Environmental Impacts of Farming...9 of 18 © Boardworks Ltd 2006 Producing artificial fertilizers...

© Boardworks Ltd 20061 of 18

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Environmental Impacts of Farming

1 of 18 © Boardworks Ltd 2006


Lea

rnin

g o

bje

ctiv

es How does the use of chemicals affect the environment?

Other environmental issues in farming.


Globally, over a hundred million tonnes of artificial fertilizers and pesticides are used every year.

The use of mineral fertilizers and pesticides have vastly increased global agricultural yields.

How has food production been increased?


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.

Fertilizers


Eutrophication


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.)

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.

The pesticide is transferred to caterpillars on

the corn.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.

Pesticides cause owls to produces weak eggs that break easily.

Problems with pesticides


Producing artificial fertilizers uses fossil fuels. Energy is also used by the machinery spraying the pesticides.

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.

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!

Other problems with fertilizers and pesticides


Types of pesticide


Lea

rnin

g o

bje

ctiv

es How does the use of chemicals affect the environment?

Other environmental issues in farming.


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…

Agriculture causes the destruction of important habitats for wildlife.

…and 1949-1974, 140,000 miles of its hedgerows.

Destruction of habitat


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.

Hedgerows


The effect of hedgerows on soil erosion


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.

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.

Pedigree cows have been selectively bred.

Genetically Modified (GM) foods


Better crops are needed to feed the world’s rapidly

growing population.

GM crops are more resistant to insectsand diseases, so farmers won’t need

to use as much insecticide.

GM crops can be made that don’t need as much water or

fertilizer, so droughts would no longer cause famine.

Crops can be engineered to give health benefits. ‘Golden Rice’ has

been engineered to contain large quantities of vitamin A.

Crops can be engineered to last longer after harvesting, so less food will be wasted.

The argument for GM foods


We can’t predict what

effects GM crops could have on human health.

GM crops are resistant to herbicides, so stronger weed-killers can be used – this could wipe out many wild plants.

GM crops could spread uncontrolled through cross-pollination. Wild plants and non-GM crops could be pollinated by nearby GM crops.

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.

The argument against GM foods


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