Global Trends of Urbanization

Cities are the manifestation of the cultural, economic and social acceleration that we have experienced in our modern history. In 1950 about 2/3 of the population worldwide lived in rural settlements and 1/3 in urban settlements. By 2050, we will observe roughly the reverse distribution, with more than 6 billion people living in the messy, burgeoning athmosphere of urbanized areas.
According to the Sustainable Urbanization Policy Brief, urban centres currently occupy less than 5% of the world’s landmass. Nevertheless they account for around 70% of both global energy consumption and greenhouse gas emission. Innovation in urban infrastrucure and technology is essential when addressing this issue. For instance, greenhouse gas emissions could be reduced by up to 1.5 billion CO2e annually by 2030, primarily through transformative change in transport systems in the world’s 724 largest cities[1].

Urban planning decisions and strategic design thinking in the context of rapid urbanization account for social equity, mobility patterns, global competitiveness and energy-efficiency. In that sense a brief comparison between Atlanta and Barcelona shows at a glance that cities with similar populations can have very different carbon emissions[2], depending on how the urban layout is conceived. With urban area of 4,280 km2, Atlanta’s carbon emissions are ten times higher than those in the city of Barcelona, whose built-up area is 162 km2. Both cities have population of about 2.5 million people.

Atlanta vs. Barcelona

Source: The New Climate Economy Report | Chapter 2 | Cities

As densities decline, city areas grow faster than city populations [3] and affect environmental sustainability at a local, regional and global scale. How we manage this unprecedented urban growth in the following years is likely to determine the outcome of our sustainability endeavours.


Percentage urban and location of urban agglomerations with at least 500,000 inhabitants, 2014

Percentage urban and location of urban agglomerations with at least 500,000 inhabitants, 2014. Source: UN | World Urbanization Prospects: The 2014 Revision, Highlights

Between now and 2050, 90% of the expected increase in the world’s urban population will take place in the urban areas of Africa and Asia [4] . In other words the projected urban growth will be concentrated in cities in the developing world where the correlation of the rate of urbanization with economic growth has been weaker.

The global trends of urbanization in the first decades of the 21st century are significantly different from what we have experienced so far in terms of urban transition. Urbanization is taking place at lower levels of economic development and the majority of future urban population growth will take place in small- to medium-sized urban areas in developing countries. Expansion of urban areas is on average twice as fast as urban population with significant consequences for greenhouse gas emissions and climate change[5].


Global Urban Population Growth 1990-2030

Source: UN | World Urbanization Prospects: The 2014 Revision, Highlights

According to this year’s United Nations report on World Urbanization we will observe the following trends:

  • Continuing population growth and urbanization are projected to add 2.5 billion people to the world’s urban population by 2050, with nearly 90% of the increase concentrated in Asia and Africa.
  • The fastest growing urban agglomerations are medium-sized cities and cities with less than 1 million inhabitants located in Asia and Africa.
  • Most megacities and large cities are located in the global South.
  • Just three countries — India, China and Nigeria – together are expected to account for 37 per cent of the projected growth of the world’s urban population between 2014 and 2050. India is projected to add 404 million urban dwellers, China 292 million and Nigeria 212 millions.
  • Close to half of the world’s urban dwellers reside in relatively small settlements of less than 500,000 inhabitants, while only around 1/8 live in the 28 mega-cities with more than 10 million inhabitants.
  • The number of mega-cities has nearly tripled since 1990; and by 2030, 41 urban agglomerations are projected to house at least 10 million inhabitants each.
  • Tokyo is projected to remain the world’s largest city in 2030 with 37 million inhabitants, followed closely by Delhi where the population is projected to rise swiftly to 36 million.


Contribution to the increase in urban population by country, 2014 to 2050

Contribution to the increase in urban population by country, 2014 to 2050. Source: UN | World Urbanization Prospects: The 2014 Revision, Highlights

Urban scaling holds both the key to long-term sustainable development and irreversible damages to our planet. The expected increase in urban land cover during the first three decades of the 21st century will be greater than the cumulative urban expansion in all of human history [5]. These unprecedented rates of urbanization put enormous pressure on environmental sustainability thresholds and indicators. Tackling strategic components of urban form such as density levels, land use patterns and connectivity will have a major impact on the global economy and climate.




