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Transcript
An ecosystem is defined as a biological
community of interacting organisms and
their physical environment.
Ecosystems
at Risk
Geography
Geography
Ecosystems at Risk
Table of Contents
1.
Biophysical Interactions Which Lead to Diverse Ecosystems & Their Functioning .................... 6
a.
What is an Ecosystem? ............................................................................................................... 6
b.
Classifying Ecosystems .............................................................................................................. 6
i.
c.
Ecosphere ............................................................................................................................... 7
Ecosystem Structure and Functioning ...................................................................................... 7
i.
Energy Flows .......................................................................................................................... 9
ii.
Nutrient Cycling.................................................................................................................... 10
d.
Ecosystem Cycles ...................................................................................................................... 11
e.
Monsoonal Ecosystems Powerpoint ....................................................................................... 11
f.
Factors Affecting the Functioning of Ecosystems .................................................................. 12
2.
a.
Introduction .......................................................................................................................... 12
b.
The Atmosphere ................................................................................................................... 12
c.
The Biosphere ....................................................................................................................... 12
d.
The Hydrosphere...................................................................................................................13
e.
The Lithosphere ....................................................................................................................13
Vulnerability and Resilience of Ecosystems ................................................................................ 14
a.
Causes of Ecosystem Vulnerability.......................................................................................... 14
i.
Location ................................................................................................................................ 14
ii.
Extent ................................................................................................................................... 14
iii.
Biodiversity ............................................................................................................................15
iv.
b.
1.
Genetic Diversity ...............................................................................................................15
2.
Species Diversity ...............................................................................................................15
3.
Ecosystem Diversity ..........................................................................................................15
Linkages .................................................................................................................................15
Natural and Human-Induced Environmental Stress............................................................... 16
i.
Natural Stress ....................................................................................................................... 16
ii.
Human Induced Stress ......................................................................................................... 16
iii.
Human Threats to Biodiversity ............................................................................................ 18
c.
Human Induced Modifications to Ecosystems ....................................................................... 18
i.
Modifications to Natural Vegetation .................................................................................. 19
ii.
Intentional Ecosystem Change............................................................................................ 19
iii.
Change Through Negligence ............................................................................................... 20
d.
Measuring Human Impacts ..................................................................................................... 20
HSC
[1]
Geography
i.
Magnitude of Change .......................................................................................................... 20
ii.
Rate of Change..................................................................................................................... 20
e.
3.
Ecosystems at Risk
Population Pressure .................................................................................................................. 21
The Importance of Ecosystem Management and Protection ................................................... 22
d.
The Maintenance of Genetic Diversity .................................................................................... 22
i.
Thylacine ............................................................................................................................... 23
e.
Utility Value .............................................................................................................................. 23
f.
Intrinsic Value ........................................................................................................................... 25
g.
Heritage Value .......................................................................................................................... 27
h.
The Need to Allow Natural Change to Proceed ..................................................................... 27
4.
Evaluation of Traditional and Contemporary Management Strategies .................................... 28
i.
Contemporary Management Approaches .............................................................................. 28
i.
Evaluation Criteria ................................................................................................................ 29
ii.
Minimising Human Impacts on Ecosystems ....................................................................... 30
ii.
5.
Traditional Management ......................................................................................................... 30
i.
Manipulation of Ecosystems ................................................................................................31
ii.
Long Term Management Practices ......................................................................................31
Case Study 1: Intertidal Wetlands ................................................................................................ 32
a.
Introduction ............................................................................................................................. 32
b.
Spatial Patterns and Dimensions ............................................................................................ 32
i.
Location ................................................................................................................................ 32
ii.
Altitude ................................................................................................................................. 32
iii.
Size, Shape and Continuity .................................................................................................. 32
c.
Biophysical Interactions .......................................................................................................... 33
d. Adjustments to Natural Stress and the Nature and Rate of Change Affecting the
Ecosystem Function ......................................................................................................................... 36
i.
ii.
e.
HSC
Salinity .................................................................................................................................. 36
1.
Mangroves........................................................................................................................ 36
2.
Salt Marshes ..................................................................................................................... 36
Tidal Movements ................................................................................................................. 36
Human Impacts on Wetlands .................................................................................................. 37
i.
Atmosphere.......................................................................................................................... 37
ii.
Hydrosphere......................................................................................................................... 37
iii.
Lithosphere .......................................................................................................................... 37
[2]
Geography
Ecosystems at Risk
iv.
Biosphere.............................................................................................................................. 37
v.
Human Modifications of Intertidal Wetland Ecosystems .................................................. 38
vi.
Positive Impacts ................................................................................................................... 38
vii.
Negative Impacts ............................................................................................................. 39
viii.
Why Protect the Intertidal Wetland Ecosystem? ........................................................... 39
1.
Maintaining Genetic Diversity ......................................................................................... 39
2.
Utility Value ...................................................................................................................... 39
3.
Intrinsic Value ................................................................................................................... 40
4.
Heritage Values ................................................................................................................ 40
5.
The Need to Natural Processes to Continue .................................................................. 40
i.
Traditional and Contemporary Management Practices......................................................... 42
i.
Traditional Management Strategies ................................................................................... 42
iii.
Contemporary Management ............................................................................................... 42
j.
Mangroves................................................................................................................................ 43
k.
Salt Marshes ............................................................................................................................. 47
6.
Towra Point Nature Reserve ....................................................................................................... 48
a.
Spatial Patterns and Dimensions ............................................................................................ 48
b.
Biophysical Interactions .......................................................................................................... 48
i.
Mangroves............................................................................................................................ 49
ii.
Salt Marshes ......................................................................................................................... 49
iii.
Rainforests ........................................................................................................................... 49
iv.
Sand/Mud Flats..................................................................................................................... 50
v.
Freshwater Wetlands........................................................................................................... 50
vi.
Seagrasses ............................................................................................................................ 50
vii.
Forests .............................................................................................................................. 50
1.
Casuarina Forest............................................................................................................... 50
2.
Dune Sclerophyll Woodlands .......................................................................................... 50
viii.
c.
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Importance ........................................................................................................................51
Human Impacts .........................................................................................................................51
i.
Erosion ...................................................................................................................................51
ii.
Weeds ....................................................................................................................................51
iii.
Horse Riding ..........................................................................................................................51
iv.
Boating ..................................................................................................................................51
v.
Feral Animals .........................................................................................................................51
[3]
Geography
vi.
Fragmentation ..................................................................................................................... 52
vii.
Development and Construction ...................................................................................... 52
d.
7.
Ecosystems at Risk
Traditional and Contemporary Management Strategies ....................................................... 52
i.
Traditional Management ..................................................................................................... 52
ii.
Contemporary Management ............................................................................................... 53
The Great Barrier Reef ................................................................................................................. 54
a.
Spatial Patterns and Dimensions ............................................................................................ 54
i.
Location and Altitude .......................................................................................................... 54
ii.
Size ........................................................................................................................................ 54
iii.
Shape .................................................................................................................................... 54
iv.
Continuity ............................................................................................................................. 54
b.
Biophysical Interactions .......................................................................................................... 55
i.
The Role of the Atmosphere ............................................................................................... 55
ii.
The Role of the Lithosphere ................................................................................................ 55
iii.
The Role of the Hydrosphere .............................................................................................. 55
iv.
The Role of the Biosphere ................................................................................................... 55
v.
Biogeographical Processes.................................................................................................. 57
c.
1.
Rates of Reef Growth ...................................................................................................... 57
2.
Resilience .......................................................................................................................... 57
3.
Coral Spawning ................................................................................................................ 57
4.
Ecological Succession ...................................................................................................... 57
Nature and Rate of Change Affecting the Ecosystem Functioning ...................................... 57
i.
Natural Impacts .................................................................................................................... 57
1.
Impact of Sea Levels on The Great Barrier Reef ............................................................ 57
a.
The Nature of Change .................................................................................................. 57
b.
The Rate of Change...................................................................................................... 58
2.
Crown-of-thorns Starfish Infestations ............................................................................ 58
a.
The Nature of Change .................................................................................................. 58
b.
The Rate of Change...................................................................................................... 58
3.
ii.
a.
The Nature of Change .................................................................................................. 59
b.
The Rate of Change...................................................................................................... 59
Human Impacts .................................................................................................................... 59
1.
HSC
Tropical Cyclones ............................................................................................................. 59
Climate Change ................................................................................................................ 59
[4]
Geography
Ecosystems at Risk
2.
Boating and Commercial Shipping ..................................................................................60
3.
Overfishing .......................................................................................................................60
4.
Tourism .............................................................................................................................60
a.
Importance ...................................................................................................................60
b.
Impacts of Tourism ......................................................................................................60
5.
Land Clearing .................................................................................................................... 61
6.
Agriculture ........................................................................................................................ 61
d.
Human Impacts ........................................................................................................................ 62
e.
Traditional and Contemporary Management Strategies ....................................................... 64
i.
Contemporary Management Strategies ............................................................................. 64
1.
ii.
HSC
Tourism ............................................................................................................................. 64
a.
The Role of Education .................................................................................................. 64
b.
The Impact of Geographical Concentration ............................................................... 64
c.
Pontoons ...................................................................................................................... 65
d.
Recreational Boats ....................................................................................................... 65
e.
Disturbance to Wildlife and Breeding Cycles.............................................................. 65
f.
Whale Watching ........................................................................................................... 65
g.
Turtles ........................................................................................................................... 65
h.
Role of the Tourism and Recreational Reef Advisory Committee ............................66
2.
Improving Water Quality .................................................................................................66
3.
Anchoring and Mooring ................................................................................................... 67
a.
Public Mooring ............................................................................................................. 67
b.
Restrictions to Anchoring ............................................................................................ 67
Traditional Management Strategies ................................................................................... 67
[5]
Geography
Ecosystems at Risk
Ecosystems at Risk
1. Biophysical Interactions Which Lead to Diverse Ecosystems & Their
Functioning
a. What is an Ecosystem?
