03 January 2013

Adaptive Processes

Adaptive processes are the structures, fluxes, and interactions that allow systems to adjust to sudden or gradual changes.  Social and biogeophysical features can contribute to the adaptive capacity of urban systems. 

Adaptation is familiar and fundamental in evolution.  Evolutionary adaptations constitute the mechanisms that determine how an organism performs in a specific environment (Figure 1).  In evolution, adaptation is usually considered to be driven by genetics.  The genetic makeup of an organism is responsible for the physical, behavioral, physiological, and life-cycle attributes with which it confronts the external environment.  There is sometimes flexibility in adaptive features of organisms which can be influenced by events during development or acclimation to changed conditions.  Such plasticity itself, of course, has a genetic basis. 

Figure 1. A mayfly nymph, adapted to live in streams by its streamlined body shape, and behavioral tendency to cling to surfaces.  These adaptations help prevent these juvenile phases of mayflies from being swept away by normal flows.  http://www.glerl.noaa.gov

Adaptation can also be considered to exist in other ecological or social units because there are many mechanisms by which adjustment to an environment can be accomplished.  Ecological communities are assemblages of different organisms occupying a common habitat.  Communities can adjust to environmental changes through altered species relationships or three dimensional arrangement of the members in space.  Ecosystems can adapt through shifting the rates or pathways involved in the processing of water, energy, or matter, as well as through the allocation of structure to different forms and locations.  Social groups adjust via institutional, political, behavioral norms, and in the largest sense, culture.   An example of social adaptation is the initiation of the American system of public education, ideally aimed at training a workforce and preparing youth for civic engagement in the democratic process.  Settlement houses were a social adaptation to the migration of rural and foreign-born persons to growing industrial cities in the late 19th and early 20th centuries (Figure 2).  These institutions helped new residents adjust to an unfamiliar physical and cultural environment, and compensated for lack of resources in some cases.

Figure 2. Hull-House, Chicago, from the 1906-07 Hull-House Yearbook. This was the first settlement house in the United States.  The idea spread to many other cities, and over time, their identity as “settlement houses” declined as other constituencies besides immigrants were also served.  Today, many institutions modeled on the principles that guided the establishment of settlement houses continue to serve new, marginalized, or disempowered individuals and communities in cities and suburbs.  (Photo from the Jane Addams Papers Project)

In some of these examples the adjustment is intentional and planned.  However, in many cases, especially those involving genetic shifts, the adjustment is accomplished by the “blind” process of natural selection rather than intention of an organism or a group. 

Key adaptive processes can be identified in both the social and in the biophysical realms (Figure 3). 

Figure 3. Adaptive processes in both social and biophysical realms.  Together these features illustrate the kinds of things that contribute to the capacity of socio-ecological systems to adapt to changing conditions.  See Yohe and Tol (2002) and Walker et al. (2004) for examples of source lists. 

Why Important?
In socio-ecological systems where much of the structure and behavior is the result of intentional human control and intervention, it is important to know what features might make positive adaptation possible, and what features get in the way of desired outcomes in the system.   In designing more sustainable urban systems it is important to consider the social and biophysical options that are available.  Furthermore, how intervening in each one might affect others in both the social and biophysical realms is important.  These are the features that must be monitored, assessed, and modeled under in  changing environments or design scenarios.

For More Information:
Gunderson, L.H. and C.S. Holling, editors. 2002. Panarchy: understanding transformations in human and natural systems. Island Press, Washington DC.
Folke, C., S.R. Carpenter, T. Elmqvist, L.H. Gunderson, C.S. Holling, B. Walker, J. Bengtsson, F. Berkes, J. Colding, K. Danell, M. Falkenmark, L. Gordon, R. Kasparsson, N. Kautsky, A. Kinzig, S. A. Levin, K.-G. Mahler, F. Moberg, L. Ohlsson, P. Olsson, E. Ostrom, W. Reid, J. Rockström, H. Savenije, and U. Svedin. 2002. Resilience and sustainable development: building adaptive capacity in a world of transformations. Ministry of the Environment, Stockholm.
Walker, B., C.S. Holling, S.R. Carpenter, and A. Kinzig. 2004. Resilience, adaptability and transformability in social-ecological systems. Ecology and Society 9:Article 5.
Yohe, G. and R.S.J. Tol. 2002. indicators for social and economic coping capacity -- moving toward a working definition of adaptive capacity. Global Environmental Change 12:25-40.


