Preparing for the BES Year of Theory

As the New Year rings in, it is time to prepare for 2014 as the BES Year of Theory.  This designation highlights our concerted efforts to improve our ability to integrate across different scales of theory, from the most general and abstract, down through mid-level theories, and ultimately to specific models and hypotheses.  Further, we hope to improve our ability to integrate across our various social and biophysical research realms. 

To begin this effort it is important to understand the largest context of BES III research – the understanding of social-ecological heterogeneity over the long term.  Although BES III addresses the transformation of the sanitary to the sustainable city, the still larger theoretical context that is not flagged in the title of our current proposal.  There are many large theories of urban systems, but the one that we have followed from the very beginning is a theory of social-ecological heterogeneity.  That is, we have adopted a theory of the nature and effects of spatial pattern and the relationships across space of the components of human ecosystems.  The theory emphasizes the feedbacks between the social and the biophysical components of the human ecosystems of cities, and invites us to hypothesize and examine the interactions between these two components.

In order to navigate from the general theory to operational models and testable hypotheses, we have chosen three conceptual lenses: the theory of locational choice, the theory of urban metacommunities, and the theory of the urban stream dis/continuum.  These are three lenses to focus some of the immense detail of factors that affect – and are affected by – social-ecological heterogeneity. 

These three areas are not arbitrary, but they represent three necessary, general components of heterogeneity in urban systems: social differentiation; biotic potential; and flow of materials.  The interactions of these three very general features are sufficient to explain heterogeneity of structure and processes in both the social and biophysical realms of urban systems. 

The details of how these three processes work can be further understood by employing the five core research areas of the LTER Network: 1) productivity; 2) the movement of inorganic matter; 3) the movement of organic matter; 4) populations; and 5) disturbance.  The urban LTERs were additionally required to address two additional conceptual areas: 6) human effects on land cover change and their reciprocal relationships with ecosystem processes; and 7) social-ecological data and analysis.  These seven conceptual areas indicate the breadth of long-term data that must be linked to the theoretical structures.

The presentation is intentionally general and abstract.  The abstract diagrams and sketches of our general theory, its division into three major areas, each represented by more operational models, are intended to guide our statement of hypotheses and integrative activities.  This structure may also provide a “strategy screen” for evaluating new initiatives and the proposed continuation of existing activities.  The structure is a framework to be filled in through our meetings and activities over the next two years. 

Quarterly Project Meetings

Our Quarterly Project Meetings will promote theoretical clarification and intellectual integration.  Here are the general topics for the first three meetings of 2014

January 2014: Use of stormwater detention basins for integrated social-ecological research and application.  Meeting will include introduction and needs for intellectual integration.

·        April 2014: Clarification of the three theoretical lenses and hypotheses for integration.

·        June 2014: Assessment of existing and potential data streams relative to 7 LTER core areas and theoretical areas.

An Introductory Presentation

As an introduction to the work we will be doing the overview presentation is available in several places:

The BES Website.  This link will download the PowerPoint presentation directly to your computer.  Start the slideshow and the narration will run and the slides will advance automatically.  http://beslter.org/docdrop/BES-III-Theories-Format-2-Narrated.pptx

Google Drive.  On this platform, you can preview the slides.  The recorded narration does not appear on the Google preview app.  However, you can download the file to your computer, and play it in Microsoft’s PowerPoint. 

https://drive.google.com/file/d/0Bx-QKDoShVRkMGdUdFlwUTJzMnM/edit?usp=sharing

If you want a non-narrated form, but with notes embedded on the notes pane for each slide in Powerpoint, go here: https://drive.google.com/a/caryinstitute.org/file/d/0Bx-QKDoShVRkTXFkQ3lOLVFabUU/edit?usp=sharing

Also see the November 2013 post on the Year of Theory in general.

The BES Year of Theory

Important Needs for Theory

Two things are clear about theory in BES.  First, it is an extraordinarily important and well recognized tool for integration and motivation in our long-term social-ecological research and education activities.  Theory features prominently in the proposal for BES III, and we are actively exploring three important theoretical lenses as ways to view and link our long-term  research, including modeling and comparative studies.  However, it is equally clear that we can do a much better job of explaining our theories to others, and using them to integrate among our various data streams and conceptual areas.

Our Strategy for Improving Use of Theory

In order to help us clarify and improve the use of theory in BES, 2014 will be the BES Year of Theory.  This will involve several linked and reinforcing activities:

• The BES Book of the Year will be Scheiner and Willig's The Theory of Ecology, published by the University of Chicago Press.
• We will conduct web-based seminars to examine several chapters in Scheiner and Willig's book, and links with social theory.
• Our Quarterly Project Meetings will focus on the three theories we have chosen as motivating and integrative tools, as well as on  research opportunities that cross disciplines and theories.
• We will seek a plenary speaker for our 2014 Annual Meeting who can address theory in a way suitable to a multi-disciplinary audience.
• We will conduct multi-disciplinary "walk-abouts" or field trips in Baltimore to promote shared understandings of place, research opportunities, and educational potential of our theoretical structure.

The Project Management Committee will explore other strategies for meeting the goals of clarifying and better using theory.  Please share your thoughts with me or with other members of that committee so that we have the best menu of choices available.

The BES Book of the Year.

In order to facilitate our use of theory as an integrative tool in our long-term social ecological research, an important book on The Theory of Ecology, edited by Samuel M. Scheiner and Michael R. Willig has been chosen as the 2013-2014 Baltimore Ecosystem Study Book Of The Year.  Published by the University of Chicago Press in 2011, the book’s 404 pages contain 15 chapters.

The strategy of the book is to lay out a general, very fundamental theory of ecology in Chapter 1, with the bulk of the book examining the more specific theories that contribute to the general theory.  Although all chapters will help us understand how to better articulate and employ theory in our empirical, long-term research, of particular interest in BES are the chapters on the metacommunity (by Leibold), on succession (by Pickett, Meiners, and Cadenasso), on ecosystems (by Burke and Lauenroth), on global change (Peters, Bestelmeyer, and Knapp), and gradients (by Fox, Scheiner, and Willig). 

