Sunday, December 10, 2017

Ecology Of the City is Twenty Years Old

The phrase "ecology of the city" was introduced in 1997 as a simple rhetorical device to highlight the novelty of the approach to urban ecology adopted in the initial proposal for the Baltimore Ecosystem Study LTER (Pickett et al. 1997).  We and our colleagues in the other urban LTER, located in Phoenix AZ, were anxious to differentiate the proposed work from the usual approach to urban ecology that had been used in the United States, and indeed most studies elsewhere, up to that time (Grimm et al. 2000).   

I have been surprised that the label and its contrast with the ecology in the city has become an organizational and framing tool in many of the contemporary textbooks of urban ecology (Adler and Tanner 2013, Douglas and James 2014).  However, over the intervening 20 years, the label has become more than a superficial framing strategy.  It has become invested with explicit theoretical and empirical content, moving well beyond metaphor (Zhou et al. 2017).  However, it may not be clear to most people that the label in fact now connotes a field of study and a mode of application.  The evolution of how the idea is used also serves as an indicator of how the field of urban ecology itself has developed over that 20 year span.

The predominant approach to urban ecological research in 1997 was called ecology in the city.  It is defined as a research approach focusing on biological organisms and ecological processes that are located in distinct natural, seminatural, or biologically-dominated patches within the fabric of cities, towns, suburbs, and exurbs.  These habitats can be considered to be analogs of those outside of cities, whether those outside locations are rural or wild.  Ecology of the city is defined, in contrast to ecology in the city, as a research approach that integrates biological, social, and technological aspects (Grimm et al. 2016) of urban structures and functions, and focuses on the feedbacks among the components of urban ecosystems that represent these three aspects.  The two approaches share a foundational concern with the spatial structure, heterogeneity, and functioning of urban systems ranging from single neighborhoods to urban megaregions (Figure 1).
Figure 1. Urban megaregions in Asia. The ecology of the city approach applies to all urban scales.

The two approaches can also be differentiated by the way they conceive of spatial heterogeneity, the models they use to represent spatial fluxes, and their implications for management and sustainability.  Such differences have been described in more detail in an earlier post (  The contrast can also be exemplified by describing how the nine components of theory (Pickett et al. 2007) differentiate the two approaches (Table 1).

Here, I present a new diagram that may help clarify the relationship of ecology of and ecology in cities (Figure 2).  Ecology in, as a focus on the biological structure and function of "green" patches in cities, is a core and ongoing interest of urban ecology.  This is because such patches are widely recognized as important sources of ecosystem services in the urban landscape (Haase et al. 2014).  They can also be the locus of evolutionary novelty associated with urban environments (Johnson and Munshi-South 2017).  Understanding how these biologically-dominated patches are put together, what biological resources they contain, what ecological and evolutionary functions they support, what benefits and burdens to humans exist within them, or what services emanate from them, are important outcomes of research focusing on ecology in the city.
Figure 2. A conception of the contrast among ecology in as core research, with conceptual and spatial extension to ecology of the city, and ending with the most inclusive approach of ecology for the city, specifying a mode of application.

The contrasting approach of ecology of the city continues to work with biologically-dominated patches, but extends its interest to all habitat types in the urban mosaic (Table 1).  Thus, it asks "what ecological and evolutionary structures and functions, environmental benefits and burdens, exist in and move among all patches in an urban area?"  This inclusive focus means that ecological research under the umbrella of ecology of the city investigates patch types that may not contain obvious biological components.  Ecology of the city must therefore be social-ecological research, rather than only biological research.

Table 1. The components of theory (see Pickett et al. 2007) and an instance of each in the contrasting approaches of ecology in the city and ecology of the city.  The examples of each component are not complete or comprehensive.  Several of the examples focus on a "filter" of concern with spatial structure as a driver of urban function.  Note that "urban" or "city" here refer to the entirety of urban systems, whether investigated as a whole or not.
Biotically-dominated urban patches
Hybrid social-ecological-technological patches
2. Assumptions
Drawn from biology and bio-ecology
Additions from social-ecological science
3. Facts
Biodiversity, traits, genetics, population dynamics
Additions from social-demographic diversity, land cover and institutional attributes, information, organizational dynamics
4. Generalizations
Succession; disturbance; stress; natural selection; stream continuum
Resilience cycle; socio-economic disturbance; cultural selection; engineered stream continuum
5. Laws
Law of succession
Law of adaptive cycle
6. Models
Patch-corridor-matrix; Island biogeography
Landscape mosaic/hybrid patch dynamics; metacity model
7. Translation modes
8. Hypotheses
Patterns and mechanisms of biotic impairment
Adaptive capacities and limits
9. Framework
Nested hierarchy of key components to explain biological features and processes in "green" patches in cities
Nested hierarchy of key components to explain hybrid features and processes in all patches in urban mosaics
Biological conservation
Sustainability planning and assessment

