Two Ways to Discover Disturbance

Ecological disturbance is often defined as an event that disrupts the structure of a specific system (Pickett & White, 1985).  This kind of material or physical disruption is important because it can result in changes in behavior of the system, or leave heterogeneous structural legacies that affect the system in the future (Pickett, Cadenasso, & Jones, 2000; Wiens, 2000).  Such a general and potentially significant ecological process requires conceptual clarity in order to use it successfully (Pickett, Kolasa, Armesto, & Collins, 1989).  As is often the case, seemingly simple definitions actually require great subtlety in their application.  Disturbance invites that kind of attention. 

This essay shows that disturbance can be recognized in two ways.  The first is based on empirical experience with events that have, in the past, commonly acted to disrupt structure of various systems.  This approach can be called event-based detection of disturbance.  The second approach allows disturbance as structural alteration to emerge from the comparison of different kinds of trajectories in a system.  Using such a lens, disturbance shows up as the intersection of long-term data about phenomena or processes with long-term data on system structure or function.  This second approach can be labeled emergent detection of disturbance.  This distinction may be important when disturbance is studied in systems where there is little prior empirical experience, or where interaction of events may be particularly complex.

Background: Disturbance as Process

Although disturbance is one of ecology's fundamental processes, the concept continues to be refined as more examples are brought to bear on understanding disturbance (Peters et al., 2011).  Disturbance can be conceived as a process, of which a conspicuous or powerful event is only a part.  

The process as a whole actually involves interaction between the forces embodied in the event and the characteristics of an ecological system that is exposed to the event.  The system characteristics govern how the forces can affect the system of interest.  In this sense, disturbance can be seen as a complex process because of the multiple interactions between an event and a place. 

The description above requires a caveat.  The term system can be used in different ways in reference to disturbance.  One arises because it may be reasonable to consider disturbance itself as a conceptual system of interacting components and phenomena.  "Disturbance as a system" refers to a conceptual model of the event, forces, and characteristics of places that may be affected by disturbance (Figure 1).  In contrast to a conceptual model involving disturbance, "the system of interest," uses the word system to refer to a concrete location, habitat, place, or ecosystem. 

Figure 1. Disturbance as a complex process (based on Peters et al. 2011 and Grimm et al. 2017)

Event-Based Detection of Disturbance

The refined conceptualization of disturbance, assumed here as background, suggests that there is more than one way to recognize or detect a disturbance.  The first is familiar, and rather intuitive when applied to scales comfortable to humans.  If we can travel through a system, and observe its dynamics at multiple points in time, it is usually easy to identify what a disturbance is.  Walking through a forest after a major wind storm may reveal newly fallen canopy trees, with their upturned roots, and the soil pit from which the roots were wrenched.  In that forest, some trees may have been snapped by wind, and saplings and immature trees may have been broken or bent as canopy trees fell on them.  The scene may be a complex jumble of altered forest structure from the canopy to the subsoil.  This is clearly a disturbance to the formerly intact forest ecosystem, and the motive force of wind equally clear as a driver.  Similarly, walking into a forest some time after a fire, whether one that "crowned" and burned the canopy, or one that was restricted to the litter layer on the ground, shows structural disruption of the prior forest structure.  New seedlings, surviving saplings released from competition with canopy trees, and understory herbaceous plants may respond by faster growth or enhanced reproduction following disturbance.  Such a human-scaled, intuitive recognition of disturbance events has led to familiar, if imprecise, statements that floods, fires, ice storms, landslides, hurricanes, and tornadoes "are disturbances" a priori.

The general model of disturbance (Figure 1) captures these intuitive cases that are linked to human size and experience quite well.  The model suggests though, that understanding exactly how the force of wind, the weight of ice, or the chemistry of combustion affected particular parts of an area require that the nature of the potentially impacted system or area to be known.  This requirement may be realized by rigorous and long-term observation of a system.  But generally, the focus on events matches the requirements of the general model well.  This use of the model is an example of the event-based approach to detecting disturbance.

Emergent Detection of Disturbance

Emergence is a contrasting approach to discovering disturbance.  Not everything that causes disturbance may be the result of a familiar or human-scaled kinds of event, like a hurricane or a flood.  In such cases, the disruption of system structure may result from the application of unexpected or non-intuitive forces.  Non-intuitive forces may exist on scales difficult for individual people to comprehend intuitively.  In addition, such unfamiliar drivers of disturbance may be especially characteristic of social-ecological systems.  The difficulty here is that powerful social-ecological drivers may seem ordinary and unexceptional to people in daily life.  Processes of real estate investment, employment opportunities, or government regulation may not seem at first glance to be the stuff of disturbance.  This invisibility of social-economic drivers is in part a result of the hybrid nature of such systems.  Hybridity or social-ecological-technological system structure means that the forces may have material and social momentum. 

