From The Changing Illinois Environment: Critical Trends, 1994, Summary Report of the Critical Trends Assessment Project
Nothing affects more land in Illinois than growing crops. Some 80% of the state is farmed--two-thirds of it planted in row crops such as corn and soybeans, the rest in pasture, forage crops, orchards, and woodlots. Making farming possible on this scale required by far the most significant of the changes humans have wrought on the state's ecosystems.
THE EVOLUTION OF FARMING
The traditional 19th-century Illinois farm homestead was a diverse and productive landscape, in many respects a simplified version of the mixed woodland-grassland ecology it replaced. Beginning in the 1880s and continuing into the 1930s, a succession of innovations came into wide enough use to transform this bucolic Illinois farmscape. These included the following:
Higher yields. Commercial fertilizers and hybrid varieties of corn made possible such higher yields that, beginning about 1940, profits from grain sales rivaled those earned by animal husbandry. The average Illinois cornfield that yielded about 50 bushels per acre in 1945 yielded nearly 120 bushels per acre in 1990. (Figure 8-1)
Figure 8-1. Corn Yield 1945-1990
Source: Ecological Resources, Illinois Natural History Survey, 1994
Different crops. In 1990 total acreage of small-grain crops (like wheat and oats) and of forage crops (such as hay) was only 44% that of 1945. In their place farmers have planted row crops, especially soybeans, acreage of which has more than doubled since 1945. By 1990 there were more acres planted in beans than were planted in corn in 1945. (Figure 8-2 )
Fewer kinds of major crops. Illinois once sustained a locally significant production of orchard fruits and vegetables for the canning industry. The 1980s saw significant declines in the acreage devoted to the latter, and production of apples and peaches (the main orchard crops) also dropped somewhat.
Fewer animals. Livestock (especially hogs) became a specialty crop, produced less and less as part of ordinary farm operations and more and more in factory-scale facilities. Livestock remains a significant income-producer mainly on land less favored for row-crop agriculture, such as the hilly districts of west and northwest Illinois.
More use of chemicals. Low-cost commercial nitrogen has made it possible to plant twice the once-standard number of rows of corn plants per acre. Since World War II, chemical weed killers have made labor-intensive field cultivation unnecessary. Illinois farmers have used substantially more herbicide since 1964; by the early 1990s more than 96% of all cropland in Illinois was treated for weeds at least once each year. (Figure 8-3)
Figure 8-3. Herbicide and Insecticide Application by Illinois Farmers
Source: Ecological Resources, Illinois Natural History Survey, 1994
Larger farms. Illinois terrain and soils are especially suited to large-scale farm operations. Since 1950 the size of the typical Illinois farm has expanded more than twofold--from 150 acres in 1950 to 350 acres in 1990. (Figure 8-4)
Figure 8-4. Farmland and Farm Size in Illinois 1950-1990
Source: Ecological Resoures, Illinois Natural History Survey, 1994
Illinois' long growing season is a crucial factor in its agricultural productivity. There is a trend detectable over recent decades toward longer growing seasons in Illinois, in spite of a cooling trend overall. Speculation that global warming may alter that seasonal cycle cannot yet be confirmed.
Illinois enjoyed generally moderate summers during crop-growing seasons of the 1960s and 1970s. Virtually all the technological advances that define today's agriculture were tested and adopted during this interval of relatively benign weather, which also was the era in which virtually all Illinois farmers now working learned their craft.
A summer dry spell of several weeks that coincides with a crucial growing period can devastate farm crops even if it does not dry up streams or deplete surface reservoirs used as public water supplies. Illinois suffered persistent and extreme drought in the 1930s, and the 1980s saw a return to hotter, drier weather. (The severity of the 1988 summer drought was equaled only twice in the years since 1900.) As insurance against such calamitous shortfalls of rain, Illinois farmers have been expanding irrigated acreage statewide, from 40,000 acres in 1970 to about 240,000 in 1987.