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An ecosystem is a delicately balanced natural system in which there are complex
interactions between:
o Plants
o Animals
o Micro-organisms and
o Their non-living (abiotic) environment
Another term for ecosystem is an ecological system.
Ecosystems are identifiable systems of interdependent relationships between living
organisms and their biophysical environments.
Community: a group
of interdependent
They are systems through which incoming solar energy is captured
organism living
and channelled through a hierarchy of life forms.
together in a
Each ecosystem has its own characteristic plant and animal community.
common
Components in an ecosystem can vary naturally or from human intervention.
environment and
Each variation affects other components in the ecosystem.
interacting with one
another.
b. Classifying Ecosystems
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Ecosystems are usually classified according to their dominant feature such as:
o Climate (e.g. polar ecosystem)
o Physical features (e.g. mountain ecosystem)
o Vegetation (rainforest ecosystem)
The more small scale the ecosystem the more likely it will be named after a physical
feature.
Land Based Ecosystems
(forests, grasslands, deserts)
A.K.A Terrestrial ecosystems or
biomes.
Theses will vary according to
changes in temperature and
precipitation.
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Water Ecosystems – Aquatic Ecosystems
(ponds, lakes, rivers, reefs, inland
wetlands)
These will vary according to variations in
dissolved nutrients, salinity, depth of
sunlight penetration and average
temperature.
Ecosystems rarely have distinct boundaries, instead they blend into adjacent ecosystems
via a zone of transition called a ecotone.
Ecotones contain organisms common to both ecosystems, but may also have unique
organisms. Therefore ecotones have greater biodiversity than surrounding ecosystems.
[6]
Geography
i.
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Ecosystems at Risk
Ecosphere
The ecosphere is the collection of living and dead organisms (biosphere) interacting with
one another and their non-living environments.
An ecosphere is therefore the total of all world ecosystems.
Ecology is concerned with interactions that occur at five levels of organisation:
•The total of all world ecosystems.
Ecosphere
Ecosystems
•A collection of living and dead organisms interacting
with each other and their non-living environment.
Community
•Groups of populations of different organisms in a
defined location.
•Groups of individual organisms living in habitats.
Population
•Any living thing, single-celled or multi-celled.
Organism
c. Ecosystem Structure and Functioning



HSC
Ecosystem functioning is the ability of an ecosystem to capture, store and transfer
energy, nutrients and water.
The productivity of an ecosystem is expressed by:
o The amount of biomass produced in an area (the mass of new living matter
produced per metre squared – or within a volume of water)
o Energy flows (the amount of energy in kilojoules that is locked into all the
organisms in an area per unit of time)
Both of the above rates depend on:
o Available energy and nutrient in the environment
o The efficiency in which energy and matter are incorporated into producers and
passed up the food chain or food web.
[7]
Geography
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Ecosystems at Risk
Ecosystem functioning depends on
o Energy Flow
o Nutrient Recycling
These processes in turn link the energy, chemicals and organisms of an ecosystem.
The word trophic means ‘food’ or ‘nourishment’.
Most of the available food or nutrients for any ecosystem are found in the top layer of
soil and leaf litter.
Hence the biomass of food available is in the lowest trophic levels.
At each trophic level there is a los of energy which perhaps explains why there are
numerous small plants and insects at the lower tropic levels and many herbivores plus
fewer carnivores and less energy to support them at the tertiary level.
Lower trophic levels have a surplus of nutrients and energy, but there is a deficit at higher
trophic levels.
Abiotic
Biotic
Solar Energy
Tertiary Consumers
Precipitation
Secondary
Consumers
Organic Material
Water
Primary Consumers
Soil Decomposers
Soil and Rocks
Producers
Soluble Chemicals
HSC
[8]
Geography
Tertiary
Consumers
Secondary
Consumers
Primary
Consumers
Producers
Detritivores
i.
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HSC
Ecosystems at Risk
•Fourth Trophic Level
•Top carnivores that feed on other carnivores
•Includes: Omnivores and scavengers
•Third Trophic Level
•Carnivores
•Feed on smaller plant eating consumers
•Second Trophic Level
•Herbivores
•Feed directly on producers
•First Trophic Level
•Plants
•Convert elements such as carbon, oxygen and hydrogen to usable inputs (food)
•Includes decomposers and detritus feeders
•Feed off dead organisms and their waste products
•Detritus feeders include: earthworms, crabs, temites and slaters
•Decomposers are consumers like bacteria & fungi that break down or recycle organic
material to get nutrients
Energy Flows
All life depends on energy from the sun
Energy flows through ecosystems by means of food chains
Producers, consumers and decomposers form a chain that allows the flow of energy from
the sun through plants to animals.
Sun  Plant  Herbivore  Carnivore  Second Carnivore  Top Carnivore
The different levels of a food chain are known as feeding or trophic levels
At the first trophic level are the producers:
o Land – plants,
o Sea – phytoplankton
At the next trophic level are the consumers:
o Herbivores – primary consumers
o Carnivores – secondary consumers
[9]
Geography
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ii.
Ecosystems at Risk
o Omnivores – meat and plant eaters
o Detritivores – bacteria, fungi
Simple food chains are rare as some animals feed at more than one trophic level and
provide a food source at different trophic levels
The complex network of feeding relationships is called a food web.
At each trophic level there are thermodynamic heat losses. A plant will use up to 50% of
the energy it receives through photosynthesis. Consumer organisms will lose up to 8090% of energy available.
In fact only abut 1/10 of the energy received is passed on
Nutrient Cycling
Nutrient Cycling: The flow of energy through food webs that allow nutrients to be recycled
from non-living environments to living environments then back to non-living environments
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HSC
The consumption of herbivores by carnivores passes nutrients through the food web.
Nutrient cycles are driven either directly or indirectly by the sun
Examples of nutrient cycles include
o Carbon
o Oxygen
o Hydrogen
o Nitrogen
o Phosphorous
o Sulphur
o Water
[10]
Geography
Ecosystems at Risk
d. Ecosystem Cycles
Nitrogen
Cycles
Phosphorous
Cycles
Carbon
Cycles
•Living matter needs nitrogen to make proteins
•Nitro comes from soils
•Recycled through food chain
•Released by weathering rocks
•Dissolves in water, taken up by plants
•Recycled through food chain and returned to soils through decaying matter
•Carbon a basic building block of compounds necessary for life
•Carbon obtained through pores in leaves by land plants
•Phytoplankton from CO2 dissolved in water
•Photosynthesis converts carbon in CO2 to glucose which is used as energy
source and for plant growth before being passed down the food chain
•O2 is biproduct of photosynthesis.
e. Monsoonal Ecosystems Powerpoint
HSC
[11]
Geography
Ecosystems at Risk
f. Factors Affecting the Functioning of Ecosystems
a. Introduction
The four components of the biophysical environment are:
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Atmosphere
Biosphere
Hydrosphere
Lithosphere
These components interact within ecosystems and ultimately affect the development of an
ecosystem
Time is also a factor in ecosystem development:


Natural changes can take place over tens of thousands of years.
Human induced changes are typically too rapid for natural systems to adjust.
b. The Atmosphere
 The atmosphere is the main source of climatic factors that impact on ecosystem
functioning.
 Temperature and the amount of rainfall determine the nature of all the factors within
the ecosystem and the speed at which they function.
 The effects of atmosphere on ecosystems are diverse.
 The atmosphere is the main source of nutrients
o Nitrogen
o Carbon
o Oxygen
o Water
 Circulation patterns in the atmosphere determine the spread of pollutants.
c. The Biosphere
 The biosphere is the domain on or near the earth’s surface where solar energy produces
chemical changes necessary for life.
 The biosphere is all living and dead organisms on the earth’s surface.
 The biosphere is in a narrow zone from about 200m below the surface to about 9km
above sea level
 The biosphere has two types of organisms:
o Autotrophic Organisms (producers)
 Self sufficient manufacturers of food.
 Mainly green plants that make organic compounds via photosynthesis.
 Form the base of any food web
o Heterotrophic Organisms (Consumers)
 Can’t make their own food.
 Includes herbivores, carnivores, omnivores and decomposers.
HSC
[12]
Geography
Ecosystems at Risk
d. The Hydrosphere
 The hydrosphere is closely linked to the atmosphere and determines the nature of the
water cycles.
 Large bodies of water moderate temperatures of adjoining land masses because water
heats and cools more slowly than land.
 Polar Regions:
o Have annual rainfall less than 250mm and little fresh water
 Tropical Rainforests:
o Large volumes of rainfall in short spaces of time.
o Creates an ecosystem with high levels of biodiversity.
o This has a vigorous hydrological cycle that quickly leaches soil and erodes land.
e. The Lithosphere
 The lithosphere determines the nature of soils and provides habitats for many
decomposer organisms that recycle the minerals essential to the plants forming the basis
of the food web.
 The capacity of the soil to store nutrients and store water helps determine the nature of
particular ecosystems.
o Non-porous clays can lead to wetlands as water is trapped close to or above the
surface.
o Sandy soils allow water to drain quickly leaving a very dry soil profile.
 Climatic factors affect the role soil plays in an ecosystem.
o Climatic conditions in the tundra creates a permafrost (soil frozen for most of the
year).
o Landforms also affect ecosystems.
o Small differences in elevation result in marked differences in plant communities.
HSC
[13]
Geography
Ecosystems at Risk
2. Vulnerability and Resilience of Ecosystems
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All ecosystems function in a state of dynamic equilibrium or a continual state of balanced
change.
This state of dynamic equilibrium is the product of the interrelationship of the elements in
the ecosystem: the atmosphere, lithosphere, hydrosphere and biosphere.
Change occurs because the interrelationship between minerals, energy and communities
differs over time.
It is the interdependence that makes an ecosystem vulnerable: a change beyond the
limits of the equilibrium in any of these elements means that the system as a whole
cannot exist.
a. Causes of Ecosystem Vulnerability
All ecosystems have some ability to withstand stress. They tend to resist being disturbed or
altered and will restore themselves to their original condition ¡f not disturbed too drastically. In
other words, ecosystems maintain themselves within a tolerable range of conditions. A number
of factors are relevant to how vulnerable ecosystems are stress. These include location, extent,
biodiversity and linkages.
i.