What does such hybridity of forces mean in concrete terms?  If disturbance is an event that disrupts system structure, what counts as an effective event depends very much on what the model of the system is.  The requirement that an explicit model be used to determine what is and what is not a disturbance is an often neglected fundamental of disturbance studies.  Models of hybrid systems can express very different kinds of structures, all of which are important facets of the larger, more inclusive urban ecosystem.  The models state what components the system contains, and how the components of the system are networked together.  For example, social-ecological systems can have structures that serve to transfer information, or transmit social expectations.  Information may include the flows of capital or credit, and expectations may be transmitted in the form of such things as social norms or neighborhood cohesion. 

What can alter the such a socially inflected structure?  Of course, the physical disruption of communication infrastructure can be a disturbance.  This is very much like classical disturbance in ecology.  Alternatively, the physical networks may persist while the capacity of the social network to transfer information may break down due to the removal of an institutional node in the flow of information.  Or restriction of loans in specific areas may disrupt the financial resources that permits people to maintain and refurbish housing stock; ultimately this disruption of the financial system may appear as a material disruption in the urban fabric as buildings are abandoned and perhaps demolished. 

Examples of social features of structure can be labeled a "social contract," or an "ecology of prestige," each of which communicates expectations that influence how people interact in particular places.  A social contract in a African American neighborhood is a structure that can be disrupted by the novel, and perhaps conflicting, expectations about how public space is used and regulated that are put in place by gentrification.  The ecology of prestige is a place-specific social structure expressing a shared aesthetic that directly affects environmental form and management.

Figure 2. Illustration of emergence of disturbance as the intersection of a trajectory of lightning strkes and increasing density of wood stems.  Below a certain threshold density an ignition will not result in fire spread. Hence, there would be no disturbance of the larger landscape.

Disturbances of this kind are particularly complex, and may be more readily discovered by examining the trajectories of change in urban systems than by focusing on specific kinds of physical events (Figure 2).  Trajectories in important biophysical features of urban systems should of course be monitored, as should drivers from outside the system that can cause structural disruption.  However, the events that contribute to disturbance as a process can also arise within the system due to the interaction of changes in various system components. 

The fact that disturbance can arise in two ways in social-ecological-technological systems is a part of the complexity of urban ecology that has helped refine the understanding of one of ecology's basic phenomena.  The fact that the Long-Term Ecological Research program listed disturbance as one of the five core areas for research in its study sites is a symbol of the importance of disturbance across a range of system conceptions including populations, communities, landscapes, and ecosystems.  Disturbance can be hypothesized a priori in for some kinds of models, but must be detected analytically in others.

Steward Pickett

Literature Cited

Grimm, N. B., Pickett, S. T. A., Hale, R. L., & Cadenasso, M. L. (2017). Does the ecological concept of disturbance have utility in urban social-ecological-technological systems? Ecosystem Health and Sustainability, 3(1). doi:10.1002/ehs2.1255

Peters, D. P. C., Lugo, A. E., Chapin, F. S., III, Pickett, S. T. A., Duniway, M., Rocha, A. V., … Jones, J. (2011). Cross-system comparisons elucidate distrubance complexities and generalities. Ecosphere, 2, art 81. doi:10.1890/ES11-00115.1

Pickett, S. T. A., Cadenasso, M. L., & Jones, C. G. (2000). Generation of heterogeneity by organisms: creation, maintenance, and transformation. In M. L. Hutchings, E. A. John, & A. J. A. Stewart (Eds.), Ecological consequences of habitat heterogeneity. Malden, MA: Blackwell.

Pickett, S. T. A., Kolasa, J., Armesto, J. J., & Collins, S. L. (1989). The Ecological Concept of Disturbance and Its Expression at Various Hierarchical Levels. Oikos, 54(2), 129–136. doi:10.2307/3565258

Pickett, S. T. A., & White, P. S. (Eds.). (1985). The Ecology of Natural Disturbance and Patch Dynamics. Orlando: Academic Press.

Wiens, J. (2000). Ecological heterogeneity: an ontogeny of concepts and approaches. In M. J. Hutchins & A. J. A. Stewart (Eds.), The ecological consequences of environmental heterogeneity. Malden, MA: Blackwell.

The Evolution of Urban Heterogeneity Thinking

The heterogeneity of cities has been acknowledged as one of their most striking features for a very long time.  Spatial heterogeneity characterized the ancient, cosmologically oriented cities of the Middle East, Asia, and the Americas (Lynch 1960; e.g. Fig. 1).  Social heterogeneity of cities, compared to rural village life, was recognized by the founders of modern sociology (Wirth 1945).  Urbanists, including urban designers, planners, community organizers, architects, among others, continue to be impressed with, engaged by, and responsive to the heterogeneity of cities and urban regions (Lefebvre 2003). 

