02 May 2013

Adaptive Cycle

The adaptive cycle is a conceptual model intended to expose the degree to which a complex system is resilient.  It is equally applicable to biophysical systems, social-economic systems, and joint human-natural systems.  It combines insights about the accumulation of resources or capital within the structure of systems, with insights about the increasing complexity that results from ecological succession or social problem solving (Scheffer et al. 2002).  The adaptive cycle acknowledges that episodic stresses and disturbances can cause systems that had accumulated capital and built complexity to suddenly collapse and reorganize.  The adaptive cycle includes a growth phase, leading to a conservation phase.  Disturbance and stress, whether internal or external, can lead do a release phase, and if the resource base available to the system is not depleted by the disturbance, a reorganization phase can set the stage for a subsequent growth phase (Fig 1). 

Figure 1.  The adaptive cycle as represented by Biggs et al. (2010).

Cycling through the series of phases repeatedly can maintain a system in a given structural and functional realm.  That is, the system is resilient.  Resilience can be prevented in two general kinds of situation (Biggs et al. 2010): Resource loss can establish a new system with a different structure on the impoverished resource base, while social and institutional arrangements that “lock in” the mechanisms of conservation can prevent the system from taking advantage of inevitable release. 

An example of a primarily biophysical adaptive cycle is the patch dynamics of a desert system driven by animals digging for the bulbs of perennial herbs.  For example, relatives of tulips in the Negev Desert produce below ground bulbs that are sought out as food by porcupines.  Harvesting the bulbs creates a small pit, roughly 15 cm (6 in) across and equally deep.  This activity breaks up the soil crust, which is a structure consisting of small mosses, lichens, and cyanobacteria and their sticky byproducts.  Such crust retards the infiltration of water, and prevents wind or water borne seeds of other desert herbs from finding a safe site to settle.  With the crust disrupted, water and organic matter, along with seeds accumulate in the pit.  The pit thus becomes a hospitable site for plant establishment in the generally arid environment.  As the pit fills in with sediment, it no longer serves the establishment function.  In addition, if the porcupine did not consume the entire bulb, or all bulbs beneath a clump of perennials, the site can come to support not only the invading annuals, but also a new generation or reinvigorated perennials.  The system as a whole is resilient because excavation of bulbs, transport of seeds, filling of pits, establishment and growth of a small plant assemblage in the old pit, and subsequent digging by porcupines is spatially patchy and asynchronous.  In addition, different years often exhibit different timing and amount of rainfall, further complicating the spatial and temporal processes.  An area of desert on the order of at least a few hundred square meters thus traces out an adaptive cycle and represents a resilient system.

Social-ecological adaptive cycles are illustrated on a much larger scale in ancient Mesopotamia (e.g. Redman and Kinzig 2003).  The establishment of urban and hydrological agriculture are familiar topics.  However, they are instructive when placed in the context of the adaptive cycle.  The settlement of the Uruk Period were widely dispersed and were a novel strategy for exploiting the widely scattered resources that had not previously been used to generate agricultural capital.  This release phase was followed closely by a reorganization phase in which regional organization accompanied by writing and shared artistic patterns.  This led to an exploitation phase in which various forms of urbanization, including relationships to agricultural hinterlands, were tried.  This phase was characterized by the building of regional political arrangements.  This organized urban-agricultural complex was ripe for conquest and the establishment of a complex, administratively integrated nation state.  Codes of law, imperial conquest and colonial administration emerged during this phase.  However, the initial conservative structures apparently became inflexible in the face of resource fluctuation.  The collapse of the first nation state led to a simplification back to city states.  Such fluctuations in organization continued in Mesopotamia for some 1,500 yr (Redman and Kinzig 2003).  Both social and environmental aspects interact in the ancient Mesopotamian adaptive cycles.

Why Important?
The adaptive cycle is a model template that helps expose the mechanisms that can support or prevent resilience in systems (Biggs et al. 2010).  The cyclical model alerts researchers and policy makers concerned with meeting societally constructed goals of sustainability of the fact that change is a part of urban systems, that internal and external shocks can change the local structure and function of neighborhoods, districts, or entire urban agglomerations, and that there are dangers in losing capital or locking in conservation strategies that prevent release and reorganization.  The cycle helps apply important ideas such as marginal return on investment in social complexity (Tainter 1988, 2006), and the role of creative destruction.

For More Information:
·         Biggs, R., F. R. Westley, and S. R. Carpenter. 2010. Navigating the back loop: fostering social innovation and transformation in ecosystem management. Ecology and Society 15:Article 9.
·         Redman, C. L. and A. P. Kinzig. 2003. Resilience of past landscapes: resilience theory, society, and the longue duree. Conservation Ecology 7:Article 14.  This article not only presents two interesting case studies of applying the adaptive cycle to archeological studies, but early sections present a clear overview of the resilience concept and the adaptive cycle.
·         Tainter, J. A. 1988. The collapse of complex societies. Cambridge University Press, New York.
·         Tainter, J. A. 2006. Social complexity and sustainability. Ecological Complexity 3:91-103.
·         Scheffer, M., F. Westley, W. A. Brock, and M. Holmgren. 2002. Dynamic interaction of societies and ecosystems -- linking theories from ecology, economy, and sociology. Pages 195-239 in L. H. Gunderson and C. S. Holling, editors. Panarchy: understanding transformations in human and natural systems. Island Press, Washington DC.

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