Environmental Impacts of Farming

Environmental
Impacts of Farming
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Learning objectives
How does the use of chemicals affect
the environment?
Other environmental issues in farming.
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How has food production been increased?
The use of mineral fertilizers and pesticides have vastly
increased global agricultural yields.
Globally, over a hundred million tonnes of artificial
fertilizers and pesticides are used every year.
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Fertilizers
What are artificial (or mineral) fertilizers?
Fertilizers generally encourage plant growth.
They come in salt or liquid form and are mixed with water
so that plants can absorb them as a weak solution.
Artificial fertilizers are specifically designed for a particular
crop. For example, a plant grown mainly for its leaves will
need a fertilizer with a high nitrogen content.
Farmers spray about 150-200 kg of
fertilizer onto every hectare of cereal crop.
This can be washed into rivers and lakes
causing eutrophication.
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Eutrophication
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Eutrophication
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Pesticides
What are pesticides?
A pesticide is a substance used to prevent,
destroy or repel a pest.
The pests you want to control could be
insects, mice and other animals, weeds, fungi
or micro-organisms (bacteria or viruses).
Insecticides kill insects
Herbicides kill plants
Fungicides kill fungi (mildews, molds, etc.)
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Problems with pesticides
One problem with pesticides it that they can poison wildlife.
This is because pesticides accumulate along the food chain.
Corn is sprayed
with pesticide.
Each shrew eats
lots of caterpillars,
so the poison
accumulates in
their bodies.
Each owl eats
lots of shrews, so
they get an even
higher dose.
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The pesticide is
transferred to
caterpillars on
the corn.
Pesticides cause
owls to produces
weak eggs that
break easily.
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Other problems with fertilizers and pesticides
Producing artificial fertilizers uses fossil fuels. Energy is
also used by the machinery spraying the pesticides.
Today, it takes about 1.2 barrels of oil to produce a
single tonne of grain in more developed countries.
This is some 7 times greater than in 1950!
Artificial fertilizers and pesticides
can also end up in our water
supply. It costs Britain £121 million
each year to monitor and remove
pesticides from the water.
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Types of pesticide
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Learning objectives
How does the use of chemicals affect the
environment?
Other environmental issues in farming.
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Destruction of habitat
Agriculture causes the destruction of important
habitats for wildlife.
Since 1949, the UK has lost:
95% of its lowland grassland
40% of its lowland heaths on acid soils
30-50% of its ancient lowland woods…
…and 1949-1974, 140,000 miles of its hedgerows.
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Hedgerows
Why are hedgerows important?
They provide a habitat for animals and birds.
They reduce soil erosion.
They act as windshields, stopping the wind from
blowing away the topsoil. The roots of the
hedgerows also help by binding the soil together.
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The effect of hedgerows on soil erosion
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Genetically Modified (GM) foods
What are genetically modified (GM) foods?
All organisms have genes. Genes contain a sort of code that
tells each organism how to develop. GM crops
have had their genes altered by scientists.
Some farm animals and crops have
been ‘genetically modified’ for
centuries using selective breeding.
Pedigree cows have
been selectively bred.
However, modern genetic engineering allows scientists
to mix genes from plants and animals that would never
normally be able to breed together. For example, a
gene from a fish could be put into a tomato.
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The argument for GM foods
Better crops are needed to
feed the world’s rapidly
growing population.
Crops can be
engineered to
last longer after
harvesting, so
less food will be
wasted.
GM crops can be made that
don’t need as much water or
fertilizer, so droughts would
no longer cause famine.
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GM crops are more
resistant to insects
and diseases, so
farmers won’t need
to use as much
insecticide.
Crops can be
engineered to give
health benefits.
‘Golden Rice’ has
been engineered
to contain large
quantities of
vitamin A.
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The argument against GM foods
We can’t predict what
effects GM crops could
have on human health.
GM crops could spread
uncontrolled through
cross-pollination.
Wild plants and nonGM crops could be
pollinated by nearby
GM crops.
GM crops are resistant to
herbicides, so stronger weedkillers can be used – this could
wipe out many wild plants.
We don’t need GM.
There’s enough food
in the world for
everyone, it’s just
that many people
can’t afford to buy it.
Bio-tech businesses would control agriculture.
They can make plants that produce barren seeds,
forcing farmers to buy new seeds every year.
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Plenary
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