Figure 1: The ancient Aztec city of

Tenochtitlan, a cosmological, 

political city.  Heterogeneity appears

as water, land, made land, ceremonial

and residential structures, and

agricultural areas. 

Although ecologists are admittedly relatively new comers to the city and the urban region as a subject of study, they come with a significant toolkit to deal with heterogeneity (Tischendorf and Fahrig 2000).  There is also a rich conceptual foundation for understanding heterogeneity within ecology (Wiens 1995, Pickett et al. 2001, Wu and David 2002).  In particular, a recent treatise on the theory of ecology illustrates the conceptual drawer of this toolkit (Scheiner and Willig 2011).  They summarize the most inclusive foundations of ecology in eight principles (Box 1).  Fully five of these principles mention heterogeneity by name or embed the core concept of heterogeneity within their scope.  These fundamentals are operationalized with such more specific disciplines within ecology as landscape ecology, metapopulation and metacommunitiy theories, succession, biogeography, evolutionary ecology, and ecosystem ecology.  

--------------------------------------------------------

Box 1.  Principles of General Ecological Theory, from Scheiner and Willig (2011: 13).  Quoting [With some explanations inserted in brackets, and the term heterogeneity or conceptual equivalents italicized]:

1. Organisms are distributed in space and time in a heterogeneous manner.

2. Organisms interact with their abiotic and biotic environments.

3. Variation in the characteristics of organisms results in heterogeneity of ecological patterns and processes.

4. The distribution of organisms and their interactions depend on contingencies. [Contingencies may be defined as heterogeneities in events, processes, resources, and stresses.]

5. Environmental conditions as perceived by organisms are heterogeneous in space and time.

6. Resources as perceived by organisms are finite and heterogeneous in space and time.

7. Birth rates and death rates are a consequence of interactions with the abiotic and biotic environment.

8. The ecological properties of species are the result of evolution. [N.B. Evolution by natural selection rests on the heritable heterogeneity or variation in organisms, and the degree to which it matches the prevailing, heterogeneous environment.]

-------------------------------------------------------

The practical tools of ecology also address heterogeneity, and do so increasingly.  Most conspicuous among these tools are those supporting landscape ecology.  In this genus of ecology, the concern is with the reciprocal relationship of pattern and process.  Consequently, ways to measure spatial differentiation are central to the discipline.  Gradients, patches, and patch mosaics are measured via field study, remote sensing, and statistical modeling.  Parameters such as patch size, patch shape, boundary thickness and porosity, nearest neighbor features, and so on, suggest and are applied to spatially-oriented questions.  Heterogeneity can be assessed in genetic, behavioral, and communication activities in populations, or in the distribution of competitive and facilitative interactions among species.  Changes in spatial heterogeneity over time is measured when concern is with such phenomena as succession, disturbance, migration, and ecosystem process rates, for example.  There is, simply, no facet of contemporary ecology that does not address and profit from understanding spatial and temporal heterogeneity (Tilman and Kareiva 1997, Lovett et al. 2005, Leibold 2011).

Fig. 2. Heterogeneity as cause and
consequence, or driver and outcome.

The urban realm – cities, suburbs, exurbs (CSE), and the urbanized regions they constitute – presents both the need and the opportunity to meld the heterogeneities recognized by the social sciences with that recognized by biophysical sciences (McGrath and Pickett 2011).  Thus sociology, economics, political ecology (a social science), diffusion of innovation, social network theory, and governance theory among others, and the various flavors of biophysical sciences, such as soil science, hydrology, biogeochemistry, plant and animal community ecology, biotic population ecology, microbial ecology, and others, must be in dialog.  And that dialog must address a variety of heterogeneities.  Not all heterogeneities must appear in all interdisciplinary models, but hypotheses about particular couplings will guide which heterogeneities are relevant over the long term.

The joint concern with heterogeneity by the social and the biophysical sciences in urban areas suggests a large hypothesis:  Spatial heterogeneity acts as a driver and an outcome that affect ecological processes in cities, suburbs, and exurbs (Figure 2).

Spiral Causality in Heterogeneity

This feedback model (Figure 2) may seem at first glance to be hopelessly circular.  But pull the circle apart, like a mental slinky, and a spiral form of hypothetical argumentation appears.  The spiral plays out over time.  The abstract spiral model of heterogeneity as driver-outcome-driver-outcome, etc., would need to be filled in by particular features and moved forward by particular ecological or social events.  This is how that might look (Figure 3):

Fig. 3. Converting apparently circular causality to spiral causality in which the action of different kinds of heterogeneity

can be understood and studied as linked outcomes and drivers.  The spiral begins with a set of boundary conditions or

initial heterogeneity.  Human or natural events convert that heterogeneity into a driver for further interaction.

