Monday, November 26, 2012

Dr. Emma Rosi-Marshall Named Director Designate of BES

Dr. Rosi-Marshall will be the next Director of the Baltimore Ecosystem Study, Long-Term Ecological Research project, a role that is targeted to begin in 2016.  At this time, we hope that BES would be entering its next phase of support as an NSF-funded Long-Term Ecological Research project.  Dr. Rosi-Marshall is an Associate Scientist at the Cary Institute of Ecosystem Studies, where she has been on the staff since 2009.  Her expertise in stream ecology, and her interests in the presence and role of pharmaceutical and personal care products in streams caused us to invite her to become a member of BES, and she has become an enthusiastic contributor to the program.

Background Information about Dr. Rosi-Marshall

According to the Cary Institute web site, “Dr. Rosi-Marshall conducts research on factors that control and influence ecosystem function in human-dominated ecosystems. Freshwater is one of our most vital and threatened resources; understanding how human-driven global change impacts freshwater ecosystem function is essential. Dr. Rosi-Marshall's research focuses on several aspects of human modifications to freshwater ecosystems such as land use change and restoration, widespread agriculture and associated crop byproducts, urbanization and the release of novel contaminants, and hydrologic modifications associated with dams.”

Dr. Rosi-Marshall earned the PhD from the University of Georgia in 2002.  She conducted Post-doctoral research at the University of Notre Dame, and was on the faculty of Loyola University of Chicago between 2004 and 2009, where she rose to the rank of Associate Professor.  More information on Dr. Rosi-Marshall’s career and interests can be found on the Cary Institute web site at

Why Having a Director Designate is Important

It is important to have overlap in the leadership of LTERs.  This is why I am happy that Dr. Rosi-Marshall has agreed to be the next director of BES.  Long-term studies are intended to observe, experiment on, and model ecological processes over long periods of time.  This is because many processes in which organisms, environment, and social phenomena interact unfold slowly.  In some cases, the complex and indirect interactions in human-natural systems only become clear when some unusual event occurs, or when a new comparison is conducted.  Long-term studies are a research platform allowing these crucial and impactful changes to be understood.  Dr. Rosi-Marshall in her new role in the project, will participate in the Project Management Committee, and will be closely involved in the decision making processes in BES.  The substantial period of overlap during which Dr. Rosi-Marshall will learn the ropes of BES and of the LTER Network is important for continuity. 

Other Components of Project Sustainability

Dr. Peter Groffman will continue to serve as Deputy Director after the planned 2016 transition, and I anticipate substantial overlap in the official Co-Principal Investigators and members of BES through that transition.  I am delighted that Dr. Rosi-Marshall has agreed to perform this crucial role in the sustainability of BES.

Monday, November 5, 2012

A Successful 2012 BES Annual Meeting

BES has just concluded a very successful Annual Meeting.  This was the 14th annual meeting and it had two components.  First was a Steering Committee meeting on Tuesday 23 October.  This meeting, as is our tradition, was open to all members and collaborators of the Baltimore Ecosystem Study, Long-Term Ecological Research (LTER) project.  This committee of the whole helps us plan the Quarterly Project Meetings for the coming year, and work on both intellectual synthesis and practical management and policy issues.  The meeting took four hours, which is typical for this important project wide activity.

Planning for the Mid Term Review

During this session, we worked on plans for the Mid-Term review by a visiting committee to be organized by the National Science Foundation’s LTER program.  We alerted all members of the project that next year’s Annual Meeting will overlap with the visit of the Mid-Term Review Committee.  This is being done in order to permit maximum participation by BES members, including PIs, Post-docs, graduate students, program coordinators, project staff, and collaborators.  We are embarking on a year of activities to prepare this broad constituency for effective interaction with the Mid-Term Review Committee. 

The 2013 Quarterly Project Meetings

As a part of the preparation for the Mid-Term Review, our Quarterly Project Meetings were scheduled and scoped.  We will focus the three meetings leading up to the 2013 Annual Meeting/Mid-Term Review on the overarching conceptual framework and integrative tools of BES.  So each meeting will discuss and deepen our understanding of the concepts of sustainability, resilience, adaptive processes, and pulse-press feedbacks.  In addition, each meeting will focus on one of the three new integrative theoretical areas: 1) the urban stream dis/continuum, 2) the metacommunity concept in the urban setting, and 3) the theory of locational choice by households and firms.  We will prepare summary and overview documents to help folks prepare for the meetings.

Image courtesy Brian McGrath,
Parsons The New School for Design
Two of the Quarterly Meetings will be extended for additional time in order to allow us to develop the new initiative of science and the arts in BES, and to update our ongoing activities in education.  The schedule of the Quarterly Project Meetings will be posted soon in the BES news:
The Steering Committee Meeting also afforded us the opportunity to advance plans for our synthesis volume.  This edited book will summarize the conceptual foundations and the important finding of BES over its 15 year history.  In addition, it will provide the opportunity to highlight our new theoretical themes, and to look forward as BES moves to understand the transition from the sanitary to the sustainable city.

Sharing Results and Outcomes

The second main component of the Annual Meeting comprised our technical presentations of results and research or project plans.  This was introduced by a keynote talk by Professor Sherry Olson from McGill University.  The themes that she highlighted were the cycles of growth in cities, and their relationships to the flows of energy and matter.  This is a potential area in which the work of BES could be enhanced. Members of BES then presented an exciting series of 26 talks and 17 posters.  The abstracts are available here  Senior PIs, graduate students and postdocs, and advanced undergraduates reported on their work.  Notable was how commonly a speaker noted the work of colleagues, both within and across disciplines.  Furthermore, examples of connections to our new theoretical themes appeared through the meeting.

In addition to being scientifically sound and practically significant, the presentations were of high quality.  Most talks followed best practices: good contrast between text and background, heavy lines defining graphs, and relatively little extraneous framing or graphical decoration.  The vast majority of speakers kept to the 12-minute target for their talks, leaving a short interval for questions and for introduction by the moderator. 

A New Way to Engage Posters

The poster session was scheduled after lunch, and was designed to give adequate attention to this medium.  To engage the participants in the poster session, we opened the poster session with a lightning round in which each poster was introduced by its author in a few sentences while the poster was projected on the screen.  The intent was not to read the poster, but to associate the poster with the author so that meeting participants could easily choose the posters they wanted to be sure not to miss.  We will use this method in the future as well.

BES and the Arts and the Annual Meeting

The first official BES Artist-In-Residence, Lynn Cazabon, exhibited several of the photographs from her “Uncultivated” portfolio.  These striking photographs graced the grand stairway hall of the Vollmer Center and the Cylburn Arboretum.  Their theme, volunteer plants in the city, resonated with the scientific and educational messages of BES that the city-suburb-exurb matrix is an ecosystem, in which both the built and the natural intermingle.  Mark Twery, Chair of the BES Science and Arts Committee presented an overview of activities and plans that this new committee is discussing.

