Urban Expansion and Cultivated Lands

On August 28 the Lincoln Institute of Land Policy will publish Planet of Cities. This post is a modified excerpt from the sixteenth chapter — Urban Expansion and the Loss of Cultivated Lands.

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.