Ninety-five percent of the nation’s land area is rural. This rural land is incredibly diverse; it reflects the nation’s highly variable geography, climate, hydrology, soils, water, and vegetative cover conditions. How this rural land is used by people varies considerably, too: as cropland intensively managed for production of food; as grazing lands for livestock production; as forests managed for timber production; as forests reserved for parks and wilderness; as open space, such as wetlands, tundra, and deserts, protected to conserve biological resources. The rural landscape is also dynamic and constantly changing in response to natural disturbances, climatic change, and human activities. Natural processes, such as species range extensions, can result in perceptibly small annual changes while anthropogenic changes, such as deforestation and development, can happen quickly.

Interest in the complex and changing nature of the rural landscape is seen from different perspectives. For environmental scientists, information on the rate and direction of change in land use and land cover has important implications for understanding how nature works, identifying historic trends and current environmental conditions, uncovering cause and effect relationships between human activities and environmental change, and increasing awareness of the environment and the place of human in it. For farmers and agricultural specialists, understanding how land is used is critical for insuring adequate food supplies for domestic and foreign use and for dealing with agro-environmental issues such as soil erosion, water quality, wildlife conservation, and farmland preservation. For natural resource managers, land-use and land-cover change data play important roles in developing sound management practices, evaluating human impacts, and selecting undeveloped landscapes for parks and wilderness areas. For meteorologists and geologists, land use/cover information is used to identify human populations at high risk to destructive natural hazards such as hurricanes, tropical cyclones, tornadoes, flooding, mudslides, earthquakes, and volcanic eruptions.

This chapter examines current conditions and historical changes in the rural landscape of the United States and explores the relationship between natural events, human activities, and terrestrial resources.

TRENDS

Land Use

The total land area of the contiguous United States is approximately 1.9 billion acres; counting Alaska and Hawaii, it totals 2.26 billion acres. The three major uses of land in the lower 48 states are grazing land, forest-use land, and cropland, in that order (Figure 7.1). Twenty-four percent of Alaska’s 365 million acres in forest-use and 75 percent is classified as miscellaneous other land, which includes tundra. Hawaii has 4 million acres nearly evenly divided between grazing land, forest land, and special use land, which includes parks, wildlife areas, and urban; only 7 percent of Hawaii’s land is used for cropland.

Grazing Land

According to the 1997 Census of Agriculture and other federal sources, the nation has about 773 million acres of grazing land, including 566 million acres of grassland pasture and rangeland, 106 million acres of grazed forest land, and 65 million acres of cropland used for pasture. In 1992, about 55 percent of grazing land is privately owned, with the rest on federal lands in 11 western states and Alaska (36 percent), on state and local government land (5 percent), and on land managed by the Bureau of Indian Affairs held in trust for Indian tribes and individuals (4 percent). Most of the nation’s grazing land is found west of the Continental Divide.

Grazing land area has declined throughout the 20^th century. Reasons for the decline include conversion to cropland, forestland, and developed land, improved forage quality and productivity of existing grazing lands, and decline in the number of domestic animals, particularly sheep and draft animals. According to the USDA National Resources Inventory, the amount of nonfederal pastureland declined by 41.4 million acres between 1982 and 1997. Much of the decline resulted from pastureland being converted to cropland (38 percent), forestland (33 percent), and developed land (13 percent). Nonfederal rangeland declined by 23.5 million acres over the period primarily due to conversion to cropland (29 percent), water areas and federal land (18 percent), and developed land (17 percent). Also see Grazing Land Conditions later in this chapter.

Forest Land

When Europeans settled what is now the United States, forests covered about one billion acres of the land. Since then, land clearing for settlements and agriculture, particularly during the 18^th and 19^th centuries, destroyed about 300 million acres of forestland. During the 20^th century, U.S. forest area remained relatively stable (Figure 7.2), although there have been changes in ownership, regional extent, and species mix.

