How much of the world’s land has been urbanized, really? A hierarchical framework for avoiding confusion

Zhifeng Liu, Chunyang He, Yuyu Zhou, Jianguo Wu

Research output: Contribution to journalArticle

108 Citations (Scopus)

Abstract

Urbanization has transformed the world’s landscapes, resulting in a series of ecological and environmental problems. To assess urbanization impacts and improve sustainability, one of the first questions that we must address is: how much of the world’s land has been urbanized? Unfortunately, the estimates of the global urban land reported in the literature vary widely from less than 1–3 % primarily because different definitions of urban land were used. To evade confusion, here we propose a hierarchical framework for representing and communicating the spatial extent of the world’s urbanized land at the global, regional, and more local levels. The hierarchical framework consists of three spatially nested definitions: “urban area” that is delineated by administrative boundaries, “built-up area” that is dominated by artificial surfaces, and “impervious surface area” that is devoid of life. These are really three different measures of urbanization. In 2010, the global urban land was close to 3 %, the global built-up area was about 0.65 %, and the global impervious surface area was merely 0.45 %, of the word’s total land area (excluding Antarctica and Greenland). We argue that this hierarchy of urban land measures, in particular the ratios between them, can also facilitate better understanding the biophysical and socioeconomic processes and impacts of urbanization.

Original languageEnglish (US)
Pages (from-to)763-771
Number of pages9
JournalLandscape Ecology
Volume29
Issue number5
DOIs
StatePublished - May 1 2014

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urbanization
surface area
administrative boundary
Antarctica
land
world
environmental impact
urban area
sustainability
built-up area

Keywords

  • Built-up area
  • Global urban land
  • Hierarchy of definitions
  • Impervious surface
  • Urban area
  • Urbanization

ASJC Scopus subject areas

  • Nature and Landscape Conservation
  • Ecology
  • Geography, Planning and Development

Cite this

How much of the world’s land has been urbanized, really? A hierarchical framework for avoiding confusion. / Liu, Zhifeng; He, Chunyang; Zhou, Yuyu; Wu, Jianguo.

In: Landscape Ecology, Vol. 29, No. 5, 01.05.2014, p. 763-771.

Research output: Contribution to journalArticle

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