The third approach, ecology for the city, is defined as the co-production of urban research questions, and the pursuit of social ecological research intended to inform sustainable transformations in cities.  This approach is discussed more fully elsewhere (Childers et al. 2015).  But for this essay, the important idea is that the three approaches to ecological research about cities are not distinct from each other, but in fact interact.  They can be depicted as concentric circles, with ecology in being the core, ecology of being inclusive of in, and the ecology for embracing the knowledge and approaches of the first two.  Ecology in the city supports the social-ecological research exploring the ecology of the city.  Similarly, work pursuant to these two approaches supports the more transdisiplinary, co-produced research of ecology for the city.  Looking in the "opposite direction," each larger circle can be considered to require the input and knowledge provided by the more focused and included domain (Figure 3). 
Figure 3. The conception of ecology in, of, and for as an inclusive theoretical framework, showing their relationship to the disciplinary approach each takes.

The three approaches seen this way become nodes of interest and action in the larger field of urban ecological science.  None is "the" urban ecology.  Rather they are complementary and individual researchers may shift their focus and program among these approaches as time and circumstances permit or require.

The twenty years of research, education, and community engagement motivated by the first expansion of our attention in Baltimore from ecology in to ecology of the city, has continued to invite conceptual clarification.  It also suggests that the empirical content of research of the entire field continues to require understanding the biology within green patches, but also requires understanding how biologically-driven processes contribute to the functioning of patches in which biology may at first seem absent.  The ecology of the city points to the relevance of ecological research and knowledge throughout the city-suburban-exurban mosaic, and demands an interdisciplinary social-ecological stance toward research.  Finally, the necessity and ethical requirement for effective engagement in urban ecological systems has been codified by the ecology for the city approach.   

All Three approaches as defined here make up urban ecology, and together are relevant to the integration of ecological knowledge in urban decision making, ranging from the scale of households to that of entire metropolitan authorities.

Steward Pickett

Literature Cited
Adler, F. R., and C. J. Tanner. 2013. Urban Ecosystems: Ecological Principles for the Built Environment. Cambridge University Press.

Childers, D. L., M. L. Cadenasso, J. M. Grove, V. Marshall, B. McGrath, and S. T. A. Pickett. 2015. An Ecology for Cities: A Transformational Nexus of Design and Ecology to Advance Climate Change Resilience and Urban Sustainability. Sustainability 7:3774–3791.

Douglas, I., and P. James. 2014. Urban Ecology. Routledge, New York.

Grimm, N. B., E. M. Cook, R. L. Hale, and D. M. Iwaniec. 2016. A broader framing of ecosystem services in cities: Benefits and challenges of built, natural, or hybrid system function. Pages 203–212 in K. C. Seto, W. D. Solecki, and C. A. Griffith, editors. The Routledge Handbook of Urbanization and Global Environmental Change. Routledge, New York.

Grimm, N., J. M. Grove, S. T. A. Pickett, and C. Redman. 2000. Integrated Approaches to Long-Term Studies of Urban Ecological Systems. BioScience 50:571–584.

Haase, D., N. Frantzeskaki, and T. Elmqvist. 2014. Ecosystem Services in Urban Landscapes: Practical Applications and Governance Implications. Ambio 43:407–412.

Johnson, M. T. J., and J. Munshi-South. 2017. Evolution of life in urban environments. Science 358:eaam8327.

Pickett, S. T. A., W. R. B. Jr, S. E. Dalton, and T. W. Foresman. 1997. Integrated urban ecosystem research. Urban Ecosystems 1:183–184.

Pickett, S. T. A., J. Kolasa, and C. G. Jones. 2007. Ecological Understanding. Academic Press, San Diego.

Zhou, W., S. T. A. Pickett, and M. L. Cadenasso. 2017. Shifting concepts of urban spatial heterogeneity and their implications for sustainability. Landscape Ecology 32:15–30.

Monday, November 6, 2017

Outcomes of an Urban Sustainability Research Network

From 2011 through 2017, the National Science Foundation (NSF) supported a collaborative research project on "Urban Sustainability: Research Coordination and Synthesis for a Transformative Future."  This project was jointly organized and directed by the Baltimore Ecosystem Study LTER and the Central Arizona Phoenix LTER.  Prof. Daniel L. Childers and I were Co-Directors of the project. 