Celebrating and Fellowship

Undoubtedly the most fun part of the annual meeting was the Community Greening Celebration and the BES Open House, held on Wednesday evening.  Music and refreshment accompanied the acknowledgement by the Parks & People Foundation of community groups that had performed exemplary greening and revitalization efforts in the city over the previous year.  This was an excellent opportunity to meet and converse with members of the communities in which our work takes place.


The series of formal, technical, informal, and fun activities are a highlight of the BES year.  Thanks to Project Facilitator Holly Beyar, Program Chair Morgan Grove, and Information Manager Jonathan Walsh for their contributions to the success of these meetings.  Thanks to those who presented their results and activities, and for doing so in clear and engaging ways.

Thursday, November 1, 2012

Introducing the BES Urban Lexicon

The members of BES represent a wide variety of disciplines and backgrounds.  Some are educators, some are experts in community engagement, and some are researchers whose interests span from physical to social sciences.  It is no surprise that such a diverse community might use the same words in different ways, or have vocabularies that emerge from different theoretical assumptions and particular practical applications. 

A Tool for Synthesis and Conceptual Integration

In order to promote communication and shared meaning across this heterogeneous intellectual landscape, we introduce a lexicon – a roster of terms and their meanings.  Go here for the lexicon: .  This list of words was assembled by a call for suggestions from the BES community.  Many different people contributed definitions.

But each definition also includes an example or two, a statement of why the term or idea is important, and some suggestions of additional sources of information on the topic.  Importance can reside in intellectual or practical realms.  Many of our concepts in fact have a dual life – as fundamental idea and as practical
application.  A figure, map, graph, or photograph may also accompany the entries.

How to Find a Term.

The BES Urban Lexicon takes the form of a web log, so the entries appear in the order in which they were posted.  In order to see an alphabetical list of the terms, users should consult the navigation pane to the left hand side of the web page.  Clicking on the term in the navigation pane reveals the entry.

Do You Want to See a New Term In the Lexicon?

If members of the BES community or the readership at large would like to see additional terms defined by us, please send suggestions to our Project Facilitator (  We can’t promise that we will find an author for all terms suggested, but we’ll give it a try.  If you are a member of the BES community and wish to define a term, send it to us in an e-mail following the format of terms already posted. 

We hope this collection of ideas and terms appropriate to contemporary urban ecological science is useful.  

Tuesday, October 30, 2012

A New Book on Urban Ecology

A new book on urban ecology is about to appear.  Three urban ecologists from the University of Quebec in Montreal, Beatrix Beisner, Christian Messier, and Luc-Alain Giraldeau, have compiled an engaging series of essays to share with general readers and students the richness of ecological processes and phenomena in cities, suburbs, and exurbs (CSE).  I was very excited to obtain an advanced copy of this book at a recent meeting on urban biodiversity in Montreal.

The book starts out with a statement that will be uncontroversial to biophysical ecologists and the other researchers who work with them: “Above all else, ecology is a science.  Ecology is not a philosophy or a way of being, and even less is it a panacea to save the planet” (Beisner et al. 2013: 1).  Of course sound ecological knowledge is of extraordinary utility in identifying and solving environmental problems, but this is because of the scientific foundation it provides.  Ethics, philosophy, and action are the tools by which scientific knowledge come to play its key role in personal and social decision making.  In its 147 pages, this book comprises 25 essays that range widely across the ecological principles, processes, and responses relevant to urban systems in the broadest sense.

Readers will come away with an understanding of the fundamental processes of biological production and decomposition as they occur in CSE systems.  The technical vocabulary needed for this understanding is gently introduced, and for the forgetful, a glossary appears at the end of the book.  Each essay includes a few beautiful line drawings and illustrations to engage the reader visually in the topic as well.

Although the titles of the essays do not always alert the professional ecologist to the technical content, rest assured that the conceptual coverage is broad.  Ponds and aquatic organisms, the function of plants and the composition of vegetation, the role of invasive species, evolution and adaptation, population dynamics, pollution, and social ecology are among the many topics exemplified in the essays. 

In addition to understanding some of the key points of ecological knowledge needed to understand and better manage and plan CSE systems, readers will come to appreciate the nature of ecological science itself.  Controversies, conflicting hypotheses, and problematic interpretations are highlighted in some of the essays.  All of the essays include questions, a point to discuss, or an invitation for rigorous observation that can involve readers in the thinking and doing that are the core of science. 

Watch for this little book in 2013, in either paper or e-book formats, as a stimulus for teaching and learning about the inextricable meshing of the ecological in our cities, suburbs, and towns. 


Beisner, B., C. Messier, and L.-A. Giraldeau, editors. 2013. Nature all around us: a guide to urban ecology. University of Chicago Press, Chicago.  (Readers in French will want to look for the publication under the title L’ecologie en ville published by Editions Fide in 2006.)

Wednesday, September 12, 2012

A Disturbance Primer for Urban Systems


The fundamental definition of disturbance is a physical disruption of the structure of a specified system.  The term may also be applied to the specific event that causes that disruption (Pickett et al. 1989, Peters et al. 2011). 

[Box 1 An Example of Disturbance: Sixty-four acres of Baltimore’s central business district was destroyed by a fire in 1904.  The origin of the fire is unknown.  It was extinguished when winds changed and backed the fire against the Jones Falls stream.  Fire fighting equipment brought in from other cities could not be used due to the incompatibility of the hose fittings with Baltimore hydrants.  Referred to as the Great Fire, this event was one of the last unintentional fires in a major American city. Note that the 1906 post-earthquake fire in San Francisco owed much of its origin to intentional generation of firebreaks. (Olson 1997)]

The basic definition of disturbance is neutral.  It is independent of scale, level of organization, or kind of ecological research approach.  Furthermore, it does not indicate what the subsequent effects of the physical disruption are, or whether any such effects are “good” or “bad” for the system as a whole or for different components of the system.  

[Box 2 Disturbance Effects: The high rates of infant mortality experienced in late 19th century Baltimore as a result of water-borne cholera epidemics led those who could to abandon the low-lying areas of the city for higher ground and suburban locations.  Prior to that migration, poor and minority Baltimoreans had lived relatively near their places of factory or domestic work.  Especially for domestic workers, racial and class segregation were very fine scaled, often involving differentiation between street dwellings for employers and alley residences for domestics. The suburban migration of the 1880s was thus a cluster of events that started Baltimore down a road of segregation that was reinforced by policy and differential access to resources over the next 100 years (Hinman 2002).  Migration from cholera-infested low elevation areas was good for those who could afford it, while putting those who could not afford or who were not permitted to move at a significant disadvantage.  It would only be in 1911 when Baltimore installed sanitary sewers and prevent waterborne diseases.]

