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34 S C I E N T I F I C A M E R I C A N M AY 2 0 0 7

One of the least appreciated but most remarkable developments of the past 60 years is the extraordinary growth of

American agriculture. Farming now accounts for about one tenth of the gross domestic product yet employs less than 1 percent of all workers. It has accomplished this feat through exceptionally high growth in productivity, which has kept prices of food low and thereby contributed to rising standards of living. Fur-thermore, the exportable surplus has kept the trade defi cit from reaching unsupport-able levels. Agriculture not only has one of the highest rates of productivity growth of all industries, but this growth appears to have accelerated during the past two decades.

Over the period 1948 to 2004, total farm production went up by 166 percent. But as

the chart shows, productivity per person improved so much that only one quarter as many hands were needed in 2004 as in 1948. Furthermore, the arable land used for farm-ing dropped by one quarter over the 56-year period, and investment in heavy farm equip-ment and other capital expenditures de-creased by 12 percent.

Several developments drove these chang-es, beginning with the replacement of the remaining horses by tractors immediately after World War II and with the expanding

use of fertilizers and pesticides. Later came the adoption of hybrid seeds, genetic engi-neering of plants and improved livestock breeding. A key element was the U.S. De-partment of Agriculture’s extension service. Operating through land-grant universities and other organizations, it educated farm-ers on biotechnology, pest management and conservation.

For many years, critics have claimed that modern agriculture is not sustainable, one of the major assertions being that it encour-ages erosion, which will eventually wash away most of the topsoil. Lost topsoil, the argument goes, is virtually irreplaceable be-cause it takes up to 300 years for one inch of soil to form. Indeed, the fear of topsoil loss has dogged agriculture since the days of the 1930s Dust Bowl.

But a detailed study of two large areas, the Southern Piedmont and the Northern Mississippi Valley Loess Hills, showed that based on 1982 data, soil loss has dropped sharply from the very high rates of the 1930s. The conclusion of the analysis, which appeared in the July 14, 2000, issue of Sci-ence, was that if 1982 erosion rates contin-ued for 100 years, crop yields would decline by only 2 to 4 percent. The study attributed the decrease in soil erosion to the USDA, which urged farmers after World War II to adopt conservation practices such as strip cropping, whereby alternating rows are planted, and leaving plant residues in the fi elds year-round to inhibit water runoff.

Despite being a robust contributor to the U.S. economy, modern agriculture is not without a dark side. Runoff of fertilizers, antibiotics and hormones degrade the envi-ronment and can upset the local ecology. If not grown properly, genetically modifi ed crops could spread their DNA to conven-tional species. And the industrial approach to food has contributed to America’s obe-sity epidemic as well as to sporadic but widespread Escherichia coli outbreaks.

Rodger Doyle can be reached at rodgerpdoyle@verizon.net

Food BoomAGRICULTURAL PRODUCTIVITY SUSTAINS THE U.S. ECONOMY BY RODGER DOYLE

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Overall productivityof U.S. agriculture

Materials costs

Capital expenditures

Land use

Labor costs

Year1950 1960 1970 1980 1990 2000

Chan

ge in

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ince

194

8 (p

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nt)

200

175

150

125

100

75

50

25

0

–25

–50

–75

FURTHER READING

Agricultural Productivity in the United States. Mary Ahearn,

Jet Yee, Eldon Ball and Rich Nehring. U.S. Department of Agriculture Bulletin No. 740,

January 1998.

U.S. Soil Erosion Rates—Myth and Reality. Stanley W.

Trimble and Pierre Crosson in Science, Vol. 289,

pages 248–250; July 14, 2000.

Productivity and Output Growth in U.S. Agriculture.

Eldon Ball in Agricultural Resources and Environmental

Indicators. Economic Research Service, U.S. Department of

Agriculture, 2006. Available at www.ers.usda.gov/

publications/arei/eib16/

Food and Agriculture Organization of the United Nations:

www.fao.org

AMERICAN MONOCULTURE

The Food and Agriculture Organization (FAO) of the United

Nations advocates the maintenance of a permanent or

semipermanent organic soil cover. To achieve this condition, it

recommends farming practices that include little or no tillage and

varied crop rotation—measures that the U.S. follows to a limited

extent. The FAO also insists that the future of agriculture depends

on biodiversity. The U.S., however, has largely continued to practice

monoculture: 82 percent of harvested acreage in 2005 was

in four crops (corn, soybeans, hay and wheat), a rise from

78 percent in 1985.

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