There are two distinct definitions of monoculture:
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Scientific definition - Vegetation composed of a single species |
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Agricultural definition - Field composed of a single crop rather than multiple crop species. |
Modern agriculture has changed the character of the arable ecosystem. Farming practices change and new technology enables better control of some components of the agroecosystems (i.e. weeds & pests). Monocultures in grassland are a relatively recent phenomenon. Many grassland systems, such as hay meadows and chalk grasslands , have a high species diversity. In the case of chalk grasslands, this diversity has arisen following many years of grazing. On nutrient poor calcareous soils some of the species found are rare.
Advantages of monoculture:
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Reduced plant competition for nutrients, space and solar radiation |
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Control of undesirable (unprofitable) organisms |
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Reduction of costs by limitation of specialized machinery required for arable operations |
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Maximize profit from the growing of high gross margin crops |
Monocultures can take many forms and are not necessarily environmentally 'unsound'
History of arable monocultures
The arable ecosystem pre-dates many other managed ecosystems (See week 1. A History of Agriculture) such as coppiced woodlands, heather Moorlands and perhaps even chalk grassland. Specialized management has created suitable growth conditions for a large number of specialist plant species (crops) suited to a disturbed but fertile soil environment. In Britain, prior to the use of herbicides and inorganic fertilizers, the cereal ecosystem contained about 17% of all flowering species. Many insects (arthropods) are associated with cereal ecosystems, utilizing both crop and weed species for food, nectar, resting and breeding. These insects also serve as pollinators and are therefore vital to the success of the crop. Only a few bird species exist entirely within arable fields, however most birds of grassland, Moorland and heath land, woodland and hedgerow habitats will at some point, feed on arable crops, or within arable fields. Few, if any mammals are exclusively associated with arable fields but many will feed there (i.e. rabbits, roe dear).
CLICK HERE for definition of biodiversity
Pause for thought.............List 5 advantages of having a diverse selection of plants and animals.
Effects of arable and grassland monocultures:
Flora: Nearly all arable weed species are now in decline through:
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Improved seed cleaning, therefore not being resown |
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Move toward winter cereals |
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Ploughing up to the hedge bottom |
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Increased herbicide, fertilizer and lime inputs restricting species |
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Limited species composition of temporary grass leys |
Left: Recently 'topped' grassland. Right: Thistle on untopped/sprayed grazing land
Arthropods:
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Reduction of available food plants through use of selective herbicides, which indirectly effects predatory species |
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Insecticides used to kill herbivores such as aphids often kill predators and pollinators |
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Reduction in plant species reduces arthropod diversity, for specific food sources and reproduction |
Birds and mammals:
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Reduction of arthropod food sources through factors outlined above (survival rate of some game bird chicks is now at a lower level than that required to maintain populations). |
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Toxicity of arthropod food sources |
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Reduction in habitat structure and diversity (i.e. some birds prefer tussocky grass species, often undesirable in agriculture) |
CLICK HERE for definitions of intensive and extensive agriculture
Pause for thought .......List 4 scenarios in modern farming systems that utilize multiple species on the same area.
