New research initiatives in urban ecology in North America, Asia, and Europe provide inspiration and opportunities for dialogue integral for informing ecologists, social scientist, planners, and designers about the future of cities worldwide.
The United Nations estimates that the number of urban dwellers will exceed the number of rural dwellers by 2010. Along with this trend come other long-term environmental changes within and surrounding cities, or "urban ecosystems" as they have come to be known, such as alterations in habitat, climate, and water resources.
| Research Findings in Urban Ecology: "Plant Diversity and the Luxury Effect" |
|
CAP LTER research has revealed that biodiversity in urban/suburban yards directly correlates with household income. "The line flattens out at about $50k/year," says Charles Redman, co-director at the CAP LTER site, which is brainstorming for their renewal proposal due in 2003. Although the same plants exist in nearly all parks in all neighborhoods, CAP investigators found more species of birds at parks in "upscale" neighborhoods, which correlates to the native plants in surrounding yards of these neighborhoods. These findings are surmised from baseline data gathered in CAP’s 200-point survey (see Fall 2001 LTER Newsletter). "When investigating urban systems, we must re-conceptualize biodiversity in terms of human choice, and how choices are made and why," Redman says. |
The ESA annual meeting symposium "Cities of Resilience" highlighted how ecological principles could be integrated into urban planning, design, policy, and management. Charles Redman and Nancy Grimm (Central Arizona-Phoenix LTER or ‘CAP’) and Steward Pickett and Mary Cadenasso (Baltimore Ecosystem Study LTER or ‘BES’) were among the presenters. The CAP LTER focuses on an arid-land ecosystem profoundly influenced, even defined, by the presence and activities of humans and is one of only two LTER sites that specifically studies the ecology of an urban system. The Baltimore Ecosystem study focuses on a five county metropolitan region in which watersheds are used as the stage on which to understand the reciprocal interactions of the social, biophysical, and human-built environments, using watershed function as a synthetic indicator and target for model development. Both urban LTER sites will soon be submitting renewal proposals for the next cycle of funding and are contemplating how the past five years of study will affect the next six years. Both sites are reflecting on the lessons they learned from the first LTER funding cycle and how to apply them and others, to the next.
RECONCEPTUALIZING BIODIVERSITY: The Urban Ecology of Central Arizona-Phoenix
At the CAP LTER project, biological, physical, and social scientists work together to study the structure and function of the urban ecosystem, to assess the effects of urban development on surrounding agricultural and natural desert lands, and to study the relationships between residents’ decisions and ecological processes. Interdisciplinary investigations of these relationships in the rapidly growing metro-Phoenix area are of broad relevance for the study of social ecological systems, and for "cities of resilience."
Explosive growth is among the issues facing CAP investigators. The Phoenix metro area grew from 300,000 residents to more than 3,000,000 residents in just 50 years. "We acknowledge that cities are taking over the world," says Charles Redman, CAP project co-director. "We don’t diminish human impact as entirely negative. Our study proves, as much as anything, that ecological theory must be modified to include urban ecology." It’s to these modifications that the next six years of CAP will contribute most, Redman says.
For example, CAP investigators have found that nitrogen loads in urban waterways can be as much as 10 times the loads in natural systems. "Does that much difference result in systemic differences, which our current tools cannot detect or quantify?" Redman asks. "We must constantly consider how we look at the urban ecosystem, as well as what we look at." Moreover, CAP’s urban ecologists are arguing that there may be qualitative differences in ecological processes between urban and non-urban ecosystems. The introduction of completely new chemical compounds, for instance, requires a reconceptualization of biogeochemistry for the urban milieu.
METAPHORS WE LIVE BY: The Baltimore Ecosystem Study LTER
Nearing the end of the first cycle of the Baltimore Urban LTER program , Steward Pickett, Mary Cadenasso and the other BES investigators realize it’s time for a new paradigm, a new vernacular, and a new metaphor for considering the ecology of people in a modern metropolitan area.
