The conceptual and methodological approaches to the study of human-ecological urban system are undergoing rapid change. There are two major threads: systems and complexity, and advances in the landscape ecology research traditions. The first focuses on how to more appropriately capture the joint dynamics of both human and ecological needs. The second focuses on methodology. Both are briefly reviewed here.
The Recognition oF Human-Ecological Ecosystems
The sustainability movement has placed an artificial wedge between human needs and environmental needs. Analytical models associated with the sustainability movement simplify either the human dimension to reach an ecological conclusion or simplify the ecological dimension to reach a human conclusion. For example, the classic economic models based on the Alonso bid-rent dynamics do not consider the environment at all; conversely, urban ecosystems models such as those developed by Odum and follows tend to simplify human needs, wants, and behaviors.
To overcome these methodological dilemmas and to foster an understanding of the human-ecological interface as an integrated system, a series of research efforts are underway that emanate from the landscape ecology research community. Alberti (2008) and others have develop an integrated human-ecological model of urban ecosystems.
Urbanization changes land use from a formerly pristine ecological regime to another regime. In so doing, the process of urbanization fragments the earlier ecosystem. The resulting urban eocystems are “heterotrophic ecosystems” – dependent on large amounts of energy and materials and a vast capacity to absorb emissions and waste.
But, detailed knowledge about this overall phenomenon is lacking, due in large part to methodological inconsistencies among studies. Alberti and others have asked the general question: is there a relationship between patterns of urbanization and environmental performance? For planners, the answer to this question must be YES! Yet scientists have yet to confirm this conclusion, due in large part to faulty thinking and the failure to recognize the scale implications of their work.
Advances in Understanding the Human-Ecological Ecosystems
The conceptual and methodological approaches to the study of human-ecological urban system are undergoing rapid change. There are two major threads: systems and complexity, and advances in the landscape ecology research traditions. The first focuses on how to more appropriately capture the joint dynamics of both human and ecological needs. The second focuses on methodology. Both are briefly reviewed here.
Advances in human-ecological thinking seem to focus on the work of five research nodes: Marina Alberti’s at the University of Washington, Nancy Grimm at Arizona State University (e.g., 2000), Stewart Pickett and colleagues at the Cary Institute of Ecosystem Studies in New York (e.g., 2001), Mark McDonnell at the Australian Research Center for Urban Ecology (e.g., 2000), and Herbert Sukopp in Germany (e.g., 1995). In this body of work, much emphasis is placed on the twin notions of cities as systems and complexity theory.
Perhaps the most fundamental idea is that cities and regions can be represented as systems. In a system, there are four major elements: drivers, patterns, processes, and effects/changes. The dynamic is basically from “inside-outside” but there are two important feedback loops: one internal between patterns and processes; and one external in which changed conditions lead to changes in the behavior of the drivers.
Drivers are external events but are of three types: socio-economic forces, natural forces, and planned interventions. Patterns are mostly physical representations observable at a general scale. Processes are also physical but are generally observable at different scales. Effects and changes are differences in the levels of some behavior. This is the area of environmental performance. How is it measured? What does it mean?
The normal environmental performance variables include things such as clean air, clean water, and more recently, reduction of GHG and other carbon related things. Characterization of the human-ecological urban system is not enough to capture how such systems operate. Complexity theory, which underlies most system characterizations and whose rudiments can be found in Nicolis and Prigogine (1997), Portugali (2000), Batty (2005) among others, contains a number of important concepts including: emergent properties, feedback, self-organization, and resilience.
Landscape ecology is generally understood as the science of analyzing and improving the dynamics between urban land uses and ecological processes at a variety of scales. It is generally agreed that the word landscape refers to a spatially heterogeneous area characterized by diverse interacting patches or ecosystems, ranging from the relatively natural terrestrial and aquatic systems such as forests, grasslands and lakes to human-dominated environments including agricultural and urban settings. These are captured in the general notion of a “landscape signature” (Alberti, 2008).
The word ecology refers to the interdisciplinary study of the interactions between organisms and their environment, or more colloquially, ecosystems. Landscape ecology is the scientific study of the relationship among pattern, process, and scale, and more recently of the need to couple biophysical and socio-economic systems. Wu and Hobbs (2002) suggest that there are five topics of current interest: (1) ecological flows in landscape mosaics, (2) land use and land cover change, (3) scaling, (4) relating landscape pattern analysis with ecological processes, and (5) landscape conservation and sustainability.
Patches are the basic units of the landscape. They simultaneously exist and change. The literature devoted to the categorization and measurement of patches is illustrated by the work of Mora and Iverson (2002), Watson (2002), Watling and Donnelly (2006) among others. A patch is normally defined as a discrete area of relatively homogeneous conditions. We distinguish between patch characteristics and patch dynamics.
Patch characteristics can be defined by/as: shape and configuration, centers, boundaries and edges, scale, and connectivity. Patch dynamics, which are the processes and change and fluctuation, normally focus on the spatial structure, function, and changes in the above set of relatively discrete concepts or elements. The emphasis is on changes in values of any of the variables above. Clearly, if a human-ecological ecosystem is improving it will exhibit, among other things, a stronger center, better defined edges, resilience, connectivity to larger ecosystems, etc. The key idea is to capture processes occurring over time.
