Ecosystem as Place; Ecosystem as Network

The most frequently cited definition of the ecosystem concept owes its origin to Sir Arthur G. Tansley in 1935 (Pickett and Grove 2009).  It has proven to be a very flexible concept, and can be applied to any scale that includes aggregations of physical environment and organisms, plus the interactions among all physical and biological components.  The interactions are just as important as the material, energy, and organisms that exist within ecosystems.  Nevertheless, ecosystems are usually specified as locations or places, that is volumes of some part of the Earth, whether watery, dry land, or wetland (Figure 1).

Figure 1. Experimental watersheds at the Hubbard Brook Ecosystem Study in New Hampshire as ecosystems.  Using the ecosystems as place perspective, the watersheds, with boundaries set by the flow of surface water into the receiving stream, are recognizable ecosystems for the purposes of research and modeling. A photograph of a landscape may represent one or many ecosystems, but it is necessary for the researchers or managers to specify the boundary of each system that the photo might show.

Ecosystem as Interaction

Yet, there is a view of ecosystems that places the interactions themselves as the focus.  This usage is most often heard in the vernacular or in discussions about corporate products and the services they deliver.  Hence, one hears about such things as the "Apple ecosystem," or the "Google ecosystem," or the "health care ecosystem."  Clearly such usages place the connections and flows of information, products, or outcomes at the center of concern.  A bounded and contiguous place is not the point in this use of ecosystem as a network.

Networks are a primary concern of many sciences.  Information sciences, neurosciences, industrial ecology, and studies of governance (Figure 2) often emphasize connections and flows of information, power, influence, materials, and energy.  Traffic engineers and planners envision their topic in terms of networks, although those networks can be seen to serve both close and distant territories.  The network rather than the territory or place is the point.

Figure 2. A network approach to a system.  This is a governance network, showing the connections between government agencies, non-governmental organizations, and community associations concerned with environmental stewardship. The connections represent the sharing of finances, resources, staff, or information. (From Romolini and Grove, 2013.)

So it may seem that the network perspective and the place-delimited view of ecosystem are contradictory and divergent approaches to science.  But this is not the case.  In fact, ecology is a science of interaction.  A traditional definition of ecology states that it is the study of the interaction between organisms and their environments.  However, this definition can be expanded to acknowledge the variety of units or entities other than just organisms that are involved in those interactions.  For example, in the 1950s ecology expanded to consider ecosystems as entities in which biogeochemical processes were the concern.  In the 1980s in the United States, landscape ecology was imported and adapted to emphasize the interactions that involved spatially heterogeneous mosaics at various scales.  Even populations and communities came to be seen as comprising subsets that interacted across space, as in metapopulation or metacommunity theory.  The explicitly interaction-focused definitions of ecology (Box 1) work equally well with the place-based or the network-based approachs to systems.  

Box 1: The Cary Institute Definition of Ecology.  The scientific study of the processes influencing the distribution and abundance of organisms, the interactions among organisms, and the interactions between organisms and the transformation and flux of energy and matter.

A network is also a system, but specifically a system of interaction pathways, mechanisms, or flows.  In other words, a network can be considered to be an infrastructure or a process that takes place over that infrastructure.  Networks as infrastructure may involve materially connected continuous pathways, like roads or wires.  But infrastructural networks can also involve fields, like broadcast via electromagnetic radiation (McGrath and Shane 2012).  Certainly, the underlying fields are continuous, but the function of networks that rely on electromagnetic media seem more discontinuous, since the information can travel great distances with no tangible expression of the network until the message is delivered and decoded.

Joining Networks and Places 

Some theories in urban ecology attempt to deal simultaneously with the place-based and network-based conceptions of systems.  For example, the continuum of urbanity recognizes that local to global connections are key to understanding urban systems now (Seto et al. 2012, Boone et al. 2014).  The fine scale connections can be via road, rail, pipes, fiber, or copper.  Even at regional scales, these physical networks remain important.  Shipping lanes and airline routes are a different kind of infrastructure, but they support regional to global connections in which urban areas partake.  Satellite communications, radio, and wireless act at various scales and can be seen as virtual networks.  The regional and global networks have become a part of daily urban system functioning.   

These networks connect places, and those places embody lifestyles, livelihoods, and environmental conditions that are key drivers of urban ecosystem structure, function, and change.  The continuum of urbanity expresses the seminal role of connections when it acknowledges that rural, urban, and wild places -- ecosystems in the sense of Tansley -- contain and are parts of extensive continuous and virtual networks.  So ecosystems are both place and network.

Literature Cited

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 313–330in K. C. Seto and A. Reenberg, editors.Rethinking urban land use in a global era. MIT Press, Cambridge.

McGrath, B., and G. Shane. 2012. Introduction: metropolis, megalopolis, and metacity. Page in C. G. Crysler, S. Cairns, and H. Heynen, editors. The SAGE handbook of architectural theory. SAGE, Washington, DC.

Pickett, S. T. A., and J. M. Grove. 2009. Urban ecosystems: what would Tansley do? Urban Ecosystems 12:1–8.

