Urban expansion necessarily entails the loss of cultivated lands. How much cultivated land will be consumed by urban expansion and what are the policy implications? Global data on the expansion of cities into cultivated lands are only starting to become available, so the answer to this question at the planetary scale must be exploratory and tentative.

The total land area of all countries on the planet is 130 million square kilometers (km²). In the year 2000, 15.2 million km²—11.7 percent of the total land area of countries—were in arable land and permanent crops, most of it under cultivation; 40.9 million km² (31.5 percent) were forested; 33.4 million km² (25.7 percent) were in permanent meadows and pastures; and 40 million km² (30.8 percent) were in other land uses (including deserts and treeless tundra). Urban land cover takes up a much smaller share of the area of countries, an estimated 600,000 km² (0.47 percent) of land were in urban use in 2000. In that year, urban land cover amounted to some 4 percent of cultivated land.

Jason Parent and I recently estimated the amount of cultivated land that will be lost due to the global urban expansion that will take place between 2000 and 2050. To do so, we assumed a 2 percent average annual decline in urban densities—the worst-case scenario in terms of the potential loss of cultivated lands to urban expansion. Under this assumption, we expect urban areas—including smaller cities and towns—to expand by 2.4 million km² worldwide, from 0.6 million km² in 2000 to 3 million km² in 2050. This fivefold expansion will entail the loss of 1.2 million km² of the land that was under cultivation in the year 2000. Cities in developing countries will account for two-thirds of global urban expansion. Half of the urban expansion in the developing world, about 0.8 million km² worth, will occupy cultivated lands.

In this scenario, the loss of cultivated lands by 2050 amount to 5.7 percent of the total land under cultivation in 2000. Some regions can be expected to lose higher shares: Southeast Asia may lose more than 10 percent of its cultivated lands; Western Asia and North Africa, close to 10 percent; South and Central Asia, 8 percent; and East Asia, close to 7 percent. Though these losses could be considered worst-case scenarios, they offer quite realistic orders of magnitude of how much new land will need to be put under cultivation to meet projected food needs.

Moving forward, the UN Food and Agriculture Organization estimates that annual food production will need to increase by 70 percent by 2050 “to cope with a 40 percent increase in world population and to raise average food consumption to 3,130 kcal (kilocalories) per person per day” (Bruinsma 2009). It expects 90 percent of the increase in production to come from higher yields and 10 percent will come from the expansion of land under cultivation. According to these FAO estimates, which do not account for the loss of cultivated land from urban expansion, arable land would need to expand by 700,000 km² by 2050, less than 5 percent of the land under cultivation in 2000 (Bruinsma 2009). If the FAO projects that an additional 700,000 km² of land will need to be brought into cultivation by 2050 to meet world food needs, we will need to nearly triple that amount to replace the expected 1.2 million km² that will be lost to urban expansion—a task that, by no means easy, is well within reach.

Cultivatable land that is suitable for rain-fed crop production constitutes one-quarter of the total land area of the planet, or 33.3 million km², of which 7.4 million km² are in forest ecosystems and only 15.2 million km² were under cultivation in the year 2000. Substantial amounts of land are available for the expansion of food production in future decades. Without encroaching on forests, land under cultivation can increase by 70 percent. The FAO’s estimates that the area for cultivation only needs to expand by 5 percent to reach 2050 food production goals. Our revised estimate suggests that land under cultivation would need to expand by 12.5 percent of the land under cultivation in the year 2000—a bigger increase to be sure, but still well within the realm of feasible expansion.

For the global food supply to remain plentiful and affordable, urban expansion will need to go hand-in-hand with the expansion of lands under cultivation. Cities should be allowed to expand into the cultivated lands on their immediate periphery, as they must if they are to accommodate their growing populations in the most accessible locations. New cultivated lands should be brought into agricultural production in suitable areas that are uncultivated or undercultivated. Yields must be increased on lands that are already under limited cultivation and more of the surplus generated by skyrocketing land values in the world’s cities must be captured and invested in converting new lands on the rural fringe into efficient food production.