Definition: A physical disruption of the structure of a specified system.  Disturbance may also refer to the specific event that causes the disruption (Pickett et al. 1998, Peters et al. 2011).  Such events tend to have sharp onset and short duration, although their effects can be long lasting.

Explanation: For a long time ecologists ignored disruptive events in the systems they studied.  In fact, they would most often seek out ecosystems or communities that were presumably free from disturbance.  However, as more long term data accumulated over time, and as historical studies extended the record into the past, it became apparent that disturbance were a part of ecological systems in many places.

Whether an occurrence of a fire or hurricane is a disturbance or not depends on two things: the nature of the system involved and the intensity of the event.  Floods in general are not disturbances.  Whether any given flood acts as a disturbance requires an investigator to state what the structure, limits, and interactions in a system are.  Only then can it be determined whether some particular event acts as a disturbance (Pickett 2012).

Example: In non-urban systems there are many examples of disruption of system composition or architecture by high winds, ice or snow loading that breaks trees and thins canopies, flooding that kills dominant plants or causes uprooting or breakage of stems, fires, and herbivore outbreaks (Figure 1). 

Figure 1. A treefall gap in forest canopy.  Such openings are created by windstorms, for example.  Light, moisture, and nutrient conditions change in the understory as a result, providing opportunities for suppressed or new plant species to flourish.  Certain animals also often respond to such gaps.  Photo © S.T.A. Pickett.

In urban systems fires, wind damage, riots, and shifts in real estate and other investments can alter the structure of urban systems over relatively short time periods (Figures 2, 3).

Figure 2. Aftermath of the Great Baltimore Fire of 1904.  The fire itself burned 64 acres of downtown Baltimore, but the debris was dumped along the harbor, disturbing the structure of the transitional environments that had existed there previously.


Figure 3. Abandonment in residential, commercial, and industrial neighborhoods is a disturbance common to many cities.  This boarded up house in Baltimore represents both a physical disturbance and a rupturing of the social structure of the neighborhood.  Many abandoned houses deteriorate to the extent that they must be torn down, creating a second wave of disturbance in under served neighborhoods.  Photo © Baltimore Ecosystem Study LTER.

Why Important: Disturbance events change the availability of resources, alter the environmental signaling by patterns of temperature or moisture, make space available for establishment or ascendancy of invading or suppressed individual plants, and shift the patterns of dominance by different species. 

Some components and processes within ecological systems depend on the periodic or infrequent structural disruptions generated by disturbance.  So disturbance is “good” for some aspects of systems at the same time it disrupts others (Reice 2001).  There are of course some disturbances that are so intense that they wipe out a system entirely, but many produce gaps within a persistent system.

Disturbance is a part of urban as well as wild and rural systems.  In cities, suburbs, and exurbs, disturbances may include not only naturally generated events like earthquakes, floods, or encroaching wildfires, but also sudden closures of factories and other businesses, shifts in availability of financing or economic investment in particular places, or the migration of different demographic groups into or out of districts or entire urban areas. 

Disturbance is thus potentially a major component of urban ecological structure, and can influence resource availability and stress in ecosystems.  The social and biological resources available and required, the biodiversity and social institutions in urban areas, the fluxes of fresh and waste water, the amount and structure of green spaces, and the vulnerability of people and biological organisms to stress are all features that can be affected by disturbance.

For More Information:
Peters, D. P. C., A. E. Lugo, F. S. Chapin, III, S. T. A. Pickett, M. Duniway, A. V. Rocha, F. J. Swanson, C. Laney, and J. Jones. 2011. Cross-system comparisons elucidate disturbance complexities and generalities. Ecosphere 2:art 81.
Pickett, S. T. A. 1998. Natural processes. Pages 11-19 in M. J. Mac, editor. Status and trends of the nation's biological resources. U.S. Department of Interior, U.S. Geological Survey, Reston, VA.
Pickett, S.T.A. 2012. A disturbance primer for urban systems.  BES Director’s Corner Blog. http://besdirector.blogspot.com/2012/09/a-disturbance-primer-for-urban-systems.html
Reice, S. R. 2001. The silver lining: the benefits of natural disasters. Princeton University Press, Princeton.