Michele Romolini, J. Morgan Grove. 2013. Assessing and comparing relationships between urban environmental stewardship networks and land cover in Baltimore and Seattle. Landscape and Urban Planning 120:190–207.

Seto, K. C., A. Reenberg, C. G. Boone, M. Fragkias, D. Haase, T. Langanke, P. Marcotullio, D. K. Munroe, B. Olah, and D. Simon. 2012. Urban land teleconnections and sustainability. Proceedings of the National Academy of Sciences of the United States of America 109:7687–7692.

Steward Pickett

Where did Urban Ecology Come From? Zev Naveh and the Total Human Ecosystem

Encountering Zev Naveh - A force of nature

One answer to the question of where urban ecology came from has to point to Zev Naveh.  When I first heard Zev Naveh (1919-2011) a professor at Israel's Technion, talking about the "total human ecosystem," I didn't get it.   Zev, whom I later hosted on a sabbatical visit to Rutgers University, was way beyond my thinking about people and ecology at the time.  I had been working on how communities of annual plants that colonized disturbed, post-agricultural lands were put together.  I was also developing and generalizing ideas about natural disturbance, and working to put succession in a connected, dynamic landscape perspective.  I was just beginning to seriously think about humans and nature as a big picture.  But at the time "landscape ecology" was just coming together.  Zev was one of the people who was developing that big new field at the time. 

One of his main points was that people were parts of real ecological landscapes.  That much I got.  That idea resonated with Richard Forman's seminal definition of landscape, exemplified by the book written with Michel Godron in 1986.  Richard and I were colleagues on the faculty of Rutgers University for about seven years.  In fact, Forman had invited Zev to Rutgers for that sabbatical year, but had been lured away by Harvard before Zev arrived.  So I became Zev's host and colleague for that academic year.  Since that visit, I had often seen Zev at national and international ecological and landscape meetings.  But I must admit, that the idea of the total human ecosystem had become a little rusty in my memory. 

Reminders

A few days ago, I was assembling papers to prepare for writing a new paper.  As is often the case, digging around in the bibliography of one paper leads to new papers, or reminds one of things that one had neglected for a while.  I came across a citation of a published lecture of Zev's that I hadn't read.  It was in an obscure publication, but fortunately The Technion had archived some of Zev's papers on an accessible website.  Here's what I was reminded of.  And the embarrassing admission is how useful Zev's thinking  -- summarized in 1992 -- about urban ecosystems remains.  Here are some nuggets, admittedly filtered through my current lens of urban ecological thinking.

• It is really useful to think of urban ecosystems as landscapes, and landscapes can exist at any scale.  There is no single landscape scale.

• Patches are actually three-dimensional things.

• Urban systems integrate biological, physical, ecological, technological, economic,  and cultural components.  This is summarized as his" total human ecosystem" idea.  Zev uses classical terms like biosphere, technosphere, and noosphere (the global network of ideas), but insisted that they are integrated in landscapes.

• Ecology's origin as a biological science colored its application to cities, where most attention was on what organisms were present and where.  Some of us later called this the ecology "in" cities approach (Pickett et al. 1997).

• A hierarchical, systems theory approach is useful for organizing thinking and suggesting both bottom up and top down control in focal components of landscapes in general -- and urban systems.  This is the holon perspective long used in systems theory, for which he cites Koestler (1969), for the idea.

• Technology is a part of urban systems, so the contemporary emphasis on social-ecological-technical systems (SETS) has a deep precedent.

•  Globalization is part of his thinking: He acknowledges that even then nearly 50% of Earth's people lived in urban areas; furthermore, technology is represented as a global system, not just a local set of tools and constructions.

• Landscape ecology -- and by extension -- urban ecology, must be transdisciplinary.

• He calls for the use not only of ecological knowledge in improving the role of urban-industrial (fossil and nuclear added to biomass powered) systems, but also ecological wisdom and ethics.  Alas, anthropologist Joseph Tinker suggests that social systems -- as drivers of environmental degradation -- are hardly ever voluntarily limited.  Rather, the collapse with the administrative and social costs of increasing complexity.)

• Ecological knowledge is crucial for urban design, and cities need "green and watered" components, perhaps ideally constituting 10% of urban land, in his opinion.

The total human ecosystem has a long history.

·        There are deep literatures in the components he brings together, going back to plant ecologist and iconoclast Frank Egler (1970) for the total human environment idea first used in discussing industrial agricultural impacts.  His brief literature cited contains classics of hierarchy theory, systems theory, and complexity theory.  Jantsch (1975) is another key contributor to Zev's thinking on complexity.

Well, it's a little sobering to find so many ideas that many of us take as hallmarks of "modern" urban ecology so well articulated and well foreshadowed so long ago.  But on the other hand, it is comforting to know that one of the inventors of landscape ecology, and one of the champions of systems theory and understanding spatial heterogeneity in ecology was pointing to the path urban ecology has followed.