In addition, the book includes two chapters by philosophically trained authors, Jurek Kolasa and Jay Odenbaugh. The editors conclude the book with a synthesis statement  on the state of theory in ecology.

In order to stimulate all members of our diverse and dispersed community to delve into this book, and to apply its insights in our own research and synthesis, we will hold web-based seminars using portals such as Google Hangouts or Go-To-Meeting.  We will also address social theory in some of our webinars.  Theory is a crucial tool that we can use to promote clarity and integration in our project. 

I strongly encourage all members of BES to read deeply in this book.

Bibliography

Publication details on the Scheiner and Willig volume can be found here: http://press.uchicago.edu/ucp/books/book/chicago/T/bo11161054.html  The book is available in paper or e-book editions.  (Well, hardcover too, of course.)

As background, you will not be surprised that I recommend the following:

Pickett, S. T. A., J. Kolasa, and C. G. Jones. 2007. Ecological understanding: the nature of theory and the theory of nature, 2nd edition. Springer, New York.  http://store.elsevier.com/product.jsp?isbn=9780125545228

Director’s Award 2013 to Prof. William R. Burch, Jr.

Bill Burch is one of the people without whom the Baltimore Ecosystem Study LTER would not exist.  Bill has been a pioneer in community and social forestry.  He also was a leader in establishing the research tradition of recreation behavior and ecotourism in wild, preserved, and urban places.  His work has enriched knowledge and communities not only in Baltimore, but in Asia, South America, and Europe.

Bill introduced me and my biological colleagues to Baltimore and the exciting work he and colleagues had been doing there since 1989.  His decade of experience in Baltimore was established the social network on which BES was founded.  He was instrumental in making connections with the Parks & People Foundation, which continues to provide much of our leverage and glue linking us to communities, agencies, and other important Non-Governmental Organizations in Baltimore. 

Bill has continued to be a source of social-ecological insights,http://environment.yale.edu/profile2/burch

a wise guide to the literature at this intellectual interface, a stimulus to critical thinking, a model of inspired yet realistic strategy for community engagement, and a model citizen.  Additional details of Bill’s career and contributions can be found on the website of the Yale School of Forestry and Environmental Sciences:

For all these reasons, the BES Project Management Committee unanimously and enthusiastically voted to award Bill our 2013 Director’s Award at our Annual Meeting at Cylburn Arboretum on 22 October this year.  The award includes a framed print of one of A. Aubrey Bodine’s classic black and white photographs of Baltimore along with our commemorative plaque.

Many thanks, Bill, for your myriad contributions to BES, and best wishes!

Weeds and the City

Few ideas are as loaded -- and as controversial -- as that of “weed.”  Combine this familiar term with the equally problematic term urban, and surely, confusion is guaranteed to reign. 

However Zachary Falck, an environmental historian, acts as a knowledgeable and confident guide into this troubled intellectual territory.  He has written the well documented and very readable Weeds: An Environmental History of Metropolitan America, published by the University of Pittsburgh Press in 2010. 

My slowness in discovering this book is no indication of its importance.  In fact, I recommend it to denizens and friends of the Baltimore Ecosystem Study LTER as a compelling exploration of the interface of the social and the biological through the lens of plants that are themselves vessels of complex connotation. 

What's In A Name?

Chickory, photo by Erica Tauzer.

Weeds have many other names, and each name collects its

own bouquet of connotations, biases, and values.  This group of plants can be called colonizers, ruderals, and volunteers; invaders, pioneers, or any number of more technical terms.  Falck introduces some intentionally novel terms in order to avoid, or perhaps highlight, some of the assumptions so deeply, yet silently, embedded in the term weeds.  Perhaps Falck’s primary goal in the book is to make readers look for the hidden social and cultural assumptions that so often accompany the reference to weeds.

One reason I am so impressed with the job Falck does in examining weeds as a window onto urban systems, with both the changes and consistency of the thinking about nature in urban systems, is that my roots as an ecological scientist trace back to studies of the germination behavior of the seeds of common ragweed, Ambrosia artemisiifolia. 

These studies, conducted in the lab of Drs. Jerry and Carol Baskin at the University of Kentucky, showed that common ragweed was extraordinarily well adapted to colonizing physically disturbed soils, and its dormant seeds could persist for years buried in the soil between episodes of such disturbance.  Yet, the adult plant demands high levels of light and other resources, and as plant communities changed after disturbance, ragweed was displaced by other species that could use lower levels of light and soil resources.  Jerry Baskin and I (Pickett and Baskin 1973) concluded that the best management strategy for ragweed was to leave it alone.  Soil treatments designed to uproot common ragweed would in fact promote a new crop the next year.  Falck reviews the history of ragweed control efforts in some major American cities, and notes their consistent failure.  That failure was almost guaranteed by ignorance of the biology of the  species and the mismatch between that biology and the management strategies employed.  But there are other riches in this book.

Weeds As Social Signifier

Weeds have been addressed as a biological phenomenon, of course, but Falck richly documents how they have also been used as a social signifier.  On the one hand, weeds stand for elements, both social and biological, that are deemed suitable for eradication or exclusion from American cities.  Hence, disfavored ethnic and racial groups, immigrants from other countries of from rural regions of the US, and persons who engage in what others sometimes or nearly universally define as harmful behaviors, are labeled as weeds.  On the other hand, weediness stands for an admirable ability to flourish in polluted, hazardous, or otherwise unfavorable conditions.  This description has been applied to plants, animals, and, again, to different social groups.

The troubling thing about all these assumptions is that they are so rarely rigorously questioned.  The term weed is so familiar and so intuitive that people seem to use it without question or examination.

