1. Human impact Biology Stage 1 Biology Stage 3 Chapter 5 & 6
Biology ATAR Year 11
Chapter 6

2. Keywords Australia’s biodiversity is unique and globally significant
Environmental degradation is mostly as a result of urbanisation, agriculture and industry
Human impact
Urbanisation
Agriculture
Habitat destruction
Habitat fragmentation
Disruption of water flow
Eutrophication
Salinity
Biomagnification
Climate change

3. Human impact
Modification of ecosystems to exploit resources and provide living space

4. Deforestation & habitat destruction
Clearing of native vegetation for agriculture and urbanisation is the main reason for habitat destruction
This process is known as deforestation
Since 1750, more than 20% of Australia’s forests have been cleared
The areas that have been cleared have the most fertile soils

5. Land cleared since 1750

6. Deforestation & habitat destruction
Consequences
Loss of biodiversity
Ecosystem
Species
Genetic
Reduced cycling of matter between the biotic and abiotic environments
Soils become infertile and degraded
May lead to desertification and salinity problems

7. Habitat fragmentation
When native vegetation is cleared, habitats that were once continuous become fragmented
These separate areas are isolated from each other by crop land and pasture
This process is known as habitat fragmentation
Small fragmented areas can only support small populations
These small populations are more vulnerable to extinction

8. Urbanisation Urbanisation causes rapid changes on a large scale
Local biodiversity is reduced and the ecosystem is permanently changed
The outward expansion of cities
Example
Perth expanding down to Mandurah

9. Inputs & outputs Urbanisation disrupts the cycling of matter
There is little recycling of matter between the biotic community and the abiotic component of the urban ecosystem
Additional inputs of energy and matter are needed from other ecosystems to maintain the community

10. Urbanisation & outputs - wastage
There is also an increase in output of wastes, disposed of into the air, onto the land and into the waterways
Landfill sites filled with food scraps and other organic materials produce methane, a greenhouse gas
An average household produces more than 27 tonnes of greenhouse gases a year
6.9 billion plastic bags are used annually, each bag taking 500 years to break down

11. Agriculture
40% of earth’s land surface converted to cropland & permanent pasture
Results in near-complete loss of native vegetation
Most productive ecosystems converted are first: grasslands & forests
High population densities can cause pressure to modify less productive ecosystems - this can cause further degradation

12. Agricultural practices - monoculture
The growing of only one of two types of crops over a large area for a large number of consecutive years
Example
Wheat farm, cattle station
Requires the use of:
Fertilisers
Pesticides
Herbicides
Irrigation or redirection of waterways (dams)
May lead to:
Soil infertility
Soil salinity

14. Monoculture – soil degradation
Growing the same crop year after year depletes the soil of nutrients
Artificial fertilisers can contribute to:
soil salinity
imbalances in soil pH
Top soils can be degraded and lost due to:
Over exposure to the elements eg. wind, rain and heat because of reduced tree cover and reduced cycling of nutrients
Compaction from large and heavy machinery
Over grazing

15. Monoculture – soil degradation
Dust storms can carry away large quantities of topsoil, further eroding the land
Example
2009 dust storm in NSW and QLD

16. Monoculture – salinity
Irrigation of crops contributes significantly to increasing the level of groundwater, which is often very saline
This raises the water table and causes waterlogging and salination

17. Disruption of water flow
Urbanisation and agriculture disrupt water flow
This changes the water cycle and affects ecosystems

18. Disruption of water flow
Major engineering works
dams and reservoirs; vegetation downstream is affected
Drainage of wetlands
habitat destruction
wetlands process pollutants – keep waterways clean
Degradation of streams & waterways
drainage of stormwater changes the natural water flow
Desnagging
the removal of logs to improve water flow has reduced habitats and increased erosion
Irrigation
places demands on water supply and affects the cycling of water

19. Eutrophication Algal blooms are a symptom of eutrophication
Rain and floods move salts and other substances such as fertilisers off the land and into the streams
This causes algal blooms
Algal blooms use up all the available oxygen in the water and may also release toxins
Algal blooms are a symptom of eutrophication
Eutrophication is the enrichment of water by nutrients, particularly phosphorus and nitrogen
Example
Peel estuary – Dawesville Cut

20. Marine environments
Marine ecosystems provide:
Food
Recreation
Transport
Repository for wastes
Marine ecosystems are under pressure because of:
Fishing practices
Over-harvesting
By-catch
Pollutants such as oil spills
Marine ecosystems are also affected by bio- magnification. This is an important concern when fish is intended for human consumption.

21. Introduced species Introduced species upset the balance of ecosystems
They can become pests, especially if they do not have natural predators to keep their numbers in check
Examples
Rabbits
Foxes
Veldt grass
A pest species will compete with native flora and fauna for:
Space
Shelter
Food / nutrients
Water
They are often capable of breeding quickly, giving them a competitive advantage

22. Introduced species
Exotic garden plants can escape into native bushland.
Example
Gazania sp. has become a problem in many ecosystems

23. Introduced species Rabbits Out compete native herbivores Foxes
Prey on native fauna
Cats
Pigs
Destroy vegetation, increasing erosion
Camels
Damage trees and compete with native fauna
Goats
Overgraze native vegetation, increasing erosion
Cane toad
Poisonous glands kill predators, out competes many native fauna
Exotic plant species
Out compete native flora

24. Desertification
Desertification is the process whereby fertile land becomes infertile desert
It usually happens as a result of a number of factors that degrade and erode the land
Mismanaged human activity
Drought and other natural disasters
These include:
Agricultural practices
Overgrazing & over- cultivation
Improper irrigation
Deforestation
Increased erosion
Soil salinity

25. Possible desertification

26. Climate change Greenhouse gases CO2 and methane Reasons for increase
Burning of fossil fuels for electricity
Industry
Clearing of land – reduces vegetation and decreases CO2 absorption for photosynthesis
Increased food production – cattle, sheep, rice paddies – increases methane gas

27. Climate change Changes in climate may include More hot days
Increased risk of fires
Increased evaporation and decreased water supply
An increase in the intensity of rainfall but a drop in the total amount of rain
Increasing number of cyclones that move further south
Drier conditions in South-West WA
The predicted effect of increased greenhouse gases is an increase in average surface temperatures
Different models are continually being updated as new information becomes available
These models are used to predict how an increase in temperature will affect ocean currents and climatic patterns