In 1997, according to the recent USDA Resource Planning Act (RPA) assessment, forests covered about 747 million acres in the United States. The South and the Pacific Coast (including Alaska and Hawaii) each contained 29 percent of U.S. forest area while the North supported 23 percent and the Rocky Mountains 19 percent. Much of today’s eastern forestland has evolved by reversion of abandoned and depleted agricultural land to forest, starting in the mid-1800s and accelerating during the Great Depression. (Also see Forest Land Conditions later in this chapter.)

Cropland

Total cropland consists of cropland used for crops, cropland idled, and cropland used for pasture. While total cropland has varied up and down and generally declined since 1969, even greater shifts have occurred between cropland used for crops and cropland idled, mostly because of federal programs (Figure 7.3). Cropland used for pasture has shown less variation. More cropland was used for crops -- cropland harvested, failed, and summer fallow -- in late 1990s than during most of the 1980s and early 1990s when more cropland was idled by federal farm programs (Figure 7.4). Most cropland used for crops is harvested, but typically 2 to 3 percent experiences crop failure and 5 to 10 percent is cultivated summer fallow. In 1998, farmers harvested one or more crops on an estimated 314 million acres of cropland.

Special-Use Lands

Land developed for urban use, though a relatively small fraction (5 percent) of all land in the nation, has increased rapidly, particularly in the past 50 years. As the U.S. population expanded rapidly after World War II, there was a progressive transformation of productive agricultural land to urban use. Between 1945 and 1997, land used for homes, schools, office buildings, shopping centers, and other commercial and industrial uses increased from 15.0 million acres to 70.4 million acres (Figure 7.5). Studies by the USDA National Resources Inventory, USGS Land Use History of North America Project, and American Farmland Trust show that as the boundaries of Metropolitan Statistical Areas (MSAs) expanded during this time period, a significant portion of the nation’s most productive agricultural land — prime farmland — has been lost to urban sprawl. For example, the National Resources Inventory shows that between 1982 and 1997, 7.5 million acres of non-federal prime farmland were consumed by MSAs. This trend is particularly noticeable around Boston, New York, Rochester, Buffalo, Philadelphia-Trenton, the Baltimore-Washington corridor, Richmond, and areas near Cleveland, Detroit, Chicago, and Cincinnati. Farmland in west coast urban areas surrounding Los Angeles, San Francisco, Portland, and Seattle is also declining. The trend is not without controversy as it fuels conflict between urban and agricultural neighbors and raises questions about sustainable development and food security.

Land use for recreation and wildlife areas also increased significantly in the second half of the 20^th century. Most of the growth came from the establishment of federal wilderness areas and national parks. Land in transportation uses increased between 1945 and 1982 as the United States built more highways, roads, and airports in rural areas; land in this category has since declined, primarily due to the abandonment of railroad facilities and the inclusion of some transportation corridors into urban areas. Land in other special uses — national defense facilities, industrial areas, and farmsteads — has also declined (Figure 7.6 ).

Farmland

Farmland is defined as "land in farms" and can encompass a mixture of cropland, grazing land, forest land, other unimproved land, and land around barns, farmhouses, and other dependencies. Since the turn of the 20^th century, according to the Census of Agriculture, the number of farms in the United States has declined by more than 60 percent while the average farm size has nearly tripled. American agriculture is now dominated by large farms of 500 acres or more, which represent an increasing percentage of total farm acres (Figure 7.7). In 1998, according to annual estimates by the National Agricultural Statistics Service (NASS), the average farm size was 432 acres (Figure 7.8).

Agricultural Productivity: Outputs vs. Inputs

Agricultural productivity is commonly expressed as a ratio of total outputs (crops, livestock) to total inputs (chemicals, machinery, labor). Sources of gains in outputs and productivity are both internal and external to agriculture. They include weather, economic conditions, scale of production, efficiency, and technological changes.

From 1948 to 1996, U.S. agricultural output grew at an annual rate of 1.8 percent while real expenditures on agricultural inputs declined by 0.09 percent per year. The resulting annual growth in productivity was 1.89 percent (Figure 7.9). The transition from animal power to tractors, the use of hybrid seeds, improved livestock breeding, and more agricultural chemicals, and the increasing demand for U.S. exports contributed to an annual 1.84 percent output growth in crops and an annual 1.66 percent output growth in livestock over the 1948-1996 period. Labor input use declined while purchased inputs (mainly pesticides, fertilizer, energy, seeds, feed, and livestock) increased.