Falck, however, shows that the richness of conceptual, demographic, political, and even biological ideas that “weed” can refer to is immense.  Even in legal uses -- in which one hopes for clarity -- social values, biology, social class, power, and knowledge are confounded and intertwined.  For example, the aesthetic of the park-like, shared American front lawn thwarts the establishment of meadows or prairie as a landscaping approach.  But such limits seem most likely in the small yards of the working and middle classes, and would be less likely to limit the choices of wealthier holders of large properties.  Also, much of the decision making about “weediness” of yards strikes me as arbitrary, based on plant height, the assumption that mowing is the main management tactic, and the assumption that urban disamenities such as rats are associated with these arbitrarily defined weeds.  Oddly, many of these assumptions are not in fact based on data.  Rats, for example, live in built structures or beneath hard surfaces that provide them protection.  They do not live in open vegetation, whether “weedy” or otherwise.

Weeds and Continuing Urban Dyanamics

One lesson of the book is that weeds, or as I might

Dr. Yvette Williams, studies a vacant lot in
Baltimore.  Photo by Erica Tauzer.

say as a plant ecologist, plants adapted to open sites with uncontested resources, have been a consistent part of our urban enterprise.  They occupy lands that are recently enfolded into municipal boundaries, but which have yet to be built upon.  At the other extreme, they dominate in sites where the retreat of industrialization and the reduction in residential density have left vacant parcels.  Well funded and extensive efforts to eradicate weeds from our cities have conspicuously failed.  The New York City program to abolish ragweed is a powerful example examined in detail by Falck.  We will always have weeds in our city-suburban-exurban systems. 

Falck’s book examines many fascinating aspects of the relationship of weeds with the dynamics of cities and the social and legal processes that shape urban places.  Legal status of weeds illustrates concern with individual responsibility and the perceptions of public good and of nuisance.  Mandates for management are based on perception, such as the association with criminal activity.  Often such perceptions are driven by the occasional splashy correlation, rather than careful consideration and evaluation of causality.  This is perhaps not surprising given the deep and powerful social view of weeds as sources of pestilence, as threats to productivity, and as indicators of personal slovenliness.

A New View of Weeds for the 21st Century

As the 21^st century dawns, Falck suggests that rather than reevaluating the role of volunteer or pioneer plants in urban systems, citizens and managers continue to fall back on tradition and long-held biases.  If anything, the fervor of eradication long focused on weeds is now shifting to exotic, introduced species.  Unfortunately, the risk that unexamined social biases merely transfers from weeds to exotics is great.  Rather, threat, benefit, adaptation, and life cycle, should be examined from both social and ecological perspectives.  Otherwise, the excesses and failures of eradication of plants well and long adapted to human-generated habitats and stresses, will continue to sap resources and limit some of the benefits that these resilient plants may well provide to our continually evolving cities, suburbs, and exurbs.

For Further Reading 

Falck, Z. J. S. 2010. Weeds: an environmental history of metropolitan America. University of Pittsburgh Press, Pittsburgh.

Pickett, S.T.A., and J.M. Baskin.  1973.  The role of temperature and light in the germination behavior of Ambrosia artemisiifolia.  Bulletin of the Torrey Botanical Club 100:165-170.  (now the Journal of the Torrey Botanical Society.)

What Did BES Do Last Year? The 2012 Annual Report

Who did this work?

The Baltimore Ecosystem Study, Long-Term Ecological Research Program is a large, complex, and active endeavor.  Its participants include 40 researchers, educators, and leaders in community engagement.  In addition, there are five Post-Doctoral Associates who participated in the project last year.  This community of senior professionals mentors and works with more than 100 graduate students at some 21 universities.  

What has this group been up to?

The detailed answer is provided in our 2012 Annual Report, a comprehensive document of 103 pages (http://beslter.org/bes_annual_reports/bes_annual_report_2012.pdf).  In it, readers will find overviews of the activities in research, education, and community engagement, as well as key findings of nearly thirty disciplinary and integrated social-ecological research projects.  The activities and findings are divided according to which of the BES III research topics each mainly addresses: Locational Choice of Households and Institutions; The Urban Stream Dis/Continuum; and Urban Metacommunity Theory.

 

Locational Choices:

·         The development of environmental inequities can be

traced through time, and are more than incidental spatial correlations (C.G. Boone, reporting).

·         Most tree regeneration in cities is volunteer rather than planted, but in Baltimore and 16 other cities, tree cover declined significantly in the recent past (C.J. Nowak, reporting).

·         Exurban land subdivision from 1995-2007 was extraordinarily scattered and low density, with the vast majority comprising only 2 or 3 lots.  Developers apparently favor small subdivision due to the shorter times taken to have them approved (E.G. Irwin, reporting).

·         A novel, agent based econometric model accounting for basic market conditions generates fundamentally different predictions than standard urban economic theory (E.G. Irwin, reporting).

·         A strong statistically negative relationship was found between tree canopy cover and crime in Baltimore City and Baltimore County.  The models accounted for a dozen socio-economic control variables (A.R. Troy, reporting).

Urban Stream Dis/Continuum:

·         How urbanization affects floodplain sedimentation and subsequent biotic controls on nutrient assimilation constitutes a crucial historical legacy (D.J. Bain, reporting).

·         The role of groundwater dynamics on urban stream flow and water quality, especially through the role of aging and over-connected water infrastructure systems, is emerging as a key process (K.T. Belt, S.S. Kaushal, and C. Welty, reporting).

·         Phosphorus, one of the important pollutants in Baltimore streams and the Chesapeake Bay, shows increased loading with impervious cover, and a shift to export during high-flow conditions.

·         Pharmaceuticals and personal care products, along with illicit drugs, are detectable in streams, and stream primary producers are sensitive to some of these contaminants (E.J. Rosi-Marshall, reporting).

·         Leaf litter input into the urban “headwaters” of gutters and storm drains constitutes a major source of carbon pollution downstream, and suggests new management needs (K.T. Belt, S.S. Kaushal, reporting).

Urban Metacommunity:

·         The tree composition of different land use types shows great turnover or beta-diversity across types, suggesting a predominant role of human choices concerning management (C.M. Swan, reporting).

·         Along a gradient of management, local diversity of low-intensity sites was higher than patches managed at medium-intensity.  However, there was lower species turnover among low-intensity management sites compared to medium intensity sites.  The role of high levels of dispersal among sites is suggested (C.M. Swan, reporting).