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Location
The location of an ecosystem affects its functioning.
At a global scale, latitude, distance from the sea and altitude play decisive roles in
determining climate and ultimately the nature of particular ecosystems.
The microclimatic features of a location can be significant enough to create a range of
distinctive ecosystem types within relatively small areas.
Some ecosystems are located in environments considered extreme deserts (extreme
heat and/or aridity), the polar regions and high mountain peaks (extreme cold),
hvpersaline lagoons (extreme salinity and areas of nutrient deficiency.
Organisms capable of living in such conditions are, by necessity; highly specialised. T
he greater the degree of specialisation an organism has to a particular set of
environmental conditions the more vulnerable that organism is to changes in those
conditions.
An example is coral: Corals are highly specialised organisms that flourish in the relatively
shallow nutrient deficient waters of the tropics. An increase of just a few degrees above
the usual summer temperature can be devastating.
ii.
Extent
 The extent (size) of any ecosystem is the product of a variety of factors.
 The boundaries of ecosystems tend to overlap each other (ecotones)
 Ecosystems that are restricted to small areas or have already been disturbed extensively
are especially vulnerable.
 Tropical forests for example have relatively small populations of a large number of
species confined to relatively small, localised communities. The loss of even small areas of
rainforest can lead to the extinction of plant and animal species.
HSC
[14]
Geography
Ecosystems at Risk
iii.
Biodiversity
Biodiversity is usually considered at three levels: genetic diversity, species diversity and
ecosystem diversity.
1.
Genetic Diversity
Genetic diversity is the variety of genetic information contained in all individual plants, animals
and micro-organisms.
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Genetic diversity favours the survival of a species, because it increases the chance that
some members of the species will have characteristics to aid their survival if the
population is subject to stress.
Often a gene has costs as well as benefits.
2. Species Diversity
Species diversity is a measure of the number of species at each trophic level of an ecosystem.
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In simpler terms, the greater the species diversity, the more robust the ecosystem: if the
population of one producer or consumer organism crashes, there are other producers
and consumers available that can fulfil a similar function in the ecosystem.
When ecosystems are diverse, there is a range of different pathways for the ecological
processes, such as nutrient recycling. If one pathway is damaged or destroyed, there are
other pathways that can be used as an alternative and the ecosystem can continue to
function as normal.
If the level of biodiversity is greatly diminished the functioning of the ecosystem is put at
risk.
Therefore the greater the level of diversity, the greater the opportunity to adapt to
change.
A species can be vulnerable even if the whole ecosystem is not
3. Ecosystem Diversity
Ecosystem diversity refers to the diversity present within ecosystems in terms of habitat
differences, biotic communities and the variety of ecological processes.
iv.
Linkages
Interdependence, or linkages, is related to biodiversity. The greater the level of interdependence
within an ecosystem the greater its ability to absorb change.
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HSC
The loss of a primary consumer from a food web is unlikely to have a major impact on
secondary consumers if there is a range of alternative primary consumers on which to
feed.
Ecosystems that have low levels of interdependence are much more vulnerable to
change.
For example, impacting the number of krill in an Antarctic ecosystem will directly impact
the number of whales the ecosystem can support.
[15]
Geography
Ecosystems at Risk
b. Natural and Human-Induced Environmental Stress
i.
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Natural Stress
In nature, change tales place slowly.
The biome gradually adapts as animal and plant species that have characteristics unsuited
to the change die out and those more suited remain, breed and pass on their
characteristics.
This process is known as natural selection.
Throughout history there have been natural disasters that caused whole species to die
out instantly because they had no time to adapt.
These disasters are, however, rare.
Catastrophic
Drought
Flood
Fire
Volcanic Eruption
Earthquake
Landslide
Change in Stream Course
Disease
Natural Sources of Environmental Stress
Gradual
Climatic Change
Immigration
Adaptation/Evolution
Ecological Succession
Disease
ii.
Human Induced Stress
 Humans are able to instigate large scale environmental change, pushing dynamic
equilibrium beyond its limits.
o Damming a river, draining a wetland, clearing natural vegetation for agriculture
 lost habitat and a destruction of a species
 The result is that humans have needed to re-establish some degree of dynamic
equilibrium by utilizing resources found elsewhere.
o Agricultural monoculture (growing a single crop) may lead to the need to add
inputs of fossil fuel and fertilizer, pesticides and herbicides.
 Today human activities destroy or seriously threaten species and more importantly
destroy or degrade their habitat. Such activities include:
o Industrialisation
o Urbanisation
o Deforestation
o Afforestation
o Desertification
o Agriculture
HSC
[16]
Geography

Ecosystems at Risk
The causes of environmental degradation in today’s world are:
o Massive population growth
o Developing world poverty and the crippling burden of debt
o Non sustainable consumption
o Environmentally damaging waste generation in the developed world
o Non-sustainable agricultural practices in many countries
o Environmentally damaging industrualisation
o Exploitation of natural resources especially in poor countries struggling for
export earnings
Effects of Environmental Stress
Population Level
Community Level
Population increase/decrease
Disruption of energy flows
Change in age structure (old,
Disruption of chemical cycles
young and weak may die)
Simplification
Loss of genetic diversity and
 Reduction in species
adaptability
diversity
Extinction
 Reduction or elimination
of habitats
 Less complex food webs
Human impacts can have a global dimension too when there is an interdependent global
environment.
Organism Level
Fewer or no offspring
Genetic defects in offspring
Behavioural changes
HSC
[17]
Geography
iii.
Ecosystems at Risk
Human Threats to Biodiversity
Species
Introduction
Hunting
Habitat
Destruction
•Either deliberately or accidentally e.g. exotic species can wipe out local flora
and fauna
•This disrupts the flow of energy in ecosystems which gets magnified through
the food chain
•Leads to uncontrolled exploitation of and trade inw ildlife resulting in
decimation of species.
•Overfishing of herring and cod, leephants targeted by poachers for their
ivory
•Considered the major threat to biodiversity
•Takes several forms:
•Outright loss of areas for native species when converted to human use.
•Fragmentation and degradation where native species deprived of food,
shelter and breeding areas end up being squeezed into smaller and smaller
areas.
•Major threat to aquatic and land ecosystems e.g. acid rain's impact upon
lake ecosystems and forest ecosystems in northern and eastern Europe.
Pollution
c. Human Induced Modifications to Ecosystems
Because people are part of the biosphere, they play a role in maintaining or disturbing the
dynamic equilibrium of any ecosystem.
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Early hunters are believed to have destroyed populations of megafauna across multiple
continents.
Australian ecosystems have adapted to be fire resistant due to years of Aboriginal fire
stick farming.
[18]
Geography
Ecosystems at Risk
The planet is an ecosphere that is the amalgamation of a large number of interrelated
ecosystems. In turn these ecosystems are made up of a series of smaller interrelated
communities.
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Humans have the ability to simplify natural ecosystems in order to grow food, build
habitats and remove or extract resources.
The great environmental challenge now facing humans is how to maintain a sustainable
balance between simplified human ecosystems and the neighbouring, more complex,
natural ecosystems on which the simplified ecosystems depend.
Globally environmental damage is extensive. There are massive areas of sever marine and
river pollution and radioactive and chemical contamination, as well as a large number of
cities with air quality problems.
i.
Modifications to Natural Vegetation
The use of ecosystems by humans is best described as degrees of modification to natural
vegetation.
Removal
Replacement
Utilisation
•Clearing native vegetation and disruption of ecological processes.
•Urban settlement, transport, industrial development and extractive industries.
•Native vegetation may be removed and then replaced with intensively managed systems:
agriculture, horticulture and plantation forestry.
•Utilisation refers to the exploitation of native vegetation, with some consequent degree of
modification: forestry (in a native forest), pastoralism and recreation in natural areas.
•Pastoralism: raising grazing animals, such as cattle, on large, open grasslands
•Conservation involves the maintenance of natural vegetation for conservation and scientific
purposes with minimum deliberate modification of natural processes.
•National parks, nature reserves, uncommitted governmental land and Aboriginal land are all
Conservation examples of conservation.
ii.
Intentional Ecosystem Change
It is not always easy to distinguish between the intentional and unintentional modification of
ecosystems.
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Some intentional modifications result in unintended consequences over the longer term.
Aboriginal fire stick farming was intentional, though had an unintentional long term
effect on the evolution of Australian vegetation.
Some cases are inarguably intentional, like the Kuwait oil fires and the pouring of oil into
the Persian Gulf during the 1991 Gulf War.
[19]
Geography
Ecosystems at Risk
iii.
Change Through Negligence
Meeting the needs and wants of humankind and a rapidly increasing human population will
inevitably bring about large scale environmental damage.
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An explosion of population in the biosphere is compensated for by an adjustment
somewhere else in the biosphere
An increase in grasshoppers will decrease the plants they feed upon, reducing the
grasshopper population back to usual.
This is an example of dynamic equilibrium.
d. Measuring Human Impacts
There is no standard measurement except to observe and note changes, though a starting point
is necessary.
Students May Assess:
Lost
species
i.
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Loss of
habitat
Loss of
biodiversity
Magnitude of Change
Magnitude of change is the extent that an ecosystem has been stretched beyond its state
of dynamic equilibrium.
o It could be a small extent.
o Or extremes like totally wiping out the ecosystem.
o It may replace an ecosystem e.g. Urban environment.
To measure magnitude of change a comparison must be made between known data and a
benchmark.
ii.
Rate of Change
 Ecosystem change relates mainly to:
o Rapid population growth.
o Increasing demand for resources disproportionately by the developed world.
HSC
[20]
Geography
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Ecosystems at Risk
Most ecosystem degradation is in the developing world, however it is often the demand
for resources by the developed world that has caused a great deal of destruction.
Developing countries are forced to rely on the exploitation of raw materials in order to
pay for imported goods and repay debts.
The technology that enables the exploitation is often supplied by transnational
corporations.