Nutrients

U.S. commercial fertilizer use (nitrogen, phosphate, and potash) for all purposes rose from 7.5 million nutrient tons in 1960 to a record 23.7 million tons in 1981. Total nutrient use dropped from this level, along with total crop acreage, to 21.3 million tons in 1995 and then increased slightly over 22 million tons by 1998 (Figure 7.10).

Economically recoverable animal wastes, primarily manure, have provided 9 to 24 percent of total nutrients available for crop production since 1974. Because of transportation costs, use of animal waste as fertilizer is economically feasible only if on-farm or nearby sources exit, and thus occurs on relatively few acres.

Sewage sludge is also applied to agricultural land as a soil enhancer; however current application data are not available. (Also not available is a breakdown of fertilizer use on lawns, golf courses, home gardens, and other non-farm lands.)

Effective nutrient management, which includes assessing nutrient need, timing, and placement, can help reduce nutrient losses to the environment while sustaining long-term productivity. The efficacy of each practice is strongly influenced by field conditions, management knowledge and skill, economic factors, and weather. See Chapter 6, Aquatic Resources, for information on the effects of nutrient enrichment in estuaries.

Pesticides

Prior to the introduction of synthetic pesticides in the 1940s, farmers controlled weeds by tillage, mowing, site selection, crop rotation, using weed-free seeds, and hoeing or pulling by hand. Insect pests and diseases were controlled by using resistant crop varieties, crop rotation, adjusting planting dates, and other cultural practices. Adoption of synthetic pesticides came quickly because they were inexpensive, more effective than cultural methods, and easy to apply.

Estimates by USDA Economic Research Service (ERS) show that pesticide use on major field crops, fruits, and vegetables first peaked in 1982, reflecting increased planted acres, greater proportion of acres treated with pesticides, and higher application rates per treated acre. Between 1982 and 1991, pesticide use declined as commodity prices fell and land was taken out of production by federal programs. In 1996 and 1997, total quantity pesticides edged above the 1982 peak (Figure 7.11), due mainly to expanded use of soil fumigants, defoliants, and fungicides on potatoes, fruits, and vegetables. Also contributing to the increase were more intensive insecticide treatments on cotton and potatoes and an increased share of wheat acres treated with herbicides.

EPA estimates of pesticide use in all U.S. sectors -- agriculture, industry and commercial, and home and garden — declined between 1975 and 1997. (Note that ERS and EPA data are not directly comparable because of different survey methodologies. In addition, EPA’s estimates cover pesticide use in all sectors, including agriculture, while ERS’s estimate covers major crop use only.) Over the 1979-1997 period, total agricultural pesticide use dropped about 13 percent, from 1,089 to 944 million pounds of active ingredients. Over the same period, pesticide use in the industry and commercial sector dropped by about 38 percent, from 243 to 151 million pounds of active ingredients, while use in homes and gardens decreased by 12 percent, from 155 to 136 million pounds (Figure 7.12).

Pesticide use has raised concerns about human health risks from pesticide residues in food and drinking water and exposure to humans when mixing and applying pesticides or working in treated areas. Pesticide use has also raised concerns about impacts to fish, wildlife, and sensitive ecosystems, impacts to beneficial insects (including natural enemies of pests), and pest resistance to pesticides.

