Agriculture: modern problems

Categories: Agriculture; economic botany and plant uses; environmental issues

Monoculture

Modern agriculture emphasizes crop specialization, also known as monoculture. Farmers, especially in industrialized regions, often grow a single crop on much of their land. Problems associated with this practice are exacerbated when a single variety or cultivar of a species is grown. Such a strategy allows the farmer to reduce costs, but it also makes the crop, and thus the farm and community, susceptible to widespread crop failure. The corn blight of 1970 devastated more than 15 percent of the North American corn crop. The corn was particularly susceptible to harmful organisms because 70 percent of the crop being grown was of the same high-yield variety. Chemical antidotes can fight pests, but they increase pollution. Maintaining species diversity or varietal diversity—growing several different crops instead of one or two—allows for crop failures without jeopardizing the entire economy of a farm or region that specializes in a particular monoculture, such as tobacco, coffee, or bananas.

Genetic Engineering

Growing genetically modified (GM) crops is one potential way to replace post-infestation chemical treatments. Recombinant technologies used to splice genes into varieties of rice or potatoes from other organisms are becoming increasingly common. The benefits of such GM crops include more pest-resistant plants and higher crop yields. However, environmentalists fear new genes could trigger unknown side effects with more serious, long-term environmental and economic consequences than the problems they were used to solve. GM plants designed to resist herbicide applications could potentially pass the resistant gene to closely related wild weed species that would then become “super weeds.” Also, just as pests can develop resistance to pesticides, they may also become resistant to defenses engineered into GM plants.

Erosion

An age-old problem, soil loss from erosion occurs all over the world. As soil becomes unproductive or erodes away, more land is plowed. The newly plowed lands usually are considered marginal, meaning they are too steep, nonporous or too sandy, or deficient in some other way. When natural vegetative cover blankets these soils, it protects them from erosive agents: water, wind, ice, or gravity. Plant cover “catches” rainwater that seeps downward into the soil rather than running off into rivers. As marginal land is plowed or cleared to grow crops, erosion increases.

Expansion of land under cultivation has not been the only factor contributing to erosion. Fragile grasslands in dry areas have also been used more intensively. Grazing more livestock than these pastures can handle decreases the amount of grass in the pasture and exposes more of the soil to wind, the primary erosive agent in dry regions. Overgrazing can affect pastureland in tropical regions, too. Thousands of acres of tropical forest have been cleared to establish cattle-grazing ranges in Latin America. Tropical soils, although thick, are not very fertile. After one or two growing seasons, crops grown in these soils will yield substantially less than before.

Tropical fields require fallow periods of about ten years to restore the soil after it is depleted. That is why tropical farmers using slash-and-burn agriculture move to new fields every few years in a cycle that returns them to the same place years later, after their particular lands have regenerated. Where there is heavy forest cover, soils are protected from exposure to the massive amounts of rainfall. Organic material for crops is present as long as the forest remains in place. When the forest is cleared, however, the resulting grassland cannot provide adequate protection, and erosion accelerates. Lands that are heavily grazed provide even less protection from heavy rains, and erosion accelerates even more.

The use of machines also promotes erosion, and modern agriculture relies on machinery such as tractors, harvesters, trucks, balers, and ditchers. Machinery is used intensely in industrialized nations, and its use has been on the rise in developing countries such as India, China, Mexico, and Indonesia, where traditional, nonmechanized farming methods were previously the norm. Farming machines, in gaining traction, loosen topsoil and inhibit vegetative cover growth, especially when farm implements designed to rid the soil of weeds are attached. The soil is then more prone to erosion.

Eco-fallow farming has become more popular in the United States and Europe as a way to reduce erosion. This method of agriculture, which leaves the crop residue in place over the fallow (nongrowing) season, does not root the soil in place as well as living plants do, so some erosion continues. Additionally, eco-fallow methods require the heavy use of chemicals, such as herbicides, to “burn down” weed growth at the start of the growing season. This contributes to increased erosion and pollution.

