Is your system as resilient as nature’s?
My good friend John Peterson, founder of Public Architecture, asked me the other day what lessons nature had for those working to increase resilience in city infrastructure. I mumbled something incoherent as we ran up our usual Marin Headlands trail, and I hope he blamed my declining state of cardiovascular fitness for the muddled answer. I’ve given the question a little attention since, however, and here’s what I’ll try to convince him I said.
A biological approach to design: Two departure points
I’m sure it’s amusing to professional ecologists to hear the term “resilience” bandied about so gratuitously by generalist designers like me, and I’m also sure that there is some wincing on their part over how we interpret the term. C.S. Holling, emeritus eminent scholar and professor in ecological sciences at the University of Florida, is largely credited with introducing it in a 1973 article in the Annual Review of Ecology and Systematics, “Resilience and the Stability of Ecological Systems.” In it he defined what has now become known as “ecological resilience” as “the capacity of a system to absorb disturbance and reorganize while undergoing change so as to still retain essentially the same function, structure, identity, and feedbacks.”
What the definition says is important, but what it does not say is of equal note. For example, it does not say that the system has to return to its original state, but rather to performing its core functions with comparable form and behavior patterns intact. This is important because it means that multiple stable states are possible.
This is, perhaps, the first, broadest lesson for designers and urban planners: They are not looking for one answer when developing systems with resilience. Broad as the lesson is, it translates down to the smallest detail as designers search for the conditions conducive to multiple successful states, rather than winnowing out the best static alternate plan. It is more like gardening, if you will, than house building. A simple model might be the micro-financing of small craft businesses and the connecting of those producers and their goods with a wider world market. There are many paths to success, but the basic requirements of startup capital and a more reliable chance to profit are what these programs focus on.
Holling and others describe four key characteristics of resilience:
1. Latitude: the maximum amount a system can be changed before losing its ability to recover (before crossing a threshold irrevocably). Material engineers might call this “durability” in, say, a material that can be stretched (stressed) only so much before losing its shape and integrity (strained).
2. Resistance: the ease or difficulty of changing the system; how resistant it is to being changed. This might be called “strength” in material terms, as materials resist different forces acting upon them to greater or lesser degrees.
3. Precariousness: how close the current state of the system is to a limit or threshold. This would be analogous to how close a stressed material, or one with a force placed upon it, is to becoming strained, or changed in structure.
4. Panarchy: the degree to which a certain hierarchical level of an ecosystem is influenced by other levels. This last aspect is unique to nested systems and, unlike the previous three, pertains only to the system-wide level, and not subsystems within it. Panarchy was chosen as a term because the authors recognized the consequential and dynamic interplay across scale levels within ecosystems. They further delineated the phases of this cross-level dynamism in the “adaptive cycle”: growth, conservation, release and reorganization.
These aspects suggest a second important lesson for urban problem-solvers that stems from the first, beyond just the cyclical nature of natural systems. You should be looking for an optimum balance of your conducive conditions, not a maximization of any one thing. Moreover, if you are searching for balance within a system, then relationships are as important as actors (and often more so). Finally, if you are to truly mimic nature, then you eventually will have to study how to solve a problem in a hierarchy of scales. Integrating the scales of your solution, while difficult, can be a powerful innovation.
Building with vines image by Jairo via Flickr
Mechanisms that enable resilience
With these two departure points -- that we are designing dynamic conditions conducive to success and that we are integrating these conditions across scales and subjects -- we can begin to investigate the mechanisms that support resilience in a system.
Andrew Zolli and Ann Marie Healy have compiled a good list of principles for large system resilience in their 2012 book “Resilience: Why Things Bounce Back.” Not surprisingly, most, if not all, of these principles sail under the banner of bio-inspired design, because they had been observed originally in the study of natural systems. I have added my sense of what they bring to a design. They contribute the following:
• Tight feedback loops: saves material, energy and time
• Dynamic reorganization: allows for more success options in the face of changing conditions (in other words, reduces precariousness)
• Built-in counter-mechanisms: avoid time-induced failure, reduce costs
• Decoupling: not building a house of cards in which one component failure brings down the house, avoids system failure, reduces precariousness
• Diversity: brings a mix of options, capabilities and resistance to extinction
• Modularity: increases latitude, streamlines costs, resists system-level failure
• Simplicity: reduces costs and sub-system failures
• Swarming: reduces costs, increases flexibility and capabilities
• Clustering: adds value, capabilities and resistance
The authors argue that such mechanisms indeed can be translated to man-made endeavors and cite a few examples, such as the self-organized swarming of volunteer software developers who built an emergency information system for the quake victims of Haiti. The system was based on mobile phones, was operational in a matter of days, and was reputed to have gotten emergency messages from victims received, translated and mapped for responders on a central board in an average of two minutes.
Where we can use these nature-inspired mechanisms
There is a role for bio-inspired design in all levels of community infrastructure planning and design. First is the systems-based conceptual approach discussed above. If you call anything in your community or organization a system, then nature has some advice for you, whether you’re concerned with regional transportation, irrigation or anything in between. Predictive models of physical phenomena, examples of efficient flows and multi-scale spatial structures are just a few possible exemplars.
Second, even if you don’t call something a system, maybe you should. We tend to think of skin, for instance, as a single solid covering over us, but it really isn’t. It is a wonderfully complex system of parts working dynamically to achieve many tasks such as spatial sensing, temperature control and structural integrity. The same potential resides in the cladding of our buildings. Redesigning them along systems lines, for example, can improve the resilience of buildings and communities.
Third, communities and the infrastructure within them are built by and for people. The organizational and communication forms that we choose will influence the success of our endeavors. Nature offers a wide range of models for cooperation, competition, co-existence and communication.
Three questions to ask
Organizations and communities are faced with an uncertain world full of risk, and they need to maintain their operational capabilities despite changing and unpredictable external conditions (otherwise known as homeostasis). It seems logical that most would desire to do three things: reduce or eliminate risk and uncertainty, respond effectively to threats that cannot be foreseen, and simultaneously carry on with the core mission despite changing conditions and whatever burdens they impose.
Resilience is a term from ecology that is an appropriate framework and aspiration for human systems as we recognize their interdependence with nature. The Resilience Alliance has defined this term with three criteria, and I repeat them here as questions for any organization:
1. What amount of change can your system undergo and still retain the same controls on function and structure?
2. To what degree is your system capable of self-organization?
3. What capability does your system have to build and increase its capacity for learning and adaptation?
Anyone hoping to answer these questions ultimately must look to nature for models.
Building with vines image by Jairo via Flickr