Some Examples from Warsaw Poland
We frame and conduct three types of studies for the city of Warsaw, Poland: (1) the comparison of “landscape signatures” for two land segments; (2) the comparison of “landscape signatures” in a gradient-type analysis on five sections along the Vistula River; and (3) a discussion of the changing “landscape signature” for Wilanow, the site of a major ongoing development. The study areas are shown in Figure 1.
Urbanized Versus Rural Landsapes
To show the difference between an urbanized landscape and a more pristine suburban landscape, we mapped the number of patches in each of two areas, see Figure 2. This comparative analysis between the Bielany and Wawer regions generally shows what would be expected. The Bielany area contains many more fragmented patches, patches which are not functionally related to each other, but indeed adjacent to one another.
Thus, for example, there are commercial patches next to industrial patches. There is no set of connected green or natural ecosystems (there is a low level of connectedness, there is no apparent network, sizes and shapes vary wildly, etc.). On the other hand, the Wawer region contains a strong single ecosystem. There is a strong core to the patch and boundaries are relatively easy to identify. Patches adjacent to the main central patch are more appropriate to the center core.
While this comparison is, to some degree, extreme by choice, the comparative analysis does show how important “landscape signature” elements vary between the two areas. Similar types of studies could be developed for other comparative areas throughout the city.
Gradient Analysis along the Vistula River
Here, we partitioned the landscapes along the Vistula River into five sections (or study areas) starting in the center, and doing a gradient analysis “away” from the center. The basic hypothesis is that ecological characteristics would vary among these sections. Even though the Vistula is a “wild river”, we expect to see different ecological dynamics and processes in these three different sampled sections.
Patches are identified for each section along the river, see Figure 3. As can be seen, ecological patches in areas three and four are dominated by urbanized uses. Only area five starts to show more pristine ecological areas. The sizes of the individual patches tend to increase with distance from the city center, a finding anticipated from the literature, which is confirmed by our analysis. The green areas along the Vistula are narrower in sections 1, 2, and 3 showing the historic pressure for development close to water-based transportation. Only in section 5 do we find ecological patches consistent with the expectation of riparian ecosystems.
While the mapping of patches along five different segments of the Vistula provides evidence of urbanization effects on the natural water-based ecosystem, further hydrological models are needed to determine the true biodiversity and other characteristics of water-based issues in these ecosystems.
Wilanow Project Area
The third case study is an example of a single district, in this case one that is currently under development. Wilanow possesses both a precious cultural and natural heritage as well as huge development potential. The Wilanow West project is a 420 ha site of post-agricultural land that is being developed in accordance with the overall master plan (see location on Figure 4). The surrounding landscape is highly natural with majority of open space, the lowest development density in Warsaw, and several areas of nature protection.
Under the current development, the status of Wilanow West has been changing from an undeveloped area of fields and meadows, abandoned and growing with a birch wood, to a highly urbanized area with the development density factor exceeding 1 or even 1.5 which is typical for a city center. Such a change involves several effects, especially in the environmental performance of the area. For sure the micro-climate will begin to exhibit urban heat island, the flow of storm water will grow, and noise and pollution will increase. Furthermore, biodiversity and GHG absorption will dramatically fall with the elimination of more natural habitats. Although the master plan provides around 40% of biologically active area on the building lots, which has mitigating meaning, it will be still an anthropogenic landscape, designed and built, and it will need time to achieve full performance.
Finally, it is fair to say that this project, which will eventually provide housing for 40-50K people, that the impacts on the surrounding areas (that is, the rest of the metropolitan region) have not been fully assessed in terms of environmental performance.
Conslusions / Extensions – The Size of the patch … matters
Mapping of human-ecological patches leads to different landscape signatures for different types of geographical areas. Both in the terrestrial comparison and in the riparian gradient, significant differences were found and illustrated. The human-ecological approach seems to offer a better way to consider human impacts on the environment and environmental impacts on urbanization that either does from a singular perspective.
The key idea is that urbanization creates discontinuous and smaller patches, which are further modified with further human interaction. Patch performance, defined in terms of typical variables such as biodiversity, etc. are related to patch size. The general conclusion is that larger patches perform better in terms of most environmental variables than smaller ones.
The fragmentation of formerly large patches into a series of smaller patches created by the urbanization process, limits the ability to the ecosystem to perform at high levels.
The major recommendation is the pursuit of more sophisticated ecological data sets and models that capture the human-ecological interactions.
Although we have barely touched the surface in this paper, this led us to a conclusion, that a relationship between patterns of urbanization and environmental performance can be illustrated by a model based on the approaches outlined here.
The model would overlay identified patches with their their ecological data and environmental conditions, in order to examine their interactions and functioning. In our opinion a complex patch model of the city would help to solve the conflict between human and environmental needs, and let the city develop in a more sustainable way.
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Agnieszka Kowalewska, Warsaw University of Technology, Warsaw, Poland. Email: [email protected]
David C. Prosperi, Florida Atlantic University, Fort Lauderdale, USA. Email: [email protected]