Cerdá’s plan for Barcelona, the New York City Commissioners’ Plan of 1811, the Topographical Bureau’s 1900 plan for New York, and the 1904 plan for Buenos Aires were not utopian dreams. They were pragmatic plans that were implemented quickly, and all three cities soon outgrew them. These cities show that there is nothing new in making generous plans for urban expansion, yet it is difficult to identify one urban plan that has allowed for such generous expansion of a metropolitan area in recent decades. The need exists, however, since the 30 cities in our global representative sample expanded sixteenfold in a matter of 70 years, on average, during the twentieth century. We can subscribe the absence of such plans to a failure of imagination or a failure of nerve. But it is exactly this kind of imagination and nerve that must be rekindled to realistically project the expansion of many cities in the rapidly urbanizing countries of the developing world in the coming decades. – See more at: http://urbanizationproject.org/blog/making-generous-plans-for-urban-expansion-barcelona/#sthash.4TpvJHA9.dpuf

Between 1810 and 2010 Buenos Aires made a transformation typical of many global cities. It shifted from a walking city to a monocentric city to a polycentric city, driven primarily by changes in transportation technology. In 1810, the city’s population of 45,000 occupied some 200 hectares at a density of 225 persons per hectare. Life centered on the port and people primarily got around on foot. The city thrived on a combination of commerce, banking, trade, and its position as the seat of the federal government.

By 1869, the city had 171,000 residents and an area of 714 hectares. The average density in the historical center remained the same, but density declined rapidly with distance from the center. The omnibus—a multiseat carriage pulled by horses on unpaved roads—was the major form of public transportation but it did not extend much beyond the walking city perimeter. The omnibus notwithstanding, Buenos Aires remained a predominately walking city. People who worked in the city center typically lived there as well.

The mid-1860s saw the introduction of the horsecar—a horse-drawn carriage pulled on rails. Horsecars were substantially faster than omnibuses, allowing the city’s perimeter to expand even as they reinforced the dominance of the city center. Horsecars transformed Buenos Aires from a walking city into a monocentric city.

The city extended its administrative boundary in 1888. The wide Avenida General Paz formed the new city limit and the area 207 sq km within it became known as the Capital District. By 1898, the electric trolley began to replace the horsecar, greatly extending the reach of public transportation into the urban periphery. Compared to horsecars, the trolleys were faster, more reliable, and operated for longer hours (Sargent 1974).

Railways extended the commuting range during this period as well. “The number of inbound daily trains to Buenos Aires increased from 306 in 1898 to 751 in 1914,” and the number of passengers increased fivefold during this period (Sargent 1974, 69). The steam-powered trains of this era were more suitable for lines with long distances between stops, but their increased frequency made land adjacent to stations more attractive for commuters, especially those coming from destinations beyond the reach of the trolleys.

By 1910, the population of Greater Buenos Aires increased to 1.41 million and its built-up area increased to 255 sq km. The electrification of the railroads in 1916 enhanced the dispersal of Buenos Aires even further. The electrified railroads dominated the development of the suburban alrededores. “Passenger volumes in the alrededores rose sharply from an estimated 6,400,000 in 1896 to 82,000,000 in 1930” (Sargent 1974, 96). By the end of the 1930s, the expansion of residential suburbs followed the railway lines into the periphery.

As long as workers relied on radial transportation lines to commute, Greater Buenos Aires remained a monocentric city. But as early as the 1930s, the shift to a polycentric city was underway. As the wider spread use of cars and trucks increased congestion and lengthened commuting times into the Capital District, industrial plants began to relocate from the center into the periphery. Between 1935 and 1994, the share of industrial jobs in the Capital District decreased from 80 percent to 37 percent.

By 2001, the population of Greater Buenos Aires was 12 million and its built- up area had reached 2,071 sq km. The Capital District had a population of 2.8 million and a built-up area of 165 sq km. By 2010, the share of trips in Greater Buenos Aires that had the Capital District as their destination decreased to 18.6 percent, of which 6.6 percent originated in the district itself. In other words, more than four-fifths of all destinations by transit were in municipalities outside the Capital District. The center no longer held its dominant position in the city’s life. The Capital District continues to provide a large number of jobs and residences, but by 2010 Buenos Aires was a decidedly polycentric city.

Honest and justifiable attempts to stop people from moving to cities and to prevent construction on the urban periphery, however pitiful in retrospect, have been with us for centuries and are still with us today. The proclamation issued on 7 July 1580 by Queen Elizabeth I was one such exercise in futility. As later documented by John Strype in 1720:

The official reasons for issuing the queen’s proclamation are eminently sensible and not unfamiliar to the modern reader: an influx of poor and unskilled people; inconveniences caused by congestion; price inflation caused by increasing demand; the dangers to public health caused by overcrowding; unfair competition by newcomers flooding markets with cheaper goods of compromised quality; and claims “that the City could scarcely be well governed, by reason of such Multitudes flocking to live there.” Official consternation with the unruly multitudes crowding into theaters to enjoy Shakespeare’s plays in those years would surely have resulted in a ban on theaters as well, but for the queen’s fondness for this form of entertainment and the fact that theaters were built in the suburbs outside the city’s jurisdiction to make sure they were not closed down by the authorities.

