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Definitions,
sources of data, and estimation techniques have varied little over time in the
Major Land Uses series. The following definitions and explanations
of the data are for the most recent year, but generally
apply to all previous years as well.
Estimates
of major land uses for 2002 are the latest in a series of land use inventories
based on available statistics conducted by the Economic
Research Service (ERS) and its predecessor agencies within
the United States Department of Agriculture (USDA). This
series, which began in 1945, is comparable in categories
and area coverage. Part of the series—cropland
used for crops—is consistent back to 1910 on a
yearly basis. These periodic inventories are useful because
even though numerous public agencies develop land use data,
no other single agency, except ERS, accounts
for the use of all land (public and private for all 50
States) in the United States. The inventories provide a
framework within which changes in the supply and demand
for land for agricultural and other purposes can be measured
and analyzed.
The estimates, with few exceptions, were synthesized or
otherwise adapted, modified, or adjusted from available
data, rather than compiled and used exactly as developed
by source agencies. This process is necessary because land
use data, regardless of origin or utility for specific
objectives, have limitations for comprehensive inventory
purposes. The data are typically obtained from surveys
differing greatly in scope, methods, definitions, and other
characteristics. The individual sources account for only
one or a few uses and for only a limited part of the total
land area. The available data contain conflicts and overlaps
that must be reconciled or removed.
Definitions
(Names correspond to the spreadsheet file names. Categories in upper case are
major uses, while those in lower case are subcategories
of the major uses.)
CROPLAND—Total cropland
includes five components: cropland harvested, crop failure,
cultivated summer fallow, cropland used only for pasture,
and idle cropland. The estimate of total cropland in 2002
includes total cropland as reported by the 2002 Census
of Agriculture (NASS, 2004) plus an upward adjustment
to conform to data on principal crops harvested reported
by USDA's National Agricultural Statistics Service (NASS)
for 2002.
Cropland used for
crops—Three of the cropland acreage components—cropland
harvested, crop failure, and cultivated summer fallow—are
collectively termed cropland used for crops, or the
land input to crop production. Regional acreage in
these components are developed annually in a separate
but coordinated series. The annual estimates of cropland
harvested are based on both census data and the series
on principal crops harvested maintained by NASS. Annual
estimates of crop failure are based on differences
in planted and harvested acreage of principal crops
from the NASS series. Annual estimates of cultivated
summer fallow historically have been based on fragmentary
data from a variety of sources. More recently they
have been based on data from the Census of Agriculture
and unpublished NASS data.
Cropland harvested
includes row crops and closely sown crops; tree fruits,
small fruits, and tree nuts; vegetables; other minor
crops and hay. In 2002 about 4 percent of this acreage
was double cropped (double cropped acres were only
counted once).
Crop failure consists
mainly of the acreage on which crops failed because of
weather, insects, and diseases, but includes some land
not harvested due to lack of labor, low market prices,
or other factors. The acreage planted to cover and soil
improvement crops not intended for harvest is excluded.
In 2002 crops failed on about 5 percent of the acreage
planted.
Cultivated summer fallow
refers to cropland in sub-humid regions of the Western
United States cultivated for a season or more to control
weeds and accumulate moisture before small grains are
planted. This practice is optional in some areas but necessary
in the drier cropland areas of the West. Other types of
fallow, such as cropland planted to soil improvement crops
but not harvested, and cropland left idle all year, are
not included in cultivated summer fallow.
Cropland
used only for pasture generally is considered in the long-term crop rotation,
as being tilled, planted in field crops, and then re-seeded to pasture at varying
intervals. However, some cropland pasture is marginal for crop uses and may remain
in pasture indefinitely. This category also includes land that was used for pasture
before crops reach maturity and some land used for pasture that could have been
cropped without additional improvement. Cropland pasture and permanent grassland
pasture have not always been clearly distinguished in agricultural surveys. Idle
cropland includes land in cover and soil improvement crops and completely
idle cropland. Some cropland is idle each year for various physical and economic
reasons. Acreage diverted from crops to soil-conserving uses under Federal farm
programs is included in this component. Cropland enrolled in the Federal Conservation
Reserve Program (CRP) is included in idle cropland. GRASSLAND PASTURE and RANGE—Grassland
pasture and range consists of all open land used primarily for pasture and
grazing. It includes shrub and brush land types of pasture and grazing land
such as sagebrush and scattered mesquite; all tame and native grasses; legumes;
and other forage used for pasture or grazing.