Heterogeneity as Driver and Outcome: A Baltimore Scenario

A hypothetical example, likely to soon to be a testable reality in Baltimore and many other American cities located in the Eastern Deciduous Forest Biome, is the interaction of the invading emerald ash borer with the distribution of planted and volunteer ash trees (Fraxinus spp.).  Ash trees are not uniformly distributed across CSE space.  Nor are the invading beetles.  This suggests the first link in a spiral of causation involving spatial heterogeneity (Figure 4).  It is based on the interaction between the initial heterogeneous distribution of ash trees, the presumably patchy invasion of the emerald ash borer, AND the patchy management by people of both the ash population and the insect.  These interventions and events result in a second kind of heterogeneity, the spatially distributed mortality (including preemptive removal) of ash trees. The initial condition is labeled an outcome, the events of invasion or management act on that outcome to produce a new spatial pattern – ash mortality, that then becomes a driver for further spatially explicit outcomes and the interventions or events they stimulate in nature or in society.  This same logic is played out in the remainder of the cascade involving patchy altered thermal environments, human risk of heat stress, and social and individual responses to heat stress in the altered environment (Figure 4). 

Fig. 4. A hypothetical model of the relationship of different kinds of heterogeneity that might exist and be causally linked following the invasion of the emerald ash borer in Baltimore or other cities.  The boxes attached to the event arrows can be
both biophysical and human generated.

Heterogeneity and the Urban Ecosystem

This is the kind of logic we wish to explore to generate specific testable hypotheses about 1) heterogeneity as both a driver and an outcome affecting ecological processes in the urban system of Baltimore, 2) the integration of human and natural processes in the urban ecosystem, and 3) the intersection of two of ecology’s fundamental concepts: heterogeneity and the ecosystem as it is manifested in urban areas.  BES IV will investigate the role of spatial heterogeneity as a driver and outcome as it underlies and affects the basic structures and interactions in the urban ecosystem (Figure 5).

Fig. 5. The human ecosystem, consisting of biotic, physical,

social, and built components, all interacting within the

context of spatial various kinds of heterogeneity that

affect the interactions among components, and therefore

the structure and function of the components.

References

Lefebvre, H. 2003. The urban revolution. University of Minnesota Press, Minneapolis.

Leibold, M. A. 2011. The metacommunity concept and its theoretical underpinnings. Pages 163-183 in S. M. Scheiner and M. R. Willig, editors. The theory of ecology. University of Chicago Press, Chicago.

Lovett, G. M., C. G. Jones, M. G. Turner, and K. C. Weathers, editors. 2005. Ecosystem function in heterogeneous landscapes. Springer, New York.

Lynch, K. 1960. The image of the city. MIT Press, Cambridge, MA.

McGrath, B. and S. T. A. Pickett. 2011. The metacity: a conceptual framework for integrating ecology and urban design. Challenges 2011:55-72.

Pickett, S. T. A., M. L. Cadenasso, and C. G. Jones. 2001. Generation of heterogeneity by organisms: creation, maintenance, and transformation.in M. L. Hutchings, E. A. John, and A. J. A. Stewart, editors. Ecological consequences of habitat heterogeneity, the annual symposium of the British Ecological Society. Blackwell, London.

Scheiner, S. M. and M. R. Willig. 2011. A general theory of ecology. Pages 3-18 in S. M. Scheiner and M. R. Willig, editors. The theory of ecology. University of Chicago Press, Chicago.

Tilman, D. and P. Kareiva, editors. 1997. Spatial ecology: the role of space in population dynamics and interspecific interactions. Princeton University Press, Princeton 

Tischendorf, L. and L. Fahrig. 2000. On the usage and measurement of landscape heterogeneity. Oikos 90:7-19.

Wiens, J. A. 1995. Landscape mosaics and ecological theory. Pages 1-26 in L. Hansson, L. Fahrig, and G. Merriam, editors. Mosaic landscapes and ecological processes. Chapman and Hall, New York.

Wirth, L. 1945. Human ecology. American Journal of Sociology 50:483-488.

Wu, J. G. and J. L. David. 2002. A spatially explicit hierarchical approach to modeling complex ecological systems: theory and applications. Ecological Modelling 153:7-26.

The Human Ecosystem: What's Missing?