·         Mosquito traps in the most highly urbanized sites predominantly captured invasive species, while rural reference sites included both invasives and native, often non-human biting species (S.L. LaDeau, reporting).

·         The role of discarded materials that can support mosquito breeding and the role of garden and lawn watering are associated with contrasting socio-economic characteristics of neighborhoods, but they have temporally distinct effects (S.L. LaDeau, reporting).

·         A global survey of urban bird communities indicates that avian communities are unique across different urban regions, with only a few having cosmopolitan distributions (C.H. Nilon and P.S. Warren, reporting).

Actionable Science

We have been pleased that many of our results and projects, some conducted in collaboration with city, county, and state agencies, have played a role in environmental policy and management in our region.  For example, BES has contributed to:

·         Planning for increasing Baltimore City’s urban tree canopy, and providing information on the physical and social structures of different neighborhoods;

·         Laying the foundation for a Chesapeake Bay Landscape model that should aid efforts to reduce water pollution in the Bay,

·         Assessing the functional outcomes of stream restoration originally judged based on channel morphology,

·         A better understanding of the common and contrasting features of urban biodiversity across cities, which can help meet requirements of the Convention on Biological Diversity;

·         An understanding of how urban design interacts with biodiversity and other functional aspects of city and suburban biogeochemistry.

This is just a brief scan of some of our work.  We invite you to peruse the annual report for more projects and greater detail.  A list of publications and web resources is also included in the report.

The Cover Art

Finally, it is with considerable pleasure that I note that the cover photograph on the report is one of the wonderful photographs taken by BES 2012 Artist-In-Residence, Lynn Cazabon.  See http://www.lynncazabon.com/ for more of her work.

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.

What Does Collapse Tell Us About Resilience?

The adaptve cycle is key to understanding resilience as an integrated ecological and social construct.  The cycle is introduced elsewhere in this Web Log (http://besdirector.blogspot.com/2011/01/resilience-ecology-evolution-and.html) as well as briefly defined in the BES Urban Lexicon (http://besurbanlexicon.blogspot.com/search/label/Adaptive%20Cycle).  One of the key aspects of the cycle is the movement of systems in a conceptual space defined by the accumulation of capital in the structure of the system, and the increasing complexity of the system at the same time (Figure 1).

Fig. 1. Capital and complexity as two axes of the
adaptive cycle of resilience. r-K contrasts
trace out the blue trajectory.

Ecological Foundation of Increasing Complexity

As an ecologist, I find these these increases easy to understand, since they parallel changes that have long been understood from ecological succession.  One of these shifts is based on resource capture.  Dominance of the plant community shifts from species that specialize in the capture of resources that are freely available in the environment, to dominance by species that specialize in conserving the resources they have already captured.  Think of fast growing, high resource-demanding colonizing species or weeds, compared to slow growing, resource hoarding trees that get by on modest fluxes of nutrients and light.  This kind of contrast is labeled in both plants and animals as r versus K strategies. 

The biological contrast in complexity emerges from the similar successional differences.  For example, later successional communities typically have a larger number of canopy layers, as well as greater spatial heterogeneity.  These patterns result from the growth of long-lived canopy-forming plants, insertion of lower layers dominated by shade-tolerant species, and the emergence of species that spread clonally.  The massive, long-lived, and spatially extensive structures are good at storing and allocating assimilated resources. 

However, the slow growth rates and massive structures associated with dominance in late successional comminities also make those systems vulnerable to external disturbances, such as wind, fire, or disease outbreak.  The same species that manage assimilated resources have evolved structures and processes that ill suit them to deal with environments where resources are freely available.  This is what sets up the adaptive cycle of r-K shift with subsequent release and reorganization.

In social systems, accumulation of capital or wealth is a familiar trajectory.  Settlements are often initiated in sites where resources or the opportunity to concentrate resources is high.  In such situations the external resources, be they rich soil for crops, industrially valuable minerals, or fossil fuels for example, are initially untapped.  As the settlement accumulates more residents and built structure, it assimilates more resources.  Furthermore, urbanization is associated with increasing capacity to assimilate and process more resources.  All this is expressed as wealth embodied in the system.

Driving Complexity in Social Systems

But what strategic contrast might explain the shift in the social complexity of the system?  Joseph Tainter's (1988, 2006) analysis of the collapse of social systems exposes the sources of social complexity.  The built structure of settlements clearly becomes more complex.  In addition to raw density of structures, often the height and heterogeneity of structures increases.  Infrastructure to move people, goods, resources, and wastes is developed.  Specialization of jobs and lifestyles emerges, and the demographic differentiation of the population typically increases as residents are drawn from other settlements or different rural areas.  Of great importance is the elaboration of increasingly layered, spatially extensive administrative and governance structures.  Specialized knowledge and training echo the increasing administrative compelxity.   

This suite of differences, along with many others, consolidate into fixed, self-perpetuating structures that are initially adaptive.  As an already complex society attempts to solve its problems it can only add additional layers or kinds of organizational complexity.  Yet, each new innovation involves a cost that necessarily produces less return on the investment.  Thus, according to Tainter, the growth of complexity in societies will trace out a curve of decreasing marginal return over time.  Once marginal return declines to lower levels, the society is poised to disintegrate because the fixed investment leaves the society vulnerable to such things as resource depletion, invasion, internal unrest, or simply voluntary migration to a less burdensome region.  Environment and resources play a role, but the lens through which the crisis comes into focus is through the economics of marginal return on investment.

Tainter’s model explains the social component of the “front loop” of the adaptive cycle in social-ecological systems.  Many analyses in the literature have focused on the inertia and rigidity that result from high levels of social complexity (Biggs et al. 2010).  What Tainter exposes is the mechanism for the increase in social complexity.  Social complexity results from the accumulation of incremental solutions to the problems that society identifies.  Such complexity may interact with external and internal shocks of either social or biophysical origin to either cause collapse or to generate adaptive reorganization.

References

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.

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.

