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

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

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

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

Land cleared since 1750

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

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

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

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

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

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

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

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

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

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

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

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

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 1990- 1994

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.

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

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

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

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

Possible desertification

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

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