Irrigation

Irrigated farmland is predominantly in the 17 Western states. In 1997, 43.0 million acres were irrigated in the West, up slightly from the early 1990s but still less than the 43.2 million acres that were irrigated in 1978. Irrigated acreage in other states has increased steadily in recent decades, growing from 7.2 million acres in 1978 to 12.1 million acres in 1997. By 1997, the nation had a total of 55.1 million acres of irrigated farmland (Figure 7.13). Changes in irrigated acreage are partially attributable to regional weather patterns, but also to competing demands to reduce irrigated acreage, changes in federal farm programs, and shift in crop mix on irrigated cropland. Much of the increase in irrigated acreage is due to changes in federal commodity programs that idled irrigated area in the past. Paradoxically, there has been a 25-percent reduction in irrigation water application rates since 1969, enough to offset the increase in irrigated acreage and maintain total water applied near the level of 25 years earlier. Application rates vary regionally and in accordance with crop water requirements (e.g., from less than 6 inches for soybeans in Atlantic States to as much as 5 feet for rice in the Southwest).

Resource Conditions

Cropland Conditions

Conservation provisions, first introduced in the 1985 Farm Bill, require certain resource conservation activities in return for benefits from selected federal agricultural programs. Farmers can lose these benefits if they produce crops on highly erodible land (HEL) without applying approved conservation practices or if they convert wetlands for agricultural production (swampbusting). In 1997, approved conservation systems were in place for 95 percent of HEL subject to conservation compliance, reducing erosion by two-thirds on such lands. More than 50 percent of all conservation practices involved conservation cropping sequences, conservation tillage, crop residue use, or a combination of these practices. Since 1986, a total of 280,000 acres have been found in violation of HEL conservation practices and 26,597 acres of wetlands have been drained in violation of swampbuster provisions.

There has been a significant increase in the use of conservation tillage on U.S. cropland since the late 1980s (Figure 7.14). Conservation tillage leaves sufficient residue from the previous crop to help protect the soil surface from wind and water erosion, slow surface water runoff and enhance infiltration, improve runoff water quality by intercepting nutrients and pesticides, and improve soil productivity. Additional benefits over conventional tillage systems include fuel and labor savings and lower machinery investments. In 1998, conservation tillage (which includes no-till, ridge-till, and mulch-till cultivation) was used on about 109.2 million acres (37.2 percent of all planted acres) and reduced tillage was used on 78.1 million acres (26.2 percent of the total). In contrast, intensive (conventional) tillage was used on only 36.2 percent of all planted acres, down from nearly 50 percent in 1989. (See Figure 7.14 for definitions.)

Buffer strips are another conservation practice used to control erosion and runoff. In 1997, over 2.1 million acres of cropland were devoted to some type of buffer, such as windbreak, herbaceous wind barrier, cross-wind sediment trap, grassed field border or filter strip, and grassed waterways. This is an increase of 74.6 thousand acres from 1996. Terraces -- linear conservation practices that perform similar functions such as diverting water and trapping sediment -- were used on an additional 28.0 million acres of cropland in 1997.

Land retirement and farmland protection programs also conserve cropland resources. The highly successful Conservation Reserve Program (CRP) retired nearly 36.4 million acres of highly erodible cropland during the first 10 years of implementation (1986-1995). In 1998, a record 18.6 million acres of highly erodible cropland were idled by the federal program .

As a result of conservation practices, soil erosion on cropland has been reduced from levels occurring in the early 1980s. Soil erosion -- the wearing away of soil by water, wind, and other forces -- has long been considered a major agent in soil degradation, reduction in soil productivity, and contributor to water and air quality problems. About 40 percent of all erosion in the United States results from such activities as construction, logging, and off-road vehicle use, or natural events such as fire, flooding, or drought; the rest comes from intensively used agricultural land. (See Chapter 5, Air Quality, for data on fugitive dust emissions and Chapter 6, Aquatic Resources, for data on sedimentation rates). Over the 1982-1997 period, soil loss from sheet and rill erosion on cropland decreased from 4.0 to 2.8 tons per acre per year, while losses from wind erosion declined from 3.3 to 2.2 tons per acre per year (Figure 7.15). Farmers have also reduced erosion on nonfederal pasture and rangeland, although the soil savings have not been as great as on cropland.

