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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:
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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
Disadvantages
Crop 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
2. GM Crops
• 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
Pros
Cons
GM crops allow farmers to
No guarantee that crops will
decrease their use of
remain resistant to disease
chemicals without decreasing
their yield
GM crops reduce the
quantity of crop lost
Some people believe these
crops carry a risk to human
health
3. Fertilisers & Pesticides
• 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
Nutrient
Function of Nutrient in Plant
Nitrate
To make nucleic acids and amino acids
Magnesium 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
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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
Freshwater invertebrates
Relative number of
bacteria and
concentration of oxygen
Untreated organic
waste added
bacteria
oxygen
biodiversity
Distance downstream
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 examples
Advantages of BC
Disadvantages of BC
Reduces effects of harmful Only effective in small
chemical pesticides that may growing areas
kill other organisms
Bioaccumulation does not
occur
In some cases the natural
predator has become the
pest!