The text here is the "plain language" public outcomes report as submitted to the website.  We hope it gives you some sense of how BES and its partners are helping to promote the understanding and application of the popular and important idea of sustainability.  The report is divided into the two sections required by the National Science Foundation -- Intellectual Merit and Broader Impacts.

Intellectual Merit

The Urban Sustainability Research Coordination Network (RCN) was designed to improve the understanding of urban sustainability and to better position ecologists to interact with policy makers and managers concerned with sustainability in cities, suburbs, and urban regions.  It was important to focus on urban areas because sustainability research and practice had mainly focused on natural resources, rural systems, or conservation.  Because urban systems are becoming ever more important in the United States and around the world, improving the understanding of urban sustainability is a crucial need.  Intentionally limited to working with existing data, the Urban Sustainability RCN had four main objectives: 1) to improve the availability of knowledge about the sustainability of urban systems; 2) to generate conceptual frameworks that unify the crucial disciplines needed to understand and facilitate urban sustainability; 3) to identify research needs to enhance the future understanding and application of urban sustainability; and 4) to build a diverse network of sustainability researchers and practitioners. 

This RCN began with 37 participants from the United States and 4 other countries.  The Network grew to engage 80 researchers, educators, and practitioners from 50 cities in 20 countries.  This extensive network brought together a large amount of data, broad experience with cities of different sizes and types, and the insights of various cultural and professional backgrounds.  The large size of the Network helped to spread the insights of the intellectual integration very widely around the nation and globe.  The growth of the Network also reflected the widespread interest in the topic.

The RCN convened three meetings of the entire group over the course of the grant, plus smaller thematically oriented meetings.  The themes evolved during the project based on the "all hands" meetings, and the activities of the working groups.  Ultimately, the RCN addressed these themes: 1) conceptual models for urban sustainability; 2) the influence of different formal and informal governance structures on urban sustainability; 3) the role of interdisciplinary insights and contributions of the humanities to improved urban sustainability;  4) how ecologically informed urban design can improve sustainability through attention to adaptive resilience; 5) how urban metabolism, that is, the control of nutrient and energy flow, contributes to  sustainability; and 6) the use of scenario planning as a tool to improve sustainable urban futures.  

The RCN increased understanding of the social, economic, and environmental triggers that have led cities to crisis and transition, including discriminating the different scales on which the triggers act.  This information has been especially useful to reinforcing partnerships with urban sustainability officers.  The RCN also employed the idea that urban areas are complex systems, in which triggers affect the adaptive mechanisms that lead toward or away from sustainability.   Finally, the RCN employed the interactions between water resources and energy resources to understand important trade-offs that can affect the ability of cities to transition to sustainability.

Broader Impacts

Several specific outcomes illustrate the practical success of this RCN.  One is its serving as a seed bed for the Urban Resilience to Extremes Sustainability Research Network (UREx SRN).  This multi-institutional program of research and application, headquartered at Arizona State University, uses several of the conceptual advances generated by our RCN as the stimulus for new data collection.   A second major project that emerged from this RCN was funded by Future Earth to investigate sustainability from the perspective of urban phosphorus dynamics.  Phosphorus is a significant limiting nutrient in ecosystems and a can be a serious pollutant of surface waters.  A third outcome is cementing interactions with the Research Center for Eco-Environmental Sciences of the Chinese Academy of Sciences, to help develop sustainability research in the context of the rapid urbanization now underway in China and elsewhere in developing countries.  Interchanges with Network members in South Africa and in Latin America ensure that the insights and needs of very different kinds of urban change have been accounted for in our concepts and in our communication with urban design, planning, and management practitioners.  An additional important outcome of the RCN was better linking engineering and urban design perspectives with the important biological basis of sustainability in urban systems. 

The RCN trained several students and early career scientists.  A total of 20 post-doctoral associates participated as full members of the RCN.  The RCN employed Post-doctoral associate Meredith Garten for 2.5 years. She is now a faculty member at Ohio University.  Chris Sanchez, Laboratory Manager for PI Childers, assisted with logistics for the RCN after Dr. Gartin’s departure; he is now a doctoral student at Arizona State University.  Nicholas Weller, also a doctoral student with Childers, won an NSF EASPI grant to assist with field work on the urban sustainability pilot project funded by the CAS in Beijing in Summer 2016.  The interactions with many sustainability practitioners are ongoing.  So the network established by this RCN project, continues to advance the conceptual understanding and pathways for application of sustainability.