Because
of the diversity in vegetative composition, grassland pasture and range are not
always clearly distinguishable from other types of pasture and range. At one extreme,
permanent grassland may merge with cropland pasture; at the other, grassland may
intermingle or form transitional areas with forested grazing land. No single
agency, other than ERS, accounts for all public and private land used for pasture
and range. The estimates in this report are composites of data from the Census
of Agriculture, Bureau of Land Management, U.S. Forest Service, Natural Resource
Conservation Service and several other Federal agencies. FOREST LAND—Forest
land, as defined by the U.S. Forest Service, includes land at
least 10 percent of which is stocked by trees of any
size, or land formerly having had such tree cover that will
be naturally or artificially regenerated. Forest land
includes transition zones, such as areas between heavily forested and nonforested
lands that are at least 10 percent stocked with forest trees and forest areas
adjacent to urban and built-up lands. The total includes pinyon-juniper
and chaparral areas in the West and afforested areas.
There are a number of components to total forest land, a few of which are described
below.
The U.S. Forest Service inventoried
749 million acres of forest land in 2002, 98 million of which were estimated to
be in the Major Land Use Category of Special Uses, leaving 642 million in the
MLU defined category of Forest-Use Land. These special uses include parks, wildlife
areas, and similar special-purpose areas. Similar exclusions of forested land
in special uses were made in earlier reports. The extent of the exclusion in each
Census year is indicated in a footnote in Table 8. Although this helps eliminate
double counting of land in multiple uses, it was not feasible to eliminate all
overlap that exists between forest land and special use land. The Forest
Service has historically conducted a continuous, rather than periodic, survey
of forest resources. At any point in time, the forest area data for individual
States may vary in age by several years. This system may adversely affect estimates
of other areas, especially pasture and range. However, this system provides a
good overall measure of forest area and is useful in explaining changes and trends
in land use. Forest land receives less emphasis than cropland and pasture in the
Major Land Uses report series because the U.S. Forest Service periodically surveys,
analyzes, and provides reports (containing considerable detail) on the Nation's
forest resources.
Forest-use land grazed—Forested pasture
and range consist mainly of forest, brush grown pasture, arid woodlands, and
other areas within forested areas that have grass or other forage growth. The
total acreage of forested grazing land includes woodland pasture in farms plus
estimates of forested grazing land not in farms. For many States, the estimates
include significant areas grazed only lightly or sporadically. The Census of
Agriculture and the U.S. Forest Service are the principal sources of data.
Historical data from these and other sources have assisted in the development
of approximations. The residual of total forest land minus forest-se land grazed
is defined as forest-use land not
grazed.
SPECIAL USES—Special
uses in the Major Land Uses report series include areas
in highway, road, and railroad rights-of-way and airports;
Federal and State parks, wilderness areas, and wildlife
areas; national defense and industrial uses; and urban
areas. Estimates of the area in special uses were developed
because some of these uses affect the supply of agricultural
land and all help account for changes in land use.
Urban
areas as defined by the Census Bureau are densely-populated areas with at
least 50,000 people ("urbanized areas") and densely-populated areas with 2,500
to 50,000 people ("urban clusters"). Rural
transportation uses include highways, roads, and railroad rights-of-way, plus
airport facilities. Rural parks and wildlife
areas include Federal and State parks, wilderness areas, and wildlife refuges.
Farmsteads, farm roads, and lanes plus
other miscellaneous farmland are included in special uses.
OTHER or MISCELLANEOUS LAND—Includes
miscellaneous uses such as industrial and commercial sites
in rural areas, cemeteries, golf courses, mining areas,
quarry sites, marshes, swamps, sand dunes, bare rocks,
deserts, tundra, rural residential, and other unclassified
land.
For further definitions see more Definitions
and Explanation of
the Data.
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