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Jump to: [Introduction] [The Availability of Productive Land] [The Green Revolution] [Towards Improved Agriculture] [World's NPP] [Summary]
As we have seen, world population is projected to continue increasing well into the next century. Can global food production be increased to provide for the coming population expansion? Because many people are malnourished today, it will be necessary to increase current levels of food production more than proportional to population growth, so as to provide most humans with an adequate diet.
Whether food supply can keep pace with an expanding human population is an old question. In 1798, Thomas R. Malthus predicted that population growth would outstrip food supply, causing great human suffering. In the early 1960s, most nations were self-sufficient in food, but alarm about a rapidly growing population (~2% annually) caused many to echo Malthus' prediction. Then, the Green Revolution (high-yield crops and energy intensive agriculture) brought about remarkable increases in crop production. World grain output expanded by a factor of 2.6 from the 1950s to the 1980s. Today, per capita production has now slowed and appears to be declining.
To increase food production, we can farm more land, or we can increase the yield from each unit of land. As we shall see, the future lies in increasing yields. We shall also see that humans are appropriating an ever-larger fraction of the world's productive capacity.
The Availability of Productive Land
Of the world's total land area of 150 million km2 (16 X the area of the US), much is not suitable for agriculture. Arable land comprises 10% of the total. Permanent crops are 1%; meadows and pastures, 24%; forest and woodland, 31%. The remaining 34% is land surface that supports little or no vegetation: Antarctica, deserts, mine sites, urban areas. Nearly all of the world's productive land is already exploited. Most of the unexploited land is either too steep, too wet, too dry or too cold for agriculture. In Asia, nearly 80% of potentially arable land is now under cultivation.
In Global Change I, we saw that the ecosystems of the world varied greatly in their net primary production (NPP). Isn't it surprising that some parts of the Earth's land surface are much more productive than others. Most of the "good bits" have been in agriculture for a long time. Some of the remaining land surface, such as tropical rain forests, is highly productive under native vegetation (hence not much use for feeding people), and, at least with the farming methods of today, not very productive when converted to agriculture. In fact, cropland per capita is declining world-wide, as agriculture land is degraded, or urbanized. Increasing the yields from available farmland appears to be the key to increased food production.
The Green Revolution
The overall consequence is that per capita food production has contradicted the doom-sayers of the 1960s: during the greatest episode of population growth in human history, food supply per capita grew. Note that Asia did better than the world average, while Africa did worse. The Green Revolution's great success with rice explains the former; lack of success with breeding new arid-land crop varieties, combined with a large dose of political instability, explain Africa's worsening condition. Per capita grain production in Africa is down 12% since 1981 and down 22% since 1967. Some 20 years ago, Africa produced food equal to what it consumed; today it produces only 80% of what it consumes.
From the perspectives of feeding a growing population, the Green Revolution was a smashing success. Lurking behind this success story, however, are some disturbing issues:
Continued improvements in agricultural practices and land management, hopefully will allow us to both increase yields and minimize some of the negative effects of agriculture. Some areas that hold much promise include: better pest management, water-conserving irrigation, conservation tillage, and development of new crops through breeding or genetic modification.
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