A New School of Urban Ecology: Contributions from Baltimore

Modern American urban ecology can be said to have come to fruition to a large extent in Baltimore.  Of course there are other cities where parallel, reinforcing, or complementary research and engagement activities are taking place, and all contribute to the emerging edifice of contemporary urban ecology.  But the work in Baltimore has a distinct flavor that helps understand what is novel about today’s urban ecological science.  Much of this is summarized in the book by Grove et al. (Grove et al. 2015).

The Relationship of the Baltimore School to the Baltimore Ecosystem Study

The Baltimore School owes a great deal to the Baltimore Ecosystem Study.  The Baltimore Ecosystem Study, like its sibling the Central Arizona-Phoenix project, is a National Science Foundation-supported research and education project, first funded in 1998. Indeed, the long-term funding of integrated urban social-ecological research started by the NSF in these two projects is a major reason that contemporary urban ecological science now exists as a part of mainstream ecology and as an important cross-disciplinary effort.  Additionally, urban research in Seattle, Chicago, New York and Boston has also grown rapidly over the last 20 years.  Deeper roots of urban ecology in Europe and Asia have “hybridized” with the emerging American contributions to produce a broad, integrated, and rapidly evolving discipline (McPhearson et al. 2016).

A good way to describe the Baltimore Ecosystem Study is to examine its mission statement.  Briefly, the mission of the Baltimore Ecosystem Study is to:

• Pursue excellence in social-ecological research in an urban system; 

• Maintain positive engagement with communities, environmental institutions, and government agencies;

•  Educate and inform the public, students, and organizations that have need of scientific knowledge; and

• Assemble and nurture a diverse and inclusive community of researchers, educators, and  participants.

What is a School of Thought?

It turns out that this multifaceted mission can be said to suggest the existence of a school of thought and practice (Cadenasso and Pickett 2013).  A school comprises a set of related and reinforcing components (Morris 2015 p. 201).  Schools consist of 1) theories, concepts, and models; 2) linked research approaches, 3) a network of student and professional training; 4) modes of application to practical issues, and 5) a community that shares and advances goals unifying the other components. Schools are often invisible, and their basic assumptions and approaches are rarely stated and even less rarely evaluated.  And of course, schools may differ from one another.  We believe that as a mode of thought and practice, the Baltimore School represents a scientific culture that actually extends well beyond the confines of the Baltimore Ecosystem Study and its study region.

One reason that we articulate a Baltimore School is to contrast it with the classical Chicago School of Urban Ecology (Cadenasso and Pickett 2013).  This school was developed in the opening decades of the 20th century in the department of sociology at the University of Chicago.  This was the founding department of American sociology, and its members were anxious to codify a novel approach to studying the social structure and dynamics of cities.  Although such a study would be important in an of itself, because Chicago was the fastest growing city in the world -- ever -- at that time, there was the added urgency of developing a sociology adequate to the task of understanding a new kind of city.

The Chicago School was clearly a sociological invention.  Yet, it has been called a school of urban ecology.  This labeling has persisted or re-appeared ever since Park and Burgess's pioneering book on The City (Park and Burgess 1925).  Some sociology textbooks of the last few decades even explain the long-standing critiques that led to the demise of the Chicago School in the 1930s in terms of ecological flaws (Gottdiener and Hutchison 2000).  So several of us (Cadenasso and Pickett 2013, Grove et al. 2015) thought it wise to reinforce knowledge that 1) the Chicago School was not the contemporary representation of ecological understanding of urban systems, and 2) that there were new approaches, intellectual tools, and integrated networks that were worthy replacements.  Hence, we articulated the tenets of a school of social-ecological science that could be labeled a school.  We have been heartened that Sharon Kingsland, a leading historian of science at Johns Hopkins University specializing in ecology, agreed with the use of the term school for this effort.

The positive aspects of the Chicago School include 1) its focus on urban rather than rural settlements, 2) the use of the case history approach, 3) empirical techniques such as interviews and field surveys, 4) the use of a clear theoretical framework motivated by competition among different uses and community types within the city, and 5) a recognition of cities as dynamic and mutable.  Many of these features are conspicuous advances over the urbanism that preceded the Chicago approach, which employed a more physical or formal, and a more static view of cities.  

The Chicago School - first wave of US urban ecology.