A model of the system of interest is required to understand what constitutes a disturbance and what its effects might be (Pickett et al. 2000).  An explicit model of the system would specify such things as the spatial extent, spatial grain, temporal extent, temporal grain, physical components, functional connections among components, and the kinds of dynamics involved in those connections.  In the general terms of systems models, a disturbance removes or damages a component, or removes a physical connection between components. 

It is important to separate the causal event or physical disruption from the effect of the disruption.  An explicit system model helps to accomplish this separation (Peters et al. 2011). 

[Box 3: Response to Disturbance.  Post-fire changes in Baltimore included such things as standardization of fire hose fittings, zoning changes, and altered construction regulations.  Physical environmental changes include the reshaping of Baltimore’s shorelines by the dumping of fire debris and subsequent building on those new surfaces.  Indirectly, the need to rebuild downtown led the state of Maryland to empower Baltimore City in ways that had been withheld previously.  These changes suggest a model of the system, and the isolation of cause and effect promote the analysis of social and political causes and social, political, and environmental consequences]


Ecological experience with disturbance suggests features of the concept that are likely to be equally important in its urban application.

Disturbance is often said to have a sharp onset, or to be a relatively discrete event.  This implies that events may have sharp, slow, or stepped onset, may have short or long duration, and may have rapid, slow or stepped decay over time.  As the understanding of disturbance has matured in ecology, gradations among events in terms of onset, duration, or decay have been recognized and exploited (Pickett and Cadenasso 2009).

No kind of event -- like fire or flood -- is always a disturbance.   This caution is especially important for complex human activities.  Certainly, considering humans per se, or urbanization, or agriculture as disturbances a priori, may lead to confusion.

Complex activities, like those mentioned above, must be disaggregated into separate events so that their effect on systems of various scales can be determined (Bart and Hartman 2000).  For example, farming may include such diverse activities as site preparation, fertilization, weeding, harvesting, grazing, and cover cropping.  The nature of these specific component activities may change depending on the crop or kind of livestock, the market opportunities, and the various sources of income and kinds of regulatory constraints and opportunities that exist.  Furthermore, the specific activities can change over long time periods as access to markets, technology, and fashion change. 

Even natural occurrences, such as hurricane, are complex combinations of specific events.  Hurricanes, for example, may act as disturbing events through the direct effects of wind, the direct and indirect effects of soil saturation by associated rainfall, riverine flooding, coastal storm surge flooding.  Not all hurricanes, even those acting in the same geography, will possess or combine all those events in the same way.

The specific order of events may be important to the realization or effect of disturbance.  For example, hurricane winds that act before soils are saturated by wind may generate different kinds and severity of physical changes in forest canopy than those which arrive after long periods of rainfall. 

The nature of the receiving system can determine the magnitude and location of disturbance.  For  example, the effect of a hurricane may depend upon its speed of travel over a region, the amount and timing of rainfall, wind speed, relationship to the tidal cycle, relationship to prior saturation of the soil, successional stage of vegetation, and slope and aspect of sites in the path of the storm.  The built components of systems exposed to potentially disturbing events may suffer different amounts of damage depending upon structural soundness, orientation, whether the buildings have been secured, and other management and design decisions in place.

Related Concepts

The term disturbance was introduced in the mid 1980s to encapsulate the growing appreciation of the ecological community that physical disruptions of communities and ecosystems were not uncommon.  Indeed, the structure and function of many ecological systems owed a great deal to the spatial and temporal patterns of periodic events.  This was counter to the emphasis of ecology on systems perceived as climax, stable, or unaffected by humans.  The term was intentionally provocative, but as its technical use settled in, the need to abandon the vernacular baggage was emphasized in ecology. 

Disturbance Regime.  Although the occurrence of any single event might have stochastic behavior (like weather), the existence of a temporal and spatial distribution of such events was statistically predictable over some time and space frame (like climate).  The temporal and spatial pattern of disruptive events is labeled a disturbance regime.  Disturbance regimes, or lack thereof, are an important part of the environmental drivers in various systems.  Examples include the long-term space/time patterns of crown-destroying wildfires in many coniferous systems, the role of drought in mesic regions, or riparian-structuring floods.  Species adapt to different aspects of the disturbance regime and aftermath, and the composition and function of ecosystems adjusts to the patterns and effects of disturbance regimes over the long term (Pickett 1998).

Perturbation.  While this term also refers to a disruption of system structure, it connotes an equilibrium or linear system dynamic which is altered by some event.  Often return to that equilibrium or previous trajectory is of interest.

Stress.  This concept has be used in ecology to refer to processes that directly alter the performance or behavior of a system rather than its structure.  Disturbance affects three dimensional structure, that is anatomy or architecture, of a system.  Stress on the other hand affects physiology or activity of the system of interest.  Stress may ultimately lead to a physical disruption of system structure.   The relationship between stress and disturbance is one reason that this essay has not discriminated between endogenous and exogenous sources of disturbance.

Press and Pulse
.  These terms contrast events that have sharp attack and short duration -- Pulses -- with events that establish persistent new conditions.  While the term "pulse" may be essentially the same as disturbance, press can have either the direct physical effects like disturbances or the more physiological effects of stresses.  Note that the term pulse does not necessarily imply a regular rhythm of events.

Intervention.  In ecology, this neutral term does not have the same connotations as either perturbation of stress.  However, it is not neutral in other disciplines, where it may stand for certain theoretical approaches, or critical stances.  In ecology, it may be a useful substitute for disturbance in situations where 1) focus is on the action taken by humans to achieve some social or institutional goal; 2) either anatomical/architectural or physiological/functional origin of the change would be of interest; and 3) complex or indirect effects are envisioned that combine stress and disturbance or have not yet been successfully disaggregated into the immediately causal events.  Intervention as a term may be a useful place holder, or a term that invites smoother interaction with certain other disciplines such as social scientists and urban designers.

Z.  In a model of system i, consisting of specified components, during time period t,and over extent l, let z equal…

The Urban Context

The basics of disturbance must be kept in mind in exploring how that concept applies in urban ecosystems.  My initial explorations of disturbance took place in systems such as primary forest in Pennsylvania, old-field succession in New Jersey, riparian zones in South Africa, and the Negev Desert.  But I am certain that the clarity that has emerged in my mind from struggling with the need to both generalize across these and other situations, and to understand the specific mechanisms and constraints that operate in specific sites will be helpful in urban areas.

Too often, disturbance has been misapplied in urban contexts.  Treating urbanization itself as a disturbance does not necessarily promote an open minded understanding of this complex process and its equally complex and mutable product.  Nor does considering people to be primarily a disturbance agent, external to some pristine ecosystem within urban boundaries or as a disturbance with regional extent, lead to an understanding of people as parts of ecosystems that combine natural, built, and managed places and processes.