Myth and Memory of Rivers and Shorelines

One of the first things I experienced when learning how to get around Baltimore was the mash up of its multiple street grids.  First I have to admit that most of old Baltimore streets are laid out in a grid pattern, with right angle intersections.  So Baltimore reflects a Renaissance or Enlightenment rational street pattern by and large.  This is a contrast to the famous Medieval and cow-path arrangement Boston is said to exhibit.  Of course Baltimore does have its radial streets that reflect old farm market roads.  And the northwest ray of Reisterstown Road has the hallmarks of an even earlier Native American path that would have followed the high ground of the watershed ridge between the Gwynns Falls and the Jones Falls drainage basins.  But fundamentally, getting around old Baltimore is a matter of navigating a checkerboard of square blocks.  

Baltimore's Grids

Actually, it’s a matter of navigating several different checkerboards that meet at odd angles. Why doesn’t Baltimore have just ONE street grid.  It is clear that the early layouts of Baltimore weren’t worried about following topography, with the exception of some of those radial roads.  Such willful application of the rationalist grid ignores the rolling hills and the occasional valleys of a location that straddles the Coastal Plain and Piedmont geomorphic provinces.  Attemps from the early 20^th century on have only partially obliterated the clash of grids in Baltimore.  But the question remains: “Why several grids rather than one grid?”

1864 Baltimore. 

Baltimore has several grids because each of them was oriented to a different shoreline.  Baltimore’s original shoreline was extremely heterogeneous.  In the territory that would become the city, three major streams came down to the harbor in three separate valleys.  The larger Patapsco River entered the Harbor from the west, and established its own complex shoreline patterns.  Jones Falls entered the Harbor as a marshy estuary which extended well upstream.  The grid of Little Italy is anchored to the old edge of Jones Falls.  So too, farther upstream, is the northwest angled grid that incorporates such neighborhoods as Bolton Hill, Penn North, and Druid Heights.  This anchoring is likely a reflection of the importance of the water powered industry along the Jones Falls.

 

Anchoring Grids

The anchoring of grids along diverse stream and harbor shores is a physical memory of the intersection of water and land.  But the physical nature of that intersection is affected by how people think about shores.  In other words, there are perceptions that might be called the mythology of shores.  Grace Brush earlier in this Web Log (http://besdirector.blogspot.com/2011/09/swamps-and-city-part-ii-special-guest.html), noted that the original shore lines of streams and estuaries would have included extensive marshes and forested wetlands.  Along streams, peripatetic populations of beaver would have created shifting mosaics of wetlands, pools, and dams as a result of their feeding and denning.  Shores not engineered by people are ragged in outline and mucky.  Tidal action in the coastal marshes would have made a habitat unsuitable for trees, and have maintained broad areas dominated by grasses and sedges, and would have made excellent habitat for larval fish and crabs.

1792 Shoreline in blue, today in green.
Baltimore Watershed Partnership

The historical reality and ecological complexity of unsettled shorelines are not the way that people represent or, in fact inhabit, shores.  A comparison of the map of the coast around Baltimore with a less urbanized shoreline elsewhere on the Chesapeake Bay reveals the power of our shore mythology.  Baltimore’s shore has largely been straightened to accommodate the piers required by industry and shipping, promenades for people, the waterfront condos of the wealthy, and the bars and restaurants overlooking the harbor enjoyed by tourists and residents.  Even in residential suburbs abutting the water, marshes and riparian forests have been replaced by gently sloping lawns of introduced turfgrass.  But beyond the urban and the urbanized outposts of wealth, the maps reveal shorelines of streams and the Bay that are jagged, wrinkled lines.  On the ground, muck and wet soils, marsh plants, or riparian trees that are adapted to wet soils having low levels of oxygen, form the suture between land and water.  These sutures are hybrid habitats that are in no way well represented by the boundary lines that people so readily draw at the edges of their towns and cities.

Using the history of Philadelphia’s establishment and growth, Dilip da Cunha (http://link.springer.com/chapter/10.1007/978-94-007-5341-9_12) has shown how people mythologize city streams and rivers.  Philadelphia is famously taken as an ideal of the gridded colonial city, rationally housing the centers of power and opportunities for settlement, and the relationship to defining features.  Philadelphia is said to be centered on city hall, and its grid fits the – supposedly straight – frame of the Schuylkill and Delaware Rivers.  da Cunha shows that it was in fact the rivers that were the first anchors of Philadelphia.  Even here, though, the relationship of the rivers was simplified – mythologized – into straight lines.

The Mythology of Straight Shores

The Rockland millrace, Pennsylvania.
Oldindustry.org

The current reality of city shores is, however, often a series of straight lines. Think of the Embankment along London’s Thames, the sea wall in Sydney, or Louisville’s cobblestone wharf dating from the days of steamboats.  In many cases, such straight lines are not merely a matter of controlling flooding from upstream, or of mowing grass or cutting trees.  But in most cases, urban shorelines are now literally constructed features.  Millraces and dams on creeks and large streams have existed since the early industrial revolution as constructed linear features that alter the relationship of water to shore.  More extensive shore features such as Baltimore’s piers and docks are also constructed.  A great deal of Baltimore’s current shoreline is the result of filling and draining.  After the Great Fire of 1904, for example, the rubble from clearing the debris from the 64 acre conflagration was used as fill along the Harbor.  The myth and the reality become congruence.  Then the reality reinforces the myth.

So neither in Baltimore, Philadelphia, nor any other river or shore city, are straight lines reflective of the form of the rivers that first invited settlement.  All have lost curvy, swampy or marshy, productive and protective shorelines.  And we have lost the public understanding that land and water have a sloshy, fluctuating and porous relationship.  The sea level rise occasioned by climate change, the retreat of waters during drought, the upland flooding from hurricane rains, and the inundation by coastal storm surges are all reminders that land and water still have a relationship of flux, in spite of the linear tendencies of our clashing grids.

Preparing for the BES Mid-Term Review: What Does NSF Want?

