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
Next page: Building communities with bio-inspired design