Biology:Monoculture

Short description: The agricultural practice of producing a single crop at a time

Monoculture is the agricultural practice of producing or growing a single crop, plant, or livestock species, variety, or breed in a field or farming system at a time. Polyculture, where more than one crop is grown in the same space at the same time, is the alternative to monoculture. Monoculture is widely used in both industrial farming and organic farming and has allowed increased efficiency in planting and harvest.

Continuous monoculture, or monocropping, where the same species is grown year after year, can lead to the quicker buildup of pests and diseases, and then rapid spread where a uniform crop is susceptible to a pathogen. The practice has been criticized for its environmental effects and for putting the food supply chain at risk. Diversity can be added both in time, as with a crop rotation or sequence, or in space, with a polyculture.

Diversity of crops in space and time; monocultures and polycultures, and rotations of both.

			Diversity in time
			Low	Higher
				Cyclic	Dynamic (non-cyclic)
Diversity in space	Low	Monoculture, one species in a field	Continuous monoculture, monocropping	Crop rotation (rotation of monocultures)	Sequence of monocultures
	Higher	Polyculture, two or more species intermingled in a field	Continuous polyculture	Rotation of polycultures	Sequence of polycultures

Oligoculture has been suggested to describe a crop rotation of just a few crops, as is practiced by several regions of the world.

The term monoculture is frequently applied for other uses to describe any group dominated by a single variety, e.g. social monoculturalism, or in the field of musicology to describe the dominance of the American and British music-industries in Western pop music, or in the field of computer science to describe a group of computers all running identical software.

A monocultivated potato field

Land use

The term is used in agriculture and describes the practice of planting the same cultivar over an extended area. Each cultivar has the same standardized planting, maintenance and harvesting requirements resulting in greater yields and lower costs.

It also is beneficial because a crop can be tailor-planted for a location that has special problems – like soil salt or drought or a short growing season.

When a crop is matched to its well-managed environment, a monoculture can produce higher yields than a polyculture. In the last 40 years, modern practices such as monoculture planting and the use of synthesized fertilizers have reduced the amount of additional land needed to produce food. However, planting the same crop in the same place each year depletes the nutrients from the earth that the plant relies on and leaves soil weak and unable to support healthy plant growth. Because soil structure and quality is so poor, farmers are forced to use chemical fertilizers to encourage plant growth and fruit production. These fertilizers, in turn, disrupt the natural makeup of the soil and contribute further to nutrient depletion. Monocropping also creates the spread of pests and diseases, which have to be treated with yet more chemicals. The effects of monocropping on the environment are severe when pesticides and fertilizers make their way into ground water or become airborne, creating pollution.

Forestry

In forestry, monoculture refers to the planting of one species of tree. Monoculture plantings provide greater yields and more efficient harvesting than natural stands of trees. Single-species stands of trees are often the natural way trees grow, but the stands show a diversity in tree sizes, with dead trees mixed with mature and young trees. In forestry, monoculture stands that are planted and harvested as a unit provide limited resources for wildlife that depend on dead trees and openings, since all the trees are the same size; they are most often harvested by clearcutting, which drastically alters the habitat. The mechanical harvesting of trees can compact soils, which can adversely affect understory growth. Single-species planting also causes trees to be more vulnerable when they are infected with a pathogen, or attacked by insects, or affected by adverse environmental conditions.

Lawns and animals

Examples of monoculture include lawns and most fields of wheat or corn. The term is also used where a single breed of farm animal is raised in large-scale concentrated animal feeding operations (CAFOs). In the United States, The Livestock Conservancy was formed to protect nearly 200 endangered livestock breeds from going extinct, largely due to the increased reliance on just a handful of highly specialized breeds.

Disease

Crops used in agriculture are usually single strains that have been bred for high yield and for resistance to certain common diseases. Given that all plants in a monoculture are genetically similar, if a disease strikes to which they have no resistance, it can destroy entire populations of crops. Polyculture, the mixing of different crops, reduces the likelihood that one or more of the crops will be resistant to any particular pathogen. Studies have shown that planting a mixture of crop strains in the same field can combat disease effectively. Ending monocultures grown under disease conditions by introducing crop diversity has greatly increased yields. In one study in China, the planting of several varieties of rice in the same field increased yields of non-resistant strains by 89% compared to non-resistant strains grown in monoculture, largely because of a dramatic (94%) decrease in the incidence of disease, making pesticides less necessary. (As of 2009) the wheat leaf-rust fungus occasioned a great deal of worry internationally, having already decimated wheat crops in Uganda and Kenya, and having started to make inroads into Asia as well. Given the very genetically similar strains of much of the world's wheat crops following the Green Revolution, the impacts of such diseases threaten agricultural production worldwide.

In Ireland, exclusive use of one variety of potato, the "lumper", led to the Great Famine of 1845-1849. Lumpers provided inexpensive food to feed the Irish masses. Potatoes were propagated vegetatively with little to no genetic variation. When Phytophthora infestans arrived in Ireland from the Americas in 1845, the lumper had no resistance to the disease, leading to the nearly complete failure of the potato crop across Ireland. Had the farmers used multiple varieties of potato, the famine might not have occurred.

Many of today's livestock production systems rely on just a handful of highly specialized breeds. Focusing heavily on a single trait (output) may come at the expense of other desirable traits - such as fertility, resistance to disease, vigor, and mothering instincts. In the early 1990s a few Holstein calves were observed to grow poorly and died in the first 6 months of life. They were all found to be homozygous for a mutation in the gene that caused Bovine Leukocyte Adhesion Deficiency. This mutation was found at a high frequency in Holstein populations worldwide. (15% among bulls in the US, 10% in Germany, and 16% in Japan.) Researchers studying the pedigrees of affected and carrier animals tracked the source of the mutation to a single bull that was widely used in the industry. Note that in 1990 there were approximately 4 million Holstein cattle in the US, making the affected population around 600,000 animals.

Humans rely heavily on a relatively small number of food crops and farm animals for food. If disease hits a major food crop - as happened during the 19th-century Irish potato famine - food supplies for large populations could come under threat. Maintaining and increasing biodiversity in agriculture could help safeguard world food-supplies.

Sociology

Monocultural land-use can have effects at the level of society. Seasonal peaks in harvesting activity can place demands on labor availability.

Polyculture

The environmental movement seeks to change popular culture by redefining the "perfect lawn" to be something other than a turf monoculture, and seeks agricultural policy that provides greater encouragement for more diverse cropping systems. Local food systems may also encourage growing multiple species and a wide variety of crops at the same time and same place. Heirloom gardening and raising heritage livestock breeds have come about largely as a reaction against monocultures in agriculture.

See also

• Biodiversity
• Crop diversity
• Genetically modified organism
• Gros Michel bananas
• Heirloom plant
• Kil'ayim (prohibition)
• Neglected and underutilized crop
• Permaculture
• Seed bank
• Three Sisters
• Great French Wine Blight
• Crop rotation

External links

• Monoculture and disease
• Modern Agriculture: Ecological impacts and the possibilities for truly sustainable farming