But the Chicago School ultimately declined for many reasons.  The social shortcomings of the Chicago School have been well known for a long time (Hawley 1986).  It took rural and small settlement life as a desirable norm, and cast many urban phenomena in terms of pathologies.  It explained changes in neighborhoods and districts as interactions of unitary human communities.  It idealized spatial interactions and assumed sequential replacement of different residential and commercial zones.  It neglected individual or household behaviors.  It adopted explanatory models from plant ecology via analogy, but without recognizing that some of these, such as succession, were being challenged and refined in their home discipline even at the time (Light 2009).  Furthermore, because they adopted competition among communities as the predominant mechanism of urban change, they neglected positive social interactions.  It is also notable that they based many of their social assumptions on what are now seen as fixed, social-Darwinist view of races and immigrant groups.  Their distress at the massive arrivals of new immigrant groups -- African Americans from the South, and Europeans from southern and eastern countries -- is palpable in the 1925 book (Park and Burgess 1925).  Notable in this regard is their apparently willful ignorance of the more dynamic and empirically open approach to social science pioneered by W.E.B Dubois 20 years prior to the height of the the Chicago ascendancy (Morris 2015).

Contemporary Urban Ecology as a School of Thought and Practice

The Baltimore School is much more than a point-by-point refutation of the Chicago School.  Indeed, some of the practices of the Chicagoans, such as case study and empirical studies on the ground in communities, are mainstays of contemporary social-ecological understanding.  However, there are features that have emerged in contemporary urban ecology that are worth highlighting (Cadenasso et al. 2006a).

First, the Baltimore Ecosystem Study focused on an extensive metropolitan area as a social-ecological system.  Urban ecology must now extend well beyond “the city” (Boone et al. 2014).  Furthermore, the social and the biological are given equal intellectual weight, and the ultimate goal is to understand the urban system -- city, suburbs, and exurbs -- as an integrated social-ecological system.  This has required consistant interaction across a long list of disciplines.  Sociology, demography, geography, anthropology, economics, and history have melded their voices with plant ecology, wildlife ecology, remote sensing, hydrology, soil science, atmospheric science, geomorphology, metacommunity ecology, and stream ecology.  Within the social features of the system a vast array of power, technological, cultural, and political processes must be explicitly recognized.  We have found the human ecosystem framework to be a useful tool to enhance integration (Machlis et al. 1997, Pickett et al. 1997).

Second, the Baltimore School does not assume that cities and urban systems are pathological.  This is not to say that urban areas do not have environmental or social problems.  However, the goal of urban ecology is fundamentally to understand the structure and function of integrated social-ecological systems in all their spatial, temporal, and organizational complexity (Cadenasso et al. 2006b).  Urban ecology can and does often turn its attention to research questions that address important concerns of communities, managers, and policy makers.  But drivers and interactions that have positive, negative, and unintentional effects are all investigated without prejudice in contemporary urban ecology.

The phrase “spatial, temporal, and organizational complexity” used above is key to the Baltimore School.  Urban ecology must investigate complex spatial mosaics of regional extent.  Investigations focus on local to regional scales, and even extend to understanding the global influences on local and regional urban processes. Thus, spatial scale is a key concern of contemporary urban ecology.  

Temporal complexity sets urban ecology in a deep historical perspective, acknowledging that past decisions and the social and structural legacies they engender are important determinants of current system processes.  Furthermore, temporal change is ongoing in cities, and the dynamic models of particular times and places may not apply to other locations or trajectories of change.  Shrinking, post-industrial, sprawl, ghost, and shanty cities or districts are examples of the variety of dynamics urban areas are now experiencing (McHale et al. 2015).  

Organizational complexity introduces another important dimension of scale.  It indicates that decisions and behaviors can originate at individual, household, community, governance, and jurisdictional levels, for example.  Given that the institutions that exist on different organizational levels have different spatial extents and different longevities, the opportunity for complex, non-linear effects is great.

Go Where the Data Lead You

One facet of the Baltimore School is to not be bound either by vernacular "urban legends" or by preconceptions.  Urban areas are already the home of more than 80% of residents in wealthy nations, and globally, the urban population stands at greater than 50%.  This means that some manner of urban settlement -- whether dense city, compact suburb, suburban sprawl or exurban retreat -- is a matter of deep personal experience of most of humanity.  In other words, we all "know what a city is" and have personal opinions about the benefits, frustrations, or vulnerabilities of our urban (sensu latu) homes and workplaces.  But personal experience can be misleading and must be questioned when we enter the realm of urban ecological science.  We have debunked urban legends elsewhere (Pickett et al. 2008), and myths about trees and crime, misunderstanding the relationship of mosquitoes breeding and trees, the low biodiversity of vacant lots, are among "legends" currently being clarified.  The key is to follow the scientific approach of going where the data lead us, and to examine assumptions about social-ecological pathologies, ecosystem services, and structure-function relationships (Pataki 2013).  While these assumptions may reflect legitimate human values, and thus are quite legitimate motivators for research. The conclusions must arise from the data and not from the assumptions. 

The relationship of data to decision making brings with it an obligation for contemporary urban science to engage in the civic dialogs shaping and managing urban systems.  Science cannot ethically impose its wishes on urban systems, but it must legitimately share and explain its conclusions in the civic dialog, and engage with urban designers, planners, managers, and policy makers in their quest to improve the sustainability of urban systems and city life (Childers et al. 2014).