There is much still to learn about disturbance in the urban context.  Some general questions, which will have local and thus more specific versions, are these:  What disruptions of the physical structure of urban areas have biophysical effects?  How do they lead back through social processes to affect vulnerability or resistance to subsequent disturbances?  How are disturbance and stress in cities related?  What social, political, and economic interventions disturb urban systems, either in whole or in part?  What peoples and institutions are sensitive to those disruptions?  What features of urban systems contribute to ecological resilience in the face of disturbance and stress?  Note that this last question refers to ecological or evolutionary resilience, as defined by (Holling and Gunderson 2002), and not
“engineering” resilience as capacity to return to a fixed equilibrium point.

Disturbance in urban systems can result from changes in regulations, shifts in financial investment, changes in policy that affect the wealth and access of persons to power.  Disturbance in urban systems can also result from certain flood, ice storm, or other weather events.  And of course, biophysical and socio-economic disturbances can interact, and can each result in stress in the system as well as alteration of the physical structure of the system.   All of this potential benefit of applying the disturbance concept in urban areas results from the clear application of the basics laid out above, and to equal attention to social and biophysical structures and processes.

Literature Cited

Bart, D. and J. M. Hartman. 2000. Environmental determinants of Phragmites australis expansion in a New Jersey salt marsh: an experimental approach. Oikos 81:59-69.
Hinman, S. E. 2002. Urbanization and public health: a study of the spatial distribution of infant mortality in Baltimore, Maryland, 1880. Master of Science. Ohio University, Athens Ohio.
Holling, C. S. and L. H. Gunderson. 2002. Resilience and adaptive cycles. Pages 25-62 in L. H. Gunderson and C. S. Holling, editors. Panarchy: understanding transformations in human and natural systems. Island Press, Washington, DC.
Olson, S. H. 1997. Baltimore: the building of an American city. The Johns Hopkins University Press, Baltimore.
Peters, D. P. C., A. E. Lugo, F. S. Chapin, III, S. T. A. Pickett, M. Duniway, A. V. Rocha, F. J. Swanson, C. Laney, and J. Jones. 2011. Cross-system comparisons elucidate disturbance complexities and generalities. Ecosphere 2:art 81.
Pickett, S. T. A. 1998. Natural processes. Pages 11-19 in M. J. Mac, editor. Status and trends of the nation's biological resources. U.S. Department of Interior, U.S. Geological Survey, Reston, VA.
Pickett, S. T. A. and M. L. Cadenasso. 2009. Altered resources, disturbance, and heterogeneity: a framework for comparing urban and non-urban soils. Urban Ecosystems 12:23-44.
Pickett, S. T. A., M. L. Cadenasso, and C. G. Jones. 2000. Generation of heterogeneity by organisms: creation, maintenance, and transformation. Pages 33-52 in M. Hutchings, E. A. John, and A. J. Stewart, editors. Ecological consequences of habitat heterogeneity. Blackwell, New York.
Pickett, S. T. A., J. Kolasa, J. J. Armesto, and S. L. Collins. 1989. The ecological concept of disturbance and its expression at various hierarchical levels. Oikos 54:129-136.

Saturday, September 8, 2012

A Poster Introducing BES III

BES at the All Scientists' Meeting

Every three years, the participants in the Long-Term Ecological Research (LTER) Network meet to share and compare results, and to plan for the future.  this effort, involving more than one thousand researchers, educators, artists, and other collaborators in LTER, is called an All Scientists' Meeting. The details of this large meeting can be found on the website of the LTER Network:

Members of BES will be presenting posters, plenary talks, and workshops.  We'll report on some of the highlights after the meeting is done.

An Overview of BES for the ASM

Each LTER site is required to present a poster at the meeting.  The posters measure no larger than 4 x 4 feet, but in order to make them legible to readers viewing the posters some 3 to 4 feet distant, remarkably little text can be included.  It is a challenge to choose a breadth of research and education, and keep the poster legible and clear.  I hope that I have managed to do that with this year's poster.

The poster starts in the middle column, providing a point-by-point abstract of the nature of Phase III of BES.    It indicates that BES III builds on the integrative concepts that have motivated our research, education, and community engagement since 1997.  However, due to the increasing concern with issues of sustainability in the Baltimore region, and the capacity of this coastal metropolis to adapt to the effects of climate change, we chose to focus on that shifting policy environment as a way to move BES forward.  As mentioned in earlier posts, we adopt the idea that Baltimore metro is aiming to move from the existing sanitary to an envisioned sustainable city.  

The new guiding question for BES flows from the sustainability focus, and employs a resilience framework that relies on adaptive processes in both the social and the biophysical aspects of the interacting urban system.  Follow the arrows in the poster to build your understanding as you move through it.

The new guiding question and its subquestions then flow out into nine examples of conceptual or empirical work in BES III. 

Trees, Vegetation: Patchiness, Change, and Function

Four examples are groupse in the left hand panel.  These results  focus on the status and change of trees, tree canopy, and the vegetated components of the urban land cover complex.  The results are these:

1. Total forest cover has remained the same from 1914 to 2005, but the size of individual forest patches has decreased markedly.  Fragmentation is evident in this survey of the Gwynns Falls Watershed.  The work is published by Zhou et al. (2011).

2. Nowak and Greenfield (2012) showed that 17 of 20 US cities had less tree canopy over two times separated by about 5 years in the recent past.  Baltimore was among the decreasers.  Only Syracuse, NY had an increase in tree canopy.  This result is perhaps surprising given the policies and programs that many cities have put in place to increase their tree canopy coverage.

3. The heat island is one of urban ecology's most robust generalizations.  However, what kind of heterogeneity is there at fine to medium scales in the heat stress experienced within cities, and who suffers as a result?  Huang et al. (2011) show that in the Gwynns Falls Watershed, which encompasses patches that represent both old and new suburbs,  dense old residential areas, commercial, transportation corridors, agriculture, and parks, among others, that neighborhoods with less social-economic wherewithal were more susceptible to the hotspots in the heat island. 

4. There is controversy concerning the relationship of trees to crime.  A statistical analysis was conducted by Austin Troy and colleagues (2012).  They discovered that tree canopy was almost always associated with less crime in Baltimore City and Baltimore County.  They determined that other variables did not confound the general relationship.  However, the exceptional neighborhoods, where trees were in fact associated with higher crime, were those in which volunteer tree vegetation was present on abandoned industrial parcels adjacent to residential areas.

The Urban Stream Dis/Continuum: Patterns and Processes

1 - 2. The results clustered in the right hand panel of the poster focus on streams.  Kaushal and Belt (2012) have proposed a conceptual refinement to the stream continuum concept to apply this widely used comparative tool to urban systems.  They emphasize the role of engineering, and the effects of enhanced connections in hydrological flow paths, along with the effects of disruptions in hydrological flows.  Some of these connections and disconnections are intentional, while others are incidental to the way water is routed.  They present data to show that stream contamination depends on where in this complex dis/continuum a sampling station is located.