Grazing Land Conditions

The condition of federal and nonfederal grazing land has improved somewhat in recent years as a result of conservation efforts. The Bureau of Land Management, which manages about 169 million acres of land for grazing, estimated in 1998 that 5 percent of its grazing land was in excellent condition and nearly 30 percent was in good condition. Since 1936, land area in these two condition categories has doubled (Figure 7.16). The Forest Service manages over 72 million acres of grazing lands with range management objectives. Of these, 7 million acres do not meet forest plan standards and 13.6 more require further analysis to determine their status. The Natural Resources and Conservation Service estimated in 1992 that 6 percent of nonfederal rangeland was in excellent condition and nearly 35 percent was in good condition. The amount of nonfederal rangeland in the good condition has doubled since 1963 while that in excellent condition has remained about the same (Figure 7.17). For both BLM and nonfederal rangeland, the share of land in poor condition has declined sharply since the 1960s.

Timberland Conditions

Roughly two thirds of all U.S. forestland (504 million acres) is classified as timberland -- forests capable of producing 20 cubic feet per acre of industrial wood annually and not reserved from timber harvest. Another 52 million acres are reserved from harvesting and managed as parks or wilderness, and an additional 200 million acres include urban forests and unreserved forests which are incapable of producing industrial wood under natural conditions because of adverse site conditions.

Most of the U.S. timberland (291 million acres or 58 percent) is owned by farmers and other private landholders (including Native Americans). About 13 percent (67 million acres) is owned by the forest industry, 22 percent (109 million acres) is federal land, about 6 percent (29 million acres) is owned by the states, and the remainder is owned by counties and municipalities. Since 1953, the total area of timberland has decreased by 5.2 million acres as a result of withdrawals for wilderness and other land uses that do not permit commercial timber harvest. At the same time, timberland acreage owned by the forest industry and the states has grown, while that of other landowners has declined (Figure 7.18).

Timber Growth, Removals, and Mortality

In the 1920s, annual timber growth nationally was about one-half the rate of removals. (Removals include harvest, logging residues, pre-commercial thinning, and land clearing with resultant removal of timber.) By the 1940s, improved forest growth rates (partly because of forest protecion from fire), as well as declines in removals, resulted in timber growth and removals coming into approximate balance. Since 1952, timber growth has consistently exceeded removals, even though timber harvest rates have risen steadily (Figure 7.19).

Nationwide, net timber growth was estimated at 23.6 billion cubic feet in 1996 (the most recent data available), while removals was estimated at 16.0 billion cubic feet. By region, 46 percent of the nation’s annual timber growth and almost 64 percent of annual removals came from southern forests. Softwoods accounted for more than half (57 percent) of all timber growth and two-thirds of all timber removals in 1996. Annual timber growth continues to be concentrated on nonindustrial private and National Forest land (with about 55 percent and 17 percent of timber growth, respectively). In 1996, over 59 percent of timber removals came from nonindustrial private forests and another 30 percent from industrial forests, representing the continuation of a long-term trend.

Annual timber mortality from natural causes, such as insects, disease, fire, and windthrow, removed another 6.3 billion cubic feet in 1996, up from 3.9 billion cubic feet in 1952. The distribution of mortality is consistent and predictable, except for periodic catastrophes; it is generally greatest in the largest concentrations of timberland. In 1996, the mortality was highest on nonindustrial private timberland (48 percent of the total), followed by that on National Forest land (29 percent of the total). By region, mortality was highest in the South (35 percent of the total) and lowest in the Rocky Mountains (16 percent of the total).

Because net annual growth has exceeded annual removals and mortality has remained fairly consistent since the 1950s, net timber volume of growing stock has increased since then. Nearly all of the increase occurred in hardwood growing stock, which increased from 184 to 352 billion cubic feet over the 1953-1997 period, while the net volume of softwoods has remained fairly stable at around 450 billion cubic feet (Figure 7.20). Most of the hardwood volume (72 percent of the total) occurs on nonindustrial private land and most of the softwood volume (46 percent of the total) occurs on National Forest land. By region, almost all of the nation’s hardwood volume occurs in the North and South (47 percent and 43 percent of the total, respectively) while the nation’s softwood volume is split between the Pacific, Rocky Mountains, and South (44 percent, 24 percent, and 22 percent of the total, respectively).

