Making Room for a Planet of Cities

By Vishnu Prasad, IFMR Finance Foundation

In a report titled “Making Room for a Planet of Cities”, Shlomo Angel et al examine how the prevailing planning paradigm of containment, which is predicated on the containment of sprawl in cities, is unsuitable for rapidly urbanizing countries like India. The report is based on a study of the historical evolution of urban land cover in 120 cities, including 30 cities for which maps and data are available from 1800.

The key findings of the report are:

  1. Persistent Decline in Urban Density: Analysing a global sample of 120 cities, the report finds that average built-up area density reduced from a mean of 144 p/ha (people per hectare) in 1990 to 112 p/ha in 2000. Examining a representative sample of 30 cities (for which data is available from 1800), it becomes clear that declining urban density is a feature observed throughout the 20th century. Urban densities peaked circa 1894. Densities have declined from their peak of 430 p/ha to an average of 100 p/ha in 2000.
  2. Reduced fragmentation of City footprints: Fragmentation or discontinuous development of the city (often referred to as sprawl) has been measured using two complementary metrics- openness index is a neighbourhood level scale that measures the average share of open space within a walking distance circle (1 km2 in area) about every built-up space in the city and city footprint ratio, a city level metric, defined as the ratio of city footprint (the total built-up and open area in a city and its suburbs) to the city’s built-up area. The mean value of the openness index in the global sample reduced from 0.47 in 1990 to 0.42 in 2000. The mean city footprint ratio also reduced marginally from 2.01 in 1990 to 1.93 in 2000.This means that on average, cities today contain as much urbanized open space as their built-up area.
  3. Growth in urban land cover outpaces growth in urban population: In the global sample of 120 cities, urban population growth averaged 1.60% p.a between 1990 and 2000. During the same time period, urban land cover grew at 3.66% p.a. At this rate, the world’s urban population will double in 43 years while urban land cover will double in just 19 years. Accra’s explosive growth (below) provides us a glimpse of the scale of urbanization challenges facing the world.

Why has the containment paradigm failed?

The containment paradigm believes that it is in the public interest to contain unrestrained urban expansion, typically decried as sprawl, and to make cities more compact. It argues that

  1.  the current density of urban land is too low and needs to be increased;
  2. there is an excessive amount of vacant land within the built-up areas of cities that needs to be filled in; and
  3. land on the urban periphery needs to be left largely undisturbed.

The classic example of this planning paradigm is Seoul, where the establishment of a green belt in 1971 which prevented the conversion of land to urban use in a 1482 km2 area surrounding the city (Figure 2). As the map shows, urban growth has burgeoned in the permitted area and led to the development of satellite towns and edge cities outside the greenbelt area. This has led to increased commuting distances and higher carbon emissions. Within the city, restricted supply of land has led to sky-rocketing house prices. Seoul’s rent-to-income ratio was 0.35; second highest in the world and twice the global average of 0.16.

Figure 2

In Sao Paulo, restriction of urban growth seeking to protect the entire countryside surrounding the city has led to virtually no available open space within the city (Figure 3). Sao Paulo has an openness index of 0.18, the lowest among the global sample of 120 cities.

Figure 3

Making Room Paradigm

The making room planning paradigm rests on four tenets:

  1. Realistic projection of urban land needs: New York City (NYC) and Barcelona are prime examples of cities that have realistically projected land needs. In 1811, NYC (with a population of 100,000) prepared an expansion plan projecting a 10-fold increase in population. Similarly, Ildefons Cerdá envisioned a 10-fold increase in Barcelona’s population. Assuming a 1% annual density decline, the report forecasts that 22 countries will multiply their urban land cover 10-fold between 2000 and 2050. Cities need to realistically project their urban land needs to prepare for such expansions in the future.
  2. Generous metropolitan limits: Metropolitan limits have to be large enough to accommodate 20 to 30 years of urban expansion based on realistic projections of population growth, density decline, and changes in fragmentation levels. The study argues that Beijing, with an administrative area 11 times its built-up area, is a best practice example of this tenet.
  3. Selective protection of open spaces: Instead of protecting too much land from urban development at no cost to the public (like Seoul and Sao Paulo) and ending up with no open space at all, this strategy aims to protect some land at a minimal cost to the public so it remains open in perpetuity. The report cites the example of Singapore that has a number of parks and open spaces distributed throughout the city area.
  4. Arterial grid of roads at 1km apart: Cities must prepare for urban growth by to securing the rights-of-way for an entire arterial road and infrastructure grid in the area within the new administrative boundaries. Toronto serves as an example of a city that has been able to build and maintain an effective public transport system that extends along an arterial road grid far into the suburbs. It now has the third-largest transit system in North America.