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Serious concerns with accelerating global warming have been translated into urgent calls for increasing urban densities: higher densities are associated with lower greenhouse gas emissions, especially those related to vehicle kilometers traveled (VKT). In order to densify meaningfully in the coming decades, cities need to make room within their existing footprints to accommodate more people. In the absence of adequate room within their existing footprints, cities create more room through outward expansion, typically resulting in lower overall densities. We introduce a quantitative dimension to this process, focusing on the population added to a global stratified sample of 200 cities between 1990 and 2014. In three-quarters of the cities we studied, the areas built before 1990 gained population and thus densified significantly. On average, however, only one-quarter of the total population added to the 200 cities in the sample in the 1990–2014 period were accommodated within their 1990 urban footprints, while three-quarters were accommodated within their newly built expansion areas. That resulted in an overall decline in average urban densities during the 1990–2014 period despite the near-global, decades-old and rarely questioned consensus that urban expansion must be contained.
Shlomo Angel; Patrick Lamson-Hall; Alejandro Blei; Sharad Shingade; Suman Kumar. Densify and Expand: A Global Analysis of Recent Urban Growth. Sustainability 2021, 13, 3835 .
AMA StyleShlomo Angel, Patrick Lamson-Hall, Alejandro Blei, Sharad Shingade, Suman Kumar. Densify and Expand: A Global Analysis of Recent Urban Growth. Sustainability. 2021; 13 (7):3835.
Chicago/Turabian StyleShlomo Angel; Patrick Lamson-Hall; Alejandro Blei; Sharad Shingade; Suman Kumar. 2021. "Densify and Expand: A Global Analysis of Recent Urban Growth." Sustainability 13, no. 7: 3835.
We introduce evidence from the Covid-19 pandemic in the United States that lends support to future political efforts to include multi-county metropolitan areas as an additional and critical institutional layer—over and above municipalities, countries, states, or the federal government—for the effective management of present and future pandemics. Multi-county metropolitan statistical areas (MSAs) accommodated 73% of the U.S. population and, as of 27 September 2020, they were home to 78% of reported cases of Covid-19 and 82% of reported deaths. The rationale for a renewed focus on these spatial units is that they are found to be densely interconnected yet easily identifiable locales for the spread of pandemics and, therefore, for their proper management as well. The paper uses available data on cases and deaths in U.S. counties as of 27 September 2020 to lend statistical support to four hypotheses: (1) The Onset Hypothesis: The onset of Covid-19 cases and deaths commenced earlier in multi-county metropolitan areas than in small-city counties or rural counties; (2) The Peak Hypothesis: The current peak of Covid-19 cases and deaths occurred earlier in multi-county metropolitan areas; (3) The Scaling Hypothesis: Multi-county metropolitan areas had more than their shares of Covid-19 cases and deaths than their shares in the population; and (4) The Neighbor Hypothesis: Levels of Covid-19 cases and deaths in counties within multi-county metropolitan areas were more strongly related to respective levels in their neighboring counties than small-city counties or rural counties. The reported statistical results demonstrate the value of adopting a metropolitan perspective on pandemics and working to empower effective institutional arrangements at the metropolitan level for managing the present and future pandemics.
Shlomo Angel; Alejandro Blei. Why Pandemics, Such as Covid-19, Require a Metropolitan Response. Sustainability 2020, 13, 79 .
AMA StyleShlomo Angel, Alejandro Blei. Why Pandemics, Such as Covid-19, Require a Metropolitan Response. Sustainability. 2020; 13 (1):79.
Chicago/Turabian StyleShlomo Angel; Alejandro Blei. 2020. "Why Pandemics, Such as Covid-19, Require a Metropolitan Response." Sustainability 13, no. 1: 79.
Urban population density has featured in a large body of literature on the Compact City paradigm as the key compactness attribute of cities, yet the shape compactness of urban footprints has hardly deserved a mention. This essay seeks to correct that. We review the literature on the Compact City Paradigm with a special focus on the relationship between urban form and climate change, and focus on twelve physical attributes of cities that make them more or less compact. Other things being equal, both population density and shape compactness help determine the average travel distances in cities, and hence affect their energy consumption and their greenhouse gas emissions. They also affect the length of infrastructure lines and the length of commutes. In principle, therefore, increasing either the shape compactness or the population density of cities can contribute—in different yet similar measure—to mitigating climate change. There are strong forces that push urban footprints to become more compact—that is, circular or near circular in shape—and these forces have evolved over time. There are also powerful forces that have pushed urban footprints to become less compact over time. We introduce these forces and illustrate their effects on particular cities. We then focus on a small set of metrics for measuring the shape compactness of cities. We use them to measure urban footprints obtained from satellite imagery in a stratified global sample of 200 cities in three time periods: 1990, 2000, and 2014. We find that the shape compactness of urban footprints the world over is independent of city size, area, density, and income and that, not surprisingly, it is strongly affected by topography. We also find that it has declined overall between 1990 and 2014 and explain some of the sources of this decline. We conclude the paper by assessing the ways in which the shape compactness of cities can be increased to make them better able to mitigate climate change in decades to come.
Shlomo Angel; Sara Arango Franco; Yang Liu; Alejandro M. Blei. The shape compactness of urban footprints. Progress in Planning 2018, 139, 100429 .
AMA StyleShlomo Angel, Sara Arango Franco, Yang Liu, Alejandro M. Blei. The shape compactness of urban footprints. Progress in Planning. 2018; 139 ():100429.
Chicago/Turabian StyleShlomo Angel; Sara Arango Franco; Yang Liu; Alejandro M. Blei. 2018. "The shape compactness of urban footprints." Progress in Planning 139, no. : 100429.
Urban transport and land use policies are informed by our perceptions of the prevailing spatial structure of cities. This structure can be characterized by five models: The Maximum Disorder model, the Mosaic of Live-Work Communities model, the Monocentric City model, the Polycentric City model, and the Constrained Dispersal model, where the great majority of jobs are dispersed outside employment centers and where workers and workplaces in a metropolitan-wide labor market adjust their locations to be within a tolerable commute range of each other. We examine evidence from a stratified sample of 40 U.S. cities and from the 50 largest U.S. cities in 2000 to show that the latter model best characterizes the spatial structure of contemporary American cities. The Constrained Dispersal model is, in essence, a hybrid model that combines elements of all other models. We found that, on average, only 1 out of 12 people live and work in the same community; only 1 out of 9 jobs is still located in the CBD; and only 1 out of 7 jobs is located in employment sub-centers outside the CBD. All in all, the great majority of jobs—3 out of 4 of them—is dispersed outside employment centers, including the CBD, and is beyond walking or biking distance. Maintaining and increasing the productivity of American cities now require a sustained focus on meeting the travel demands of this great majority of commuters, rather than promoting transportation strategies focused on improving access to CBDs and employment sub-centers, or within live-work communities.
Shlomo Angel; Alejandro M. Blei. The spatial structure of American cities: The great majority of workplaces are no longer in CBDs, employment sub-centers, or live-work communities. Cities 2016, 51, 21 -35.
AMA StyleShlomo Angel, Alejandro M. Blei. The spatial structure of American cities: The great majority of workplaces are no longer in CBDs, employment sub-centers, or live-work communities. Cities. 2016; 51 ():21-35.
Chicago/Turabian StyleShlomo Angel; Alejandro M. Blei. 2016. "The spatial structure of American cities: The great majority of workplaces are no longer in CBDs, employment sub-centers, or live-work communities." Cities 51, no. : 21-35.