			Home About us Contact

Urban Systems (urban + system)

Distribution by Scientific Domains

Humanities and Social Sciences	50%
Life Sciences	20%
Engineering	20%

Selected Abstracts

Urban Systems: Market and Efficiency

JOURNAL OF PUBLIC ECONOMIC THEORY, Issue 1 2001
David Pines
[source]

Agglomeration and the adjustment of the spatial economy,

PAPERS IN REGIONAL SCIENCE, Issue 3 2005
Pierre Philippe Combes
Urban systems; new economic geography; urban and regional policy; diagrammatic exposition Abstract., We consider the literature on urban systems and New Economic Geography to examine questions concerning agglomeration and how areas respond to shocks to the economic environment. We first propose a diagrammatic framework to compare the two approaches. We then use this framework to study a number of extensions and to consider several policy relevant issues. [source]

A Picture of the Floating World: Grounding the Secessionary Affluence of the Residential Cruise Liner

ANTIPODE, Issue 1 2009
Rowland Atkinson
Abstract:, A quarter century of financial deregulation, robber-baron corporatism and growing income polarisation has enabled the spatial partitioning of urban space into new and complex arrangements of micro-neighbourhood governance and privatism. These archipelagos of fortress homes and neighbourhoods increasingly lie outside the spaces of conventional state and city government. Yet while residential spaces of urban affluence have been unable to fully remove contact with the social diversity of the public realm, nomadic forms of super-affluence, flowing around a global,national urban system, have generated a form of networked extra-territoriality,a social space decoupled from the perceived risks and general dowdiness of the social world beneath it. This paper examines this space via the curious case of The World, a large residential cruise ship which, as its name suggests, roams the oceans and ports of the globe. Our title is taken from the name given to Japanese paintings of the new affluence and fantasy of life lived by the affluent and artists in late nineteenth century Japanese cities (O Ukiyo E, or pictures of the floating world). We suggest that The World forms a similarly disconnected realm, not only literally afloat, also detached from the reality of a world that has been strategically left behind. [source]

Multiple stressors and regime shifts in shallow aquatic ecosystems in antipodean landscapes

FRESHWATER BIOLOGY, Issue 2010
JENNY DAVIS
Summary 1. Changes in land management (land use and land cover) and water management (including extraction of ground water and diversion of surface waters for irrigation) driven by increases in agricultural production and urban expansion (and fundamentally by population growth) have created multiple stressors on global freshwater ecosystems that we can no longer ignore. 2. The development and testing of conceptual ecological models that examine the impact of stressors on aquatic ecosystems, and recognise that responses may be nonlinear, is now essential for identifying critical processes and predicting changes, particularly the possibility of catastrophic regime shifts or ,ecological surprises'. 3. Models depicting gradual ecological change and three types of regime shift (simple thresholds, hysteresis and irreversible changes) were examined in the context of shallow inland aquatic ecosystems (wetlands, shallow lakes and temporary river pools) in southwestern Australia subject to multiple anthropogenic impacts (hydrological change, eutrophication, salinisation and acidification). 4. Changes in hydrological processes, particularly the balance between groundwater-dominated versus surface water-dominated inputs and a change from seasonal to permanent water regimes appeared to be the major drivers influencing ecological regime change and the impacts of eutrophication and acidification (in urban systems) and salinisation and acidification (in agricultural systems). 5. In the absence of hydrological change, urban wetlands undergoing eutrophication and agricultural wetlands experiencing salinisation appeared to fit threshold models. Models encompassing alternative regimes and hysteresis appeared to be applicable where a change from a seasonal to permanent hydrological regime had occurred. 6. Irreversible ecological change has potentially occurred in agricultural landscapes because the external economic driver, agricultural productivity, persists independently of the impact on aquatic ecosystems. 7. Thematic implications: multiple stressors can create multiple thresholds that may act in a hierarchical fashion in shallow, lentic systems. The resulting regime shifts may follow different models and trajectories of recovery. Challenges for ecosystem managers and researchers include determining how close a system may be to critical thresholds and which processes are essential to maintaining or restoring the system. This requires an understanding of both external drivers and internal ecosystem dynamics, and the interactions between them, at appropriate spatial and temporal scales. [source]

NATURAL RESTABILIZATION OF STREAM CHANNELS IN URBAN WATERSHEDS,

JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 6 2000
Patricia C. Henshaw
ABSTRACT: Stream channels are known to change their form as a result of watershed urbanization, but do they restabilize under subsequent conditions of constant urban land use? Streams in seven developed and developing watersheds (drainage areas 5,35 km2) in the Puget Sound lowlands were evaluated for their channel stability and degree of urbanization, using field and historical data. Protocols for determining channel stability by visual assessment, calculated bed mobility at bankfull flows, and resurveyed cross-sections were compared and yielded nearly identical results. We found that channel restabilization generally does occur within one or two decades of constant watershed land use, but it is not universal. When (or if) an individual stream will restabilize depends on specific hydrologic and geomorphic characteristics of the channel and its watershed; observed stability is not well predicted by simply the magnitude of urban development or the rate of ongoing land-use change. The tendency for channel restabilization suggests that management efforts focused primarily on maintaining stability, particularly in a still-urbanizing watershed, may not always be necessary. Yet physical stability alone is not a sufficient condition for a biologically healthy stream, and additional rehabilitation measures will almost certainly be required to restore biological conditions in urban systems. [source]