3. Detention basins are designed to control the flow of stormwater and reduce the loading of copious rains into storm sewers while continuing to avoid street and structure flooding.  Neil Bettez and Peter Groffman (submitted for publication) have shown that although several kinds of detention structures were engineered to control stormwater, in fact, they are also adaptive for reducing the amount of nitrate in stormwater.  They thus can contribute to improving the water quality downstream.  Some of these engineered structures facilitate enough biological processing of nitrate that they do better than natural riparian zones in the area.

Social and Educational Processes

The bottom center panel contains two examples.  Both deal with information sharing and exchange.

1. Bess Caplan and Alan Berkowitz present a learning progression, to help understand how students ability to use scientific thinking and explanation might develop.  What students bring to the classroom, and their experience with scale, unseen forces, and the use of models beyond simple narratives are all part of the progression.  This concept is helping teachers to improve students' ability to learn scientific concepts and to prepare better for scientific citizenship.

2. Michele Romolini, a doctoral student at the University of Vermont, presents one of her analyses of stewardship organizations in Baltimore.  Dividing the organizations into non-governmental and governmental ones, helps understand the marshaling and sharing of information.  In addition, understanding which organizations are clustered around key institutions that act as information sources, and which are relatively isolated from such nodes, helps ensure the most equitable distribution of environmentally crucial information.

The poster places these results and concepts into a graphical form.  This will be on display throughout the All Scientists Meeting in Colorado during the week of 9 - 13 September 2012.  We hope it gives a little flavor of where BES is going in its third phase, motivated by the pressure of cities to become more sustainable.


Huang, G., W. Zhou, & M.L. Cadenasso. 2011.  Is everyone hot in the city?: Spatial pattern of land surface temperatures, land cover, and neighborhood socioeconomic characteristics in Baltimore, City, MD.  Jour. Environ. Manage. 92:1753-1759.

Kaushal, S.S. & K.T. Belt. 2012. The urban watershed continuum: evolving spatial and temporal dimensions. Urban Ecosystems 15:409-435

Nowak, D.J. and E.J. Greenfield. 2012. Tree and impervious cover change in U.S. cities. Urban Forestry and Urban Greening. 11:21-30.

Troy, A. J.M. Grove & J. O’Neil-Dunne. 2012. The Relationship between Tree Canopy and Crime Rates across an Urban-Rural Gradient in the Greater Baltimore Region, Lands.  Urban Plann. 106: 262-270.

Zhou, W., G. Huang, S.T.A. Pickett, & M.L. Cadenasso.  2011.  90 years of forest cover change in the urbanizing Gwynns Falls watershed, Baltimore, Maryland: spatial and temporal dynamics.  Landscape Ecology 26:645-659

Wednesday, August 29, 2012

The 2012 BES Annual Meeting

A Chance to Gather

Vollmer Center, site of BES' 2012 Annual Meeting
Every year near toward the end of October, the Baltimore Ecosystem Study Long-Term Ecological Research community meets to share results, insights, and accomplishments, as well as to look forward to the next year's activities.  Everybody who has an interest in our research, education, and community engagement is invited to attend.   Registration will be available on the BES Homepage.  This helps us keep track of attendance, and to collect the modest fees to cover the costs of lunch and a light breakfast.  There are several notable features of this year's Annual Meeting.

Keynote by Prof Sherry Olson
First, we are privileged to have Sherry Olson as our keynote speaker this year.  Prof. Olson is author of a classic book on Baltimore as well as other important works on urban geography and history.  As detailed in an earlier post (, she will talk about "The Growth Machine: Its Environmental Legacy."  This talk should put us in the mind for synthesis, which is one of the goals of our annual interactions as an inclusive community.

A Chance to Link Science and Art
This year's Annual Meeting will also feature a photography exhibit by Lynn Cazabon (  She is BES's first official Artist-In-Residence.  Building upon the success of our earlier connections with artists, BES is establishing a tradition to connect art and science.  Attendees at this year's meeting will be treated to a display of photographs from Lynn's widely known and acknowledged work.

Gearing Up for the Mid-Term Review
Midway through each six-year funding cycle, the National Science Foundation conducts an external review of the Baltimore Ecosystem Study LTER.  All LTER projects undergo this rigorous external evaluation to determine whether they are on track with the research, educational, and outreach commitments they made in their grant proposals.  These reviews also help each project prepare for its next full grant proposal to NSF.

Our mid-term review for this grant cycle will take place in October next year.  In order to make this most convenient for BES members, and to ensure a broad participation of our community, the mid-term review will overlap with part of the Annual Meeting in 2013.  Because of this, it is important for all members of the BES community to understand the mid-term review process, and to learn how to prepare to best articulate their role and contributions to the mission of BES.

Part of our preparation will be to outline the book that BES will design to synthesize what by then will be 15 years of integrated urban socio-ecological research, educational research and programs, and interaction with communities and decision leaders in the Baltimore region.  The Annual Meeting will be a chance to inform all members of BES about the plans for this book, and to be sure that all who wish to contribute have a pathway to do so.

Celebrate the Community
Lady Baltimore Statue at Cylburn
For many years now our meetings have also been associated with Parks & People Foundation's Community Greening Celebration.  This adds the dimension of interacting with individuals and groups that have made substantial improvements in Baltimore's environment and neighborhoods.  An awards ceremony, distinguished guests, food, and music are part of this celebration of the achievements of our neighbors and partners.

A Charm City Venue
Our meeting will take place at the Vollmer Center, nestled in the City's beautiful Cylburn Arboretum.  This location has been a hit with BES Annual Meeting attendees in the past. During breaks, join your firends and colleagues for walks on the many trails through the woods and gardens overlooking the Jones Falls Valley.  See you there!

Thursday, August 16, 2012

Lynn Cazabon: BES's First Artist-In-Residence

Photographer and member of the University of Maryland, Baltimore County faculty, Lynn Cazabon is the first official Artist-In-Residence at the Baltimore Ecosystem Study, Long-Term Ecological Research program.  She began her contribution to the BES community by presenting a lecture on her ongoing project "Uncultivated" at the 2011 Annual Meeting. This year of artistic residency will culminate with an exhibit of her work during the BES Annual Meeting from 24-25 October, 2012.  This meeting will take place at Cylburn Arboretum, and all members, partners, and collaborators of BES are invited to attend. 


Of particular relevance to BES, "Uncultivated" takes as its subject wild plants that thrive in urban environments and has been disseminated via public displays on billboards and transit shelters. The full project can be viewed at  Her thought provoking and creative images of Baltimore’s volunteer flora stimulated the awareness of the public about the often unappreciated plants around them, and how they fit into the metropolis.  Lynn's work has been exhibited widely in the United States and abroad. Examples of her other projects can be viewed at her website:

A Deepening Commitment to Art

BES first involved artists two years ago, when the Liz Lerman Dance Exchange performed at the annual meeting and the community open house, as well as presented a talk on their work.  The stimulation of creativity and interpretive power of art for scientific concepts and subjects has become clear to us as a result of that effort and interactions since them.  BES has been exploring how to facilitate and institutionalize connections between artists of all sorts and the scientific and educational work of the project.  A committee comprising scientists, educators, and artists has helped to shape a vision for continued interaction between our scholarship, community engagement, and the arts.  This committee, chaired by Dr. Mark Twery, has designed an Artist-In-Residence program.  We will be posting more information on how to apply for a one year residency in the near future.