Some of the key or recent publications produced by the members and working groups of the RCN are these:


Grove, M., M.L. Cadenasso, S.T.A. Pickett, G. Machlis, and W.R. Burch, Jr (2015). The Baltimore School of Urban Ecology: Space, Scale, and Time for the Study of Cities  Yale University Press.  New Haven.  ISBN: 978-0-300-10113-3

Steiner, F. R., G. F. Thompson, and A. Carbonell, editors. (2016). Nature and cities: the ecological imperative in urban design and planning  The Lincoln Institute of Land Policy.  Cambridge, MA. 

Book Chapters

Cadenasso, M.L. and S.T.A. Pickett (2018). Situating sustainability from an ecological science perspective: Ecosystem services, resilience, and environmental justice. Situating Sustainability: Sciences/Humanities/Societies, Scales and Social Justice.  Sze, Julie, Editor.  New York University Press.  New York.  ISBN: 9781479870349, in press.

McPhearson, T. and K. Wijsman (2017). Transitioning complex urban systems: The importance of urban ecology for sustainability in New York City. P 65, in Urban Sustainability Transitions  Frantzeskaki, N, V. Castan Broto, L Coenen, and D. Loorbach.  Springer.  New York.  ISBN: 978-1-315-22838-9.

Steiner, F.R. (2016). Preface/Vorwort. Energy x Change: München und Austin: regionale Zentren nachhaltiger Entwicklung/Munich and Austin regional centers of sustainable innovation  Petra Liedl.  Beuth Verlag GmbH.  Berlin.  pg 8.

Steiner, FR, and D Pieranunzi (2016). Sites v2. Ecological Urbanism Revised ed. Mohsen Mostafari and Gareth Doherty.  Lars Müller Publishers.  Zürich.  pg. 514.

Papers in Journals

Bois, P, D.L. Childers, T. Corlouer, J. Laurent, A. Massicot, C. Sanchez, and A. Wanko. (2017). Confirming a plant-mediated "biological tide" in an aridland constructed treatment wetland.  Ecosphere. 8 (3),  e01756. 

Bunn, D., B. Büscher, M.L. Cadenasso, D.L. Childers, M. McHale, S.T.A. Pickett, L. Rivers, L. Swemmer. Golden Wildebeest Days: South Africa’s Wild Life Economy from Apartheid to Neolibralism.  Environment and Planning D: Society and Space, submitted.   

Childers, Daniel, M.L. Cadenasso, J.Morgan Grove, Victoria Marshall, Brian McGrath, S.T.A. Pickett (2015). An Ecology for Cities: A Transformational Nexus of Design and Ecology to Advance Climate Change Resilience and Urban Sustainability.  Sustainability. 7  3774. DOI: 10.3390/su7043774

Grimm, N.B., S.T.A. Pickett, R.L. Hale, and M.L. Cadenasso (2016). Does the Ecological Concept of Disturbance Have Utility in Urban Social-Ecological-Technological Systems?.  Ecosystem Health and Sustainability. 3 (1),  e01255. DOI: 10.1002/ehs2.1255

Groffman, P.M., M.L. Cadenasso, J. Cavender-Bares, D.L. Childers, N.B. Grimm, J.M. Grove, S.E. Hobbie, L.R. Hutyra, G.D. Jenerette, T. McPhearson, D.E. Pataki, S.T.A. Pickett, R.V. Pouyat, E. Rosi-Marshall, and B.L. Ruddell (2017). Moving toward a new urban system science.  Ecosystems. 20. DOI: 10.1007/s10021-016-0053-4

Hersperger, A.M., C Ioja, F. Steiner, and C.A. Tudor. (2015). Comprehensive consideration of conflicts in the land-use planning process: a conceptual contribution.  Carpathian Journal of Earth and Environmental Sciences. 10 (4). 

McHale, Melissa R., Scott M. Beck, Steward T.A. Pickett, Daniel L. Childers, Mary L. Cadenasso, Louie Rivers III, Louise Swemmer, Liesel Ebersohn, Wayne Twine, David Bunn (). Democratization of ecosystem services – A radically revised framework for assessing nature’s benefits.  Ecosystem Health and Sustainability, under revision.

