common to the industrialized countries of the world.

One of the IIASA projects at that time was Ecology, which was headed by C.S. (“Buzz”) Holling, who we met in the first chapter. Holling was a profes- sor of ecology at the University of British Columbia in Vancouver, Canada. Holling arrived with a team of professors and graduate students, all focused on understanding the system-theoreti nature of ecological processes. Earlier that same year, Holling had published a path-breaking article, “Resilience and Stability of Ecological Systems,” which sparked off the interest in the idea of system resilience that is so topical nowadays. So it’s fair to say that this paper, together with the work begun at IIASA at that time, was the forerunner of the “resilience revolution” we see in the media and on the Internet today.

Formally, JC was a member of the Methodology Project, whose mission was to provide mathematical modeling and computational support to the applied projects. He soon gravitated to a collaborative mode with the Canadian ecologists, a collaboration that lasted several years. At the time, JC had just completed his doctoral dissertation on the stability theory of control systems, so was well-positioned to see the relevancy of resilience as a new system concept, one differing in important ways from the more classical notion of stability as understood by control and dynamical system theorists.

The traditional concept of stability was the idea that if a system is perturbed from its current equilibrium position, it’s stable if it eventually returns to that very same equilibrium. More prosaically, a system is stable if any disturbance from its current state eventually washes out and the system eventually returns to that state. This was the idea in JC’s head when he ran into Holling. But he soon learned that there was more on heaven and earth than were dreamed of in his mathematical philosophies!

In numerous conversations with Holling over the next couple of years, JC came away with the idea that simple stability, mathematical-style, was totally inadequate to encompass the concept of resilience. According to Holling, a resilient system wasn’t necessarily stable at all. Rather, it was a system that could “roll with the punches,” so to speak, and continue to perform its function. Moreover, the resilience allowed the system to even change its function as its operating environment dictated, so as to enhance its survivability. JC finally saw the light, realizing that resilience was a new concept in the system theorist’s arsenal of weapons for understanding the behavior of the natural world. Now let’s fast-for- ward a few decades and look at what researchers see today as a resilient system.

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The word “resilience” most likely entered the English language via the Latin verb resaltare, meaning to rebound or bounce back. But as we noted above, in today’s world the word is used in a multitude of ways, all of which revolve about the idea of adjusting and adapting to changing circumstances. Note how this differs from the simple notion of stability described earlier. Stability refers to a system that only changes its behavior in reaction to changed circumstances, but does not change its underlying structure at all. It remains the very same system as it was prior to the disturbance. In Holling’s work and most of what we see today going under the rubric of resilience, an essential part of a system being resilient is that it be able and ready to restructure and reconfigure itself in reaction to a changing environment. All this being said, the word resilience is still used in slightly different ways in different settings. Let’s look at a few of them outlined by Loup Francart in his very illuminating article, “What Does Resilience Really Mean?”

Psychology: The capacity of a person to carry on in an environment that would normally lead to a mental breakdown. In other words, resilience is the capacity to confront trauma without being later affected by it.

Economics: An economy is resilient if it can regain the ability to grow after a crisis. Biology: An organism’s ability to survive in a changing environment and overcome attacks by predators.
Ecology: The ability of an ecosystem to maintain its function in the face of a possibly unexpected disturbance.
Organizations: A firm is resilient if it has the ability to restructure itself so as to withstand a shock, and possibly even be stronger afterwards.
Societies: The capacity of a society to overcome the consequences of an attack while preserving the societal culture.
Geopolitics: The ability to reduce risk from emergencies so that people can go about their business freely and with confidence.

Francart notes that the terminology is now so widespread that even mattress manufacturers use the word to describe the ability of their mattresses to recover their original shape after someone lying on them gets up!


What is the common element in each of these semi-metaphorical uses of the term? Basically, what links each definition is that there must be some kind of shock or crisis, what we are calling an X-event, constituting a major change in the way the system goes about its business. Generally, the X-event overturns previous assumptions about the world and the way the system functions, often accompanied by new uncertainties and dangers.

Putting all these factors together, we will use the following definition of resilience in what follows in this chapter. For simplicity, we’ll call it the Four As:

Awareness—A resilient system should be monitoring early-warning signals for X-events, and be able to take action to “batten down the hatches” if the X-event seems imminent;

Assimilation—A resilient system will be able to survive the X-event. Maybe the survival will be by resistance to the event, maybe by absorbing the shock into the system’s operation, or through some other survival mechanism. But survival is a necessary condition for being resilient;

Agility—A resilient system is able to survey the new landscape that the X-event creates and have the ability to evaluate its resources and see how to deploy them to fill one or another of the new niches that the event opens up;

Adaptivity—The resilient system should be ready to change its way of doing business if it finds that a new niche offers greater potential for growth, development, and survival than its pre-shock activities.

Since the sine qua non of the entire notion of resilience rests upon the occurrence of an X-event, and since there are many, many different types of X-events, it follows that any idea of system resilience is necessarily context-de- pendent. A system may be very resilient to, say, the shock of an earthquake but totally vulnerable to the shock of a solar storm. Thus, in order to properly speak about the “resilience” of a system, we are tacitly assuming that what, precisely, the X-event is that the system is resilient against. And any notion of measuring the overall resilience of a system must take into account a spec- trum of different sorts of X-events that it may experience.

As an X-event itself is, by definition, rare and surprising, it’s a pretty tricky business creating the infrastructure needed to be resilient against all such contingencies. In fact, it’s impossible. Just like buying insurance, you can protect yourself against some types of unknown unknowns, like heart attacks and stroke but not against Ebola fever or a rare blood disease. In fact, it’s flat out impossible to buy insurance against every possible illness or accident that may befall you. So let’s revisit yet again, but briefly, the notion of an X-event and examine different aspects for building in protection against one.

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