Pollution and Silt

Besides causing resistance among harmful bacteria, insects, and weeds, pesticides inevitably wash into surface and groundwater supplies, contaminating them. Pesticides are potentially harmful to human health; there has been concern that their seepage into land and water is linked to cancer.

An increasingly heavy silt load has been choking the life out of streams and rivers. Accelerated erosion from water runoff carries silt particles into streams, where they remain suspended and inhibit the growth of many forms of plant and animal life. The silt load in American streams has become so heavy that the Mississippi River delta has been growing faster than it once did. Heavy silt loads, combined with chemical residues, have been creating an expanded dead zone. By taxing the capabilities of ecosystems around the delta, sediments have been filtered out slowly, plant absorption of nutrients has decreased, and salinity levels for aquatic life have been unable to be stabilized. Most of the world’s population lives in coastal zones, and 80 percent of the world’s fish catch comes from coastal waters over continental shelves that are most susceptible to this form of pollution.

Pesticide Resistance

With the onset of the Green Revolution of the mid-twentieth century, the use of herbicides, insecticides, and other pesticides increased dramatically all over the world. An increasing awareness of problems caused by the overuse of pesticides followed, extending even to household antibacterial cleaning agents and other products. Mutations among the genes of bacteria and plants have allowed these organisms to resist the effects of chemicals that were toxic to their ancestors. The use of pesticides leads to a cycle wherein more or different combinations of chemicals are used, and more pests develop resistance to these toxins. Additionally, the development of herbicide-resistant crop plants enables greater use of herbicides to kill undesirable weeds on croplands.

Increasing interest in biopesticides (biological pesticides) may slow the cycle of pesticide resistance. Types of biopesticides include beneficial microbes, fungi, and insects such as ladybugs that can be released in infested areas to prey upon specific pests. Biopesticides may be naturally occurring or genetically modified organisms. Their use also avoids excessive reliance on chemical pesticides.

Fertilizers and Eutrophication

Increased use of fertilizers was another result of the Green Revolution. Particulate amounts of most fertilizers enter the hydrologic cycle through runoff. As a result, bodies of water become enriched by dissolved nutrients, such as nitrates and phosphates. The growth of aquatic plants in rivers and lakes is overstimulated, which results in the depletion of dissolved oxygen. This process of eutrophication can harm all aquatic life in these ecosystems.

Water Depletion

An increasing reliance on irrigation has contributed to the mismanagement and overtapping of groundwater resources. The rate of groundwater recharge is slow, usually between 0.1 and 0.3 percent per year. When the amount of water pumped out of the ground exceeds the recharge rate, it is referred to as aquifer overdraft. An aquifer is a water-bearing stratum of permeable rock, sand, or gravel.

In Tamil Nadu, India, groundwater levels dropped twenty-five to thirty meters during the 1970s due to excessive pumping for irrigation. In Tianjin, China, the groundwater level has declined 4.4 meters per year. In the United States, aquifer overdraft has averaged 25 percent over the replacement rate. The Ogallala aquifer—located under parts of South Dakota, Wyoming, Nebraska, Colorado, Kansas, Oklahoma, Texas, and New Mexico—represents an extreme example of overdraft: the rate of depletion has annually been three times faster than its rate of recharge. The capacity of the aquifer decreased by an estimated 33 percent between 1950 and 2004. At this rate, the Ogallala aquifer, which supplies water to countless communities and farms, has been projected to become nonproductive by 2030.

Soil Salinization

In addition, continued irrigation of arid regions can lead to soil problems. Soil salinization has been widespread in the small-grained soils of these regions, which have a high water absorption capacity and a low infiltration rate. Some irrigation practices add large amounts of salts into the soil, increasing its natural rate of salinization. This can also occur at the base of a hill slope. Soil salinization has been recognized as a major process of land degradation.