Where is the Baltimore School?

Baltimore PS 103, Attended by Thurgood Marshall

 

 

This essay has sought to explain what a school is, and how the Baltimore School differs from and supersedes the long-discredited Chicago School.  The essay has not touched on other schools of urbanism, each of which has value.  The Los Angeles School (Dear and Dahmann 2008) for example, is helpful in advancing a regional understanding of urban systems.  Many of the other schools are predominantly motivated by urban design or planning concerns, or remain thoroughly rooted in social science traditions.  One of our goals in the Baltimore School is to suggest the importance of including ecological science perspectives and approaches in the study of urbanization, city/suburban/exurban mosaics, and in designing and managing for sustainability (McGrath 2013, Pickett et al. 2013).  The functional connections required to work with both ecological and social connectivities is the Continuum of Urbanity (Boone et al. 2014).  This emerging theory highlights the kinds of exchanges, influences, and effects that spread throughout and between urban megaregions even at the global scale. 

I close with a plea to see the Baltimore School as an expression of a broader and inclusive approach to incorporating ecological knowledge into understanding, envisioning, and managing the changing urban realm wherever it exists (McHale et al. 2015).  The Baltimore School isn't a little red schoolhouse at any particular crossroads, and it isn't just in or about Baltimore.  It is an invisible college and framework for an inclusive ecological-social approach to the emerging and ongoing complexities of urban systems worldwide.

References

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

Cadenasso, M. L., and S. T. A. Pickett. 2013. Three tides: the development and state of the art of urban ecological science. Pages 29–46 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.

Cadenasso, M. L., S. T. A. Pickett, and J. M. Grove. 2006a. Integrative approaches to investigating human-natural systems: the Baltimore ecosystem study. Natures Sciences Societes 14:4–14.

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

Childers, D. L., S. T. A. Pickett, J. M. Grove, L. Ogden, and A. Whitmer. 2014. Advancing urban sustainability theory and action: Challenges and opportunities. Landscape and Urban Planning 125:320–328.

Dear, M., and N. Dahmann. 2008. Urban politics and the Los Angeles School of urbanism. Urban Affairs Review.

Gottdiener, M., and R. Hutchison. 2000. The New Urban Sociology. McGraw Hill, New York.

Grove, M., M. L. Cadenasso, S. T. A. Pickett, G. Machlis, and W. R. Burch Jr. 2015. The Baltimore School of Urban Ecology. Yale University Press, New Haven.

Hawley, A. 1986. Human Ecology. University of Chicago Press, Chicago.

Light, J. S. 2009. The nature of cities: ecological visions and the American urban professions 1920-1960. Johns Hopkins University Press, Baltimore.

Machlis, G. E., J. E. Force, and W. R. Burch. 1997. The human ecosystem .1. The human ecosystem as an organizing concept in ecosystem management. Society & Natural Resources 10:347–367.

McGrath, B. P., editor. 2013. Urban design ecologies. John Wiley and Sons, Ltd, Hoboken.

McHale, M. R., S. T. A. Pickett, O. Barbosa, D. N. Bunn, M. L. Cadenasso, D. L. Childers, M. Gartin, G. R. Hess, D. M. Iwaniec, T. McPhearson, M. N. Peterson, A. K. Poole, L. Rivers, S. T. Shutters, and W. Zhou. 2015. The New Global Urban Realm: Complex, Connected, Diffuse, and Diverse Social-Ecological Systems. Sustainability 7:5211–5240.

McPhearson, T., S. T. A. Pickett, N. B. 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 Accepted for publication.

Morris, A. 2015. The Scholar Denied. University of California Press, Berkeley.

Park, R. E., and E. W. Burgess. 1925. The City. University of Chicago Press, Chicago.

Pataki, D. E. 2013. Urban greening needs better data. Nature 502:624–624.

Pickett, S. T. A., M. L. Cadenasso, J. M. Grove, P. Groffman, L. E. Band, C. Boone, W. R. Burch, S. Grimmond, J. Hom, J. C. Jenkins, N. L. Law, C. H. Nilon, R. V. Pouyat, K. Szlavecz, P. S. Warren, and M. A. Wilson. 2008. Beyond urban legends: an emerging framework of urban ecology as illustrated by the Baltimore Ecosystem Study. Bioscience 58:139–150.

Pickett, S. T. A., M. L. Cadenasso, and B. McGrath, editors. 2013. Resilience in ecology and urban design: linking thoery and practice for sustainable cities. Springer, New York.

Pickett, S. T. A., W. R. B. Jr, S. E. Dalton, T. W. Foresman, J. M. Grove, and R. Rowntree. 1997. A conceptual framework for the study of human ecosystems in urban areas. Urban Ecosystems 1:185–199.

