Productivity growth in world agriculture: sources and constraints

摘要

Prior to the beginning of the twentieth century, almost all increases in crop and animal production occurred as a result of increases in the area cultivated. By the end of the century, almost all increases were coming from increases in land productivity - in output per acre or per hectare. This was an exceedingly short period in which to make a transition from a natural resource-based to a science-based system of agricultural production. In the presently developed countries, the beginning of this transition began in the latter half of the nineteenth century. In most developing countries, the transition did not begin until well into the second half of the twentieth century. For some of the poorest countries in the world, the transition has not yet begun. During the second half of the twentieth century, world population more than doubled-from approximately 2.5 billion in 1950 to 6.0 billion in 2000. The demands placed on global agricultural production arising out of population and income growth almost tripled. By 2050, world population is projected to grow to between 9 and 10 billion people. Most of the growth is expected to occur in poor countries, where the income elasticity of demand for food remains high. Even moderately high income growth, combined with projected population growth, could result in close to doubling the demands placed on the world's farmers by 2050 (Johnson, 2000; United Nations, 2001). The most difficult challenges will occur during the next two or three decades as both population and income in many of the world's poorest countries continue to grow rapidly. But rapid decline in the rate of population growth in such populous countries as India and China lends credence to the United Nations projections that by midcentury, the global rate of population growth will slow substantially. The demand for food arising out of income growth is also expected to slow as incomes rise and the income elasticity of demand for food declines. In the interim, very substantial increases in scientific and technical effort will be required, particularly in the world's poorest countries, if growth in food production is to keep pace with growth in demand.