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Urban form in both two-(2D) and three-dimensions (3D) has significant impacts on local and global environments. Here we developed the largest global dataset characterizing 2D and 3D urban growth for 478 cities with populations of one million or larger. Using remote sensing data from the SeaWinds scatterometer for 2001 and 2009, and the Global Human Settlement Layer for 2000 and 2014, we applied a cluster analysis and found five urban growth typologies: stabilized, outward, mature upward, budding outward, upward and outward. Budding outward is the dominant typology worldwide, per the largest total area. Cities characterized by upward and outward growth are few in number and concentrated primarily in China and South Korea, where there has been a large increase in high-rises during the study period. With the exception of East Asia, cities within a geographic region exhibit remarkably similar patterns of urban growth. Our results show that every city exhibits multiple urban growth typologies concurrently. Thus, while it is possible to describe a city by its dominant urban growth typology, a more accurate and comprehensive characterization would include some combination of the five typologies. The implications of the results for urban sustainability are multifold. First, the results suggest that there is considerable opportunity to shape future patterns of urbanization, given that most of the new urban growth is nascent and low magnitude outward expansion. Second, the clear geographic patterns and wide variations in the physical form of urban growth, within country and city, suggest that markets, national and subnational policies, including the absence of, can shape how cities grow. Third, the presence of different typologies within each city suggests the need for differentiated strategies for different parts of a single city. Finally, the new urban forms revealed in this analysis provide a first glimpse into the carbon lock-in of recently constructed energy-demanding infrastructure of urban settlements.

Global urban populations are projected to increase by 2.5 billion over the next 30 years. Yet, there is limited understanding of how this growth will affect urban land expansion (ULE). Here, we develop a large-scale study to test explicitly the relative importance of urban population and Gross Domestic Product (GDP) growth in affecting ULE for different regions, economic development levels and governance types for 300+ cities. Our results show that population growth, more than GDP, is consistently the dominant determinant of ULE during 1970–2014. However, the effect of GDP growth on ULE increases in importance after 2000. In countries with strong governance, economic growth contributes more to ULE than population growth. We find that urban population growth and ULE are correlated but this relationship varies for countries at different developmental stages. Lastly, this study illustrates that good governance is a necessary condition for economic growth to affect ULE.

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Urbanization is happening differently today than in the past and occurring most rapidly in places with the fewest resources. Traditional approaches are not able to keep up, leaving billions of people with poor access to basic necessities, dragging down economies and damaging the environment. This synthesis report of the Towards a More Equal City series proposes a new way of thinking about urban development, where the metrics for a functional and thriving city are defined by the quality, reliability and affordability of essential services. The report brings together the best thinking from over six years of research and more than 160 authors and reviewers. It acts as a roadmap for how to break through sectoral silos and the status quo to make cities more equal, which will in turn create prosperity, reduce environmental damage and improve livelihoods. The report documents breakthrough innovations from numerous cities, revealing real solutions and the outcomes of investing in equitable service provision. It also offers a clear path to recovery now and resilience in the future. Human development challenges are increasingly urban development challenges, including the ways in which they relate to climate change. These findings can help cities, countries and the global community make progress on critical global objectives, from the Sustainable Development Goals and UN Habitat’s New Urban Agenda to the Paris Agreement and COVID-19 recovery.