Image Credits: 

Kanagawa Oki Nami Ura (神奈川沖浪裏), literally, Under a wave off Kanagawa, woodcut print after Katsushika Hokusai (葛飾北斎) from the series 36 Views of Mount Fuji, created in the late 1820's, and first published 1832. This version is an undated modern reprint.  From Library of Congress

 

"PS 103 Old W Balt HD T Marshall" by Smallbones - Own work. Licensed under CC0 via Commons - https://commons.wikimedia.org/wiki/File:PS_103_Old_W_Balt_HD_T_Marshall.JPG#/media/File:PS_103_Old_W_Balt_HD_T_Marshall.JPG

Baltimore and Beijing: A Learning Expedition to China

Famously Rampant Urbanization

This last summer, I had the pleasure of being hosted as a Visiting International Professor by the Research Center for Eco-Environmental Sciences in Beijing.  This center is part of the Chinese Academy of Sciences, and is the home of the State Key Laboratory of Urban and Regional Ecology.  My goal in spending three months in China was to learn about its form, magnitude, and rate of urbanization. The speed and novelty of urban growth in China are exceptional.  Although some countries have faster annual percent rates of conversion of population from rural to urban, none has a greater absolute number of participants in the process.  Nor do other countries rival China in the extent of the creation of new cities virtually from scratch across broad regions.  It is a perfect place to help put our work in Baltimore in a larger perspective.  In addition, researchers in China are excited and very well prepared to share their new knowledge about urbanization with the rest of the world.

China has for thousands of years been a largely agricultural

country.  The establishment of the People’s Republic saw the proportion of rural residents in the solid majority.  Although Chinese cities boast histories reaching back thousands of years, they were mostly distinct settlements, often retaining ancient defensive walls and sharing key aspects of their city plans.  However, starting from the late 1970s, with the establishment of new policies, the growth of its cities, and the transformation of its population from predominantly rural to mainly city-dwelling, took off.

Chinese urbanization is more than simply the growth of established cities, however.  The idea of urban agglomerations, more recently conceptually deepened in terms of urban megaregions, was one that originated to capture the extraordinary spatial scope of urban change in China and elsewhere in Asia.  There are 23 planned megaregions or urban agglomerations in China (Fang 2011).

Twenty-three existing and planned urban megaregions in China (Fang 2011)

Urban megaregions require understanding urban change in an inclusive way, as something that embraces old city cores, new neighborhoods, novel extensions within large urban administrative units, the engulfing of ancient villages by dense and often high-rise urban fabric, the replacement of agricultural villages by mixed industrial settlements, the demolition of villages and their replacement by superblocks of gated high-rise condos or apartment buildings, and even some modest development of villas, or what we in the U.S. would call single-family houses with yards. 

The richness of the kinds of change and the spatial mosaics produced are novel and not well researched at this time.  Chinese urban ecologists recognize a pressing need to understand the environmental implications of this long list of transformations.

Shifting Policy Landscape

Coming from the United States, I had the impression that China’s strong central government would make urban policy easy to understand, and would also make rational urban plans the norm.  What I learned however, was the existence of a complex, multi-level and multi-sector process of urban change.  In addition, I learned of a fluid policy landscape.  For example, until late July of this year, urban residents had to be registered.  This excluded many people who wished to migrate from the countryside from full participation in urban life and its amenities.  Children of unregistered residents were not permitted to attend public schools. Furthermore, unregistered rural migrants were often crowded into less-than ideal rental units. 

In July 2014 the central government announcemed that this policy, labeled hukou, would apply differently depending on the size cities.  Although the intent is to more evenly spread urbanization across the spectrum of cities, there may well be an pulse in migration to cities as a result.  The social and ecological consequences will be not only interesting, but very likely potent.

The revision of the hukou policy is situated within a larger trajectory of policy evolution in China.  The previous central government policy prioritized industrial development.  The term “development” is used all over the world and is the stuff of headlines and political slogans.  However, it strikes me that most uses in the public discourse in China and elsewhere are rather vague and loaded.  In the past, given the evidence on the ground (and in the heavy, polluted air!) development in China suggested an industrial pathway, and China’s prowess as a maker for the world has been rightly recognized as a result.  But the term development, again based on my personal observations of the culture of consumption that has saturated the big cities with global brands, automobiles with foreign name plates, familiar fast food restaurants, and multi-story shopping malls, also implies a growing emphasis on the provision and acquisition of luxury goods.  The urbanization policy now driving demographic and spatial change in cities, suburbs, with its implications for villages and rural life, shifts emphasis to domestic consumption as a driver for development.

Of course industrially based economic activities and infrastructure will continue to be built and operated in China.  But the new emphasis on urbanization intertwines with a new national policy on the environment.  How these two strands will be reconciled and whether there are the desired environmental – and human well being – outcomes, remains to be seen. 

Chinese urban ecologists are concerned to be part of the dialogue, and many ecological leaders are well placed to help urban planners and municipal authorities to improve the ecological processes and services within their jurisdictions.  I did, however, see evidence of some shortfalls in linking ecological and urbanization processes.