The human ecosystem concept is one of the most common tools used in the Baltimore Ecosystem Study LTER.  Adopted from a team of social ecologists and sociologists who were involved in community forestry in the Himalayas, the application of such approaches to underserved areas in American cities, and the conservation and management of US National Parks, the concept is remarkably broad and adaptive.  The human ecosystem is not necessarily tuned to emphasizing the intellectual flavor of the week or most current headline issue for cities, urbanization, sustainability, or development.  However, its inclusiveness, nested hierarchical nature, and adaptability makes it well suited to dealing with shifting or even new emphases in social-ecological systems research and application (Figure 1). 

Figure 1.  The Human Ecosystem Framework
(Adapted from Machlis et al. 1997)

What are some of the hot topics that might seem to be missed in our discussions or presentations, but which in fact have a home in the human ecosystem framework?

Political ecology.  

This is at once a scholarly area and a subject of activist attention.  As a scholarly field, it examines the relationships of politics, economics, and environment.  As a social movement, it focuses on the inequitable distribution of benefits and costs of environmental decisions.  The social movement can be seen as a part of a larger social or environmental justice agenda. 

The multidimensional relationships with which political economy is concerned exercise several components of the human ecosystem framework.  Among the bioecological features, catalogued in the “ecosystems pattern and process foundations” component of the framework, many are relevant, including the distribution of energy, water, nutrient, and biomass resources, the kinds and levels of contaminants and pollution of air, water, and soil, and the heterogeneous or mosaic distribution of all of these factors.  Heterogeneity is important because control of access to resources, exposure to hazards, or distribution of benefits is subject to social – that is power and political – control.  Not all persons, groups, or institutions may be uniformly represented across a spatial mosaic.  The social control of access, exposure, and benefit engages many of the components of the human ecosystem framework.  The social ordering by factors of identity, rank hierarchies, and norms are key to the differential power relationships in human ecosystems.  Social rank hierarchy can further be broken down into ranks based on wealth, control of territory, social status, knowledge as a kind of capital, and, tellingly, power.  Among the social and cultural foundations, the distribution of populations, including by race, class, gender, or ethnicity, and the distribution of information by various institutions may reflect power relationships.  Of course the access to or participation in the institutions of sustenance, health, justice, education, etc. are also dependent on power relationships.  Other aspects of the human ecosystem framework (Figure 1) can also be used to investigate and explain, and therefore intervene in, power relationships in the urban social-ecological systems. 

Technology.  

Recently, our colleague N.B. Grimm has emphasized the fact that social-ecological systems have significant technological content.  Grimm at the 2013 Congress of Urban Ecology, the first such international meeting of the Society of Urban Ecology (SURE), introduced the term Social-Ecological Technical System, or SETS to emphasize the role of technology in how people think about urban ecosystems. 

This healthy reminder and highlight does no violence to the human ecosystem framework.  A classical representation of the significance of technology in human environment relationships is the POET model.  Under this general model, environmental change is said to be a function of human population, the way that humans are organized, and the technology available.  Explicit recognition of the role of technology in urban systems appears in the classical work of Borchert (1967), who notes that urban form in the United States shifted with the introduction of new technologies.  

Emphasizing transportation technology, Borchert proposed five epochs of American urban change: 1) sail and wagon (1790-1830), 2) steam powered ships and initial rail roads (1830-1870), 3) national steam rail network (1870-1920), 4) interstates and propeller air transport, and finally 5) satellites and jet propulsion.  American urban transformation continues, with other epochs hypothesized to represent the “slow growth” proposed in the 1970s of the oil embargo (Phillips and Brun 1978), or perhaps an epoch defined by the technology integrating global finance, manufacturing, and consumption.  In any event, the significance of technological innovation, change, and even retrenchment are clearly major components and drivers of urban change.  These latter technologies have a great deal to do with the current global teleconnections of urban systems with each other and with more rural and wild lands (Boone et al 2014).

Baltimore is a prime example of the role of shifting technologies.  For instance, the urban fabric of Baltimore, as described in Hayward and Belfoure (1999), shifted markedly with each transition -- from the walking city, through the city of horsedrawn trolleys, through the electric commuter rail, through the automobile era.  The industrial power of Baltimore similarly reflects major technological shifts, from the water power of the “fall line” through wood fueled steam, through coal powered manufacturing and steel production.  Other overlapping shifts, such as the opening up of the American South and Southwest with the availability of air conditioning technology there, and government policy for the location of defense industries away from the vulnerability of the east coast so feared during World War II, played a role in Baltimore’s post-industrial shift to a joint service, tourism, and knowledge footing.

In the Human Ecosystem Framework, technology appears foundationally in such things as the source of energy (e.g. water power, vs. wood, vs. coal), or the path of water flow (the location at the fall line between the Piedmont and the Coastal Plain).  Technology also is reflected in the amassing and deployment of labor, as in the contrast between slavery and voluntary immigration as sources, and the shift in capital investment in water-mill industry and canals versus the creation of America’s first long haul railroad – the Baltimore and Ohio.  