Exhibit at BES Annual Meeting

Meanwhile, check out Uncultivated on line, and join us at the Annual Meeting to celebrate the connection between science and art as embodied in Lynn Cazabon’s powerful images.  Her work is a great example of how science can benefit from art.  We are delighted that Lynn will donate the use of one of her photographs to BES.

(See an earlier Director's Corner post for Background on BES and art.)

BES Book of the Year -- Baltimore: The Building of an American City

We have started a new tradition at BES.  A book of the year is a good way to focus on some important publication relevant to everyone in the Baltimore Ecosystem Study.  We start this tradition with a classic and fundamental book about the history and development of Baltimore: Professor Sherry H. Olson’s Baltimore: The Building of an American City.  Although first published in 1980, and updated in 1997, it remains a key intellectual resource on Baltimore.  Prof. Olson was on the faculty at Johns Hopkins University at the time the book was first written.  She has since moved to McGill University in Montreal, Quebec.

By highlighting this book, we hope that all members of the BES community will read this important work.  Some of course, will be returning to it as a refresher.  The book will surely repay their effort, given the plethora of details and explanations of the trajectory of change in Baltimore.  Those who are new to Prof. Olson’s book are in for a treat, because it is not only comprehensive, but engagingly written.

Our spotlight on this book will also shine on Prof. Olson herself, as she will give the keynote presentation at our Annual Meeting at the Cylburn Arboretum on 24 October, 2012.  Entitled "The Growth Machine: Its Environmental Legacy," this talk will give a chance for her to bring us up to date on her research and scholarship.  All members of the BES community are invited to delve into the book, and to hear Prof. Olson at our Annual Meeting.

See her web page for more on her research interests and publications:

Friday, April 13, 2012

BES Quarterly Research Meeting: Green Infrastructure

What's Green Infrastructure?

The BES community will meet, along with managers and policy makers, on 19 April 2012 to discuss green infrastructure. The Baltimore City Office of Sustainability has provided this description of green infrastructure: 

As opposed to ‘gray’ infrastructure, which includes transportation and utility networks, green infrastructure is interconnected ecological systems that include natural areas such as forests and streams as well as constructed elements such as urban parks, trails, streetscapes, stormwater management practices, community gardens, and urban agriculture.
 Green infrastructure provides critical environmental functions and benefits including cleaner water, cleaner air, enhanced habitat and biodiversity. It also provides key social and economic functions such as decreased energy costs, opportunities for recreation and economic development, as well as improved health and quality of life.
Why Green Infrastructure?
We are engaging in this discussion because green infrastructure provides an excellent way to both improve the social-ecological functioning of urban ecosystems, and a platform for working with policy makers and managers.  Meeting Chair Morgan Grove has lined up an excellent roster of speakers, for the morning.  These presentations will present background on the nature of green infrastructure, the hydrological components of green infrastructure, the social and economic significance of green infrastructure, and an overview of monitoring research.

Discussions to Promote Collaboration

After lunch, the group will present existing and proposed research projects with the intent of identifying how they can connect to and improve the understanding and functioning of green infrastructure in the Baltimore Metropolitan region.  The second discussion period will focus on how BES research and education can collaborate with government agencies and non-governmental organizations with existing resources.  Follow up will explore plans for developing new resources for this important collaboration.

Importance of Green Infrastructure for BES

Green infrastructure is one of the main ways in which city-suburban-exurban systems can become more sustainable.  It is important for BES to work with green infrastructure as both a research topic and an opportunity to contribute to the improvement of the quality of life and resilience of the Baltimore socio-ecological system.

See the BES News page for the agenda for the meeting:

Saturday, March 24, 2012

Baltimore's Urbanite Magazine Explores Big Urban Theory

The Urbanite ( is one of Baltimore’s cultural and intellectual treasures.  Available free at many locations, or by subscription for those who don’t get to town every month, it is always a treat to see the diverse contributions of good writing, photography, and art the editors have gathered together.

Over the past few months Urbanite ran two pieces that struck me as Big Urban Theory.  Big Theory is a general explanation of the way some phenomenon is structured or works.  Theory in its technical sense as used here doesn’t mean just a guess, or something less than certain.  One of the big theories appears in an interview by Baynard Woods of Edward Glaeser, Harvard economist and urbanist, who was in town to talk to the Downtown Partnership.  Glaeser is author of an impressive book, The Triumph of the City.  The other was a feature written by Michael Anft, entitled “City By the Numb3r5,” which summarized and explained the work of Geoffrey West and Luis Bettencourt of the Santa Fe Institute, a deep think tank focusing on complexity.

What's Right With Cities.  Glaeser touts the city as the cradle of innovation, and indeed considers it to be humanity’s greatest invention.  He argues that cities are a mechanism to promote interaction among diverse people, give space for creativity, and contain the critical mass that makes this all work.  Among his recommendations to take advantage of the power of cities is to enhance urban density by promoting vertical growth.  Such density entails efficiencies of energy and transportation.  This is one part of a very general, or big, urban theory.  

Notably, however, Glaeser neglects the biophysical aspects of urban structure and function, and gives no credit to the efficiencies that can be gained by allowing biological work to remain a part of the urban realm, or to be reinvigorated where it has been paved over or otherwise displaced.  The creative stimulus that can result from interaction of people with natural processes -- with their own rhythms, peaks, and pulses – is also absent from Glaeser’s recipe for urban creativity.  Glaeser’s main points are still quite valuable even though he neglects the biological ecology that I am so fascinated by.

Big Number Theory for the City.  In the second piece, headlined with numbers substituting for some of the letters, a la a clever high security Internet password, the allometric theory of cities is central.  This theory, exemplified by the work of West and Bettencourt, indicates that the major properties of cities are a mathematical function of their size.  Comparing cities worldwide, they discovered that for each doubling in population, the infrastructure of a city increases only 85%.  Some functions, such as carbon footprints, also increase at the same proportion, reflecting the efficiency of dense urban development.  Crime, gross domestic product, income, and innovation as measured by patents, increase on the same trend – more than a 15% advantage compared to the expectation based on a simple linear relationship.  So both positives and negatives have the same quantitative relationships to urban population density.

Such things as history, geography, and urban design or planning have secondary roles to play in the characteristics of each city in this big comparison.  However, the deviation from the trend line helps identify characteristics for which policy and design might have particular power to intervene.

