Ecological vs engineering resilience

The goal of resilience is to thrive. – Jamais Cascio

Both Claire Rubin and James Brooke were kind enough to forward to me a short piece from The Conversation, by Prof A A Batabyal of RIT (nice that someone is looking out for me!). Although the short essay started by looking at “sustainability,” it was really focused on “resilience.” In particular, Batabyal contrasts “ecological” resilience against “engineering” resilience.

He uses a lake and a bridge as exemplars: the former for ecological resilience (as defined by Hollings) and the latter for engineering resilience (as defined by Pimm). The bridge has only one stable state; the lake has more than one stable states. As the Prof points out, Hollings’ definition boils down to how much stress an ecosystem can withstand before it restructures. Pimms’ definition of resilience relates to how fast a system can return to equilibrium.

The Prof then points out that most socioeconomic systems – such as communities – “exist” in multiple states. Thus, Hollings’ definition should be favored. I disagree, for several reasons.

First and foremost, Hollings’ definition and the panarchic framework it leads to is not very useful for a community trying to become more resilient. The definition requires us to observe a system under stress and then watch it change. The amount of stress needed to force the system to change is its “resilience.” If I’m a community professional, in essence this implies I have to let the community fail before I can gauge its resilience! Of course this is nonsense – but it does point to the difficulty of predicting a community’s resilience using this approach.

One of the biggest stumbling blocks is knowing whether a community has restructured. Take New Orleans after Katrina as an example. There were several differences in the Before and After:

• The city’s population dropped by a third.
• Several new civic organizations were put in place.
• There were measureable changes in the performance of important community systems (e.g., student performance improved).
• Much of the sleaze in the French Quarter disappeared.

Did these indicate a change in structure?

Then there’s the “resilience-to” problem.In practical terms, we know that a community generally doesn’t have a single “resilience.” Rather a community’s resilience depends on

• The stressor. A community may be able to deal with a great deal of economic stress, but fold like a house of cards in the face of a pandemic.
• The speed of stress. A community may be able to adapt to a high level of stress spread over time but unable to tolerate the same stress experienced as a rapid shock.
• The amount and type of damage, and the resources available for recovery.

Pimm’s concept of “engineering resilience” has the advantage of seeming more like what people think of as resilience. As the result of a Wild Thing – some sort of extreme event – a community loses capacity or functionality. Over time, the community recovers from the Wild Thing and regains its capacity. The time required to regain its functionality is the community’s resilience. Bruneau et al’s concept of resilience is very consistent with this idea.

From a community’s standpoint, community systems are either functional or failed – they either do or don’t meet the community’s demand for their function. After the damage wrought by a Wild Thing, the community at large doesn’t really care whether the health care system, or the system providing electricity are structured the same as before. They only care whether they can obtain the same (or better) health care as before the Wild Thing. They only care whether they can get light when they flip the switch, or air conditioning when it’s hot outside. Community professionals are most concerned with determining how soon after a Wild Thing the health care system is functional; how soon the lights can come back on after power is lost.

The stress testing approach* that Jennifer Adams and I have developed provides community professionals with a way to gauge this type of resilience. To summarize, community professionals postulate a particular Wild Thing – type, intensity, timing. This leads to a prediction of the damage the Wild Thing will cause. This in turn leads to a prediction of which community systems will fail. The resilience of each system is then determined by the use of dispatchable capital over time. The resilience of the community is inferred to be the resilience (time to recovery) of the last system to recover.

Community professionals and communities themselves want to know how resilient they will be to Wild Things before they occur. Simply put, Hollings’ approach to resilience may be useful in explaing what happened to a community as a result of a Wild Thing after the fact. It’s not very useful to community professionals trying to determine their community’s “recoverability” before a Wild Thing strikes. There is a certain inevitability to the “ecological” resilience approach when applied to communities. If sufficiently stressed, they will fail and restructure. When and how and to what is unanswered. Measuring the “engineering” resilience of communities using stress testing methodology gives community professionals answers they can work with, and is more intuitive. The approach can indicate paths to reduce damage and community system failures. It can also point to which additional resources could speed the community’s recovery from a Wild Thing. Ultimately, it can make recovery surer and more rapid – and communities more resilient.

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* M. J. Plodinec, “Stress Testing of Community Resilience to Extreme Events,” Journal of Homeland Security and Emergency Management, 18(2), 151-176 (2021).