Forests in developed countries are largely stable or actually increasing whilst
deforestation in developed countries is greater than 0.8% per year.
e. Population Pressure
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Population pressure is closely related to the rate of ecosystem change.
In developing countries their governments need money to improve diet, health and
education through social and economic programs.
They then encourage TNC’s to invest in their resources to gain the funds for their
programs
There are often no environmental controls.
The need for money also leads to the giving over of land to cash crops for export.
This situation means:
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The use of damaging inputs like fertilisers and pesticides.
Use of irrigation.
Loss of prime agricultural land that supported subsistence farmers
Even aid programs can be inappropriate and problematic:
Permanent water supply  permanent settlement of nomadic herders 
overgrazing and environmental degradation
o Irrigation schemes have contributed to salinisation in marginal lands
Often developing country governments can look for a quick solution and environmental
impacts are not carefully considered.
Growing populations need food, access to fuel and water.
o In marginal lands the intensification of agriculture and fuelwood collection is
causing land degradation and desertification.
o Globally almost 11 million hectares of arable land are degraded per year
o It takes 100-2500 years to build 2.5cm of topsoil.
o
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Global action is required to reduce ecosystem destruction especially in developing countries with
high populations and economic issues.
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In developed countries a key issue is the short term exploitation of natural resources
especially soil.
o Crop harvesting removes large amounts of organic matter that would normally
decompose and return nutrients to the soil.
o This organic material also helps control erosion and nutrient leaching.
[21]
Geography
Ecosystems at Risk
o
Adding to this is the problem of contamination by chemicals used in the
production process.
3. The Importance of Ecosystem Management and Protection
The variety of life on earth is of fathomless value. It provides the basis for the preservation of people
and the environment. The conservation of the environment is therefore central to the future welfare
of the Earth and its inhabitants.
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There are a range of methods to protect the earth’s biodiversity including:
o Setting aside and protecting large areas of wilderness
o Preservation of species in zoos
o Botanical gardens
o Seed banks ( store of seeds from an endangered plant)
Unfortunately these steps alone won’t save many species from extinction or from areas
being degraded.
People need to re-examine their relationship with the biophysical environment and with
each other.
People need to adopt values, attitudes and practices that are compatible with sustainable
development
Reasons for Managing and Protecting Ecosystems:
Maintenance of
Genetic Diversity
Utility Value
(current and
potential)
Heritage Value
Intrinsic Value
The Need to Allow
Natural Change to
Proceed
d. The
Maintenance of Genetic Diversity
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Greater genetic diversity allows for different traits to survive when a species suffers a
disaster.
A diversity of traits allows for the species to have a greater chance of survival. This process is
called natural selection.
Ecosystems with greater genetic diversity generally have higher resilience than ecosystems
with lower diversity.
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Ecosystems at Risk
Species that can successfully regenerate and adapt are less vulnerable to changes in the
ecosystem.
Species with high genetic diversity often survive periods of stress because some of the
organisms are usually not affected by the change.
Up until recent decades people have not had sufficient knowledge of ecological processes.
It is expected that 10’s of 1000’s of species are yet to be discovered!
Diversity on earth has taken millions of years of evolution.
Living diversity is dynamic and increases when a new genetic variation is produced.
Living diversity decreases when species decrease, become extinct or an ecosystem is lost
Ecologists say that of an estimated 5 - 30 million species currently inhabiting the planet, only
1.4 have been identified.
The 1.4 million identified only represent 10% of all species that have actually existed on earth
90% have been lost to evolutionary extinction which causes the loss of about 1 species per
year.
i.
Thylacine
The thylacine was the largest known carnivorous marsupial of modern times. It was commonly known
as the Tasmanian tiger due to the distinctive stripes on its back. The thylacine was one of only two
marsupials to have a pouch in both genders (the male pouch is used to protect the genitals whilst
running through thick brush). The thylacine had the appearance of a small to medium sized dog with a
stiff tail and a pouch (reminiscent of a Kangaroo). The thylacine possessed a ravenous hunger for
livestock and was described as a formidable predator because of its ability to survive and hunt prey in
extremely sparsely populated areas. The thylacine was an apex predator that resided at the top of its
food chain.
The Thylacine was endemic to Australia, Tasmania and Papua New Guinea, though is now believed to
have been extinct since 1930. The demise of the thylacine is often attributed to intensive hunting
encouraged by bounties, though disease, the introduction of wild dogs, the concurrent extinction of
prey species and human encroachment on its habitat are also factors that are believed to have
contributed to its extinction. These factors occurred predominantly as a result of European
colonisation of Australia.
The thylacine is still believed to exist and many sightings
have been reported, though none have been conclusively
proven. Scientists have been experimenting with museum
stored thylacine DNA and are attempting to replicate its DNA
sequence and ‘clone’ the thylacine, though these efforts have
not yielded any proper success as only a mitochondrial
genome was replicated.
e. Utility Value
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All living and non-living elements of the Earth’s ecosphere have existing or potential value
or usefulness. This is what geographers refer to as utility value. Examples include:
o Sustaining life
o Protecting the physical wellbeing of humanity
o A source for present and future medicines
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Ecosystems at Risk
o Energy source/supply
Australia’s flora and fauna make a substantial contribution to our economy. We gain
value domestically and internationally from:
o Forestry
o The pastoral industry
o Fisheries
o Tourism
o Land reclamation
o Beekeeping
o Wildflower harvesting
o Kangaroo trade
There is enormous value in the variety of ecosystems on the planet that can play roles in:
o Protecting catchments
o Purifying water
o Regulating temperature
o Regenerating soil
o Recycling nutrients and wastes
o Maintaining air quality
The problems involving maintenance of wild species:
o The environments that contain the wild species must be preserved.
o Make it worthwhile for subsistence farmers to continue growing traditional
varieties so they don’t take up modern higher-yielding strains.
Many human diseases are cured by medicines derived from plants, animals and microorganisms.
In Australia we have:
o 2 species of corkwood that have medicinal value
o Hyascine, a plant extract that helps motion sickness, stomach disorders and the
side-effects of chemotherapy
o The vine Tylaphora – a source of the drug tylocrebrine – effective in treating
lymphoid leukemia
o A threatened species of frog (Rheobatrachus) found only in QLD has chemical
compounds that is useful in treating gastric ulcers
In rainforests
o Naturally produced chemical compounds in rainforests have protective
mechanisms that many organisms rely on to live.
o These compounds are a major pharmacological resource.
o The loss of even a small amount of rainforest could mean the loss of diseaseconquering chemical compounds.
o Medical scientists believe they have only examined about 50 000 of the estimated
250 000 pharmacologically valuable plants in the rainforests.
Whilst placing a monetary value on ecosystems could come as a reality check to some
who are willing to pay to preserve the ecosystem, it could also deter some when seeing
the figure and how much is required to protect an ecosystem.
Cash values are placed on biomes based upon the services they provide to humanity. The
value of many ecosystem services is however difficult to price.
[24]
Geography
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Ecosystems at Risk
The scientists behind TEEB (The Economics of Ecosystems and Biodiversity) believe that
‘conservation has to be seen as an investment and not a cost’.
Many ecosystems are responsible for recycling moisture, maintain the water cycle,
creating soil and performing many other functions vital to life on Earth. These functions
have yet to be valued by any ecological economist.
The basis for the world’s economy is biodiversity. Everything in the economy is a product
of biodiversity and ecosystem functioning.
The goal of reducing species loss by 2010 was not achieved. New goals will be set
involving stemming the loss of biodiversity, controlling invasive species and conserving at
least 10% of all the world’s major biomes.
Diversita’s Three Conservation Aims:
Aim
Colour
Protect human safety ad include conserving mangroves to shield coastlines against
Red
storms, maintaining coral reefs to prevent the loss of local fisheries and preventing
deforestation that causes landslides.
Protect things that societies value – sacred forests or charismatic species like the great Green
whales.
Protect key ecosystem services, like carbon sinks in forests, soils and permafrost that
Blue
help maintain the climate.
 Coral reefs have such a range in value as the value is based upon the quality of the
ecosystem. Prime locations have a higher utility value whereas poorer locations have
lower utility value.
 Scientists might disagree as woodlands play extremely important roles in providing
oxygen through photosynthesis and the removal of greenhouse gases like carbon dioxide
from the atmosphere.
f. Intrinsic Value
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Ecosystems are endowed with their own intrinsic (naturally occurring) and ethical values.
This means they have a right to exist irrespective of their utility value.
Whilst most agree that we need to protect ecosystems for the benefit of future
generations, there is still no generally agreed mechanism or strategy by which this could
be achieved.
Central to the notion of intrinsic value is a recognition that the biophysical environment
provides for many of the inspirational aesthetic and spiritual needs of people.
In an increasingly urban society, aesthetic values make an important contribution to
emotional and spiritual wellbeing.
By interacting with biophysical elements, humans are reminded that they live in an
interdependent natural world.
Aesthetic qualities are also valued for their recreational potential. For e.g
o Photography
o Trekking
o Bushwalking
o Bird watching
o Field studies
[25]
Geography
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Ecosystems at Risk
The growth of ecotourism is also closely linked to the growing appreciation of the
aesthetic and ecological qualities of environments.
The links between indigenous people and the biophysical environment are particularly
strong.
Throughout the world aboriginal people derive spiritual strength from their relationships
with the biophysical environment.
Traditional aboriginals generally have an ecocentric view.
They acknowledge through their behavior and beliefs that they are responsible for the
continuity of their world.
Beliefs about creation, spiritual and physical existence provide the framework for the way
the people live.
The intrinsic value taken to the extreme would mean that no, or minimal human uses
would take place in an ecosystem.
This would assist the long term survival of the ecosystem, though adjacent areas may
cause indirect human damage.
Intrinsic means having value in existing alone as a natural phenomenon.
Intrinsic value is used to signal amenity value – the value in providing pleasure,
enrichment or satisfaction.
Most ecosystems are inherently useful and frequently regarded by economists as natural
capital to become useful at some time in the future.