Literature Cited:

The Paper this Essay is About:

Naveh, Zev. 1992. A landscape ecological approach to urban systems as part of the total human ecosystem.  Journal of the National History Museum and Institute Chiba. 2:47-62http://tx.technion.ac.il/~znaveh/files/Landscape%20Ecology%20Theory%20and%20Global%20Applications/landscape%20ecological%20approach%20to%20urban.pdf

Supporting:

Egler, F.E. 1970. The Way of Science: A Philosophy of Ecology for the Layman. Hafner, New York

Forman, R.T.T. and M. Godron. 1986. Landscape Ecology. Wiley and Sons, New York

Jantsch, E. 1975. esign for Evolution: Self-Organization and Planning in the Life of Human Systems. George Braziller, New York.

Koestler, A. 1969. Beyond atomism and holism - The concept of the holon. In Al Koestler, and J.R. Smithies, eds. Beyond Reductionism: New Perspectives in the Life Sciences. Hutchinson, London.

The Other References:

Pickett, S.T.A., W.R. Burch, Jr., and S.E. Dalton.  1997.  Guest editorial: Integrated urban ecosystem research: Themes, needs, and applications.  Urban Ecosystems 1(4):183-184. (For ecology in/of cities)

McPhearson, Timon, S.T.A. Pickett, N. Grimm, J. Niemelä, M. Alberti, T. Elmqvist, C. Weber, J. Breuste, D. Haase, and S. Qureshi.  "Advancing Urban Ecology Towards a Science of Cities." BioScience, accepted. (for social-ecological-technical systems)

Tainter, Joseph A. (1990). The Collapse of Complex Societies (1st paperback ed.). Cambridge: Cambridge University Press. ISBN 0-521-38673-X.

An Obituary:

Antrop, M., & Pinto Correia, T. In memoriam Zev Naveh (1919 Amsterdam–2011 Haifa). Landscape Urban Plan. (2011), doi:10.1016/j.landurbplan.2011.06.003

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.

Resilience: Ecology, Evolution, and Engineering

The concept of resilience is key to BES III. This powerful concept is ideal for understanding and working with complex, human ecosystems. However, it is the object of some confusion because there are two contrasting ways to frame and theorize the concept.

Originally, engineering and physical systems were the source of the concept as applied in ecology. Under the equilibrium paradigm predominant at the time, resilience was conceived of as the ability of a system to absorb a shock or deformation and to return to its original, or equilibrium, state. A rubber band is a perfect example of such a system. The loose, floppy form can be stretched repeatedly, and still return to its general band-like shape.

Engineering or equilibrium resilience is the concept used to describe this dynamic. This sort of resilience can be called engineering resilience because it characterizes built structures and infrastructure. Key to this idea is that there is an acceptable, desired, or equilibrium state of the system. Of course, extreme deformation or perhaps consistent strong deformation over time can lead to system failure. The band breaks when stretched too far, or after years of material degradation while encircling a thick wad of forgotten papers in a hot attic.

Equilibrium or engineering resilience may be of value when it is possible to identify a desirable state that is expected to persist over some specified time or at a particular spatial scale. But for many purposes, it is best considered a special case of the concept of resilience. A more inclusive concept suitable to systems that are not at equilibrium, or which are undergoing periodic or constant change is ecological or evolutionary resilience.

Ecological resilience does not ask whether a complex system returns to a previous or equilibrium state. Rather, it asks about the changes that a system can experience and still persist in the same dynamic form. Resilience is about the ability to receive shocks and still stay in the game. Systems that can adapt to change are said to be resilient. This then is an evolutionary kind of concept since adaptation is a central feature. This is in contrast to engineering resilience which is concerned with stability or permanence. So, ecological and evolutionary resilience are concerned with adaptive capacity and adjustment to change, not to return to a stable point. Rather than asking about the ability of a rubber band to return to its unstressed state, evolution asks about the rubber band becoming something else that is better adapted to the new conditions. It is of course silly to think about a simple, physical-chemical system such as a rubber band changing in such a radical way, but evolution, adaptation, learning, and adjustment are familiar capacities of biological and social systems. In other words, they are complex systems that can adapt. Resilience in the more evolutionary sense is the idea that points toward the question of how -- and how well -- a particular system can adapt to changing conditions or sudden shocks that come at unexpected times.

Changing concepts of resilience are relevant to the BES III main theme of Sanitary to Sustainable City. The sanitary city identifies a desired state, and seeks to keep structures or processes at that level. Given that societal and regulatory decisions identify legal or desirable targets for some features people must manage, a classical or engineering definition provides guidance about how to measure success. However, under changing environmental conditions, including social, economic, and environmental alterations, it may be more appropriate to ask about the capacity of the system to adjust to those changes. Recognizing that feedbacks among social, economic, and environmental factors and processes are an unavoidable part of urban ecosystems, this suggests that we learn how to go beyond the engineering resilience concept and understand and use the contemporary concept of ecological or evolutionary resilience.

Here are some references about this contrast and the nature of ecological resilience that are relevant to socio-ecological systems.

Gunderson, L. H. 2000. Ecological resilience - in theory and application. Annual Review of Ecology and Systematics 31:425-439.

Holling, C. S. 1996. Engineering resilience versus ecological resilience. Pages 31-44 in P. C. Schulze, editor. Engineering within ecological constraints. National Academies of Engineering, Washington, DC.