Here are the current expectations as stated by the National Science Science Foundation that will be used in evaluating BES.  The Mid-Term Review will take place in October, and this Charge to the Review Team is provided to help the BES community prepare for the review:

NSF Review Criteria

The visiting review team is asked to do the following things.

The central intellectual aim of the LTER program is to understand long-term ecological patterns and processes at multiple spatial scales. Each site is organized around a unique scientific theme as articulated in a reviewed proposal, but all sites must address the same five core areas: 1) patterns and controls of primary production, 2) spatial and temporal distributions of populations selected to represent trophic interactions or food web dynamics, 3) patterns and controls of organic matter accumulation and decomposition in surface layers and sediments, 4) patterns of inorganic inputs and movements of nutrients through soils, groundwater and surface waters, and 5) patterns and frequency of disturbances.

The 25 active LTER sites were established at different times, ranging from 8 to 32 years ago. The questions and research directions proposed in a site's most recent proposal were therefore placed within the context of long-term research and motivated by data sets of varying length. This proposal, its conceptual basis, and the research proposed form the context for the mid-term site review. During the review, the site PI may choose to discuss long-term studies so that current research can be placed in a temporal perspective.

Mid-term site reviews are an essential part of the ongoing evaluation cycle of the LTER program and of each LTER site. Sites are funded for six years at a time. A mid-term site review is conducted in the third year of a six-year award to evaluate the strengths and weaknesses of a site's performance over the past three years and its plans for completing its research goals over the coming three years. The review advises NSF as to whether or not the site is

•  fulfilling its proposed research goals in a timely manner
•  collecting and managing core data sets
• carrying out research at the leading edge of ecology that will advance the field
•  managed effectively
•  maintaining a unique research focus
•  making data and metadata readily accessible
• integrating research with education, training and outreach.

The evaluation should be based on the research proposed in the site's most recent renewal award, the extent to which the PI has addressed concerns raised by review panel in 2009, and progress in accomplishing the site's proposed goals.  No funding decisions are attached to the mid-term review.

Your report is an evaluation written to NSF. We ask that you document the strengths and weaknesses of the site's activities and provide your value judgments about the extent to which it has achieved its stated goals.

Suggested sections of the report are:

I. Executive Summary: major findings viz. strengths and weaknesses. Is the site on track?  Are there any major problems or areas for concern?  Is the science cutting-edge, focused on exciting questions that require long-term data or that can only be posed after a site has been studied for a long time?  Recommendations should specify problems and weaknesses and identify solutions if possible.

II. Body of report – room to elaborate, justification for strengths and weaknesses. Suggested categories for evaluation include:

•  core data collection
• compelling, site-specific long-term ecological and related research
• cross-site or broader scale synthetic research
•  outreach, education, and training
•  information management
•  project  management, including institutional relations, personnel mgt, decision making, diversity, leadership and transitions

III. Please keep in mind that it is not the role of the site review team to suggest major changes in focus or direction that would deviate from the funded proposal.  Be careful when suggesting alternate research questions or areas for future studies.  No site can do everything with the limited funds NSF provides, so you need to be fair in your expectations. The report may include some suggestions for changes, but these should be limited and well justified.

IV. Other considerations may include PI transition plans, major new directions, investments in major experiments, and what needs to be changed or sacrificed to accommodate these.

LTER site visits are valuable opportunities for site researchers to discuss ideas with the review team. It is important for you to interact with all LTER participants - PIs, collaborators, postdoctoral researchers, students, techs, staff, etc. Please ask a lot of questions.

NSF will send the report to the PI along with a cover letter that highlights aspects of the report and your evaluations from an agency perspective.  PIs may then respond to the site review report, and your report along with the site's response will become part of the review history for that site. Please keep in mind that many LTER sites post their mid-term review reports, so you should not consider the report to be anonymous.

Budgets: During each funding cycle, sites receive a fixed, flat budget for each year. As a result, there are multiple and sometimes conflicting demands on the funds received between long-term data collection and new research directions. Most sites obtain significant research funds from other NSF programs, funding agencies or sources, with an average of about 3 non-LTER dollars for every NSF/LTER dollar. It can be difficult to sort out what NSF funds from related projects, but it is important for you to evaluate the ability of a site to retain a clear research focus that addresses important questions. The potential for a site to be come diffuse in its research is obvious when many of the resources obtained are not tied to core LTER goals. 

Patterson Clark Named BES Artist-In-Residence for 2013

I am extremely excited to announce that Patterson Clark is the BES 2013 Artist-In-Residence.  Here is a description of his work, based on text provided by the selection committee, consisting of artists Lynn Cazabon (BES 2012 Artist-In-Residence) and Jann Rosen-Querault, along with Mark Twery of the USDA Forest Service.

For the past 10 years, Patterson Clark's artwork has been dedicated to developing a complete sustainable system for creating art utilizing non-native plants he harvests from the environment in which he works. This project, which he calls "Alienweeds," began from his desire to restore a measure of balance between the native and non-native plants growing nearby his home in Whitehaven Park in Washington, D.C.

Clark uses aspects of these plants to create papers, inks, brushes, pens, printing blocks, and cordage, finally resulting in playful prints which document the amount of labor and materials used in his meticulous processes. Clark is also a visual journalist: in 2009 he created the column "Urban Jungle" for the Washington Post. Each week, Clark highlights a particular aspect of the urban ecosystem in text and illustrations, incorporating the research of scientists he interviews and cites. 

The selection committee suggested that by spending time with BES scientists as an Artist-in-Residence, Clark can be a potential conduit for wider exposure of BES research. In addition, we hope his involvement in BES will stimulate the social and natural scientists, and the educators in the project to explore new avenues and stimuli of creativity.

His work, featured in national media outlets, is explored and sampled in the web links below:

http://alienweeds.com/

http://www.washingtonpost.com/wp-srv/special/metro/urban-jungle/?media=recent

http://www.washingtonian.com/blogs/capitalcomment/washingtonian/spotlight-patterson-clark.php

http://www.npr.org/2011/02/28/134054004/the-art-of-war-on-invasive-species

Clark will participate in the April 11 BES Quarterly Project Meeting, focusing on past, current, and future interactions of science and art in BES, to be held at the USGS building.  Follow this link http://bes-news.blogspot.com/2013/04/bes-quarterly-project-meeting-11-april.html for more information, including the agenda of the meeting.  He will also attend a reception at the University of Maryland Center for Art, Design, and Visual Culture (CADVC) from 5:30 to 7:30 that day.  Refreshments will be served, and the event is designed to stimulate communication between researchers and artists.  The BES community is heartily welcomed to this event.