Many different religions’ theologies include an intrinsic value for nature
It is hard to put into words the intrinsic value of an ecosystem, it is far easier to
experience it.
Intrinsic value is related to amenity value.
 As amenity value is difficult to attach monetary amounts to, it tends to be ignored by
economists or business people.
 Such cultures have viewed the earth as ‘terra matter’ (mother earth), a very different
stance from ‘terra nullius’ (no mans land).
[26]
Geography
Ecosystems at Risk
Luther
Standing bear,
Sioux Chief
Chief Seattle of
the Suquamish
tribe
JudaeoChristian's new
ecotheology

The intrinsic worth of certain ecosystems is also enhanced by what we have left as
opposed to what has been destroyed.
g. Heritage Value
Definitions
World Heritage Conservation Council: Natural
features consisting of physical and biological
formations or groups of such formations, which
are of outstanding universal value from the
aesthetic or scientific point of view.
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Australian Heritage Commission: Those places, being
components of the natural environment of Australia or
the cultural environment of Australia, that have aesthetic,
historic, scientific or social significance or other special
value for future generations, as well as the present
community.
In Australia the concept of natural heritage is wide enough to encompass both large
areas of pristine wilderness and those sites more readily accessible to humans.
Education has played a critical role in developing public support for heritage listing.
As support has grown additional sites have been added to the list (in some cases, after
public controversy arising from a development proposal that would have degraded the
heritage values of the ecosystem).
Preserving important elements of our natural heritage for the enjoyment and wellbeing
of future generations is a responsibility that we must all share.
h. The Need to Allow Natural Change to Proceed
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HSC
The multiplicity of life on earth are a product of ongoing evolutionary process.
[27]
Geography
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Many ecologists and environmentalists argue that humans have an ethical responsibility,
and selfish rationale, to see that this evolutionary process continues relatively
unimpeded.
To ensure that this occurs it will be necessary to protect large areas of representative
ecosystems. To achieve the desired objectives these areas should
Be large enough to protect
and conserve intact
ecosystems effectively and
to allow evolutionary
processes to continue.
Have boundaries that
reflect environmental
rather than political needs.
Be surrounded by a 'buffer
zone' where human ctivity
is carefully managed.
Take into account the
interests of local people.
Be well managed and
effectively resourced.
4. Evaluation of Traditional and Contemporary Management Strategies
Throughout the world there is a growing recognition that people must accept responsibility for
protecting and managing ecosystems, especially those considered to be at risk.
We now have great knowledge of how we impact upon ecosystems but we also have great
knowledge about how to intervene.
There is no ONE measure of successful ecosystem management. Any success must be measured
over a period of time to ensure they are not part of normal fluctuations in ecosystems.
Increasingly, the environmental impact of human activity is being judged in terms of its
ecological sustainability.
i.
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HSC
Contemporary Management Approaches
A management strategy is a plan of attack – a response to a problem and a way to
achieve goals and objectives.
There are a number of approaches to the way ecosystems are managed.
Four broad approaches can be identified:
o Preservation
o Conservation
o Utilisation
o Exploitation
[28]
Geography
Ecosystems at Risk
Preservation – ‘lock it
up’
Refers to the protection
of habitat in its existing
form. It involves
prevention of all human
activities in the area
being protected.
Conservation – ‘Use a
little’
On the other hand
involves active resource
management. It is the
planned use of natural
resources in an effort to
minimise environmental
damage.
Exploitation – ‘Selfishly
use for a profit’
Occurs when an
ecosystems resources
are used irrespective
of ecological
consequences.
Utilisation – ‘Just use
it’
Involves the
replacement of an
ecosystem with a
human made
environment that is
capable of providing a
sustainable yield.
Philosophies of Ecosystem Management
Radical
Environmental
Romanticism/
Stewardship
Utilitarianism
Environmental
Imperialism
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Underpinning the main management approaches are five key attitudes that help us
define the relationship people have with the environment. These are:
o Radical Environmentalism – This includes a wide range of views ranging from
those who advocate the right of all species to survive to those against all
development.
o Romanticism – A view that values the beauty of nature. Support for the
protection of wilderness areas.
o Stewardship – This view contends that humans occupy a privileged position in
relation to the rest of nature. People have a responsibility to protect and nurture
the land for the benefit of future generations. They are custodians.
o Utilitarianism – This view is based on the belief that things only have value if they
contribute to the happiness and well being of people.
o Environmental Imperialism – This egocentric world view holds that everything in
nature is subordinated to the needs and wants of humans. Ecosystems are to be
exploited for profit.
i.
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Evaluation Criteria
Contemporary management approaches focus on the extent to which the strategies
adopted promote ecologically sustainable development (ESD).
The ultimate measure of ecological sustainability will be higher living standards within the
context of ESD.
Sustainable development is achieved by maximising peoples economic and social well
being while protecting and maintaining the biophysical environment.
ESD incorporates four important concepts:
o INTRAgenerational equity – All people in the present generation have the right to
benefit equally from the Earth’s resources.
o INTERgenerational equity – The present generation should not use resources or
degrade environments to the extent that it leaves future generations in a worse
position.
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[29]
Geography
Ecosystems at Risk
o
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The Precautionary Approach – Measure that could prevent serious or irreversible
environmental damage should not be postponed due to scientific uncertainty.
o Biological Diversity – An essential feature for the evolution and maintenance of
earth’s life support systems, as well as having aesthetic cultural value.
To achieve sustainable development there are a range of global issues that need
collective responsibility. These include:
o A reduction in political tension within and between countries.
o Provision of adequate food, shelter, clean water, fuel, health care for all people
which will reduce exploitation of ecosystems.
o Access to education and training.
o Initiatives to curb population growth.
Monitoring the progress made in addressing global issues provides an indicator to the
extent to which ESD is being achieved.
Indicators of sustainability include:
o Conservation of scarce resources
o Species diversity
o Prevalence of pests
o Ability of the ecosystem to recover from disturbance
ii.
Minimising Human Impacts on Ecosystems
 People can implement a range of strategies to minimize environmental impact and to
maximise ecosystems. They are measured against ESD and include exclusion, education,
restoration, rehabilitation, design and legislation.
o Exclusion – Ecosystems at risk are protected by excluding activities likely to have
an adverse impact.
o Education – Provides opportunity to inform people about an ecosystem, its
needs, problems and ways people can minimize their impact.
 Techniques used to address various types of degraded ecosystems include:
o No Action – because restoration is too expensive, previous attempts have failed.
o Restoration – of an area to its original species composition by a program of
introduction.
o Rehabilitation – of some ecosystem functions and some original species.
o Replacement – of a degraded ecosystem with another productive ecosystem.
o Design – when it is impractical to remove the source of stress, artificial ways must
be planned to minimize impacts of stress factor.
o Legislation – policies applying to various ecosystems.
ii.
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Traditional Management
Traditional indigenous cultures generally have a much closer affinity with the biophysical
environment.
Their attitudes emphasise respect and coexistence.
They believe that they have a responsibility to protect and nurture the land for the
benefit of future generations.
They see themselves as custodians of the land. As such the philosophy that best reflects
them is that of stewardship.
[30]
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Ecosystems at Risk
The goals and objectives of their ecosystem management focus on:
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i.
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Collection of food.
Provision of shelter with respect for the Earth.
Respect for the Earth, its fragile nature and the interdependent relationship between
people and the environment.
Self-sufficiency.
Manipulation of Ecosystems
They often manipulated and managed ecosystems.
Aboriginal Australians built artificial dikes, dug trenches and dammed rivers and used
firestick farming.
Whilst these practices did not reduce the resilience of ecosystems in some cases they did
have long term impacts.
o Sustained burning of the bush caused a modification of Australian vegetation.
o Aboriginals may have contributed to the extinction of some megafauna.
Major degradation has been caused by large scale farming, mining and industrial and
urban land uses.
ii.
Long Term Management Practices
 Planting of yams back into the holes they came from for regeneration.
 Resettled bee hives to start new ones.
 Dug pits which filled with water providing breeding places for frogs.
Other Strategies of Management Included:
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Restriction of species caught.
Closed seasons.
Taboos.
Designated areas for individuals and groups.
Leadership according to age, ecologically sound practices to be handed down from one
generation to another.
Limits to population growth.
Sustainable methods of hunting
Traditional societies are generally familiar with the cycles and processes of the ecosystem
in which they are living.
From tribe to tribe different methods of hunting, gathering, farming and food production
highlights that Aboriginals did recognise the unique characteristics of each environment.
The intricate knowledge of ecosystems is passed down.
[31]
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5. Case Study 1: Intertidal Wetlands
a. Introduction
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For many years intertidal wetlands were considered mosquito infested wastelands.
However they are in fact an integral part of marine ecosystems.
They have a vital role in the life cycles of aquatic organisms that form the basis of marine
food chains.
They sustain fisheries and an abundance of other life forms.
2/3 of the worlds fish catch begins in an intertidal wetland.
Their still waters protect both eggs and fry (younger newly hatched fish) from strong
currents and turbulence.
The dense vegetation provides some protection from predators.
Examples of intertidal wetlands include:
o Mangroves
o Salt Marshes
Intertidal wetlands are at risk from:
o Increasing coastal populations
o Being cleared for aquaculture
o Reclaimed for new land used in:
 Agriculture
 Urban landscapes
 Industrial areas
o Being used as landfill sites
b. Spatial Patterns and Dimensions
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Intertidal wetlands develop in coastal areas subject to periodic inundation (flooding)
by salty water
They are the breeding grounds and habitats for a variety of life and also protect the
quality of coastal waters by diluting, filtering and settling sediments, excess nutrients
and pollutants.
Location
Intertidal wetlands are found in coastal areas of tropical regions where:
o Air temperature
o Wave action
o Salinity levels and
o Sediment movements
Are moderated by the locational features of the estuarine environment.
They exist between 32° North and 38 North and 38° South of the Equator.
ii.
Altitude
 They exist within the limits of the tidal range.
iii.
Size, Shape and Continuity
 The area covered by intertidal wetlands is determined by the limits of the tidal range and,
increasingly, by human obstructions and imposed restrictions.
