Interest in urban form, including the suburbs, has been evident at least since cities emerged as significant human settlements. For almost as long, there have been debates around the normative question of what attributes constitute "good" urban form, and perhaps even sharper debates on what theoretical constructs are most useful in describing how that form evolves. At the same time, public awareness of what urban form is and its importance to the quality of urban life -- not to mention the political commitment to managing the processes underlying that form -- have waxed and waned over time in response to issues of public concern at the moment, whether they be inner-city slums, spatial segregation and inequalities, environmental pollution and health, political fragmentation, traffic congestion and suburban sprawl, energy shortages, or the loss of agricultural land and natural amenities.

In the last decade or two, public interest in urban form has increased, generated by concerns over the rising costs of infrastructure and service provision, and more broadly by uncertainties about the long-term sustainability of business-as-usual, low-density, auto-dependent development trends. The form of cities has again become a political -- not just a planning -- issue.

Underpinning these political debates is an impressive legacy of theoretical work and a rich inventory of research and modelling efforts. Many of these efforts have focused on the analysis of land-use patterns and densities (the traditional elements of urban form), others on the flows, linkages, and interactions that tie these elements together (the concept of urban spatial structure), still others on the role of governments. These theories have included the classical models developed by William Alonso (land), Lowden Wingo (transportation), Ira Lowry (spatial allocation), William Wheaton (flows and linkages), Charles Tiebout (political organization), and Brian Berry (social ecology), among many others. Each one emphasizes a different dimension of built form and urban structure. Although the original models are now almost forgotten in the archives of academic history, the ideas still resonate in planning circles and in urban research; indeed, they often constitute implicit, "taken-for-granted" knowledge about how cities work and how they are spatially organized. Yet, despite repeated extensions and considerable mathematical advances over the decades, there is still a sense that the classical models and their modern descendents remain incomplete descriptors of city patterning.

A number of the long-standing limitations of these models are directly relevant here. First, as early as the 1960s it was acknowledged that rapid advances in urban theory had outpaced careful empirical application and systematic verification. This situation remains the case today, even in the information age; spatially referenced data, especially on land use and built form, is either insufficiently comprehensive, detailed, and current, or is not readily available. Second, it was equally obvious that most, if not all, of the classical urban models failed to incorporate the complex processes through which cities renew themselves over time -- for example, through redevelopment, adaptive reuse and intensification of the physical built environment. Third, few of the empirical analyses on offer at the time were comparative, in the sense of allowing for systematic assessments of land-use patterns in cities located in very different settings. Fourth, few studies provided consistent metrics or indicators of urban patterning that could be applied over several cities with any degree of confidence. And fifth, the impacts of government and public institutions, specifically the effects of public policies, on the urban landscape and on the form of urban development were largely ignored.

The following report on Growing Cities addresses these gaps through a detailed comparative analysis of urban development since 1991 in three of Canada's largest and most rapidly growing metropolitan regions -- Calgary, Toronto, and Vancouver. One of a series of informative and often provocative reports on contemporary urban issues and regional planning policies produced by the staff of the Neptis Foundation, this study has relatively broad objectives, yet precise empirical goals: to illustrate a new methodology and to improve public awareness and understanding of growth and change in Canadian cities.

The report provides a wealth of statistical detail on urban development as well as richly textured and visually appealing graphics. The maps themselves, the joint product of Neptis, its consultants, and the GIS and Cartography Office in the Department of Geography at the University of Toronto, represent unique contributions to our understanding of the form and growth of these three city-regions.

The report is timely, given the prominence of current debates on the sustainability of recent trends in urban and suburban forms. It is also a targeted response to renewed attempts by governments almost everywhere to modify those trends -- to create more livable, efficient, and compact urban forms -- through growth management techniques and smart growth principles. The immediate context and primary incentive for this study is the opportunity to evaluate the unfolding impacts of the introduction of the Province of Ontario's Growth Plan for the Greater Golden Horseshoe (2006), an explicit strategy designed to reconfigure patterns of growth throughout the entire region surrounding Toronto.

The researchers developed and tested a methodology for monitoring trends in urban land use and development patterns that integrates satellite imagery and standardized census data. The assumption is that to be useful, any such methodology should be robust, easy to apply and interpret, and applicable wherever both sources of data exist. The methodology allows for the identification of the precise boundaries of the urbanized area -- a surprisingly difficult task -- and offers a standardized means of estimating rates of land use intensification. The latter refers to the proportion of new development (in this case housing, not commercial-industrial uses) taking place within a defined urban boundary compared to development on greenfield sites outside that boundary.

This method provides an empirical basis for the study's second objective: evaluating the contribution of public policies in general and regional planning strategies in particular to achieving higher-density urban forms in each of three remarkably different metropolitan regions. This second objective obviously poses a serious challenge for the authors of the report, notably the difficulty of separating the intended effects of policies from those effects -- intended and unintended -- of a range of other concurrent factors. But the analysis offers an informed and thoughtful attempt to do so.

The results of the study speak for themselves. In brief, the comparative analysis illustrates just how diverse patterns of urban development are in Canada's growing metropolitan areas. Different settings and different systems of regional governance, even in cities with similar planning regimes, tend to produce different outcomes in terms of land use configurations. Yet, despite this diversity, the report concludes that public policies have had some success in encouraging more compact and higher-density forms of urban development. One further implication is that the application of a single model of regional policy, or attempts to define a one-directional pathway to more compact development, or a uniform intensification target, will simply not work everywhere.

Intensification rates, for example, vary across the three city-regions, albeit in a more-or-less predictable fashion. But because of differences in city size, local histories, and geographical barriers, these variations are quite wide: from a high rate in the Vancouver region to moderate levels in Toronto and relatively low levels in Calgary. The conclusion is that while places do differ in their response to policy initiatives, public policy decisions and growth management strategies do matter. The challenge is that the effects of the latter are apparent only over the longer term and their reflection in built form and development patterns is itself a subject of considerable place-to-place variability.

Finally, the authors argue that achieving higher residential intensification rates, and thus higher population densities, may become even more difficult over time as the number of potential infill sites declines, unless other policies, controls, and incentives are introduced in parallel. In sum, this study sets a solid baseline on which subsequent evaluations of longer-term trends and policy initiatives in urban development can and should be constructed.

Larry S. Bourne, University of Toronto

March 7, 2010