McHale, Melissa R., Steward TA Pickett, Olga Barbosa, David N Bunn, Mary L Cadenasso, Dan L Childers, Meredith Gartin, George Hess, David M Iwaniec, Timon McPhearson, M Nils Peterson, Alexandria K Poole, Louie Rivers III, Shade T Shutters, and Weiqi Zhou (2015). A New Global Urban Realm: Complex, Connected, Diffuse, and Diverse Socio-Ecological Systems.  Sustainability. 7  5211. DOI: 10.3390/su70566

McPhearson, Timon, S.T.A. Pickett, N. Grimm, J. Niemelä, M. Alberti, T. Elmqvist, C. Weber, J. Breuste, D. Haase, and S. Qureshi (2016). Advancing Urban Ecology Towards a Science of Cities.  BioScience.   DOI: 10.1093/biosci/biw002

Metson, G.S., S.M. Powers, R. Hale, J. Sayles, G. Oberg, G.K, MacDonald, Y. Yuwayyama, N. Springer, A. Weatherley, K. Hondula, K. Jones, R.B. Chowdhury, A.H.W. Beusen, A.F. Bouwman. Socio-environmental assessment of phosphorus flows in the urban sanitation shain of diverse cities.  Regional Environmental Change, under review

Muñoz-Erickson, T.A., C. Miller, and T. Miller. (2017). How cities think: knowledge co-production for urban sustainability and resilience.  Forests. 8 (6) DOI: 10.3390/f8060203

Muñoz-Erickson, T.A., Lindsay K. Campbell, Daniel L. Childers, J. Morgan Grove, David M. Iwaniec, Steward T. A. Pickett, Michele Romolini, Erika S. Svendsen. (2016). Demystifying governance and its role in transitions in urban social-ecological systems.  Ecosphere. 7 (11),  e01564. DOI: 10.1002/ecs2.1564

Pickett, S.T.A. and Weiqi Zhou (2015). Global Urbanization as a Shifting Context for Applying Ecological Science toward the Sustainable City.  Ecosystem Health and Sustainability. 1  art5. DOI: 10.1890/EHS14-0014.1

Pickett, S.T.A., M.L. Cadenasso, Emma J. Rosi-Marshall, Kenneth T. Belt, Peter M. Groffman, J. Morgan Grove, Elena G. Irwin, Sujay S. Kaushal, Shannon L. LaDeau, Charles H. Nilon, Christopher M. Swan, Paige S. Warren. (2017). Dynamic Heterogeneity: A Framework to Promote Integration and Hypothesis Generation in Urban Systems..  Urban Ecosystems. 20 (1), DOI: 10.1007/s11252-016-0574-9

Pickett, S.T.A., M.L. Cadenasso (2017). How many principles of urban ecology are there?  Landscape Ecology.   DOI: 10.1007/s10980-017-0492-0

Pickett, S.T.A., M.L. Cadenasso, Daniel Childers, Mark McDonnell, Weiqi Zhou (2016). Evolution and future of urban ecological science: Ecology in, of, and for the city.  Ecosystem Health and Sustainability.  DOI: 10.1002/ehs2.1229

Pieranunzi, D., F.R. Steiner, and S. Rieff (2017). Advancing green infrastructure and ecosystem services through SITES.  Landscape Architecture Frontiers. 5 (1), 22. DOI: 10.15302/J-LAF-20170103

Romolini, M., R.P. Bixler, and J.M. Grove. (2016). A social-ecological framework for urban strewarship network research to promote sustainable and resilient cities.  Sustainability. 8:956. DOI: 10.3390/su8090956

Sanchez, CA; Childers, DL; Turnbull, L; Upham, RF; Weller, N (2016). Aridland constructed treatment wetlands II: Plant mediation of surface hydrology enhances nitrogen removal.  Ecological Engineering. 97  658. DOI: 10.1016/j.ecoleng.2016.01.002

Shutters, S.T. (2016). Interdependent Preferences and Prospects for Global Sustainability.  International Journal of Sustainability Policy and Practice. 12 (3),  DOI: 10.18848/2325-1166/CGP

Steiner, F.R. (2016). Opportunities for Urban Ecology in Community and Regional Planning.  Journal of Urban Ecology. 2 (1), DOI: 10.1093/jue/juv004

Steiner, F.R. (2016). The application of ecological knowledge requires a pursuit of wisdom.  Landscape and Urban Planning. 155:108.

Steiner, FR, AW Shearer (2016). Geodesign-Changing the World, Changing Design.  Landscape and Urban Planning. 156:1.
Zhou, Weiqi, S.T.A. Pickett, and M.L. Cadenasso (2017). Shifting concepts of urban spatial heterogeneity and their implications for sustainability.  Landscape Ecology. 32 (1),  DOI: 10.1007/s10980-016-0432-4

Steward T.A. Pickett, Director Emeritus