Again, the theory is relatively silent about the place of biophysical processes in the relationship.  This is a gap worth filling.  Furthermore, the theory addresses urban aggregations rather than specific districts and neighborhoods.  Given that most theories have a hierarchy of generality, with the most universal and abstract relationships on top, so to speak, and increasingly fine-scaled, detailed models of structure and function coming lower down in the hierarchy, where focus is on very specific places, events, and interactions.  Urban theory would seem to benefit from such a hierarchical structure.  

The Search for Mid-Level TheoryThe recent pieces in the Urbanite have focused on the biggest urban theories that exist so far.  Its interesting foray into this heady and exciting realm has left unaddressed the question of what “middle level theory” might be helpful in doing.  I expect that the middle level theory might help in bringing more ecological understanding to bear in urban areas, and identifying fruitful levers of intervention that neighborhood communities and local managers might take advantage of.

The Urbanite has done a marvelous job of highlighting the grand unifying theory explaining global differentiation in urban characteristics, and indicating how any city is constrained in both good and bad ways by its size.  But the grand theory leaves in obscure shadows the specific ecological functions that are of interest and value within metropolitan areas, their neighborhoods, and watersheds, for example.  For that, the finer-scaled models, data, and relevant concepts are needed.  This is a focus of the major, nationally important research effort underway in Baltimore in the form of the Baltimore Ecosystem Study Long-Term Ecological Research project.


For further reading, the two pieces in the Urbanite, as well as an original article by Bettencourt and West, and a piece in the New York Times Sunday Magazine are cited below.  

Bettencort, L. and G. West (2010). "A unified theory of urban living." Nature 467: 912-913.

Lehrer, J.  2010.  A Physicist Solves the City.  The New York Times, December 17, 2010.

Thursday, February 16, 2012

Urban Ecology HAS Changed

A Perspective on Points from Ramalho and Hobbs, As Reported by the BBC on 6 December 2011

A news report by the BBC on an article critical of urban ecology appears at  I find that the report, though true to the article by Ramalho and Hobbs, should not go without comment.  Urban ecology is not the backward pursuit that the report might lead some to believe.  The original article by Ramalho and Hobbs, entitled “Time for a change: dynamic urban ecology,” appears in TREE at

A published reply, to which I contributed, also exists.  Mark J. McDonnell, Amy K. Hahs, and I have offered a reply to the original article by Ramalho and Hobbs.  The reply has been accepted by TREE, and is published online at

Changed Already

From the BBC report: “The way researchers assess urban ecology needs to change in order to take into account the way modern cities are developing.” 

The discredited Burgess urban ring model.
Urban ecology has in fact already changed drastically over the last two decades, both because of committed long-term support for urban ecological research, and the closer integration of social and biophysical research efforts.  Since the early 1990’s, when urban ecology was reinvigorated both as a component of mainstream ecology and as an important “boundary discipline” capable of linking ecology with social sciences and with urban design, the field has gone well beyond the concepts and approaches that were available in the mid 1980s and early 1990s.  

Furthermore, urban ecology has productively employed spatially realistic and flexible models that recognize urban areas as shifting, patchy mosaics.  Complaining about ring models, such as the holdovers from the Chicago School, or about linear transects as research tools, misses much of the conceptual and empirical progress of two decades of contemporary urban ecology.

Diverse Urban Transformations
Shenzen, China. (c. Brian P. McGrath)
Interaction among bioecological researchers, social scientists, and urban designers, among others, has firmly embedded within ecological thinking the variety of modes by which cities now change.  There are shrinking, post-industrial cities, burgeoning refugee cities and districts, virtually instant cities in Asia and Africa, and even high density settlements far from traditional urban centers but which through dynamic diasporas that ebb and flow, rely on resources, capital, attitudes, and opportunities that originated in the more classically recognized cities.

Non-linear Models
The simplistic way that urban rural gradients have been interpreted by many is a disappointment.  However, there have been repeated efforts to clarify that a linear transect for studying a spatially complex mosaic is not necessarily the same thing as an urban-rural gradient (Cadenasso et al. 2006).  The vintage of the gradient concept in ecology and the sophisticated and well established strategies for studying complex environmental gradients in spatially patchy contexts (Austin 2005, Fox et al. 2011) would seem to make it unnecessary to emphasize the non-congruence of gradients and transects.  Yet, the conflation is a common one. It is no less correct for being common.  Again, the literature has more depth and richness than Ramalho and Hobbs or their BBC correspondent seem to recognize.

Contemporary Patterns
The BBC correspondent states Ramalho “explained that, historically, cities grew slowly in a relatively compact manner, through progressive rings of urban development.”  The ring model, developed in the 1920s, was almost immediately critiqued by social scientists, and improved as a sectoral model even in the 1930s.  So the insight that the concentric ring model of urban development is flawed is not a new discovery.

Contemporary patterns are said to be ‘markedly different’ from the allegedly slow, ring-like march.  The description that then appears is one of a complex, heterogeneous mosaic that includes green, blue, grey, and brown components intermingling spatially.  Ramalho is further quoted in the BBC report: “Cities are growing very rapidly, they are increasingly expansive and dispersed, sprawling in … spider-like configurations across large distances, and embedding fragments of other land uses in the rapidly changing landscape.”  (Note, ellipsis in original BBC quote.)

Is this a new insight?  Hardly.  Consider this quotation from pg 128 from Pickett et al. (2001):

Thimphu, Bhutan. Doubling in 6 yr
“Cities are no longer compact, isodiametric aggregations; rather, they sprawl in fractal or spider-like configurations (Makse et al. 1995). Consequently, urban areas increasingly abut and interdigitate with wild lands. Indeed, even for many rapidly growing metropolitan areas, the suburban zones are growing faster than other zones (Katz & Bradley 1999). The resulting new forms of urban development, including edge cities (Garreau 1991) and housing interspersed in forest, shrubland, and desert habitats, bring people possessing equity generated in urban systems, expressing urban habits, and drawing upon urban experiences, into daily contact with habitats formerly controlled by agriculturalists, foresters, and conservationists (Bradley 1995).”

It is interesting that the early concentric ring model for Chicago was in fact developed to explain and intervene in the explosive development of that city in the early 20th century: Chicago had doubled in population in a decade due to immigration from novel sources: southern and eastern Europe, and African Americans from the southern U.S.  So speed of growth is not in fact a uniquely contemporary phenomenon.  

Simple Categories?
It is manifestly true that just calling something urban, or suburban, or rural, yields little insight into what drivers may actually be in play.  However, the call for using environmentally meaningful and measurable factors to understand the effects of urban structure and urban change is not new (Pickett 1993).  Indeed, we can point to developments that seek to unpack the metaphorical labels often used in urban ecology research (McIntyre et al. 2000).  The concept of the “ecology of prestige” (Grove et al. 2006b), and a novel, integrated conceptualization of urban land covers (Cadenasso et al. 2007) are examples. 