HSC
[32]
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In wetlands the ATMOSPHERE INTERACTS
WITH other spheres for example:
-
The hydrosphere contributes high
humidity levels
-
The lithosphere (soil) contributes to gases
eg nitrogen
-
The biosphere contributes to bacteria
which are essential to the creation of
hydrogen sulphide gas in the soils
Intertidal Wetlands
In wetlands the HYDROSPHERE INTERACTS
WITH other spheres for example:
c. Biophysical Interactions
-
HYDROSPHERE
In wetlands the LITHOSPHERE INTERACTS
WITH other spheres for example:
-
-
The atmosphere’s contribution of
rainfall, which can alter the salinity level
of the wetlands soil.
The hydrosphere’s contribution to soil
moisture, especially in the mangroves
where it is necessary for plant growth
The biosphere’s organisms, such as
mangrove air-breathing snails, which
recycle nutrients.
HSC
The atmosphere’s contribution of gases
that are found in water, especially high
dissolved oxygen levels.
The lithosphere’s soil movements, which
high turbidity present in the water
coming into the wetland.
The biosphere’s organisms, such as
mangrove air-breathing snails, which
recycle nutrients.
-
ATMOSPHERE
-
-
In wetlands the BIOSPHERE INTERACTS WITH
other spheres for example:
LITHOSPHERE
BIOSPHERE
-
-
-
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The atmosphere’s contribution to the
climatic conditions required to support
intertidal wetlands.
They hydrosphere’s contribution to the
slightly alkaline conditions necessary for
some plants and animals.
The lithosphere’s waterlogged
characteristics, which are necessary for
the distinctive flora and fauna of the
intertidal wetlands.
Geography
Ecosystems at Risk
CHARACTERISTICS OF INTERTIDAL WETLANDS ACCORDING TO THE
BIOPHYSICAL ENVIRONMENT
Atmosphere
Microclimate: air temperature lower in mangroves, and higher in salt marshes, than in surrounding
areas.
•Minimal wind movement in mangroves; greater in salt marshes.
•Humidity is generally high
•Gases: hydrogen sulphide asnd nitrogen created.
Hydrosphere
Water brackish; salinity levels vary with tides and floods.
•Water temperature around 5˚ lower than air temperature.
•Phosphates higher than in olther water bodies.
•Water movement slowed by vegetation.
Lithosphere
Small soil particle size.
•Soil type dependent on region but often a clay mix.
•Soil profile, particularly in mangroves, divided into a small aerobic soil player and large anaerobic soil layer.
•Composition of soil largely organic.
•pH levels acidic in mangroves.
Biosphere
High fauna diversity; mostly visitors from other sites
•Low flora diversity, highly adapted to the conditions.
HSC
[34]
Geography
Ecosystems at Risk
Any examination of biophysical interactions affecting intertidal wetlands needs to take into account :
1. Dynamics of weather and climate
2. The geomorphic, hydrological and biogeographical processes
3. How the ecosystem adjusts to stress (d.)
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Precipitation in particular affects
the height of the water table
- Proximity of fresh water
- Soil salinity
- Photosynthesis
- Respiration
- Growth rates
- Transpiration
The stress of high rfall ->
- Rejuvenation
- Recolonisation
- Spread of wetlands
Rainfall variations also affects
migratory and sedentary terrestrial
fauna in the wetlands
HSC
Biogeographical
Processes
Relate to the
distribution of plants
and animals and e/s
DYNAMICS OF WEATHER AND
CLIMATE
Wetland distribution is largely determined
by temperature and rainfall.
Geomorphological processes
include: erosional and depositional
processes and weathering.
They modify surface material and
landforms
GEOMORPHOLOGICAL AND HYDROLOGICAL PROCESSES
Rising Sea Level
Rise of sea level after
the last ice age affected
nature and the shape
and position of
coastlines. The rivers,
inlets, estuaries of NSW
are a product of this e.g.
Sydney Harbour was
once just a valley.
In some cases previous
conditions have more
effect on plant
distribution than the
current.
E.g. Mangrove species in
North Eastern Australia
are linked to the
inundation of land
bridges to South East
Asia.
Weathering
The intertidal
wetland is where
large amounts of
weathered
material
accumulate.
Grey mangroves
produce organic
material (around
600 tonnes per
year) and all
mangroves
transfer the
organic matter the
soil where it
provides valuable
nutrients and
provides a buffer
against stress
events.
Erosion
Intertidal wetlands are
sheltered by
embayment’s that
characterise them to
accumulation of
sediment rather than
erosion.
Wetlands are designed
to absorb flood water to
reduce erosion.
Erosive power of a
storm may overwhelm
the protective capacity
of the vegetation.
The saline nature means
the bondage of soil
particles are vulnerable
to breakage which leads
to erosion from physical
pressure.
[35]
Transport & Deposition
Given the hydrology of river
catchments it is not surprising that the
sediment deposited in coastal
wetlands tends to be very fine.
Over the length of the river system the
speed and strength of flowing water
has sorted the sediment.
Often only the finest sediment makes
it to the estuarine environment. The
deposition of sediment in the
intertidal wetlands ultimately results
in the creation of new land.
The deposition of alluvial material may
be accompanied by the accumulation
of toxic pollutants which become
trapped in the sediment. Any
disturbance to the soil profile can
result in the release of these
pollutants.
Soil
Formation
Type of soil
reflects the
parent material,
topography,
climate and
vegetation.
Intertidal soils
are usually:
grey, poorly
drained, rich in
organic matter.
Soils are
constantly
shifting due to
water
movements.
Geography
Ecosystems at Risk
d. Adjustments to Natural Stress and the Nature and Rate of Change
Affecting the Ecosystem Function
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i.
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Stress can be defined as any environmental influence that causes an environmental
change,
The intertidal wetlands provide a good example of how an ecosystem responds to stress.
In the intertidal wetland ecosystem, natural stress includes, but is not limited to salinity
and tidal movements.
Salinity
Intertidal wetlands are located in coastal estuaries (where rivers meet the sea).
They receive both fresh water (from rivers) and salt water (from the ocean).
They therefore must be able to survive:
o Salt water at high tide.
o Fresh water at low tide.
o Brackish water at other times.
The saline water is a very difficult condition for plants to survive in.
Plants in intertidal wetlands have many adaptations that help them survive in saline
conditions e.g. the many adaptations of mangrove plants.
1. Mangroves
Though quite resilient, the grey mangrove is vulnerable to the changes in salinity that occurs
through human impacts e.g. altered drainage patterns that change the ratio of salt to fresh
water.
2. Salt Marshes
The plants of the salt marsh must be able to survive a range of salinity levels in both the soil
and water. Plants on lower slopes must be able to cope with being inundated with salt water
during high tides.
Glasswart (sarcocornia) is a plant that dominates this zone. It accumulates both salt and
water to keep the internal ratio low. While this adaptation allows it to cope with salty
conditions, it also makes it vulnerable to pollution, as it absorbs pollution dissolved in the
water.
ii.
Tidal Movements
 Intertidal wetlands are an example of an ecosystem that has stress-dependent organisms
and processes.
 This means that they rely on changes to stimulate biological processes.
 For example: As the tide recedes, organic material transported from the catchment area
is deposited on the roots of the vegetation and floor of the mangrove forest. This organic
material is used by crabs, snails and scavengers, which forms the basis of the detritus
food chain.
 The pneumatophores (aerial roots) of mangroves can exist under high tidal water for a
short time using gases (oxygen) stored in the roots of the tissue.
HSC
[36]
Geography
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Ecosystems at Risk
If the magnitude or frequency of inundation is changed and the roots are submerged for
too long, the mangrove tree can be pushed beyond its threshold limit.
Likewise, if substances such as oil cover the pneumatophores, their ability to absorb air
will suffer.
Intertidal wetlands have features of both aquatic and terrestrial ecosystems.
The intensity and duration of the stress is what is important when assessing its impact on
the ecosystem.
The location of intertidal wetlands means that even healthy ecosystems are vulnerable to
changes in the catchment area.
e. Human Impacts on Wetlands
i.
Atmosphere
Human modification of the atmosphere in the intertidal wetlands includes the changing of wind
patterns caused by the inappropriate location and design of buildings and the construction of
walkways within the wetlands.
The atmosphere in an intertidal wetland interacts with all three other spheres. These interactions
are:
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Hydrosphere – high humidity levels, which are affected by alteration of water flows
Lithosphere – Hydrogen sulphide produced by the waterlogged soils which produced the
rotten egg smell
Biosphere – contributes gases, especially oxygen
ii.
Hydrosphere
The straightened and mainly concrete lined storm water channel of Powells Creek is an example
of the way in which the levels of dissolved oxygen can be altered by modifications to the
hydrosphere. Water loses dissolved oxygen when it absorbs heat from the concrete walls and
base of the channel.
Industrial land uses can increase turbitiy and oil spills are a constant threat. Extensively modified
systems are unlikely to transport natural levels of organic material into intertidal wetlands, which
can increase concentrations of phosphates from detergents and garden fertilisers.
iii.
Lithosphere
The construction of bund walls can change the hydrology of a site by reducing and redirecting
the flow of water. The reduction in flow can affect soil moisture in the mangroves. This has the
potential to elevate levels of acid sulphate, damaging the health of the mangroves and adversely
affecting the decomposer organisms that recycle minerals essential to the functioning of
ecosystems.
iv.
Biosphere
The atmospheric gases necessary for plant and animal growth may be altered by pollution.
Interactions between the hydrosphere and biosphere are better understood. The widespread
death of marine organisms within these wetlands has been associated with the dumping of toxic
chemicals in the catchments waterways.
HSC
[37]
Geography
Ecosystems at Risk
The alteration of the lithosphere, especially the construction of rock and dirt bund walls, not only
alters the pattern of tidal flow but also introduces weeds into the intertidal wetland ecosystem.
v.
Human Modifications of Intertidal Wetland Ecosystems
The use if intertidal wetlands ecosystems by humans can be described by degrees of modification
to natural vegetation.
