A Global Synthesis on Urban Land Expansion and Urban Population Densities

Authors: Burak Guneralp*, Texas A&M University, Karen C. Seto, Yale University, Elizabeth Wentz, Arizona State University, Meredith Reba, Yale University, Billy U. Hales, Texas A&M University
Topics: Land Use and Land Cover Change, Urban Geography, Sustainability Science
Keywords: land change, sustainability science, urban form, population density, land sharing, land sparing
Session Type: Paper
Day: 4/5/2019
Start / End Time: 9:55 AM / 11:35 AM
Room: Coolidge, Marriott, Mezzanine Level
Presentation File: No File Uploaded

Changes in density profiles of cities directly influence their rate and magnitude of expansion at the expense of other land covers. In this study, we studied global urban expansion from the perspective of studies that reported expansion of individual urban areas using remotely sensed imagery. To this end, we conducted a synthesis of such studies that quantify urban expansion using remotely sensed imagery. We identified over 1,100 case studies covering four decades from 1970 to 2010. Almost a third of all case studies are on urban expansion in China. Globally, significant gaps in geographical coverage exist in those parts of the world that have been urbanizing rapidly such as large swaths of the Sub-Saharan Africa. The increase in urban extents since 1970s in India, eastern China, and western Africa are the most notable along. Across all regions and four decades, urban land expansion rates have generally been higher than or equal to urban population growth rates. Thus, urban population densities exhibited discernible declining trends in most of the world regions (including China, India, and North America) over the study period. Declining urban population densities mean that urban land expansion could have been more compact had urban population densities not dropped at least as large as they had. Based on those studies that estimated loss of other land covers to urban, about 60% of urban land expansion (about 40,000 km2) took place at the expense of agricultural lands. The largest losses in agricultural land happened in Europe, China, and Southeast Asia.

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