Rationale and Definition:
Cities are expected to absorb between two and three billion additional people by the year 2050. Whether they manage to do so sustainably depends on whether they harness the efficiency gains from agglomeration. Agglomeration provides the compactness, concentration and connectivity that lead to prosperity and sustainability.
More than half of the area expected to be urban in 2030 has yet to be built.1 Therein lies an extraordinary opportunity to make the future city more productive and sustainable. However, most cities are forfeiting these advantages, becoming more expansive, growing spatially faster than their population and haphazardly absorbing land needed for agriculture and ecosystem services. With impending resource limits and twin climate change and food crises, we have little time to reverse this trend.
As a measure of land-use efficiency, this indicator benchmarks and monitors the relationship between land consumption and population growth. It informs and enables decision-makers to track and manage urban growth at multiple scales and enhances their ability to promote land use efficiency. In sum, it ensures that the SDGs address the wider dimensions of space and land adequately and provides the frame for the implementation of several other goals, notably health, food security, energy and climate change.
This land use efficiency indicator not only highlights the form of urban development but also illuminates human settlement patterns. It can be employed to capture the three dimensions of land use efficiency: economic (e.g. proximity of factors of production), environmental (e.g. lower per capita rates of resource use and GHG emissions), and social (e.g. avoidance of settlement on vulnerable land, promotion of reduced travel times/distances). Finally, urban configuration largely predetermines the technologies and behavioral patterns within a city. Once built, cities are expensive and difficult to reconfigure. Fast growing cities in the developing world must “get it right” before they are beset by infrastructural constraints.
Geographic (urban / rural), region (functional metropolitan area).
Comments and Limitations:
The data for this indicator is free and publicly accessible. For more than five decades, the US Geological Survey/NASA Landsat data has been freely available, is frequently updated and its resolution is continually improving. The European Community’s Joint Research Center has developed the Global Human Settlement Layer, an even higher resolution land cover dataset with similar frequency and distribution practices as Landsat. Many researchers have used these technologies to measure land cover and urban expansion.2 Both measure built up area as buildings, compacted soils and impervious surfaces. WorldPop overlays demographic data on GIS maps.3 But over time, to ensure regular and sustainable collection of this data, NSOs might consider providing spatially continuous demographic data (not bounded by jurisdiction) in digital form and to integrate mapping into their official census data.
Preliminary Assessment of Current Data Availability:
Primary Data Source:
Satellite imagery and census data.
Potential Lead Agency:
UN-Habitat, World Bank.
Elmqvist et al (2013). Urbanization, Biodiversity and Ecosystem Services: Challenges and Opportunities. Springer.
Angel et al (2011). Making Room for a Planet of Cities. Cambridge: Lincoln Institute of Land Policy Seto et al (2011). A Meta-analysis of Global Urban Land Expansion. PLoS ONE.
Gaughan AE, Stevens FR, Linard C, Jia P, and Tatem AJ (2013). High resolution population distribution maps for Southeast Asia in 2010 and 2015. PLoS ONE, 8(2): e55882.