Timber Production

Timber production in the United States rose rapidly during the last half of the 19^th century (from 2.7 billion cubic feet in 1850 to 12.1 billion cubic feet in 1900). Production peaked in 1910, at 13 billion cubic feet. With replacement of fuelwood by coal and oil, more efficient use of wood, and use of wood substitutes, production of timber began a slow decline that lasted until after World War II. Since 1950, U.S. production of timber products has risen substantially from 10.8 billion cubic feet in 1950 to about 16 billion cubic feet in 1997, including large increases in the production of plywood, veneer, and pulp products. Over most of this period, production of lumber has remained in the range of 5-7.5 billion cubic feet annually. Fuelwood consumption, which accounted for 40 percent of total consumption at the beginning of the 20^th century, declined steadily until a turnaround coinciding with the energy crisis of the mid-1970s (Figure 7.21).

Tree Planting

Tree planting on all forest ownerships increased dramatically after World War II, particularly with incentives through the Soil Bank Program to reduce erosion on highly erodible land. Tree planting peaked in 1988, reflecting increased tree planting on CRP lands, and has remained at about 2 to 3 million acres annually since then (Figure 7.22). Forest industry, farmers, and other private forest owners account for the largest share of land planted to tree seedlings or direct seeded.

Forest Fires

With improved forest fire protection, forest land burned by destructive wildlfires has decreased by 90 percent since 1930 -- from 50 million acres per year to 7 million acres per year (Figure 7.23).

Forest Insects and Diseases

The USDA Forest Service estimates that 59 million acres of forest land in the United States is at risk of 25 percent or more tree mortality to insects and diseases over the next 25 years. Nearly half (24 million acres) of the forests are within the National Forest System. Some of the highlights of insect infestations in 1998 are described below.

The Southern pine beetle, a native insect, is the most destructive of the eastern species of bark beetles. Populations are epidemic in some parts of the South almost every year. Annually, this beetle destroys timber trees worth millions of dollars and affects recreation areas, shade trees, and general aesthetics. Infestations usually start in trees weakened by disease, lightning strikes, excessive age, storm damage, or other stress factors. In 1998, the Southern pine beetle damaged 6.8 million acres of forestland.

The Mountain pine beetle, also a native, infests western pine forests from Canada to Mexico. Beetles attack mature lodgepole pine and mature and overstocked stands of other pines, such as ponderosa, sugar, and western white. In 1998, the affected area decreased in Oregon and Washington and in the southwestern states, but increased in Colorado, South Dakota, Montana, and northern Idaho. Mountain pine beetle outbreaks have declined significantly since the early 1980s; in 1998 the beetle affected about 300,000 acres (Figure 7.24).

Damage from the Spruce budworm, a native insect found in northern New England, New York, Pennsylvania, the Great Lakes area, and Alaska, has dropped from a record high of 10.8 million acres in 1974 to 393,300 acres in 1998. In the East, all of the reported budworm activity is currently in the Great Lakes area; 87 percent of the activity occurred in Minnesota. Balsam fir is the preferred host, but the insect also feeds on white, red, and black spruce. Outbreaks generally begin in extensive and continuous areas of mature and overmature balsam fir.

The Western spruce budworm, a native insect, causes topkill, loss of growth, and some tree mortality in the Rocky Mountains from Arizona and New Mexico north to Idaho and Montana and also in Washington and Oregon. The greatest infestations have occurred in the mid 1980s through the early 1990s. In 1998, the Western spruce budworn defoliated 843,100 acres.

The Gypsy moth was imported from France in 1869 to start a silk industry. The moth escaped and spread to the south and west. Currently, all or parts of 15 states and the District of Columbia -- an infested area which extends from New England to Virginia, West Virginia, Ohio, and Michigan -- are considered generally infested. Major infestations occurred in the early 1980s and early 1990s (Figure 7.25). In 1998, defoliation in the East increased to 363, 300 acres from 47,300 acres in 1997 (the lowest acreage since 1959). The fungus Entomophaga maimaiga is keeping gypsy moth populations low in many areas, but populations are rebuilding in other areas.

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