Land Use, Value, and Management: Agricultural Land Use Change

Land Use, Value, and Management Briefing Room Major Uses of Land Agricultural Land Use Change Urbanization and Agricultural Land Farmland Protection Agricultural Land Values Agricultural Land Management Measuring Interactions Between Urban Population and Agricultural Production

• The Extensive Margin: What Land is Farmed?
• Sources of Land Converted to Agriculture
• Agricultural Land Converted to New Uses
• Changes in Agricultural Land Use

The Extensive Margin: What Land is Farmed?

Change in agricultural land use, including movement into and out of agricultural production, is called change on the extensive margin of production. That is, changes at the point or margin at which a different land use becomes more profitable than the existing use. Such changes reflect choices about what lands are farmed. The term "margin" should not be confused with "marginal" soils or "marginal" land from an environmental viewpoint.

For example, changes from cropland to urban uses, and changes in the type of agricultural production, such as changes from pasture and rangeland to cropland, are extensive margin changes. Changing land use from cropland to urban uses reveals a great deal about the relative economic returns from those uses, and will have different impacts on the environment than changing from cropland to forest use.

Trends in the extensive margin of land use are revealed in two important data sets:

• Major Uses of Land (MLU), compiled by ERS, has provided land use data every 5 years since 1945. Major Uses of Land in the United States, 2002, the latest report, presents data for all 50 States and includes Federal land uses. A detailed database providing all data since 1945 is available on this website.

• The National Resources Inventory (NRI), conducted every 5 years by the Natural Resources Conservation Service, provides land use data that show the source and eventual use of each change in land use between two periods, as well as the acres of land that remain in the same use. The NRI provides consistent land use data for four dates (1982, 1987, 1992, and 1997) for 49 States (Alaska is excluded), for all non-Federal lands. NRI data are summarized in an NRCS report.

Sources of Land Converted to Agriculture

Contrary to popular belief, land continues to be converted from less intensive uses, like forest and rangeland, to agricultural uses, like cropland and pasture. Shifts in the other direction also occur in different regions and over time.

What use did the land come from that is now used for agriculture? Forest land contributed 8.3 million acres (55 percent) of the land that shifted into agriculture from 1982 to 1997.

Of the total land converted from forest land between 1982 and 1997, more than three-fourths went to pastureland and rangeland. Of total land shifting out of agriculture, 22.7 million acres (46 percent) shifted into forest use, 14 million acres of which was former pastureland.

Much of the shift from pastureland to forest use is due to reclassification over time. As trees grow, they expand to reach the 10-percent canopy cover used to define forest land, which changes the pastureland classification to forest use.

Even though now classified as forest, the land may still be used for grazing. Shifts between grazing land and forest uses are common and though technically considered shifts into and out of agriculture, they really represent multiple, overlapping uses.

Agricultural Land Converted to New Uses

Most land shifting from agriculture to another use between 1982 and 1997 went into forest use: 22.7 million acres (46 percent) of the land shifting out of agriculture was reforested.

Land shifting into urban uses seldom shifts back. In 15 years, only 3,000 acres shifted from urban into agricultural uses, whereas 13.9 million acres (28 percent) shifted from agricultural to urban uses.

Federal land in the NRI is an ambiguity since the NRI does not inventory land use on Federal lands. The NRI shows the acres of land that convert to Federal ownership, and visa versa. But the land use—mostly rangeland and forest land—on Federal land is not collected in the NRI, nor are land use shifts.

Changes in Agricultural Land Use

At the national level, cropland used for crops decreased about 34 million acres between 1982 and 1997, or about 9 percent. Some of this cropland went into the Conservation Reserve Program, and some was idled or used for pasture. Grassland pasture and range decreased 16.5 million acres over this period, or 3 percent. Overall, agricultural land use decreased about 3 percent since 1982.

Both Major Land Use data and the NRI data show decreases in agricultural land of about 30-34 million acres from 1982 to 1997. However, the decreases differed in magnitude by region. The Major Land Use data, which is a longer data series, show different trends for earlier years. In addition, cropland and grazing land did not always both change in like proportions, or even in the same direction.

While the national trend in cropland has been fairly constant, some regional trends have not. Cropland in the Northeast region has decreased dramatically since 1945, while cropland in the Mountain region has increased. Urban pressures and a comparative disadvantage in many crops have resulted in the conversion of Northeast cropland to other uses. Conversions from grassland, pasture, and range have primarily accounted for the increase in cropland in the Mountain region. Overall, the Eastern United States has tended to lose cropland, while the Western United States has tended to gain cropland.

The above results are by Farm Production Regions. Trends can also be shown for the ERS Farm Resource Regions using NRI data. The NRI, a shorter series starting in 1982, shows that cropland decreased in all Farm Resource Regions but two, the Heartland and the Northern Great Plains. These two regions also show a decrease in cropland if CRP is accounted for separately. Here, CRP is included as idle cropland.