Although surface and groundwater resources cannot be enriched by technology, conservation and improved environmental management can make the use of precious freshwater more efficient. In agriculture, for example, drip irrigation can reduce water use by nearly 50 percent. In developing countries, though, equipment and installation costs often limit the availability of these more efficient technologies.

Urban Sprawl

With the increasing mechanization of farms, the need for farmers and farm workers has been drastically reduced. From a peak in 1935 of about 6.8 million farmers farming 1.1 billion acres in the United States, for example, the country at the end of the twentieth century counted fewer than two million farmers farming 950 million acres. In 2012, the number of farm operations was at 2.17 million, according to the US Department of Agriculture, with only 914 million acres of land in use.

Urban sprawl converts a tremendous amount of cropland into parking lots, shopping malls, industrial parks, and suburban neighborhoods. If cities were located in marginal areas, then concern about the loss of farmland to commercial development would be nominal. However, the cities attracting the greatest numbers of people have too often replaced the best cropland. Taking the best cropland out of primary production imposes a severe economic penalty.

Energy and Technological Efficiency

The increasing mechanization of farms has led to major increases in the amounts of energy consumed by these farms, particularly those in industrialized nations. Farms use large quantities of energy for irrigation, to operate machinery, to heat and cool buildings, for food processing and shipment, to spray pesticides, and to fertilize crops. The latter two are products of fossil fuels. Raising livestock on grain also consumes large quantities of fossil fuel. Large-scale livestock farmers often feed their animals grains and protein byproducts rather than employing traditional methods of foraging and consuming crop waste. Grain and protein byproduct feeding requires less land and allows for the animals to grow to market weight quickly. However, this method of feeding can be inefficient, as animals convert only a fraction of their food energy into growth; for example, it has been estimated that seven kilograms of grain are needed to produce only one kilogram of beef.

Practices such as conservation tilling, which requires less working of the soil, have helped reduce energy use on farms. Another practice is drip irrigation, in which water drips slowly to the roots of plants, thus saving on both water and fertilizer. Farmers have also begun to plant genetically modified crops that do not need pesticide, which itself has become more sophisticated and therefore used in smaller quantities than before. Other farms have opted to grow organic (pesticide-free) food and to raise animals that are not given growth hormones and that are free-range, or not always confined in tight quarters. While these practices can be expensive, they can also save on energy costs and alleviate consumer concerns about ingesting potentially harmful chemicals.

Another way farmers have learned to save money on energy is to use renewable energy sources such as wind power, solar power, and biomass products (also called biofuel). By having electric wind turbines built on their farms, farmers can produce their own energy. Wind power can be used to power an entire farm or to power a specific area of the farm, such as pumping water for cattle. Solar energy can power a farm's lighting and heating (e.g., in greenhouses), pump water, and produce electricity. It can even be used to dry crops faster and more evenly than crops left prone to damage in the fields. Many farmers grow corn to make ethanol. Other crops have begun to be used for fuel as well, since there is virtually no limit to the type of plant and organic waste that can be used to produce energy. Agriculture creates a lot of waste; there is the potential for taking that waste and converting it into energy, thus saving on energy production costs, disposal costs, and pollution. Crops grown specifically for biofuel—for farms and other consumers—can be produced in large quantities and thus become profitable when sold.

Other technologies that have made farming become more efficient—and that have saved and made farmers money—are broadband Internet access, smartphones, and Global Positioning System (GPS) technology. Use of the Internet has helped farmers quickly exchange important data with each other and has helped farmers connect directly to their markets and consumers. GPS technology has helped farmers navigate their fields in a fraction of the time it took before this invention; equipment can be guided through fields, with no overlap or gaps, so that seeds can be planted and pesticides sprayed evenly. Smartphone applications (apps) for crop scouting can help farmers identify a problem and its specific source immediately, eliminating the need to apply pesticide, for example, to an entire field in the hopes of rectifying that one problem. There are numerous other mobile applications useful to farmers as well.

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