The technologies available and the pursuits different technologies make available have powerful influence on social identity, demographic structure, community and neighborhood cohesion and the like.  For example Baltimore still embraces a historical identity as a seafaring town.  This is shown by the fact that a waterfront neighborhood is still referred to as Canton, in honor of Baltimore’s fast clipper ships that cemented trade between China and the U.S. East Coast.  Or the fact that Fells Point, the location of Baltimore’s first deep water port, still retains the ameities and reputation as a freewheeling entertainment district reflecting its early tradition of hosting sailors on leave.  The coal-fired industrial era is honored in the Middle Class Mythology of Baltimore and its blue collar ethos.  These things are all features that find a home in the human ecosystem framework, for example in cultural myths, social identity, and temporal cycles of change in demography and institutional and organizational structures.

Infrastructure.  

Another hot topic these days is infrastructure.  Strictly speaking, infrastructure is what undergirds the various components of a system.  Infra means below.  It is the supporting structure, linkages, flows in any system.  The human ecosystem may seem to be blind to the built and engineered components of urban ecosystems.  This is because the human ecosystem framework assumes those physical foundations.  In 1997, we worked to refine understanding of the bioecological foundations of the human ecosystem.  The original discussions by Machlis and colleagues certainly included the bioecological and biophysical aspects of human ecosystems in the “resource system” component.  Perhaps because buildings, streets, supply pipes, electrical wires, railroads, sewers, storm drains, and so on are such conspicuous parts of urban ecosystems, we hardly felt the need to call attention to them.  Cities are so often defined based on density of built structures and of human inhabitants that pointing toward buildings and infrastructure could be tacitly assumed.

However, a later description of the human ecosystem as a model template showing major kinds of components and their connections attempted to make this assumption clear.  Cadenasso et al. (2006) is a good example of this integration of built – and hence infrastructural – components into general interactive and classificatory models of urban ecosystems (Figure 2).  There is nothing wrong with pointing to the various components of systems as infrastructure, but in a sense, that seems redundant with saying that an urban place is a human ecosystem comprising social, biotic, built, and physical (e.g. soil, topography, climate) components.  Infrastructure is just another word for components, really.  The big idea is that cities, suburbs, and exurbs are systems that contain many specific features and connections, and that those span and connect biology, physical environment, buildings, social processes and the myriad feedbacks among components.

Figure 2. A process model template of the human ecosystem.

A healthy outcome of the infrastructure label may be helping people to remember the often invisible biological components of cities, suburbs, and towns.  Infrastructure is now often spoken of as gray, blue, and green.  This division suggests that the complex system of the city or more broadly, the urban region, depends on services and structures provided by plants, animals, and microbes, and that these services emerge not only from partly or (almost) entirely engineered features, but also from parks, yards, street plantings, derelict field and lots, open streams, wetlands, and freeflowing atmosphere.  Planning, design, management, policy, and education will be better served, and will better serve the human population when the contributions of biological infrastructures and their components are understood and effectively employed.

Conclusion

The message here is that the human ecosystem framework (Figure 1), a hierarchical enumeration of the kinds of biophysical and social structures, resources, processes, and outcomes that make up not only cities and towns, but also wilderness and production landscapes, is adequate to include contemporary and important concerns of power, justice, technology, and infrastructure.  The human ecosystem framework can be considered a causal hierarchy, in which general causes or factors are broken down into more specific mechanisms and interactions.  Specific models of human (in general) and urban (in particular) ecosystem structure, function, and dynamics will draw upon several to many of the ideas and features included in the human ecosystem framework. 

The framework is complemented by a process model template (Figure 2).  This process model template emphasizes that urban systems are composed of biological components and their interactions, physical environments and their links, social structures and interactions, and built components and the interactions among them.  This model template emphasizes the comprehensiveness of kinds of components of cities, suburbs, and exurbs, as well as the interactions among the various components.

Thus, rather than neglecting important contemporary topics in social, engineering, historical, and political realms, urban ecology has frameworks and model templates that in fact can easily accommodate these features.  Technology is a part of the built environment, Power is an aspect of the social structures, and infrastructure is a way to group various built components, networks, and interactions.

References

Boone, C. G., C. L. Redman, H. Blanco, D. Haase, J. Koch, S. Lwasa, H. Nagendra, S. Pauleit, S. T. A. Pickett, K. C. Seto, and M. Yokohari. 2014. Reconceptualizing land for sustainable urbanity. Pages 313–330 in K. C. Seto and A. Reenberg, editors. Rethinking urban land use in a global era. MIT Press, Cambridge.

Borchert, J. R. 1967. American metropolitan evolution. Geographical Review 57:301-332.