Furthermore, social complexity is recognized as a driver through such things as property regimes (Grove et al. 2005), and through institutional structures and indeed of networks of organizations (Ostrom 1990). 
Urban ecologists and social scientists have also recognized the impact of spatial context on the various patches within urban mosaics, whether they are natural, built, or the still more common hybrid patches (Grove et al. 2006a, Cadenasso and Pickett 2007, Shane 2007).  

A recent approach to factor analysis, based on updating a classical conceptual model originally developed in soil science, also illustrates how urban ecologists have been approaching this problem (Pickett and Cadenasso 2009).  Both social and biophysical factors are addressed in this framework.  Such a hierarchical framework can accommodate the sharper focus, that is, attention to detailed driving variables, as well as the aggregated variables which are sometimes useful for coarse scale analyses and comparisons.  Such a flexible, hierarchical approach has been called for by urban ecologists in the past (Wu and David 2002).

Urban Change
Change landscapes in shifting urban mosaics.
The long-term perspective illustrated by such studies as BES and the Central Arizona Phoenix LTERs has been a crucial addition to contemporary urban ecology (Grimm et al. 2000).  The role of social, political, and biophysical legacies, and the resultant path dependencies are well recognized features of urban systems (Bain and Brush 2004).  Such legacies must be considered when bringing ecological knowledge to bear in understanding and improving urban systems.  The growing data on temporal changes are already an important part of contemporary urban ecology (Boone et al. 2009, Grove 2009).  This information is not only important for conservation of native and managed biodiversity, but for designing and managing for greater urban sustainability in the future (McGrath et al. 2007).

The Bottom Line
While Ramalho and Hobbs identify many positive attributes of a contemporary urban ecology, I believe that these are already in place, and are exemplified by a lot of the work in BES as well as other urban ecology efforts around the world.  The sophistication and evolution of contemporary urban ecology as an integrated, socio-ecological pursuit (Cadenasso and Pickett 2008), but which brings the best of mainstream ecology together with cutting edge social science and urban design should be more widely recognized. 

Literature Cited
Austin, M. P. 2005. Vegetation and environment: discontinuities and continuities. Pages 52-84 in E. van der Maarel, editor. Vegetation ecology. Blackwell Science, Malden, MA.
Bain, D. J. and G. S. Brush. 2004. Placing the pieces: reconstructing the original property mosaic in a warrant and patent watershed. Landscape Ecology 19:843-856.
Boone, C. G., M. L. Cadenasso, J. M. Grove, K. Schwarz, and G. L. Buckley. 2009. Landscape, vegetation characteristics, and group identity in an urban and suburban watershed: why the 60s matter. Urban Ecosystems 13:255-271.
Cadenasso, M. L. and S. T. A. Pickett. 2007. Boundaries as structural and functional entities in landscapes: understanding flows in ecology and urban design. Pages 116-131 in B. McGrath, V. Marshall, M. L. Cadenasso, J. M. Grove, S. T. A. Pickett, R. Plunz, and J. Towers, editors. Designing patch dynamics. Columbia, Graduate School of Architecture, Planning and Preservation, New York, NY.
Cadenasso, M. L. and S. T. A. Pickett. 2008. Urban principles for ecological landscape design and management: scientific fundamentals. Cities and the Environment 1:Article 4.
Cadenasso, M. L., S. T. A. Pickett, and J. M. Grove. 2006. Integrative approaches to investigating human-natural systems: the Baltimore Ecosystem Study. Natures, Sciences, Soci‚t‚s 14:1-14.
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.
Fox, G. A., S. M. Scheiner, and M. R. Willig. 2011. Ecological gradient theory: a framework for aligning data and models. Pages 283-307 in S. M. Scheiner and M. R. Willig, editors. The theory of ecology. University of Chicago Press, Chicago.
Grimm, N. B., J. M. Grove, S. T. A. Pickett, and C. L. Redman. 2000. Integrated approaches to long-term studies of urban ecological systems. BioScience 50:571-584.
Grove, J. M. 2009. Cities: managing densely settled social-ecological systems. Pages 281-294 in F. S. Chapin, III, G. P. Kofinas, and C. Folke, editors. Principles of ecosystem stewardship: resilience-based natural resource management in a changing world. Springer, New York.
Grove, J. M., W. R. Burch, Jr., and S. T. A. Pickett. 2005. Social mosaics and urban community forestry in Baltimore, Maryland. Pages 249-273 in R. G. Lee and D. R. Field, editors. Communities and forests: where people meet the land. Oregon State University Press, Crovallis.
Grove, J. M., M. L. Cadenasso, W. R. Burch, Jr., S. T. A. Pickett, K. Schwarz, J. P. M. O'Neill-Dunne, M. A. Wilson, A. Troy, and C. G. Boone. 2006a. Data and methods comparing social structure and vegetation structure of urban neighborhoods in Baltimore, Maryland. Society & Natural Resources 19:117-136.
Grove, J. M., A. R. Troy, J. P. M. O'Neill-Dunne, W. R. Burch, Jr., M. L. Cadenasso, and S. T. A. Pickett. 2006b. Characterization of households and its implications for the vegetation of urban ecosystems. Ecosystems 9:578-597.
McGrath, B. P., V. Marshall, M. L. Cadenasso, J. M. Grove, S. T. A. Pickett, R. Plunz, and J. Towers, editors. 2007. Designing patch dynamics. Columbia University Graduate School of Architecture, Preservation and Planning, New York.
McIntyre, N. E., K. Knowles-Yanez, and D. Hope. 2000. Urban ecology as an interdisciplinary field: differences in the use of "urban" between the social and natural sciences. Urban Ecosystems 4:5-24.
Ostrom, E. 1990. Governing the commons: the evolution of institutions for collective action. Cambridge University Press, New York.
Pickett, S. T. A. 1993. An ecological perspective on population change and land use. Pages 37-41 in C. L. Jolly and B. B. Torrey, editors. Population and land use in developing countries: report of a workshop. National Academy Press, Washington, DC.
Pickett, S. T. A. and M. L. Cadenasso. 2009. Altered resources, disturbance, and heterogeneity: a framework for comparing urban and non-urban soils. Urban Ecosystems 12:23-44.
Pickett, S. T. A., M. L. Cadenasso, J. M. Grove, C. H. Nilon, R. V. Pouyat, W. C. Zipperer, and R. Costanza. 2001. Urban ecological systems: linking terrestrial ecological, physical, and socioeconomic components of metropolitan areas. Annual Review of Ecology and Systematics 32:127-157.
Shane, D. G. 2007. Urban patches: granulation, patterns and patchworks. Pages 94-103 in B. McGrath, V. Marshall, M. L. Cadenasso, J. M. Grove, S. T. A. Pickett, R. Plunz, and J. Towers, editors. Designing patch dynamics. Columbia, Graduate School of Architecture, Planning, and Preservation, New York, NY.
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.