The population of London in 1545 was almost 70,000 (Russell 1948). It was increasing rapidly, particularly after the destruction of Antwerp by the Spanish in 1572, which left London as the largest port in the North Atlantic at a time of rapid expansion of global trade brought about by the onset of colonization. In 1572, London occupied an area of 3 square kilometers (km2). Two-thirds of the area was within the city’s walls and one-third in its growing suburbs. By 1650, it was estimated that only 120,000 people lived in the city proper while 300,000 lived in the surrounding suburbs outside the city’s jurisdiction.

John Strype, the chronicler of the events surrounding the queen’s proclamation, notes, “This Proclamation could not hinder this strong Propension in the People towards building new Houses.” Other proclamations followed, to no avail. “Between 1602 and 1630, no fewer than fourteen proclamations were enacted in attempts to limit London’s growth” (Lai 1988, 28). The population of the city increased to 500,000 by 1674, to 675,000 by 1750, and to 959,000 by 1800.

By 1860 the population of London was 2.76 million, by 1929 it was 8.0 million, and by 2000 the population of Greater London exceeded 10 million. During the 200 years between 1800 and 2000, the population of London grew more than tenfold, from 1 million to 10 million, but its built-up area grew much faster. In fact, it grew sixty-three-fold, from 3,600 hectares (36 km2) to 230,000 hectares (2,300 km2). Neither London’s population growth rate nor its rate of physical expansion were atypical. Queen Elizabeth’s noble attempts to contain the growth of London are now more than 400 years old, and their utter and obvious failure should have alerted us to the futility of such attempts.

TAGS: Planet of Cities, Urban Expansion

Today, too small a share of the American population lives at urban densities that can sustain public transport. The country now produces an inordinate share of global CO2 emissions, a share that clearly needs to be reduced to a more reasonable level that is at least on par with countries with similar per capita incomes. Higher urban densities may contribute to attaining that goal.

Though densification is potentially important for the U.S., the densification agenda should be firmly rejected for most of the growing cities of the developing world. There, many cities already have very high densities and need to be decongested. Even as densities decline in many of these cities, they will remain high enough to support public transport in coming decades.

We should not forget that at the height of the Industrial Revolution and up to the beginning of the twentieth century, there were genuine concerns that urban densities in the U.S. were too high and needed to be reduced to give people more living space, more light, and more air. The tenements of New york City’s Tenth Ward, for example, often contained 20 or more 30-square-meter apartments with no indoor plumbing on a 7.5 x 30 meter lot. Each apartment contained a household of 3 to 14 persons (Dolkart 2007). Many of these units were used as a workplace as well as a residence. Politicians, reformers, and scholars were seriously concerned with living conditions in the city’s crowded neighborhoods.

Jacob Riis, a reformer, journalist, and photographer credited with exposing the overcrowding and dire living conditions in the city’s tenements, was quite pessimistic in his book, How the Other Half Lives, about the prospects of reducing overcrowding and high densities.

Riis was wrong. Other social reformers sought to reduce overcrowding through decongestion policies made possible by the development of new transportation technologies from the early nineteenth century onward. These technologies reduced the cost of movement in cities and made it possible for large numbers of people to commute over greater distances. Adna Farrin Weber in his influential The Growth of Cities in the Nineteenth Century had it right: “The ‘rise of the suburbs’ it is, which furnishes the solid basis of a hope that the evils of city life, so far as they result from overcrowding, may be in large part removed.”

There is no question that suburbanization both facilitated and accelerated the decongestion of Manhattan’s overcrowded neighborhoods.

The Lower East Side contained 398,000 people in 1910, 303,000 in 1920, 182,000 in 1930, and 147,000 in 1940. To reformers who had long pressed for the depopulation of the slums, this leveling out of neighborhoods was a welcome and much celebrated relief. (Jackson 1987)

The figure above shows census tract densities in Manhattan in 1910 and 2010. The column height displays densities in persons per hectare, not building heights, since buildings in 2010 were much higher, on average, than those of 1910, but they housed fewer people in smaller families that consumed much greater amounts of living space per person. As the figure clearly demonstrates, the high densities throughout the island and in the Lower East Side in particular were greatly reduced and overcrowding was largely alleviated as vast numbers of residents left Manhattan for the suburbs.