Shortcomings in Contemporary Urbanization

One problem is the sheer speed of urban development.  An interesting and salubrious institution in many large Chinese cities is the city planning museum or planning exhibition hall.  I visited three of these: Beijing, Tianjin, and Shanghai.  In some cases, a glance at the current iteration of the city regional plan was jarring in its dissonance with the facts on the ground.  Much of the greenspace promised by the current plan for Beijing had already disappeared under roads and buildings.  An aspect of the plan that was clearly successful was the protection of the mountain districts in the extensive megacity administrative boundaries of Beijing. These lands were well preserved under the rubric of protecting the air and watersheds on which the city depends, although as a plant ecologist I was interested to know how much impact the transplantation of large, mature trees from the forests into new city and urban developments affected the source stands. 

Tianjin’s urban plan seemed to have clearer bioecological content, and establishing boundaries to protect sensitive forests, lakes, seacoast, and rivers was a part of the plan.  Lands were set aside for parks for urban residents as well, and restoration of wetlands formerly devoted to agriculture in the city boundaries was called for.  The ecological rationale for such conservation and restoration was well laid out in Tianjin’s exhibition hall.

Another issue is the predominance of an economically driven real estate industry, a social institution not unknown in the capitalist west, of course.  My naïve view of the communitarian nature of the Chinese state did not prepare me for the news about the power and efficiency of the private real estate juggernaut in China.

The final shortcoming was the nature of many eco-cities.  As an ecologist and an urbanist who thinks that sustainability is a reasonable strategy for visualizing multi-dimensional improvements in urban social-ecological systems, I had high hopes for the eco-city idea.  However, eco-city developments seem to emphasize a rather narrow suite of strategies, such as engineering efficiencies, multimodal transportation and density, improved onsite stormwater management structures, supplementation of energy sources with renewables, such as wind.  They also have generous street tree plantings and green courtyards in the high-rise residential blocks.  However, the eco-city developments, which were conspicuous in the impressive city models in the planning exhibitions, and evident on the ground in many places, had significant lapses in my view.  I highlight several below.

The rich diversity of commercial opportunities scattered throughout the older urban neighborhoods and even in larger villages, were relegated to centralized shopping malls in the eco-cities.  Three was little to invite residents to interact on the street, and although the individual residential clusters apparently provide recreational amenities behinds their gates, the life on the street seemed depauperate.  This seems to violate one of the tenets of functional urbanism, and was a great disappointment to see so often.  Altogether, the utility of the sustainability concept, which calls for the joint attention to ecological integrity, social functionality and equity, and economic vitality, seems to be poorly realized in much of the urban growth that I saw in China.

Visualizing Urbanization: Opportunities for Enhancement

China also offers insights into the visualization of urban change, a problem that is widely shared.  The process of land conversion and of remaking existing cities is so striking that it is frequently and compellingly represented by a few contrasting colors on GIS maps.  Derived from aerial imagery, such maps represent core urban zones in red, agricultural areas in yellow, and forest and grassland in shades of green.  Because the shifts over five or ten years are so great, such color contrasts over time tell a powerful story.  

Change of land covers in Beijing from 1984 through 2010. Red is
developed urban land.  Copyright
Prof. Weiqi Zhou.  Do not duplicate without permission. 

  

But such coarse classification of urban lands – red blob mapping -- neglects much of the subtlety of urban form.  This is due to both the frequent use of coarse spatial resolutions on the order of 10s of meters, as well as to the fact that these classifications are blind to the rich array of ways in which people actually use different patches.  And here I do not mean use in the sense of simple zones like commercial, industrial, or transportation areas.  Nor does even recognizing the height of buildings reveal key social and ecological relationships that different spatially recognized patches might possess.  There is a great opportunity in China to break down the land covers within urban and urbanizing areas into more specific categories, while recognizing the three dimensional structures of patches.  This approach is one that was pioneered in Baltimore, and I look forward to exploring it with Prof. Weiqi Zhou and other colleagues in China.  The detailed spatial heterogeneity of city regions is a key dimension along which ecological and social understanding have been demonstrated to advance. 

This sort of theoretical perspective on cities also matches very well with the concerns and practices of urban designers, including architects, landscape architects, planners, as well as sociologists concerned with the patchiness of human institutions and social arrangements.  Once more subtle land cover maps are available for Chinese urban regions, the opportunity will arise to understand the social structures, norms and policies, governance arrangements, and of course, the bioecological patterns and processes that exist in those heterogeneous structural mosaics.  The power of fine scale, highly conceptually resolved land classifications in Chinese cities and their rampantly changing urban regions has hardly been tapped.

