The Skyscraper Revolution: A Global Shift in Urban Growth

For decades, cities across the globe have expanded outwards, consuming surrounding land as populations grew and economies boomed. But a new study published in Nature Cities reveals a dramatic shift in urban growth patterns: cities are increasingly building upwards, embracing the vertical dimension of growth.

Using data from space-borne sensors, the researchers analyzed the growth rates of 1,550+ cities over the past three decades, spanning the 1990s, 2000s, and 2010s. The analysis focused on two key metrics: building fractional cover (BF), which reflects the amount of land covered by buildings, and microwave backscatter (PR), which is sensitive to building volume, including height.

The Rise of the Vertical City

While both BF and PR have been increasing in most cities, the growth rates tell a different story. In the 1990s, most cities showed rapid growth in BF, with slower increases in PR, indicating a predominantly outward expansion. This pattern, however, has shifted significantly. By the 2010s, growth rates in BF decreased in most regions, indicating a slowdown in lateral expansion. However, PR growth rates increased in essentially all regions and cities, signifying a substantial shift towards vertical development.

This transition to vertical growth has been particularly evident in Asian cities, where growth rate increases were the largest. Megacities, those with populations exceeding 10 million, have been leading the charge, with the transition from lateral to vertical growth often starting in the urban core before spreading outwards. This transition, however, is not uniform and has happened at different times and extents across the world.

The Consequences of Building Up

This shift towards vertical development has profound consequences for the future of urban living, sustainability, and the global environment. Higher buildings can lead to increased population density, potentially reducing the need for outward expansion and preserving natural land. However, taller buildings also bring unique challenges. They require specialized materials, have high embodied carbon and operational energy needs, and can create distinct microclimates.

The study highlights the importance of considering both the lateral and vertical dimensions of urban growth. While increasing population density alone is necessary, it is insufficient for lowering transport emissions and achieving sustainable urban development. Cities need to be carefully designed with higher job densities, improved public transportation, and walkable environments to truly reap the benefits of vertical growth.

A Global Trend with Regional Variations

The transition to vertical growth is not confined to specific cities or regions; it is a global trend. However, the pace and timing of this shift vary significantly, reflecting the diverse economic and demographic conditions of different regions.

For instance, China has been at the forefront of this vertical development, witnessing a rapid increase in skyscraper construction driven by a real estate boom. The study identified a “fast-up-and-out” typology, characterized by rapid growth in both BF and PR, indicative of tall building construction and substantial investment in urban areas.

In contrast, Europe has shown a more gradual transition to vertical growth, with a negligible shift from lateral to vertical expansion over the past three decades. The study found that the transition to vertical growth has often been faster in larger cities, likely due to factors like higher land values and a shift from manufacturing to service-based economies.

Looking Ahead: A New Era of Urban Development

The study’s findings challenge traditional models of urban development, which have often focused solely on outward expansion. This research highlights the growing importance of understanding and planning for vertical growth, considering its potential benefits and challenges. As cities continue to grow and evolve, the shift towards vertical development is likely to continue, creating a new era of urban development with profound implications for sustainability and the future of urban living.

The Implications of Building Up

The authors argue that the shift to vertical growth has implications for various areas, including:

Sustainability

• Urban density: The transition to vertical growth can lead to higher urban densities, potentially reducing the need for outward expansion and preserving natural land.

• Carbon emissions: Tall buildings can increase embodied carbon and operational energy needs. Cities need to carefully plan for efficient building design and transportation systems to mitigate these impacts.

• Microclimate: Tall buildings can create unique microclimates, potentially impacting air circulation, temperature, and precipitation patterns. Cities need to consider these effects in urban planning to ensure sustainable urban environments.

Urban Living

• Accessibility: Vertical growth can make cities more accessible, particularly for residents who rely on public transportation. However, it is crucial to ensure that public transportation systems are adequately developed and integrated with taller buildings.

• Livability: Vertical growth can impact urban livability. Cities need to consider factors like green spaces, walkability, and community spaces to ensure a high quality of life for residents.

• Social Equity: Tall buildings can exacerbate existing social inequalities if not carefully planned and managed. Cities need to ensure that vertical development is equitable and benefits all residents, regardless of their socioeconomic status.

The Future of Urban Development

The study provides valuable insights into the changing landscape of urban growth, highlighting the transition from lateral expansion to vertical development. This shift presents both opportunities and challenges, requiring careful planning and management to ensure a sustainable and equitable future for cities. As cities continue to grow and evolve, understanding the dynamics of vertical growth will be crucial for shaping a more sustainable and livable urban future.