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Removal: Areas of intertidal wetlands have been cleared to accommodate residential and
industrial land uses, transport facilities and waste-disposal sites.
Replacement: Areas of intertidal vegetation have been replaced with a managed system
of pasture.
Utilisation: Salt marshes were modified and exploited as salt pans in the early 1800s, and
for recreation in contemporary times.
Conservation: The remnant natural vegetation of the intertidal wetland ecosystem has
been preserved for conservation and scientific purposes. The deliberate modification of
natural processes has been minimised, but there may be indirect impacts from the land
use activities on adjacent or nearby sites.
Known human disturbances to the energy and nutrient cycles of the intertidal wetland include
the introduction of feral animals, the impact of chemicals and altered soil pH on the organisms
responsible for nitrogen fixing and recycling as well as the strengthening of the bonds between
soil particles.
vi.
Positive Impacts
Impact
Explanation
Exclusion
Those responsible for the management of wetland areas often facilitate public
access to a small, designated area while restricting access to other areas. This can
be through the provision of defined walkways and boardwalks.
Education In the past, intertidal wetlands were often regarded as smelly, mosquito ridden
wastelands. Education campaigns have helped to change public perceptions and
engender public support for the protection of these highly productive yet
threatened ecosystems. Education programs need to embrace a total catchment
management approach due to the location of wetlands in the lower regions of
catchments.
Action
Too little is known about the intertidal wetland ecosystem to successfully reinstate
all natural conditions. Management can focus on rehabilitation of sites and removal
of human-induced stress factors. These can help the ecosystem recover through its
own reproduction capabilities.
Design
Design interventions have proved successful in minimising sources of
environmental stress. Hydrologists, for example, have designed structures that
maximise tidal flows and maintain the health of the ecosystem. Pollution booms
have been designed to gloat on top of the water, where oil accumulates, so that
they do not interfere with the free flow of flora, fauna or soil within the water.
Legislation Legislation and regulation is used to protect intertidal wetlands. The most
significant of these are the Ramsar Convention; the Asia-Pacific regionally based
Japanese Australian Migratory Bird Agreement (JAMBA) and Chinese Australian
Migratory Bird Agreement (CAMBA); the nationally based Wetlands Policy of the
Commonwealth Government of Australia; and the state-based New South Wales
Wetlands Management Policy and Environmental Planning Policy 14 on Coastal
HSC
[38]
Geography
Ecosystems at Risk
Wetlands.
vii.
Negative Impacts
Impact
Explanation
River
River regulation and water diversion is the principal threat to wetlands in NSW.
Regulation
Dams, weirs and other diversion structures have been constructed on rivers and
and Water
the timing and volume of river flows have been altered. Many NSW wetlands are
Diversion
receiving decreased flows of water from rivers and overland runoff. Some
wetlands have been completely isolated from the river systems that once
nourished them. River regulation and water diversion affect the plants and animals,
hydrology, water quality and geomorphology.
Development Direct impacts on wetlands from development include clearing of wetlands for
and
urbanisation and other coastal development, clearing of wetlands for agriculture
Catchment
and changes in the hydrology and nutrient levels of wetlands. Changes in a
Disturbance
catchments land use can have profound effects on the functioning of wetlands.
Downstream of development there can be increases in the loads of nutrients and
suspended solids in waterways, leading to blue-green algal blooms which have
profound effects on the food chain.
Introduction
Weeds and pest animals compete with native wetlands species and habitats and
of Weeds and may replace them altogether. Common weeds and pests in coastal wetlands
Pest Animals include lantana, salvinia, caulerpa and pigs, which can affect water quality and
destroy habitats through digging and wallowing. Weeds and pests in inland
wetlands include the introduced plant lippie, pigs and European carp, which can
displace native fish in rivers and wetlands.
Climate
Climate change will affect wetlands and the rivers that supply water to them
Change
through changes to rainfall and increased temperature and evaporation. This will
reduce surface and groundwater supply and put increased pressure on plants and
animals that rely on these sources of water. Extraction of water and modification
to flow regimes has a considerable effect on biodiversity and combined with
climate change the impacts could be much greater. Human induced climate change
has been listed as a key threatening process under the Threatened Species
Conservation Act 1995.
viii.
1.
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
Why Protect the Intertidal Wetland Ecosystem?
Maintaining Genetic Diversity
The genetic diversity of intertidal wetlands should be valued and protected.
Many of the organisms of the intertidal wetland are yet to be identified and recorded.
The animals that use the wetlands are for the most part visitors.
This means that wetland ecosystems are inextricably linked to many other ecosystems.
2. Utility Value
 The wetlands have been used in Australia’s past for the production of wood for
construction and heating purposes and the harvesting of marine life.
 Once these resources have been used, the land is often reclaimed for agricultural,
industrial and residential purposes.
HSC
[39]
Geography
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Ecosystems at Risk
The land of the intertidal wetlands of Homebush Bay has been used in the past for salt
extraction, chemical industries, public utilities such as radio towers and gas lines and as a
rubbish dump.
3. Intrinsic Value
 The intrinsic value of wetlands has often been ignored in the human oriented exploration
of these ecosystems for economic returns.
 The decrease in fish stocks and increase in harmful algal blooms have forced our society
to appreciate the unique characteristics of these ecosystems and develop an appreciation
of their intrinsic worth.
 Today wetlands are being protected for their intrinsic value and uses are limited to those
who do not exploit or disrupt the components of the ecosystem.
4. Heritage Values
 Natural areas, including wetlands, are an important part of our natural heritage and can
provide an insight into ways people lived in the past, especially their historical or cultural
significance to past communities.
 These also represent a legacy, to be passed on to future generations.
5. The Need to Natural Processes to Continue
 The area protected must be large enough to allow evolutionary processes to operate as
they would in nature.
 Buffer zones and proper management are required to allow natural processes to
continue.
 Not all wetlands have access to these and some are poorly maintained.
HSC
[40]
Geography
Ecosystems at Risk
General Impacts of Climate Change
IMPORTANCE OF INTERTIDAL WETLANDS
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Contribute a wide range of ecosystem services.
High animal diversity and high productivity.
Commercially important fish and crustacean species
are strongly linked to the area of mangroves and
salt marshes.
Boundary of terrestrial and marine environment and
thus are regions of high biogeochemical activity.
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Mangroves have an important role in
protecting coasts from storm and tsunami
damage.
Storms can have a large impact on
mangroves, with catastrophic destruction
being observed in the Caribbean and
Bangladesh, often with slow recovery or
none at all.
Intense storms can strongly influence
surface elevation of wetlands through
erosion, deposition and subsurface
processes which can influence rates of
recovery.
HSC
Adaptability of Intertidal Wetlands
Impacts of Human
Induced Climate
Change on Intertidal
Wetlands
Extreme Events (cyclones)

Position in the intertidal exposes them to a multitude of ocean and atmospheric climate change
drivers which leads to high vulnerability to climate change.
Extremely sensitive to sea level rise.
Too much flooding will drown mangroves, too little will reduce productivity and may be replaced
with salt marsh or cyanobacterial (blue-green) algae communities.
The strong regulation of productivity and species composition by soil salinity and humidity in tidal
wetlands also makes these ecosystems highly sensitive to changes in rainfall.
Southern mangroves are limited by low temperature and thus rises in air and sea temperatures is
likely to allow their movement even further south where they will enter salt marsh habitats.


Rainfall
Changes in rainfall will have a
major effect on tidal
wetlands. The predicted
changes in rainfall with
climate change are complex.
Increases in intensity are
expected, which is likely to
influence erosion and other
processes in catchments
which will affect intertidal
wetlands.
Despite their vulnerability to climate change the
adaptive capacity of tidal wetlands to climate change
is also high.
We also know that mangrove forests can grow
rapidly on newly deposited sediments and that
recovery from storms and other disturbances can be
rapid.
Increasing CO2

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CO2 concentrations are expected to double
by 2080 with potentially profound impacts
on ecosystems.
Due to high sensitivity, mangrove forests
and salt marshes are likely to be susceptible
to increased CO2
Increased CO2 can affect decomposition
processes and nutrient cycling in intertidal
wetlands.
[41]
Sea Level Rise
Mangroves, salt marshes
and salt flats are within the
intertidal zone of low
energy coasts and are thus
highly sensitive to rising sea
levels.
Geography
Ecosystems at Risk
i. Traditional and Contemporary Management Practices
i.
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Traditional Management Strategies
Indigenous Australians managed wetlands in ways that acknowledged the unique nature
of the ecosystem.
They used the wetlands as a source of food and, in doing so, took only what was needed
to meet their immediate needs.
The traditional objectives for the management of wetland areas were built around the
use of wetland resources for food, shelter and tools.
Grey Mangrove wood, for example, was used to make shields, shells were made into
fishing hooks and marine animals were used for food.
In the case of Towra Point wetlands, many aspects of traditional Aboriginal management
have been lost.
There is little/no documentation of sites sacred to the local Aboriginal people such as the
Darug.
iii.
Contemporary Management
 There are many steps being taken today to manage coastal ecosystems.
 A growing awareness of the importance as an ecosystem has helped to promote this.
 Effective Management requires that some of the following guidelines need to be
achieved:
1. Management Goals and Objectives Need to be Identified
2. Determination of the Boundaries of the Unit Under Management
 This can be difficult especially when the nature and movement of some
integral components are considered such as water.
 The wider the boundary the greater the control, but the greater the
demand on economic and human resources.
 It may entail government at all levels.
3. Develop and Implement Management Plans
 Wetlands are dynamic and so are contemporary attitudes.
 Today modern society demands the protection and management of
intertidal wetlands.
 Plans must be realistic and flexible.
 Plans must accommodate scientific and technological advances, changing
social and political attitudes.
 Plans must be consistent with Australia’s international obligations as
defined in various international treaties and conventions.
4. Select and Use Ecosystem Management Tools and Technologies
 Contemporary approaches have benefited from a growing body of
international research.
 This knowledge can be applied to particular wetlands and ecosystems.