Also in attendance will be Lynn Cazabon, BES's first Artist-In-Residence, whose work has been highlighted elsewhere in this web log: http://besdirector.blogspot.com/2012/08/lynn-cazabon-bess-first-artist-in.html  Lynn was featured in an exhibit of art linked to LTER sites that has been mounted at the headquarters of the National Science Foundation (http://www.ecologicalreflections.com/wp-content/uploads/downloads/2013/02/LTER-art-brochure-2013-2.pdf).

Please come to these events and help us explore the richness of connections between art and science in the Baltimore Ecosystem Study, Long-Term Ecological Research project.

BES Book of the Year: Austin Troy's "The Very Hungry City"

Each year, BES chooses a Book of the Year.  This allows our community to share in exploring an important work on urban ecology and urban processes in general.

For 2013, we have chosen Austin Troy's book, The Very Hungry City: Urban Energy Efficiency and the Economic Fate of Cities.  This is an important book examines the energy flows -- metabolism in a popular word -- associated with contemporary cities and suburbs in the United States and elsewhere.  How energy is used in tempering building interiors and in transportation provides the framework for examining both environmental and economic effects.

The book was published by Yale University Press.  Find more information at http://yalepress.yale.edu/yupbooks/book.asp?isbn=9780300162318

Austin will deliver the Keynote Address on the topic of his book at the BES Annual Meeting at Cylburn Arboretum on Wednesday 22 October 2013.  His talks on the topic have garnered high praise.

Read the book, discuss it with your colleagues in BES, and attend the stimulating lecture in October.

The Problem of the Urban Landscape

I was recently accused of bringing a wilderness or rural approach to urban landscapes.  This surprised me since I have long had what I think of as an inclusive concept of landscape.  Oddly, an inclusive, urban-friendly view of landscape can be considered to emerge from each of the two different ways that ecologists have used the term landscape.

Landscape as a Rung on the Scala Naturae

Fig 1: Levels of Organization

Traditionally, ecologists and philosophers of biology have found it useful to think of the world as arranged as a nested hierarchy of units.  This nested hierarchy runs something like this: atom – molecule – cell – tissue – organ – organism – population – community – ecosystem (Odum, 1971; Mayr, 1997).  From this sequence, it is clear that larger kinds of object are made up of smaller kinds, and any given kind of object can be a component of still larger objects.  Each kind of object is called a “level of organization” (Figure 1).  The ladder or stairway of units is supposed to represent increasing complexity as one climbs upward.

To give a specific example from one of the nodes above, populations of a given species are composed of all the individual organisms of that species in an area of interest.  Populations are nested within communities.  Continuing up the ladder from ecosystem, contemporary ecologists group communities into ecosystems, and in turn assemble ecosystems into landscapes.  This may be continued on up through biomes and then to the entire planetary biosphere.  In this level-of-organization approach to scientific objects, landscape is considered to be a level between ecosystem and biosphere.  Forman and Godron (1986) in their pioneering North American textbook on landscape ecology, define landscape to be a kilometers-wide area encompassing ecological heterogeneity or patchiness.  The patchiness is expressed as different ecosystem types, such as fields, forests, and lakes.  This is consonant with the way landscape has been used in art and perhaps also in design.  Forman and Godron, however, are clear that landscapes must include humans and human artifacts and settlements.  Patches, corridors, and matrix are the  fundamental kinds of elements of the Formanian landscape (Figure 2).

Fig. 2: Patch (P), Corridor (C) and
Matrix (M) in a landscape.

The characteristics of each level of organization are distinct and specific to that level.  Populations have characteristics like age structures and sex ratios.  Communities have species richness and three dimensional structure.  A mass of molecules of a particular compound will have a boiling point, but it would be silly to try to apply that kind of attribute to cells.  Cells, on the other hand, are characterized by internal structures like vacuoles, mitochondria, and so on.  Specialists studying each level of organization employ appropriate observational tools and protocols, different kinds of measurements, ask research questions, or seek applications that are especially relevant to objects on their focal level.  Unfortunately, they often argue about which level is the best to focus on, with the unjustified bias that smaller, lower levels are better than higher, more inclusive levels.  A true understanding of the differences in subject matter and methodology for different levels would do away with such arguments.

Landscape as an Approach to Analysis

The single hierarchy or stairway of nature, presents some problems, however.  Jim MacMahon and colleagues (1978) noted that if one starts with a focus on organisms, several different hierarchies can be conceived.  Leading up to organisms, they maintain the atom-through-organ nesting.  But once one has focused on organisms, several perspectives are possible.  One perspective is through the lens of evolution.  Populations are a unit within which genetic variation and subsequent natural selection are made manifest.  Along this nested hierarchy, species, genera, families, and the rest of the taxa produced by evolution are arrayed above the organism level.  Another perspective is the focus on the processes of metabolism, that is energy and matter exchange, above the level of the organism.  This arm of hierarchy might include ecosystems, biomes, and the biosphere as units within which the flow of energy and the cycling of limiting nutrients and contaminants result from the physiology and decomposition organisms and their aggregation into larger units.  A final hierarchy above organisms runs through demes, populations, and communities.  This is called a coevolutionary hierarchy, and its intention is to emphasize resource partitioning and adaptive interaction among organisms of different species.

Where does landscape fit in these sequences?  MacMahon et al. (1978) are silent about this, becsuse landscape ecology as a discipline did not become widely understood until the mid 1980s.  Often, ecologists interpose landscapes in the matter-energy flow hierarchy, to suggest that different kinds of ecosystems exist and are spatially arranged over large areas.  The ambiguity of where to place landscapes arises from the recognition that there are different hierarchies in which organisms may participate, and which of the hierarchies is chosen depends upon the research interest or observational window. 