The Reach of Urbanization

The impact of urbanization in China – or anywhere for that matter -- is not something that is confined to cities and their expanding fringes.  Rather, the growth of cities in China touches even distant villages and rural areas.  Indeed, the national urbanization policies mentioned earlier in this essay guarantee that the link between urban and rural changes will be strong. 

One thing that I explored with Prof Weiqi Zhou and members of his laboratory, was how the continuum of urbanity can be used to advance the understanding of the regional nature of China’s urbanization. 

The continuum of urbanity identifies four dimensions along which the structures and processes of urban change play out: Livelihood, lifestyle, spatial connections including local, regional, and global, and the social and biophysical nature of specific places.  The continuum of urbanity is a conceptual ordering of the shift between urban and rural influences and processes (Boone et al. 2014).  It is not necessarily a literal transect on the ground, but rather the idea applies to various scales and can be used to understand the effects of urbanization at local, regional, and global spatial scales.

The four components of the continuum of urbanity examine 1) how people support themselves and whether and how they participate in formal and informal economies, 2) the nature and expression of their social identities and the implications of social identity for consumption and symbolic decisions, 3) the spatial scope of influences and material connections, including long-distance linkages or tele-connections, and finally 4) the interaction of the other three dimensions with the biological, physical, cultural, and social environments of specific places.  Such specificity of place can apply to very local or to broader areas.  In describing the interaction with place, it is important that sometimes features of the bio-geo-cultural environment act as constraints on the other three dimensions of the continuum of urbanity, and sometimes the environment is in fact changed by the processes represented by the other dimensions.

Urban district rising on recently converted agricultural land
between Beijing and Tianjin.

It is clear that the continuum of urbanity plays out in China in many ways.  The connections between cities and villages are diverse and impactful.  Some villages are swallowed up into expanding cities, with consequent changes in livelihood and lifestyle.  Some villages continue to exist, but become sites of industrial production as factories excluded from polluted cities relocate to rural areas, while some are converted to tourist economies, for example.  In other cases, villages are bought out and the land converted to high-rise, gated apartment blocks with the associated transportation infrastructure.  

And the continuum of urbanity does not stop at China’s borders.  As the official policies to generate a more urban, domestic consumer-based society move forward, a rising middle class demands more meat, for example, which alters land use and livelihoods as far away as Australia and the Americas.  Pig farming, migration of fruit bats to cities, and shifts in bat-borne disease risk are outcomes of the continuum of urbanity that spans from China to Australia. 

The continuum of urbanity represents a useful way to organize research on the extensive effects of urban development in China.  It can focus on fine scale heterogeneity within cities, as called for above, or it can expose the continental and global effects of urbanization.  The mutual relationships of urban regions linked in a global system are eliciting greater attention in the world of economics, and ecology will change at both ends of any urban teleconnections.

An Urban Ecological Future

The changes in China’s urban realm, and its megaregional, continental, and global reach are vast research frontiers.  To summarize what I learned in China:

1. There is great need for describing, modeling, and working with spatial heterogeneity at refined conceptual resolutions and at various spatial grains.

2. Social phenomena and dynamics need to be better connected with ecological and physical data and representations of urban change.

3. The connections between both former and persistent-but-altered rural zones and villages with cities are an open research task.

4. Addressing the shortcomings of some “eco-city” approaches, and applying sustainability as a linked set of social, environmental, and economic goals are important challenges.

The richness, speed, and nature of Chinese urbanization are a useful intellectual foil to the specific history and trajectory of urban change in Baltimore.  China defines at least one extreme of the conceptual space that all urban social-ecological research and application occupy.  Opportunities for comparison and for collaboration are great.

Acknowledgments.

My trip to China was supported by an International Visiting

Professorship from the Chinese Academy of Sciences.  My hosts were Prof. Weiqi Zhou and Prof. Zhiyun Ouyang of the State Key Laboratory of Urban and Regional Ecology of the Research Center for Eco-Environmental Sciences.  The graduate students and faculty in Prof. Zhou’s lab were indispensable guides and warm friends, and I am indebted to them all for many kindnesses, including compensating for my attempts to apply New York rules for jaywalking in an inappropriate cultural context.  I know a lot more about urbanism and urban ecology now than I did when I landed in Beijing.  They also taught me how to make dumplings.

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Does Urbanization Stop?

A lot of effort in urban ecological science around the world is now focused on the process of urbanization.  This is reasonable because the demographic, social, environmental, and economic shifts toward urban in all its forms have become dominant trends for our planet.  The conversion of land from rural or wild landscapes and covers to city and suburb is considered by some to be the essence of urbanization.  