Cadenasso, M. L., S. T. A. Pickett, and J. M. Grove. 2006. Dimensions of ecosystem complexity: heterogeneity, connectivity, and history. Ecological Complexity 3:1-12.

Hayward, M. E. and C. Belfoure. 1999. The Baltimore rowhouse. Princeton Architectural Press, New York.

Machlis, G. E., J. E. Force, and W. R. Burch. 1997. The human ecosystem. 1. The human ecosystem as an organizing concept in ecosystem manageme

Phillips, P. D., and S. D. Brunn. 1978. Slow Growth: A New Epoch of American Metropolitan Evolution. Geographical Review 68:274–292.

Just One Book a Year -- That's All We Ask.

BES is a far flung, disciplinarily diverse project.  We do many things to apply centripetal force to a situation that seems naturally to be dissipative.  One centering activity is to identify a “book of the year.”  In the past, we have had two such books.  They were chosen to provide useful and interesting background on Baltimore, in the case of Sherry Olson’s Baltimore: The Building of an American City (1997), and to highlight the contribution of one of our own to urban studies, in the case of Austin Troy’s The Very Hungry City.  This year’s BES Book of the Year has a different purpose.

The edited volume by Samuel Scheiner and Michael WilligThe Theory of Ecology has been chosen to help the BES community use ecological theory better.  This goal emerges from the Mid-Term Review conducted by an external visiting committee in October, 2013.  The critique emerging from that review made clear that as a project, we need to be able to better articulate the theories that we use, to tie them together more effectively, and to link broad theories more clearly to the specific research activities which we pursue.

(2011) on

The first BES Webinar, to be held on Tuesday 4 March,

will briefly present the high points of one of the chapters in this book, and provide the opportunity for us to discuss the insights and relevance of the chapter to the structure and integration of BES research.  The purpose of this session is to learn about the nature and structure of ecological theory.   It will be more useful for BES if we treat this as an opportunity to absorb, rather than attempt to critique, a way to understand and use theory.

The main reading and the background texts all come from Scheiner and Willig’s book.  I hope that members of BES will get their own copies of this book, or will request that their institutional libraries obtain it.  If there are many members of BES at an institution, it might be a good idea to put the book on reserve.  The book is available in paper and electronic versions from “the usual suspects.”  Here are the readings for 4 March:

Main Reading:

Kolasa, J. 2011.  Theory makes ecology evolve.  Chapter 2, pp 21-49, in S.M. Scheiner and M.R. Willig, editors.  The Theory of Ecology.  University of Chicago Press, Chicago.  This chapter puts the hierarchical approach to theory to work, and gives examples of theory as an evolving pursuit throughout the history of ecology.  It clarifies the “jobs” that theory performs in science, and shows the broadest way to conceive of theory and its relationships with data and generalization.  Putting the insights of this chapter to work in BES should help clarify our own theoretical structures and the relationships to specific research activities.

Background Readings:

Scheiner, S.M. and M.R. Willig.  2011.  A general theory of ecology.  Chapter 1, pp 3-18, in S.M. Scheiner and M.R. Willig, editors.  The Theory of Ecology.  University of Chicago Press, Chicago.  This chapter emphasizes the components of theory, the hierarchical structure of theory (general, constitutive, model), and articulates the deepest and most general propositions underwriting the science of ecology.

Collins, J.P. 2011.  Foreword, pp ix-x, in S.M. Scheiner and M.R. Willig, editors.  The Theory of Ecology.  University of Chicago Press, Chicago.   By one of contemporary biology’s most profound thinkers.  A former Director of NSF’s Division of Environmental Biology, and an author of an important paper on contemporary urban ecology in the US at its birth. This introductory overview puts ecological theory in a very broad context.

This may seem like a lot to read.  But BES is a large and complex project.  We only identify one book each year as a focus of learning and discussion among all members of the BES community.  We hope that’s not too much to ask.  

Join the Webinar

Please join us via Go-To-Meeting at 2 p.m. Eastern Standard Time on Tuesday 4 March to discuss these three selections from our Book of the Year.  Go here at that time to join the meeting: https://global.gotomeeting.com/join/882708421  The meeting will be recorded and archived for those who cannot join live. Go To Meeting will load an app to permit you to contact the meeting using your computer mic and speakers (or better, headset).  If you want to join by phone, that option will also be presented.

RSVP

Please RSVP, either for acceptance or regrets to Holly Beyar, BES Project Facilitator at this email: beyarh at caryinstitute dot org.  Important background information for the webinar and its archive will be circulated to those who RSVP either way.

Don’t miss this.

Coupled? Hybrid? Or Just Systems?

