Human influences on ecosystems (4.15-4.25)

There has been a great rise in productivity of land in the past years due to many factors

%%Factors contributing improved Food Production:%%

1. Increased use of machinery
2. Fertiliser to improve yield quality and quantity
3. Use of insecticides and herbicides

→Kill insects to prevent damage to crops

→Herbicides decrease the competition for resources

4. Selective breeding
5. Monoculture

%%Monoculture%%: on a given area of agricultural land only one type of crop is grown

**%%Crop rotation: %%**the successive cultivation of different crops in a specified order on the same fields

• Maintains soil fertility
• Reduces build up of pests
• Reduced need for pesticides and fertilisers

%%Intensive Farming:%% Large number of livestock kept in a smaller area than needed

• Reducing the energy output/wastage the siza and yeild of livestock increases
• Animals are kept in small areas to restrict movement and reduce heat/energy loss
• Fed high energy foods to increase their mass and reduce waste

Advantages; Economic, Provides food security

Disadvantages; Faster spread of disease, Ethical concerns

%%Famine:%% Wide spread scarcity of food

Causes of Famine:

• The rapid rate of population increase
• Soil erosion and desertification
• Economic pressure/Poverty
• Unequal distribution of food
• Drought/ Flood
• War

%%Habitat Destruction%%

%%Acid rain:%%

• Caused by sulphur dioxide (burning fossil fuels) and nitrogen oxides (nitrogen reacting hot engines), as they dissolve and cause acid rain
• Damages trees and plants, and kills fish and other river life

→ Prevention: catalytic converters, in factories slaked lime neutralizes these acidic oxides and use of flue-gas desulfurization

%%Eutrophication: %%

1. Fertilisers put in soil by farmers
2. Fertilisers with nitrates / detergents with phosphates leach into rivers and lakes after rain
3. Water plants grow more than usual
4. They block sunlight and kill plants underneath
5. They die and sink to bottom
6. Bacteria/fungi decompose remains using the O2 and decreasing the O2 concentration
7. Fish and other creatures die from oxygen depletion

%%Global Warming:%%

• Increase in average temperature of the Earth
• Started at the same time as humans began burning fossil fuels
• Scientists believe fossil fuels are causing this – not proven yet
• Increase in carbon dioxide and methane concentrations in the atmosphere cause an enhanced greenhouse effect the leads to climate change

%%Negative impact of female contraceptive hormones in water courses:%%

• Reduced sperm count in men and feminisation of aquatic organisms

%%Sewage treatment:%%

1. Large objects such as sticks are screened out
2. Suspended grit is allowed to settle in the grit settling chamber’
3. Organic matter is digested via the ‘sludge digester’ and allowed to settle in the ‘sludge settling tank’
4. The remaining liquid goes into an aeration tank which contains stones that have microorganisms on the surface to digest other remaining organic matter
5. Water passes out and may be chlorinated to kill any remaining bacteria

%%Conservation%%

%%Extinction:%% The dying out or extermination of a species. Some factors that may cause extinction are:

• Climate change
• Habitat destruction
• Hunting
• Pollution
• Introduced species

An endangered species of animal or plant that is seriously at risk of extinction

%%Conservation of Species:%%

It is important to conserve endangered species in order to prevent extinction

• Monitoring and protecting habitats
• Education
• Captive breeding programes
• Seed banks
• Conservation programmes