Baltimore (upper right) and
Washington  DC in 1900
(J. O'Neil-Dunne, University of Vermont
Spatial Analysis Lab)

When urbanization is charted – literally mapped – it can be seen as a one way conversion.  Often on such maps, urbanized land is shown as a shade of red, agriculture as yellow, grassland and forest as different shades of green, water as blue, and so on.  Much recent work at the coarse spatial scale shows the color-coded blob of city and suburb spreading across a landscape at the expense of wild, agricultural, or even aquatic covers.  Perhaps the garish colors were chosen to highlight the almost incredible magnitude of urban changes starting about a century ago, and even growing explosively in places like China and India where the trend started more recently.  Some observers fall into a state of panic about the urban when viewing these maps.  Such negative bias about the urban was evident in the “social pathology” approach of the Chicago School of urban sociology, or even longer ago in Thomas Jefferson’s idealization of the agricultural life and the open American frontier exemplified by the Louisiana Purchase.  

Baltimore and Washington, 2001

But whatever the biases and rationales for the colors mapped, the changes are commonly represented as one-way transitions.  Urbanization, like the old-fashioned views of ecological succession, might be considered to be a linear, directional process that has a terminal point.  Such maps do tell a very useful story at the coarse scale.  The comparison of cities and of times, and the planning and management of regions can benefit from the coarse scale mapping of urban entities.

In spite of its value, the coarse mapping approach to urbanization does leave out some important subtleties.  Three big things about the urban realm need to be added: 1) within-urban spatial heterogeneity; 2) the issue of what comes after urban; and 3) the existence of city/suburban/exurban systems as qualities as well as material entities.

Urban Heterogeneity.

Urban is used here inclusively, referring to various kinds of dense, demographically diverse, infrastructurally invested systems and their various human networks and social interactions.  Urban is city, suburb, and exurb together.  It includes locations as different as central business district, leafy suburb, shantytown, strip mall, industrial park at the Interstate exchange, forested park, community gardens, vacant lots, and many more kinds of designed and accidental places. 

Social-biophysical, high conceptual
resolution land cover map (HERCULES)
in metropolitan Baltimore

Sometimes the red blobs of urban maps are shaded to represent commercial, transpiration, residential districts of varying densities.  If the maps are constructed at relatively fine grained spatial resolution, riparian, forest, park, grasslands, brownfields, and the like may be shown.  Depending on the spatial resolution and how land cover classes are defined, infill and edge sprawl development can be shown.  

But cover can be conceptualized in a way to acknowledge that it comprises both biologically-derived ecological components like trees, shrubs, grass, and socially derived components like buildings and pavement.  Human actions stand behind these heterogeneous components through migration, transportation, design, construction, management, demolition, etc.  The HERCULES land cover system reflects this multi-dimensional biological-social heterogeneity (Cadenasso et al. 2007). 

What Comes After Urbanization?

The issue of heterogeneity within coarse-scale representation of urbanized areas points to the second shortcoming of simple conceptions of urbanization.  Once a place is urbanized, it can continue to change.  In other words, the nature of urban fabric and the interactions it is entangled with can continue to change.  In fact, such change is a remarkably common feature of urban systems.  Changes range from the shifts from residential to commercial use along some transportation routes, to wholesale abandonment as population becomes sparser in the inner city, to “scrapeoffs” of older, smaller suburban houses and their replacement by lot-filling McMansions, to conversion of disused industrial structures or warehouses to residences or artistic venues.  Even the vegetation component of urbanized patches can wax and wane as street and yard plantings mature or succumb to storm, pest infestation, or neglect.  The currently growing interest in community gardens and urban farming is another example of mutability within urbanized land covers.  The urban blob is a snare and a delusion, since fine- and medium-scale changes within urban areas continue.

If the conversion of land from agricultural and wild to urban is a step function or a threshold that is not reversible at the coarse scale, still urban processes continue.  Urbanized areas continue to change, sometimes in large ways and sometimes in micro-patches.  Hence, it may be useful to conceive of urbanization in ways like ecologists have come to view community or ecosystem succession.  

Classically, succession was thought to start with a pioneer community established after some large disturbance and to proceed through dominance by higher statured plants while adding layers, and ultimately to end in a stable configuration and composition of species and metabolic processes -- the so-called climax.  Contemporary understanding of succession accepts that “stages” may be skipped or not come in the expected order, that fine or medium scale disturbances may continue to play a role in structuring the community, and that there is rarely anything like a local climax.  Urbanization may be like this – an idiosyncratic trajectory, contingent upon a specific concatenation of human and natural events, and not reaching some stable end point.  Urbanization in the current era may best be thought of as an ongoing urban processes.  In other words, to have been urbanized is not to stop changing.

Some social scientists have similar views.  For example, Gottdiener and Budd (2005:184) state that “Urbanization attempts to chart and understand the rise and fall of great cities.”  In that same article they point to some of the complexities of contemporary urbanization.  The existence of multiple kinds of urban form within the same urban system, the role of industrialization in urbanization, the role of consumption lifestyles, and the regional scope and connectivity of city and suburban settlements.  Marcotullio and Solecki (2011) note that some social and environmental problems blamed on urbanization would be better disaggregated into more distal, fundamental causes, such as affluence, lifestyle, and power relationships rather than a vague, overgeneralized variable such as urbanization.

