Landscape Ecology

, Volume 29, Issue 5, pp 763–771 | Cite as

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

Perspective

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.

Keywords

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

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Copyright information

© Springer Science+Business Media Dordrecht 2014

Authors and Affiliations

  • Zhifeng Liu
    • 1
  • Chunyang He
    • 1
  • Yuyu Zhou
    • 2
  • Jianguo Wu
    • 1
    • 3
  1. 1.Center for Human-Environment System Sustainability (CHESS), State Key Laboratory of Earth Surface Processes and Resource EcologyBeijing Normal UniversityBeijingChina
  2. 2.Pacific Northwest National LaboratoryCollege ParkUSA
  3. 3.School of Life Sciences and School of SustainabilityArizona State UniversityTempeUSA

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