In their presentation at the ESA symposium, Picket and Cadenasso emphasized the power of metaphors in science, and their ability to motivate creative activity. The phrase "cities of resilience" can serve as a powerful metaphor to stimulate urban planning activities to consult and cooperate with ecological principles. "‘Cities of Resilience’ can counterbalance equally powerful metaphors, such as ‘the garden city’ or ‘the city beautiful,’" Pickett says, ‘ which emphasize only the aesthetic value of a city, and not its integrated ecological, social, and infrastructural functions."
Even the term "ecosystem" has become a metaphor, Pickett and Cadenasso point out, "escaping the domain of ecological science." But traditional definitions of ecosystems (i.e. "A unit that covers all organisms of a given area as well as their relationship to the inorganic environment," A. Tansley 1935) do not provide urban ecological researchers sufficient tools for their investigations. "Although Tansley’s definition does provide a firm foundation for urban ecological research," Pickett says. In fact, Tansley’s 1935 paper was prescient in recognizing the need to include humans and human actions in ecology.
Traditional metaphors for ecological research are characterized by "background assumptions of closure, regulation, connectivity and producticity diversity, natural and integrity or health,’ Urban ecology, Pickett & Cadenasso assert, is "open, external, the dynamics are not probabilistic, humans are internal to the system rather than external, and disturbance is internal, rather than external." These points often run counter to traditional views that guide ecological investigation.
According to Holling, "resilience" describes the ability of system to absorb changes in state variables, driving variables and parameters, and still persist (1973). Pickett and Cadenasso believe this idea will be a useful tool for shaping a metaphor for urban ecological research. BES expects to add this concept to its toolkit to motivate improvements in linking ecology and social processes its renewal process.
For Further Reading
Baker, L. A., D. Hope, Y. Xu, J. Edmonds, and L. Lauver. 2001. Nitrogen balance for the Central Arizona-Phoenix ecosystem. Ecosystems 4:582-602.
Bolin, B., A. Nelson, E. J. Hackett, K. D. Pijawka, C. S. Smith, D. Sicotte, E. K. Sadalla, E. Matranga, and M. O’Donnell. 2002. The ecology of technological risk in a Sunbelt city. Environment and Planning A 34:317-339.
Brazel, A. J., N. Selover, R. Vose, and G. Heisler. 2000. The tale of two climates: Baltimore and Phoenix urban LTER sites. Climate Research 15(2):123-135.
Collins, J. P., A. P. Kinzig, N. B. Grimm, W. F. Fagan, D. Hope, J. Wu, and E. T. Borer. 2000. A new urban ecology. American Scientist 88:416-425.
Gober, P., and E. K. Burns. 2002. The size and shape of Phoenix’s urban fringe. Journal of Planning Education and Research 21:379-390.
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(7):571-584.
Berkowitz, A. R. , K. S. Hollweg, and C. H. Nilon, eds.Understanding urban ecosystems: A new frontier for science and education, Springer-Verlag, New York, NY.
Gunderson, L. H., and C. S. Holling, editors. 2002. Panarchy: Understanding transformations in human and natural systems. Island Press, Washington, D.C., USA.
Kinzig, A. P. 2001. Bridging disciplinary divides to address environmental challenges. Ecosystems 4(8):709-715.
Kinzig, A. P., and J. M. Grove. 2001. Urban-suburban ecology. Pp. 733-746 in The encyclopedia of biodiversity, S. Levin, ed. Academic Press, Inc.
Redman, C. L. 1999. Human dimensions of ecosystem studies. Ecosystems 2:296-298.
Stefanov, W. L., M. S. Ramsey, and P. R. Christensen. 2001. Monitoring urban land cover change: An expert system approach to land cover classification of semiarid to arid urban centers. Remote Sensing of Environment 77(2):173-185.
Wu, J., and J. L. David. 2002. A spatially explicit hierarchical approach to modeling complex ecological systems: Theory and applications. Ecological Modelling 153:7-26.