This ambiguity was resolved by Allen (1998), who reframed common ecological units not as some preexisting ranking of natural reality, but as reflections of the interaction of the observer and the material world.  In other words, criteria of observation may be a more effective way to classify ecological observables than a fixed stairway of nature. 

Criteria of observation are illustrated by the ways that MacMahon and colleagues (1978) placed organisms in several hierarchies.  One criterion is autecological – the combination of organism physiology and anatomy.  This criterion emphasizes the role of organisms in assimilation of energy and nutrients, and how they transform them into other forms.  Continuing this concern into the larger world in which those materials are in turn used by still other organisms, whether they be consumers, disease agents, or decomposers, identifies an ecosystem or biogeochemical criterion of observation.  In contrast, how organisms relate to one another through the use of the resources already captured by or sought by other organisms, is portrayed as a niche or community hierarchy.  Here, organisms are viewed as competitors, mutualists, or commensals, for example.  Finally, the hierarchy of taxonomy is an evolutionary one, reflecting the increasingly inclusive units of inheritance and deep history.

Allen and Hoekstra (1992) generalize and extend the insights pioneered by MacMahon and colleagues (1978).  The general criteria of observation include 1) physiology, 2) spatial heterogeneity, 3) evolutionary potential and mechanisms, 4) transformation of energy and matter, 5) species coexistence, and so on.  These concerns are not nested hierarchically, nor represented uniquely by specific spatial scales.  The concepts, models, and empirical understanding required by each of these criteria of observation may be applied or generated on any number of spatial scales.  Criteria of observation are scale independent, and can thus be applied on any spatial scale.

Landscape as a General Concept and Criterion

Following the view of criteria of observation, a general definition of landscape emerges.  Most simply and generally, a landscape is a collection of spatial areas that differ in some attribute(s) of interest.  These areas are often represented as patches, but landscapes may also represented by fields or gradients arrayed in three dimensional space.  Landscapes can exist at any spatial scale, and apply to any collection of areas that differ from one another in a defined way.  Note that patches do not have to be internally homogeneous.  Rather, they can represent characteristic mixtures of structural elements or processes.  All that is required is that the mixture in one kind of patch be discernibly different from the mixtures in other kinds.  The same is true for the mechanisms or outcomes of processes, if that is the way that patches are to be differentiated.

Landscape: City or Country?

Fig. 4. Riverine patchiness in Kruger
(S. Pickett)

Fig. 3. Patchiness in Baltimore
(S. Pickett)

It is clear that this general definition of landscape applies just as well to a city (Figure 3) as to Kruger National Park (Figure 4).  Spatial differentiation is notorious in cities (Clay, 1973), and is key to understanding them, managing them, and assessing environmental inequities, for example (Pickett et al. 2011).  Urban patches can be distinguished based on architecture, road patterns, the kind and amount of vegetation, the density of human inhabitation or use, and the characteristics of the human populations inhabiting different areas (Cadenasso et al. 2007, 2013).  In places like Kruger, spatial differentiation may be the result of vegetation responses to slope, elevation, and drainage.  In addition, Kruger patchiness is generated by the grazing of large ungulates, by fire, and as a legacy of local resource management.  

The message is that entire urban areas are as much landscapes in the conception of criteria of observation as are rural or wild areas.  Urban landscapes involve flows and transformations of energy, matter, organisms, and information, just as do wild and rural ones.  Of course, they also have massive flows of social capital, power, financial capital, and commodities, among others.

This may be different than some uses of landscape in urban design or landscape architecture.  Notably, landscape in the urban context as described here does not just mean the conspicuously green spaces, and certainly does not require that fluxes of energy, matter, information, and organisms take the same form as they do in wilder or more rural areas.  Landscape is an important and gereralizable concept in an inclusive urban ecological science.

Summary

• Landscapes are heterogeneous mosaics or three-dimensional spatial fields containing contrasts in structures or processes.
•  Landscapes can exist on any spatial scale.
• Wild areas and urban areas can be represented in their entirety as landscapes.
•  Landscapes can change through time, and their component patches or gradients can shift as a result.
• The areas making up landscapes can be differentially connected to each other, and to areas outside of an immediate landscape by teleconnections.

References

Allen, T. F. H. (1998).The landscape "level" is dead: persuading the family to take it off the respirator. In Ecological scale: theory and applications, 35-54 (Eds D. L. Peterson and V. T. Parker). New York: Columbia University Press.

Allen, T. F. H. & Hoekstra, T. W. (1992). Toward a unified ecology. New York: Columbia University Press.

Cadenasso, M. L., S. T. A. Pickett, and K. Schwarz. 2007. Spatial heterogeneity in urban ecosystems: reconceptualizing land cover and a framework for classification. Frontiers in Ecology and Environment 5:80-88.

Cadenasso, M. L., S. T. A. Pickett, B. McGrath, and V. Marshall. 2013. Ecological heterogeneity in urban ecosystems: reconceptualized land cover models as a bridge to urban design. Pages 107-129 in S. T. A. Pickett, M. L. Cadenasso, and B. McGrath, editors. Resilience in ecology and urban design: linking theory and practice for sustainable cities. Springer, New York.

Clay, G. (1973). Close up: how to read the American city. New York: Praeger Publishers.

Forman, R. T. T. & Godron, M. (1986). Landscape ecology. New York: John Wiley and Sons.

MacMahon, J. A., Phillips, D. A., Robinson, J. V. & Schimpf, D. J. (1978). Levels of biological organization: an organism-centered approach. BioScience 11: 700-704.

Mayr, E. (1997). This is biology: the science of the living world. Cambridge: Harvard University Press.

Odum, E. P. (1971). Fundamentals of ecology. Philadelphia: Saunders.

Pickett, S. T. A., G. L. Buckley, S. S. Kaushal, and Y. Williams. 2011. Social-ecological science in the humane metropolis. Urban Ecosystems 14:319-339.