Agricultural pollution takes two forms in Illinois--pollution by farms and pollution of farms. The former is probably less severe than it was twenty or thirty years ago, although it remains significant if only because farming affects so much Illinois land. The following factors affect the land:
Farm chemicals. Farm chemicals can move off the farm in dust, dissolved in rainwater, attached (or adsorbed) to eroded soil particles, or as volatilized gases. These migratory chemicals are a principal source of nonpoint pollution in Illinois. For example, inorganic forms of nitrogen fertilizer dissolve easily in water and thus are easily washed off fields into streams by rain; in some areas, shallow groundwater may also be affected. (Case studies have documented elevated nitrate levels in rural shallow wells; the problem is still under study.) Possible spills of agricultural chemicals at the more than 1,200 ag chemical distribution sites in Illinois could pose some risk of soil and water contamination; however, recent regulations for these sites should reduce their risks.
Errant nitrogen and other farm nutrients also can cause the eutrophication or artificial nourishment of surface waters, especially lakes, which thus produce water-clouding crops of microscopic water plants such as algae. It is impossible to say with certainty whether eutrophication is getting worse or better; most water impoundments were built in the 1950s and 1960s, after the acceleration of chemical-intensive agriculture was already well underway.
Compared with fertilizers, farm pesticides have been introduced to the larger Illinois environment in relatively small amounts since the 1950s. Unfortunately, early compounds such as DDT and other chlorinated hydrocarbons were persistent and indiscriminate in their effects. Unknown amounts of these chemicals are still present in bottom sediments of many lakes and streams, where they are thought to cause physical deformities among bottom-feeding fish.
Newer insecticide formulations are acutely toxic to nontarget organisms for only a few days. Also, various data suggest that Illinois farmers have been applying them in declining amounts. In the late 1960s, 70% of Illinois corn acreage was treated with soil insecticide to control corn rootworm, a common insect threat; by the 1990s that figure had shrunk to less than 30%. In addition, the amounts being applied per acre were generally smaller. Better monitoring of infestations makes possible more timely (and lower cost) applications, and because newer compounds are more pest specific, they are effective at lower doses.
Pollution of Illinois agricultural lands by nonfarm activities is only a minor threat to the resource. These activities include:
Mining. Since about 1885, strip mining of coal has disturbed 256,000 acres of land, which is less than 1% of Illinois' surface area. Mining regulations passed by the Illinois General Assembly in 1962 and by Congress in 1977 sought to improve reclamation so as to make surface mining a temporary use of the land by returning it to productive use. Three-fourths of the land affected by these laws has been reclaimed as pasture and 14% as row-crop acreage.
Oil production. Oil brought to the surface brings with it copious amounts of water containing dissolved salts. If allowed to spill, high concentrations of these brine wastes can be toxic to some plants at high. Incomplete surveys in 1980 and 1985 suggest that in those years 38,000 acres of Illinois land had 50% or more of its vegetation destroyed by leaks or spills of this "produced" water. Regulations now require that such water be disposed of in deep underground rock formations.
Air pollution. Illinois agricultural systems have been shown to be relatively insensitive to current levels of acidic precipitation ("acid rain"), in part because of the acid-buffering limestone added to soils by farmers. Ozone has been proven to diminish the quality and harvest of cash crops in several parts of the U.S. but limited data suggest that problematic concentrations of ozone decreased (if modestly) during the 1980s across most of the state. The impact on crops of the dry deposition of common pollutants via airborne particles and gases is less studied, as is the impact of more exotic toxic compounds deposited via both dry deposition and precipitation.
In the 1980s, research suggested that increased concentrations of carbon dioxide (CO2), the commonest of the greenhouse gases, might induce warming of the Earth's climate. The long-term effects of global warming, if any, on Illinois agriculture cannot now be predicted. Such climatic change might cause shifts in rainfall patterns or growing season deleterious to Illinois' staple crops; because CO2 is an essential building block in green plants, an increase in atmospheric CO2 might actually boost farm productivity.
The diverse farm landscape dominant in Illinois until the 1960s contained abundant wildlife. Even now some species thrive, as human manipulation of the land enhances wildlife habitat for certain species. The expansion of row-crop production onto marginal lands in the 1970s meant sizeable habitat losses for Illinois' upland game species such as quail, pheasant, and rabbit. The resulting population declines are matched by declines since 1956 in the numbers of quail and especially rabbit killed by Illinois hunters (although pheasant numbers held fairly steady).
Animals killed by hunters also declined in proportion to the "recreation days" invested by hunters. The reduced reward for hunting effort may be one of the factors causing the recent decline in the number of days spent hunting in Illinois, which are fewer (by more than half) than in 1956.