The City as Quality

Urbanization is often thought of in the environmental sciences and in the planning realm as a physical entity.  This view supports the emphasis on mapping and the colorful sprawl time-series we so often see in writings about urban policy and urban problems.  Marcotullio and Solecki (2013) do a nice job of highlighting the limitations of the approach to cities only or primarily as quantities or physical entities.  Maps of land conversion, drawing of sharp boundaries, and defining the distinctions between urban versus the rural and the wild, for example, are approaches that are reinforced by the view of cities as quantity or entity.  Social phenomena such as human density, concentration, kind of employment (agricultural vs. non-agricultural), and heterogeneity are part of the "entitation" of cities.  So are the physical features such as impervious surfaces, modification of stream networks, transportation and infrastructural grids, commuting radii, installation and management of vegetation, and the concentration of heat, contaminants, and certain resources.  All are mappable quantities.

Certainly cities, suburbs, and exurbs are physical places. 

Night life along the river in Tianjin,
China. A variety of formal and informal
activities represent the quality of an
urban area.

But they are also lived experiences and suites of interactions. These are the qualities of urban systems.  Qualities include such things as institutional arrangements and social norms, reliance upon legal versus familial strictures, connection with distant resources, opportunities, and limits.  Lifestyle and livelihood might be useful short hand for important features of the urban systems as quality.  Of course, there are many economic and social processes that scaffold these lifestyle and livelihood as quality.  Another aspect of quality is sense of place.  Sense of place reflects individual and community-held cognitive maps, the landmarks that people mentally locate themselves and also physically navigate by, the feeling of support or comfort in some locations versus discomfort and fear in others. 

Importantly, although these all reflect quality of the urban, it is possible using various sociological and anthropological methods to measure and compare these reactions to urban as quality.  Many of the features of the human ecosystem framework (Machlis et al.  1999) reflect the qualitative side of Cities/Suburbs/Exurb systems.  Myths and cultural resources, interacting individuals, and the temporal changes of households, communities, and institutions become part of the quality of urban life as well.  These qualitative features are recognized by contemporary social-ecological urban systems theory to be involved in feedbacks with the biophysical processes in urban ecosystems.  Discovering and understanding these linkages between the social qualities and the biophysical quantities remains a key goal of contemporary urban ecological science.

Is There a Better Term?

Urbanization as a term fails us by not connoting the subtleties of internal physical and social heterogeneity, the fact that urban areas never stop changing, and the idea that “cityness” is both physical quantity and social quality.  The processes are multiscalar and continue in various forms, from “the business cycle” to population growth and residential thinning.  If the suffix “-ize” means to become something – in our case to become urban -- what word will stand for the continuing changes, sometimes episodic and sometimes gradual once the urban realm has come into being?  Maybe we can shoehorn “urbanization” into this definition, and beat it into submission.  

Or maybe we can speak instead of “urbaning,” to represent the ongoing changes that old, new, and yet to be born cities, suburbs, and exurbs will be involved in.  Urbaning would mean the condition of being urban and dynamic.  Or since nobody is going to accept such a neologism, maybe we can just be careful with our conceptual, empirical, and theoretical models, and always keep urban quality, urban quantity, and urban change in clear view across scales from a neighborhood to an urban megaregion.

Bibliography

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.  Concepts and a spatial analysis approach that links socially-generated and biologically-generated sources of spatial heterogeneity at fine scales in urban, suburban, and exurban landscapes

Gottdiener, M. and L. Budd. 2005. Key concepts in urban studies. Sage Publications, London.  A conceptual dictionary of terms about urban studies from the social sciences.  Useful entries on urbanization and urbanism.

Machlis, G. E., J. E. Force, and W. Burch, Jr. 1999. The human ecosystem as an organizing concept in ecosystem management. Pages 21-36 in N. C. Johnson, A. J. Malk, W. T. Sexton, and R. Szary, editors. Ecological stewardship:a common reference for ecosystem management. Elsevier Science Ltd., Oxford.  The Human Ecosystem Framework contains many elements that represent quality of urban areas, as well as those that are physical entities or quantities.

Marcotullio, P. J. and W. Solecki. 2013. What is a city? an essential definition for sustainability. Pages 11-25 in C. G. Boone and M. Fragkias, editors. Urbanization and sustainability: linking urban ecology, environmental justice, and environmental change. Springer, New York.  A clear and compelling assessment of the quantity and quality approaches to cities, and cautions about the neglect of quality in environmental sciences.  An excellent overview of the social controversies behind this continuum.

Simone, A. 2010. City life from Jakarta to Dakar: movements at the crossroads. Routledge, New York.  Discusses the nature of “cityness,” and is thus a nice complement to Marcotullio and Solecki with many examples from the very dynamic urban processes in Africa and South Asia.