• Agroecosystem - The interaction between abiotic and biotic in a farming environment
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Features of a natural ecosystem
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Features of an agricultural ecosystem
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Reason
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Environmental effect
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Climax Community forms
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A plagioclimax is maintained = deflected succession
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Need to grow crops not a woodland
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Reduced habitat diversity, reduced niches
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Many plant species
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One species – a monoculture
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Easier to manage one crop – 2 crops in one field would make planting,
weeding and harvesting harder
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Removes natural predators of pests and makes crop susceptible to a
pest epidemic so pesticides are essential. Pesticides may contaminate food,
leach into water supplies or move up food chains, harming useful organisms –
pollinating insects or pest-eating birds for example. May lead to nutrient
deficiency as all individuals need same nutrients. Thus, artificial
fertilisers are needed
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Genetic diversity within crop species
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Reduced genetic diversity within crop
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Crop likely to be genetically engineered for a small number of
desirable characteristics
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Loss of genetic diversity that may be needed if environmental
conditions change or if a new disease/pest emerges
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Soil always covered by some plant species
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Soil often left bare after harvesting
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Not economic to plant second crop in same year/growing season may
make it impossible
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Soil erosion
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Nutrient cycling occurs via death and decomposition of plants and
animals
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Harvesting removes plants. Animals are killed by pesticides or kept
out by enclosures. So nutrient recycling is impossible. Nutrient additions
must be made in the form of fertilisers
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The crop is needed for sale. Fertilisers must be used to return the
nutrients lost when the crop was removed
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Nitrates high soluble so may leach. Phosphates erode. Entry of
nitrates and phosphates into water course leads to eutrophication. Loss of
fertilisers means more must be applied therefore more must be made which
increases the use of fossil fuels
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Relatively low productivity
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High productivity
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Crop receives huge energy input in the form of artificial fertilisers/pesticides
etc
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Energy is from fossil fuels, the extraction and burning of which leads
to global warming. Fossil fuels are finite so system may be unsustainable and
unethical – future generations will have no choice but to find alternatives
or change their agriculture systems
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