Having recently returned from the first Congress of the Society of Urban Ecology, I can report that there was a lot of talk in the plenary sessions about the nature of cities-suburban-exurban areas as systems.  In particular, it was emphasized that they were “hybrid” systems, incorporating social and biophysical components and the interactions that involve both these kinds of features.  The attendees seemed to be rather excited by the terminology of hybridity.

One advantage of the idea of hybridity of urban areas is that it avoids the conceptual distinction of human or social on one hand, and natural or biophysical on the other.  The label of “coupled” human-natural systems, while attempting to point to connections, still maintains that there are these two kinds of systems that might be separated. 

The idea of hybridization may in fact be a better choice than system coupling for C-S-E areas.  A hybrid in the biological sense cannot be taken apart.  The genotype and the phenotype seamlessly combine the characteristics and features of the two parents.  There is no way, for example, to take the horse or the donkey out of the mule.

So cities may usefully be thought of as hybrids.  There is the intent and use for human wellbeing, delight, and productivity as one parent, and the sometimes subtle processes of nutrient transformation and retention, the biological activities in soils, substrates, streams, and pipes, and the behavior, distribution, and reproduction of feral and volunteer plants, animals, and microbes on the other.  While the engineering and architecture of urban systems seem to be traditionally designed and operated as though they were purely built systems, in fact, they embody both intended and unexpected biology.  The supposed purity of the built and the biological parents of our urban systems is a myth, and a reality that cannot be maintained.

An example of the hybridity of cities is found in the large, but nearly invisible transfers and cross-contamination between supposedly distinct components of the flux of water.  Biology and the natural world might reasonably be able to claim the streams that run through and adjacent to cities, while built infrastructure might claim the water supply pipes, storm drain systems, and sanitary sewers.  In reality, these seemingly different pathways of the flow of water are surprisingly interconnected.  Leaks from the pressurized water supply pipes end up in the surface streams, or in the loosely sealed ceramic tile pipes of sewers.  Similarly, the unsealed joints of ceramic tile pipes of many older sewers release fouled water, loading bacteria, nitrates, phosphates, and pharmaceuticals, among other contaminants, into streams and ground water.  Some of this contamination enters storm water pipes where it will not be treated.

Similarly, the entanglement of human decisions, people’s wellbeing, and the structure and workings of the environment, including biological and built components, is irrevocable.  Speaking in terms of hybridity is a more powerful metaphor for the kinds of successful models and understanding of urban systems than coupling distinctly human or natural models.  Urban areas – those spatially heterogeneous but highly interlinked mosaics of city, suburb, exurb, and rural – are “just” systems.  The integration required by the concept of system as an entity comprising interacting parts is already a good enough.  Still, the label of hybrid reminds us of something important about the urban realm.

Press-Pulse Dynamics: A Hypothetical Feedback Model for Long-Term Social-Ecological Research

An important conceptual resource for BES III has recently appeared online. This publication presents the feedback cycle between social and ecological structures and functions as mediated by ecosystem services and by press and pulse events.

This conceptual framework highlights that the dynamics of press and pulse events is a key link in the integration of social and bioecological processes and structures. A version of the feedback cycle adopted for BES III, and identified by its older label of the Integrated Science for Society and Environment (ISSE) appears as Figure 2 in the BES proposal and in an earlier post on the Web Log. This framework is perhaps really best described as a model template, which can guide construction of more specific, testable models and hypotheses. This paper deserves serious study by researchers and scholars affiliated with BES.

The publication appears in the Ecological Society of America's journal, Frontiers in Ecology and Environment. Members of the Society and persons at subscribing institutions can find the paper through this Digital Object Identifier: doi:10.1890/100068

The full citation of the online publication is as follows:
Scott L Collins, Stephen R Carpenter, Scott M Swinton, Daniel E Orenstein, Daniel L Childers, Ted L Gragson, Nancy B Grimm, J Morgan Grove, Sharon L Harlan, Jason P Kaye, Alan K Knapp, Gary P Kofinas, John J Magnuson, William H McDowell, John M Melack, Laura A Ogden, G Philip Robertson, Melinda D Smith, and Ali C Whitmer. 2010. An integrated conceptual framework for long-term social–ecological research. Frontiers in Ecology and the Environment (e-View)

A key phrase from the abstract of this article is, "Here, we present an iterative framework, “Press–Pulse Dynamics” (PPD), that integrates the biophysical and social sciences through an understanding of how human behaviors affect “press” and “pulse” dynamics and ecosystem processes. Such dynamics and processes, in turn, influence ecosystem services – thereby altering human behaviors and initiating feedbacks that impact the original dynamics and processes."

Photo courtesy of University of Maryland, Baltimore County. View from the roof of the Administration Building toward downtown Baltimore.