Knowledge, networks of cities and growth in regional urban systems*

PAPERS IN REGIONAL SCIENCE, Issue 4 2007
Rafael Boix
Knowledge city; networks of cities; urban growth; external economies; spatial econometrics Abstract., Recent theories of regional growth and local development emphasise the roles of agglomeration and knowledge as the main determinants of growth, whereas the theories of the networks of cities remark that growth is a process not only within cities but also between cities. The objective of this paper is to measure the factors that affect the evolution of different intensities of knowledge in a region's cities. An adaptation of the OECD knowledge classification is used to divide the industries by knowledge intensity and to model the determinants of these intensities in a spatial context. Results suggest that higher growth rates are associated with higher levels of technology and knowledge. The growth of the different kinds of knowledge is related to local and spatial factors (agglomeration and network externalities) and each knowledge intensity show a particular response to these factors. [source]

Agglomeration and the adjustment of the spatial economy,

Urban pattern and land cover variation in the greater Toronto area

THE CANADIAN GEOGRAPHER/LE GEOGRAPHE CANADIEN, Issue 1 2007
TENLEY CONWAY
Recent epistemological shifts in environmental geography have created a space to consider the interactions between ecological and urban systems more seriously. While openness to thinking about urban ecosystems has increased in recent years, there remain fundamental gaps in our knowledge. For example, recent research has examined the impact of urban,rural gradients on ecological conditions, but major voids exist regarding the relationship between urban development patterns and land cover heterogeneity, particularly for new forms of urbanization. This article attempts to address some of these gaps by examining the relationship between urban pattern and land cover in the greater Toronto area (GTA). In particular, measures of urban pattern that reflect aspects of development density, grain and function, as well as socio-economic characteristics, are systematically analyzed in relation to land cover heterogeneity. The regression analysis shows that multiple components of urban development pattern and socio-economic conditions are correlated with vegetated land covers, while urban density variables are not related. These results indicate more detailed representations of urban pattern should be incorporated into future human,environmental interaction studies in cities. Les changements épistémologiques récents en géographie environnementale ont créé un espace dans lequel les interactions entre les systèmes écologiques et urbains sont considérées plus sérieusement. Par contre, bien qu'il existe depuis quelques temps plus de possibilités pour réfléchir aux écosystèmes urbains, des questions fondamentales subsistent. Par exemple, des recherches récentes se sont penchées sur l'impact des gradients urbain-ruraux sur les conditions écologiques. Toutefois, des lacunes importantes demeurent en ce qui concerne les liens entre les modèles de développement urbain et l'hétérogénéité de la couverture des sols, notamment en ce qui a trait aux nouvelles formes d'urbanisation. Cet article aborde certaines de ces lacunes en examinant les liens entre le modèle urbain et la couverture des sols dans la région du Grand Toronto (RGT). En particulier, des mesures du modèle urbain reflétant des aspects de la densité de développement, la texture et la fonction, ainsi que les caractéristiques socio-économiques sont systématiquement analysées par rapport à l'hétérogénéité de la couverture des sols. L'analyse de régression montre une corrélation entre plusieurs composantes du modèle de développement urbain et des conditions socio-économiques, d'une part, et le type de couverture végétale des sols, d'autre part. Les variables utilisées pour la densité urbaine ne sont pas reliées. Ces résultats font ressortir que des représentations plus détaillées du modèle urbain devraient être intégrées aux études ultérieures consacrées aux interactions humain-environnement en milieu urbain. [source]

I've Heard About , (A Flat, Fat, Growing Urban Experiment): Extract of Neighbourhood Protocols

ARCHITECTURAL DESIGN, Issue 4 2009
François Roche
Abstract Urban models are conventionally planned and intended to control urban systems. François Roche's vision is to the contrary: it is for an unpredictable organic urbanism. A biostructure develops its own adaptive behaviour, based on growth scripts and open algorithms. It is entirely reflexive, responding to human occupation and expression rather than being managed or operated at human will. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Advancing urban ecological studies: Frameworks, concepts, and results from the Baltimore Ecosystem Study

AUSTRAL ECOLOGY, Issue 2 2006
S. T. A. PICKETT
Abstract Urban ecological studies have had a long history, but they have not been a component of mainstream ecology until recently. The growing interest of ecologists in urban systems provides an opportunity to articulate integrative frameworks, and identify research tools and approaches that can help achieve a broader ecological understanding of urban systems. Based on our experience in the Baltimore Ecosystem Study (BES), Long-term Ecological Research project, located in metropolitan Baltimore, Maryland, USA, we identify several frameworks that may be useful in comparative urban studies, and may be worthy of consideration in other integrative urban ecosystem studies: (i) spatial patch dynamics of biophysical and social factors; (ii) the watershed as an integrative tool; and (iii) the human ecosystem framework. These frameworks build on empirical research investigating urban biota, nutrient and energy budgets, ecological footprints of cities, as well as biotic classifications aimed at urban planning. These frameworks bring together perspectives, measurements, and models from biophysical and social sciences. We illustrate their application in the BES, which is designed to investigate (i) the structure and change of the urban ecosystem; (ii) the fluxes of matter, energy, capital, and population in the metropolis; and (iii) how ecological information affects the quality of the local and regional environments. Exemplary results concerning urban stream nutrient flux, the ability of riparian zones to process nitrate pollution, and the lags in the relationships between vegetation structure and socio-economic factors in specific neighbourhoods are presented. The current advances in urban ecological studies have profited greatly from the variety of integrative frameworks and tools that have been tested and applied in urban areas over the last decade. The field is poised to make significant progress as a result of ongoing conceptual and empirical consolidation. [source]