Download Human Factors: Intensive farming/ Pollution

Biodiversity
Biodiversity
Biodiversity is the total variety of organisms living on Earth or
in a specific ecosystem.
Biodiversity is affected (i.e. increases or decreases) by:
Human factors/ Abiotic factors / Biotic factors
Human Factors: Intensive farming/ Pollution/
Desertification/ Deforestation/ Overfishing
Population increase
and increased food
yield
Intensive Farming
Increasing human population requires an increased food yield.
Increased food yield is achieved by intensive farming, monoculture
and GM crops.
- Intensive farming techniques rely heavily on the use of chemicals
and machinery.
- Intensive farming allows more energy to be transferred to the
intended consumer (i.e. us), since pests are removed.
Monoculture is cultivation of a single crop in a given area
- Advantage of using monocultures is that more machinery/
specialised machinery can be used so labour costs are reduced.
More machinery means planting and harvesting are speeded up.
- Advantage of using monocultures is that more than one harvest per
year can be supported.
- Disadvantage of using monocultures is that crops are genetically
identical so disease can spread more quickly.
- Disadvantage of using monocultures is that more fertilisers are needed
ear after year means as the nutrients needed by the crop are used up.
- Disadvantage of using monocultures is that removal of hedgerows
reduces habitats available to wild animals.
Fertilisers
A fertiliser is a chemical added to soil that improves plant growth
by increasing the mineral content in the soil.
Nitrates fertilisers are important for plant growth, as they are needed
to make DNA/RNA and protein (e.g. enzymes). Enzymes speed up
chemical rea ctions as such synthesis reactions needed for growth (e.g.
cell division).
Leaching /
Fertilisers can be leached from soil and washed into fresh water.
eutrophication
- Minerals contained in fertilisers are used up directly by algae
which actively divide forming an algae bloom.
- Algal blooms prevent sunlight from reaching the bottom of rivers
and lakes, as a result, aquatic plants are unable to obtain light for
photosynthesis and die. This leads to a reduction in oxygen levels in
water.
- Dead plants and dead algae (single celled algae go very quickly
through their life cycle) increase the food available for bacteria,
which then multiply and use up even more oxygen.
Pesticides
A pesticide is a chemical used to kill organisms that are in
competition with the crop plant.
Herbicides and insecticides are types of pesticides. Herbicides kill
plants and insecticides kill insects.
Bioaccumulation
Bioaccumulation: pesticides sprayed onto crops accumulate in the
bodies of organisms over time.
- As the pesticide is passed along food chains, its toxicity increases
and can reach lethal levels.
- DDT is a pesticide that was sprayed onto plants and entered the
food chain when the contaminated plants were eaten.
- Bioaccumulation of DDT caused the thinning of eggshells, meaning
that chicks hatched before they were strong enough to survive.
Biological control
Biological control uses natural predators to control pests in farming.
- Examples of biological control are ladybirds to kill aphids) and
virus (Myxomatosis) to kill rabbits.
- Advantage: reduces the need for pesticides which is beneficial for
helpful insects such as bees that act as pollinators.
- Advantage : reduces the effects of chemical pesticides as pesticides
do not enter the food chain and bioaccumulation does not occur
- Advantage: the introduced predator is specific to the pest; therefore
biodiversity is not reduced.
- Disadvantage: some predators do not limit themselves to their
intended prey and disturb ecosystems around the crop, e.g. Asian Lady
bird.
GM crops
The development of GM (genetically modified) crops has increased
food supply.
GM crops may be an alternative to the use of fertilisers.
Examples of GM crops: maize containing a gene for resistance to
insect pests.
- Advantage: GM crops increase food supply by reducing the quantity of
crop that is lost due to pests, disease and competition from weeds.
- Advantage: GM crops reduce the farmers’ reliance on pesticides and
herbicides.
- Disadvantage: There are concerns that GM crops may carry a risk to
human health and to the environment as genes may be transferred to
related weeds.
Pollution
Pollution is the addition of contaminants into the natural environment
that cause adverse changes.
Example of air pollution: Sulfur dioxide produced by the burning of
fossil fuels is detrimental to the growth of many plant species +
makes acid rain.
Example of water pollution: Organic pollution (i.e. from living things)
such as untreated sewage released in rivers. Organic waste is food
to bacteria. As their number increases, the oxygen concentration of
the water decreases as bacteria use up oxygen to respire. When
oxygen concentration drops, many species die.
Indicator species
Indicator species are species that by their presence or
absence indicate environmental quality/levels of pollution.
- Examples of indicator species are:
Lichen for air pollution: Hairy, shrubby, leafy and crusty lichens
are found in area with low sulfur dioxide concentration.
Only crusty lichens are found in are with high sulfur dioxide
- Invertebrates for water pollution:
Mayfly larvae, stonefly larvae are found in water where there is
no organic water pollution and high oxygen concentration.
Sludge worm and rat-tailed maggots are found in areas where
there is organic pollution and low oxygen concentration.