Human impact - PowerPoint Presentation

Slide1

Human impact

Biology Stage 1

Biology Stage 3

Chapter

5 & 6

Biology ATAR Year 11

Chapter

6Slide2

Keywords

Human impact

Urbanisation

AgricultureHabitat destructionHabitat fragmentationDisruption of water flowEutrophicationSalinityBiomagnificationClimate change

Australia’s biodiversity is unique and globally significant

Environmental degradation is mostly as a result of

urbanisation

, agriculture and industrySlide3

Human impact

Modification of ecosystems to exploit resources and provide living spaceSlide4

Deforestation & habitat destruction

Clearing of native vegetation for

agriculture

and urbanisation is the main reason for habitat destructionThis process is known as deforestationSince 1750, more than 20% of Australia’s forests have been clearedThe areas that have been cleared have the most fertile soilsSlide5

Land cleared since 1750Slide6

Deforestation & habitat destruction

Consequences

Loss of biodiversity

EcosystemSpeciesGeneticReduced cycling of matter between the biotic and abiotic environments

Soils become infertile and degraded

May lead to desertification and salinity problemsSlide7

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 fragmentationSmall fragmented areas can only support small populations These small populations are more vulnerable to extinctionSlide8

Urbanisation

The outward expansion of cities

Example

Perth expanding down to Mandurah

Urbanisation

causes rapid changes on a large scale

Local biodiversity is reduced and the ecosystem is permanently changedSlide9

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 ecosystemAdditional inputs of energy and matter are needed from other ecosystems to maintain the communitySlide10

Urbanisation

& outputs - wastage

There is also an increase in output of wastes, disposed of into the air, onto the land and into the

waterwaysLandfill sites filled with food scraps and other organic materials produce methane, a greenhouse gasAn 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 downSlide11

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 & forestsHigh population densities can cause pressure to modify less productive ecosystems - this can cause further degradationSlide12

Agricultural practices - monoculture

Monoculture

The growing of only one of two types of crops over a large area for a large number of consecutive years

ExampleWheat farm, cattle stationRequires the use of: Fertilisers

Pesticides

Herbicides

Irrigation or redirection of waterways (dams)

May lead to:

Soil infertilitySoil salinitySlide13
Slide14

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 pHTop 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 grazingSlide15

Monoculture – soil degradation

Dust storms can carry away large quantities of topsoil, further eroding the land

Example

2009 dust storm in NSW and QLDSlide16

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 salinationSlide17

Disruption of water flow

Urbanisation and agriculture disrupt water flow

This changes the water cycle and affects ecosystemsSlide18

Disruption of water flow

Major engineering works

dams and reservoirs; vegetation downstream is affected

Drainage of wetlandshabitat destructionwetlands 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 waterSlide19

Eutrophication

Rain and floods move salts and other substances such as

fertilisers

off the land and into the streamsThis causes algal bloomsAlgal blooms use up all the available oxygen in the water and may also release toxinsAlgal blooms are a symptom of eutrophicationEutrophication is the enrichment of water by nutrients, particularly phosphorus and nitrogen

Example

Peel estuary –

Dawesville

Cut 1990-1994Slide20

Marine environments

Marine ecosystems

provide

:FoodRecreationTransportRepository for wastesMarine 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.Slide21

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

ExamplesRabbitsFoxesVeldt grassA 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 advantageSlide22

Introduced species

Exotic garden plants can escape into native

bushland

.ExampleGazania sp. has become a problem in many ecosystemsSlide23

Introduced species

Rabbits

Out compete native herbivores

FoxesPrey on native faunaCatsPrey on native faunaPigsDestroy vegetation, increasing erosionCamelsDamage trees and compete with native fauna

Goats

Overgraze native vegetation, increasing erosion

Cane

toadPoisonous glands kill predators, out competes many native fauna

Exotic plant speciesOut compete native floraSlide24

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 landMismanaged human activityDrought and other natural disasters

These

include:

Agricultural

practices

Overgrazing & over-cultivationImproper irrigationDeforestation

Increased erosionSoil salinitySlide25

Possible desertificationSlide26

Climate change

Greenhouse gases

CO

2 and methaneReasons for increaseBurning of fossil fuels for electricityIndustryClearing of land – reduces vegetation and decreases CO2 absorption for photosynthesisIncreased food production – cattle, sheep, rice paddies – increases methane gas Slide27

Climate change

The predicted effect of increased

greenhouse

gases is an increase in average surface temperaturesDifferent models are continually being updated as new information becomes availableThese models are used to predict how an increase in temperature will affect ocean currents and climatic patternsChanges 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 rainIncreasing number of cyclones that move further southDrier conditions in South-West WA