Illinois' principal mineral resource is its soils. Waterborne gravels, clays, and rock were overlaid across much of the state with fine windblown particles known as loess. Rich in lime and other minerals, loess is the basis of Illinois' richest soils. That richness is due in part to their youth. Surface soils have been acted upon by weather for only about 12,000 years in most of Illinois, which is not long enough for leaching and exposure to seriously drain their fertile store of minerals; in far southern Illinois, surface soils have lain exposed for 60,000 years, during which time they have lost much of their original wealth of chemical nutrients.
An estimated 90% of all the soil erosion in the state--158 million tons annually in recent years--occurs on its farm fields. Not all of this soil is lost to the farmer. Soil erosion, or rather soil movement, is a natural process. Soil movement (mainly via water) occurs on even a "flat" farm field. Much of it is simply moved from one part of a field to another, or from one field to another on the same farm.
While soil loss is severe on some farms in some parts of Illinois, overall losses are approximately 0.03 inches per year. Local topsoil losses vary across the state with terrain; surface deposits around Galesburg, for instance, are older and more incised than around Champaign, and soil losses in the former area since settlement are thought to total six to seven inches. (Figure 8-5 ) Parts of unglaciated southern Illinois (whose topsoils were thinner to begin with) have lost even more than seven inches; the federal government, using Depression-era farm relief programs, bought up much of the ruined acreage and planted it in soil-saving trees, thus forming the nucleus of the Shawnee National Forest.
According to traditional definitions of soil depth, Illinois soil is several feet thick in places. However, the thinner "A-horizon" or topsoil could be eroded away in a matter of decades rather than centuries. In Bond County, for example, the lifetime of the resource, using the surface-to-bedrock definition, is calculated to be 1,300 years; using the A-horizon or topsoil definition, it is 75 years.
Soil loss in general rises and falls depending on the choices farmers make about which crops to plant, as well as where and how. Those choices in turn are affected by grain prices and government erosion-control programs. Erosion rates probably peaked in the 1970s, when high world grain prices encouraged Illinois farmers to bring even marginal land into production. Dire warnings in the mid-1970s that erosion would soon leave Illinois farms bare were not borne out; a crash in grain prices and higher input costs led farmers to do less plowing on hilly land, as did government erosion-control programs.
COMPETITION FROM NONFARM LAND USES
The amount of farmland in Illinois has declined by 10% since 1950, as farms have been displaced by houses and roads, reservoirs and other manmade lakes, landfills, and mines.
Reservoirs and landfills. Large flood control and water supply reservoirs occupy roughly 0.9% of the Illinois land surface, usually in rural areas. While most industrial and other solid waste is still disposed of on land, these operations occupy only 0.2% of the Illinois surface. Future waste disposal is not expected to be a significant competitor for agricultural land.
Coal mining. Only about 0.8% of Illinois land is, or has been, affected by the strip mining of coal. Since the 1960s the acreage affected by strip mining each year has never exceeded roughly 7,000 acres, and that figure is declining. Newer methods of underground coal mining allow for the planned, controlled subsidence of the surface; under Illinois surface mining reclamation laws, damage suffered by farmers now must be mitigated by coal companies.
Urbanization. No nonfarm land use is more permanently destructive of the agricultural potential of Illinois land than urbanization. Farming often becomes untenable even on land that is not yet built upon. Increased traffic on narrow rural roads makes it harder to move machines and material to fields; field drainage can be disrupted by construction on adjacent land; vandalism and complaints from nearby residents about farm noise, dust, and smells are common.
It has been estimated that 17 of Illinois' top 20 farming counties are located in or adjacent to urbanized areas, as defined by the U.S. Census Bureau. The phenomenon is most dramatically evident in Chicago's hinterland. The Northeastern Illinois Planning Commission estimates that between 1970 and 1990 the population of the six Chicago-area counties grew by 4%, while the amount of urbanized land expanded by 51%--a net land consumption over the two decades of more than 360,000 acres.
The trend toward the conversion of farmland to residential use varies with the robustness of the economy and underlying social forces such as changes in household size. Given the enormous size of Illinois' farmland resource, urbanization would seem to be a minor intrusion on the state's agricultural estate in the short run. (At present, cities occupy only one-seventeenth the land that agriculture does.) However, Illinois' agricultural resources are not infinite, and their continued transformation to urban uses worries many farm leaders concerned about the state's long-term ability to meet demands for food.
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