  1. The New Climate Economy Report. 2014.
  2. Bertaud, A. and Richardson, A.W., 2004. Transit and Density: Atlanta, the United States and Western Europe.
  3. Shlomo Angel, Making Room for a Planet of Cities
  4. United Nations, Department of Economic and Social Affairs, Population Division (2014).
    World Urbanization Prospects: The 2014 Revision, Highlights (ST/ESA/SER.A/352).
  5. [IPCC AR 5 WG3 Chapter 12]
  6. Sustainable Urbanization Policy Brief


Photo Courtesy of Leah Davies

Remote Sensing, Big Data and Urban Planning

“I used to measure the Heavens, now I measure the shadows of Earth.”
Johannes Kepler

Observing Earth

2014 promises to be an exciting year for Earth Observation. From monitoring urban dynamics such as traffic patterns; urban sprawl or changes in land use, to the support of decision-making and planning processes for humanitarian crisis and emergency respond – the applications of remote sensing are wide.

The world’s first near-live HD video feed of Earth, from space.”; “The largest constellation of Earth-imaging satellites ever launched.”; “The world’s first commercial high-resolution, HD video from space” – These are some of the exciting bold statements that you might have come across by the end of 2013, when the hype for space commercialization and accessibility was at its peak.

First pictures of UrtheCast's hardware on the ISS. Credit : UrtheCast

First pictures of UrtheCast’s hardware on the ISS. Credit : UrtheCast

November 2013 saw the launch of UrtheCast‘s cameras to the International Space Station. The two cameras – one high-definition, one medium-resolution – are currently waiting for their installation on the ISS and are expected to start streaming near-live footage of Earth early this year. Once the installation process is over you should be able to watch how the planet changes from space or even subscribe to your favourite spot on Earth and receive real-time notifications as the ISS travels in low orbit: a type of experience, that adds another layer to the meaning of location awareness.

Meanwhile, Planet Labs – a space and analytics company based in San Francisco, is preparing to launch Flock 1 – a fleet of 28 satellites. This would be the largest constellation of Earth-imaging satellites ever launched into orbit. The company’s ambition is to provide open access to unprecedented coverage and frequent imagery of the planet and help inform future humanitarian, ecological and commercial endeavors.

The latest generation of satellites will enable us to image the whole globe at high frequency, producing an unprecedented data set that will unlock huge commercial, environmental and humanitarian value.
Will Marshall, Planet Labs founder.

Late december 2013 Skybox released the world’s first commercial, high-resolution, HD video of Earth from space, capturing views from Tokyo, Bangkok, Baltimore, Las Vegas, and Aleppo, Syria.

The resolution is high enough to resolve objects that impact the global economy like shipping containers, while maintaining a level of clarity that does not determine human activity.

Mapping Urban Growth & Environmental Change

Satellite imagery has a long history of providing data for modelling urban growth, mapping spatio-temporal dynamics of land use and environmental changes.

Above: Extensive Ice Fractures in the Beaufort Sea. Credit: NASA Earth Observatory

For over 40 years the Landsat satellites have continuosly acquired images of the Earth’s surface turning the program’s archive into the “world’s longest continuously acquired collection of space-based moderate-resolution land remote sensing data“. The National Satellite Land Remote Sensing Data Archive holds a record of millions of Landsat images that have captured changes in urban from around the world.

Las Vegas urban sprawl,1984-2011. Credit: NASA/USGS

Las Vegas urban sprawl,1984-2011. Credit: NASA/USGS

“Over the years of the Landsat program, the desert city of Las Vegas has gone through a massive growth spurt. The outward expansion of the city over the last quarter of a century is shown here with two false-color Landsat 5 images (Landsat 5 TM bands 7,4,2).”

Landsat 5

The notorious Landsat 5, that was decommissioned in June, 2013 holds the world record for the longest-operating Earth-observing satellite mission in history. Launched in 1984, the satellite outlasted the initially planned 3-year mission and stayed in orbit for more than 29 years. Landsat 5’s legacy constitutes of about 2.5 million images that documented explosive urban growth in the last decades.

 The Dallas-Forth area. Urban growth. Image taken in 1974, 1989 and 2003

The Dallas-Forth area. Urban growth. Image taken in 1974, 1989 and 2003

The Immediacy of Urban Planning

From the commercial use of HD live video streams of the planet to the deployment of a plethora of Cubesats by NASA’s ELaNa project (Educational Launch of Nanosatellites) – there’s no doubt about the fact that these are exciting times for space exploration and earth remote sensing. And this fact relates to the future of urban planning as well.

Spatial data collected via airborne sensors and satellite remote sensing are making a significant contribution to the enormous pool of Big data sources that currently serve as a backbone for any urban-related study. And as Michael Batty states it in one of his recent lectures: The shift towards Big Data represents the shift from the longer term to the shorter term where cities are perceived as things that are happenning in the next 5 minutes or 5hours. This immediacy of urban processes is now beeing tracked at a fine-scale spatial and temporal detail and is radically distorting the way we look at planning.