Human Impact on the Environment

1. Monoculture/Intensive Farming• Humans have managed to:

• remove the threat of predation• develop vast areas of land for producing food• improve public health

• As a result, the human population continues to increase• We try to cope with this by:

• growing vast monocultures• employing intensive farming techniques• developing Genetically Modified Crops

• A monoculture is the intensive farming of plants, where only one variety of crop is grown

• Natural ecosystems are cleared to accommodate monoculture crops

• The types of plants grown as a monoculture are:– Wheat– Maize– Rice– Potatoes

• Farmers use intensive farming techniques to increase food yield from the same acreage of land

• Usually intensive farmers will:– Grow large monocultures– Rely heavily on the use of chemicals– rear animals indoors, often in confined spaces

(battery farming), leaving more energy for growth than it being lost as heat/movement

Advantages DisadvantagesCrop grown is suitable to climatic conditions

Crops are genetically identical, so disease can spread easily

More machinery can be used, so labour costs are reduced

Reduces habitats available to wild animals, reducing biodiversity

More than one harvest per year can occur

Heavy use of chemical fertilisers

• Genetically modified crops have had a useful gene from another organism inserted into their cells

• Examples of plants engineered in this way are:• Maize - resistant to insect pests• Potatoes - resistant to fungal blight• Golden Rice – contains high dose of vitamin A

2. GM Crops

Pros ConsGM crops allow farmers to decrease their use of chemicals without decreasing their yield

No guarantee that crops will remain resistant to disease

GM crops reduce the quantity of crop lost

Some people believe these crops carry a risk to human health

• A fertiliser is a chemical that is used by farmers to improve plant growth

• It is added to the soil to increase the minerals in the soil

• Nitrogen, Magnesium, Phosphorus & Potassium are commonly found in fertilisers

3. Fertilisers & Pesticides

Nutrient Function of Nutrient in Plant Nitrate To make nucleic acids and amino acidsMagnesium

Required for the formation of chlorophyll

Phosphorus

For the production of ATP and nucleic acids

Potassium For the formation of fruits/flowers

• Leaching is when fertilisers are washed from the soil into freshwater (after heavy rainfall)

• This makes the river ‘over-rich’ in minerals• Algae grow rapidly• The algae then die in huge numbers &

bacteria in the water increases• Dead plants under the water (unable to

obtain light to carry out photosynthesis) provide more food for the bacteria

• Bacteria multiply and use up even more oxygen

• Leaching causes an overall decrease in biodiversity of the ecosystem due to a lack of oxygen

4. Pesticides• A pesticide is a chemical used to kill organisms that are in competition with the crop plant• Pesticides are specific

– Herbicides are used to kill other plants– Fungicides are used to kill fungus– Insecticides are used to kill insects– Bactericides are used to kill bacteria

• Some pesticides sprayed onto crops accumulate (build up) in the bodies of organisms over time

• This is called bioaccumulation• The level of pesticide found in the bodies of organisms increase as the position in the food

chain increases

4. Pesticides• A pesticide known to cause bioaccumulation is DDT• It was used widely in the 1950s and 1960s• DDT was sprayed onto plants and entered the food chain when the contaminated plants were

eaten by other organisms• It is now banned due to its harmful effects on biodiversity

– E.g. it caused the thinning of egg shells meaning that chicks hatched before they were strong enough to survive– It has even been found in water ecosystems– It has been found in the tissues of penguins in the antartic!

5. Pollution• Pollution is the addition of substances to the

environment that cause harm to organisms• An indicator species help indicate levels of pollution

either by their presence or absence• Some examples of indicator species are: lichens,

mayfly, stonefly or sludgeworms

• There are many different types of Lichen (hairy, shrubby, leafy and crusty)

• In areas of LOW pollution, mainly hairy lichen would be found

• In areas of HIGH pollution, mainly crusty lichen would be found

Sulphur dioxide and lichen biodiversity

Sulphur dioxide concentration

hairy shrubby leafy crusty

Distance downstream

Rela

tive

num

ber o

f ba

cter

ia a

nd

conc

entra

tion

of

oxyg

enUntreated organic waste added

bacteria

oxygenbiodiversity

Freshwater invertebrates

6. Biological Control• Biological control is the deliberate use of natural

predators to control pests in farming• Ladybirds have been used to clear greenfly, as an

example of biological control

Carry out the research task for one of the examplesAdvantages of BC Disadvantages of BCReduces effects of harmful chemical pesticides that may kill other organisms

Only effective in small growing areas

Bioaccumulation does not occur

In some cases the natural predator has become the pest!