5. Clearly Identify Ecological Constrains or Limitations
 We still have a fairly limited knowledge of intertidal wetlands.
HSC
[42]
Geography
Ecosystems at Risk

This is not surprising given that it is only in recent years that modern
society has become more concerned for intertidal wetlands.
 Today too little is known of the ecological constraints and limitations of
intertidal wetlands.
 Acquisition of this knowledge is now a high priority.
6. The Collection, Analysis and Use of Economic, Social and Ecological Information
 This informs the decision making process.
 Information can be gathered by university research projects, other
government institutions and consultants.
7. Be Ecologically Sustainable
 To be effective management should conform to ecologically sustainable
ideals. In turn consideration needs to be given to:
i.
Sustainable under what conditions
ii.
Short and long term considerations
iii.
Precautionary approaches – don’t postpone measures that
prevent damage due to scientific uncertainty.
iv.
Acknoqledge the global dimension – this can be enhanced by
sharing data internationally
v.
Involve the community – include key stakeholders in the
management.
vi.
Education programs – from schools to universities to the general
public.
vii.
Environment Impact Assessment – a legislative framework that
assesses the potential impact on the wetlands.
j. Mangroves
A mangrove is a salt-tolerant plant or plant community that grows between the land and the sea
where the mud is regularly covered and uncovered by the ebb and flow of the tide.
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HSC
The greatest species diversity occurs in tropical and subtropical regions, nut they can
grow further south.
They grow successfully on mud flats, which is a difficult environment because of the high
salinity and low oxygen.
The soft sediment is a mixture of fine alluvial silt, decaying mangrove leaves, washed up
sea grass and material brought downstream by rivers.
Some species have special roots, called pneumatophores, projecting up out of the mud
to get oxygen from the air and water.
The mass of above ground roots and the soft, muddy soil make mangrove forests very
difficult for large animals (and humans) to penetrate.
Small seaweed and microscopic algae grow on the surface of the mud.
The algae, together with decaying mangrove leaves, support a rich and diverse animal
community.
Crabs feed on the organic particles in the mud; oysters attach themselves to mangrove
roots and filter small organisms from the water; and wood boring molluscs bore holes
into fallen logs and feed on the wood.
[43]
Geography

Ecosystems at Risk
The richest mangrove communities occur in areas where the water temperature is
greater than 24°C in the warmest month and where annual rainfall exceeds 1250mm.
Distribution of Mangrove Wetlands in Asia
and Southeast Asia
60
40
20
Area (100000ha)
0
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HSC
They also need protection from high energy waves, which can erode the shore and
prevent seedlings from becoming established.
Different mangrove species have different requirements.
Some are more tolerant than others.
Other factors that affect their distribution include:
o Wave energy
o Soil Oxygen levels
o Drainage
o Differing nutrient levels
Where one species finds its preferred conditions – or at least those which it is able to
tolerate better than other plants – it tends to become dominant.
Worldwide there are 181000km2 of mangroves, approximately 43% of which are located in
just four countries:
o Indonesia
o Brazil
o Australia
o Nigeria
[44]
Geography
Ecosystems at Risk
Global Distribution of Mangrove Wetlands
East Africa and the Middle East
Australasia
West Africa
The Americas
South and Southeast Asia
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Management decisions taken in these countries will have a significant effect on the global
status of mangrove ecosystems in the future.
Over million of years, mangrove species have developed a range of adaptations that
allow them to cope with constantly changing environmental conditions, high levels of
salinity and a lack of oxygen.
In addition to the ebb and flow of the tide, which inundates the mangrove community
with salty water, the mangroves must cope with floods of fresh water, especially during
periods of high rainfall.
Apart from altering the salinity levels, these fluctuations can alter water temperature.
Being salt tolerant allows mangroves to dominate in a saline environment free of
competition.
The characteristics that enable mangroves to tolerate high levels of salinity include:
The Ability to
Secrete Salt
The Ability to
Exclude Salts
The Ability to Store
or Concentrate Salt
HSC
•This occurs through special glands, which are usually found on the leaves,
where tiny white flecks of salt are frequently visible.
•This is achieved by root based cells that prevent the larger salt ions from
entering, and take in the smaller water molecules.
•Some species can exclude 90% of salt in this way.
•This is usually done in the bark or older leaves, which are an 'expendable'
part of the mangrove plant.
•Eventually, the leaves and bark fall off, taking the excess salt with them
[45]
Geography
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Ecosystems at Risk
Some mangrove species use only one of these methods, but many use two or more.
In addition, mangroves have a number of features that help to minimize water loss from
the plant.
These include thick, waxy leaves or dense hairs that reduce transpiration.
Most water loss occurs through the stomata (pores in the leaves).
These are indented below the leaf surface where they are protected from drying winds.
The leaves of many species are able to store water in fleshy internal tissue.
Mangroves have adapted to the anoxic (oxygen deficient) soil conditions by developing
ways to obtain oxygen necessary for root metabolism which include:
Pneumatophores
•These are special types of root which grow upwards from the main root system to
absorb oxygen from the air at low tide via special tissue called lenticels.
•When the roots are submerged in water, the pressure within the tissue falls as the
stored oxygen is used by the plant.
•As the root is exposed at low tide, more air is drawn in through the lenticels.
Stilt or Prop Roots
•These are another type of aerial root which grow from the trunk and lower
branches of the mangrove.
•These lenticel covered roots enable the mangrove to absorb oxygen, with the
added bonus of supporting the mangrove in unstable sediments.
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HSC
There is always a danger that the breathing roots of the mangroves may become covered
as sediments accumulate.
To avoid being buried, the pneumatophores grow vertically.
Mangroves have also developed specialised forms of reproduction.
In common with many terrestrial plants, mangroves reproduce by producing flowers and
relying on pollination by bees and insects.
Once pollinated, however, the seed remains on the parent plant where it germinates and
grows stems and roots before being dislodged.
Once in the water they travel horizontally and on reaching the brackish water they turn
vertically, making it easier for them to lodge in the mud.
Once lodged in the mud they quickly produce additional roots and begin to grow.
This gives the young tree a better chance of not being swept away by the ongoing tide.
The production of live seedlings (known as vivipary) is very rare in plants other than
mangroves.
Other species of wetland plant release their seed inside a capsule.
The capsule floats until it is deposited in a suitable location, germinates and sends out
roots.
[46]
Geography
Ecosystems at Risk
k. Salt Marshes
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Salt marshes are coastal wetlands that are flooded and drained by salt water brought in
by the tides.
Along intertidal shores in middle and high latitudes throughout the world, salt marshes
replace mangrove swamps as the dominant type of coastal wetland.
They are found on all continents other than Antarctica.
A salt marsh is an ecosystem, that is integrally part of a bigger system, that of estuarine
or intertidal wetlands.
The herbs, grasses, reeds and low shrubs in salt marshes are terrestrial in origin and are
essential to the stability of the salt marsh in trapping and binding sediments.
Salt marshes play a large role in the aquatic food web and the exporting of nutrients to
coastal waters.
Salt marshes are inhabited by oysters, crabs and prawns.
They also contain a large number of birds that stop over in the course of migration.
The distribution of salt marsh is within a vegetation zonation which depends on elevation
and hydrology.
In Australia, when salt marshes and mangroves coexist, saltmarshes are typically found at
higher elevations where they are inundated less frequently than mangroves.
When seagrass beds are found adjacent to salt marshes and mangroves, many material
links and shared plant and animal communities can exist.
The most common site for a salt marsh, after estuaries and lagoons, is the sheltered side
of a sand spit.
As plants colonise the area, they slow down the flow of water and cause additional silt to
accumulate.
The soil in salt marshes is often composed of deep mud and peat.
Peat is made of decomposing plant matter that is often several feet thick.
Peat is waterlogged, root-filled and very spongy.
Because salt marshes are frequently submerged by the tides and contain a lot of
decomposing plant material, oxygen levels in the peat can be extremely low.
The sediments contain numerous bacteria which produce the sulfurous rotten egg smell
that is often associated with marshes and mud flats.
Salt marshes are extremely productive ecosystems, but they are not very diverse.
The inner marsh zone, which is flooded most of the time, is composed almost entirely of
sedge-type plants.
Gradually, however, the grass-dominated community of plants and animals is replaced by
more complex communities that are finely tuned to the variations in salinity, alternate
drying and submergence, and extreme daily and seasonal temperature variations.
Diversity within the marsh tends to increase with distance from the zone of inundation.
Only a small percentage of the salt marsh vegetation is eaten by animals. The rest dies,
decays and becomes suspended as fine particles (detritus) in the water.
Most of the nutrients produced are recycled within the marsh.
Adaptations
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Ecosystems at Risk
Oxygen in the water in the soil is used up, often by the activity of decomposers like
bacteria.
Marsh plants have air spaces in their stems which allow oxygen to move from the leaves
to the roots.
They generally have thick roots with a corky layer and without root hairs.
Other marsh plants are able to survive in low oxygen conditions by relying on anaerobic
respiration (respiration that does not use oxygen).
6. Towra Point Nature Reserve
a. Spatial Patterns and Dimensions
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Towra point is located between 151°8’0” E, 34°1’40” S and 151°12’30” E, 31°0’0” S
Towra Point Nature Reserve is located on the southern shore of Botany Bay about 16
kilometres from the Sydney CBD.
Towra Point Nature Reserve covers an area of 603.7 hectares and the area of the Ramsar
site is 386.5 hectares.
b. Biophysical Interactions
HSC
[48]
Geography
Ecosystems at Risk
The above map shows the distribution of mangroves, salt marshes, terrestrial vegetation,
beaches, sand spits and freshwater wetlands at Towra Point Nature Reserve.
i.
Mangroves
Two species of mangrove can be found at Towra Point Nature Reserve:
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The grey mangrove (Avicennia marina) which has a large number of pneumatophores
allowing it to breathe.
The river mangrove (Aegiceras corniculatum) which, along with the grey mangrove, has
the ability to excrete salt out of its leaves and change salt water into fresh.
The leaf litter provided by the mangroves creates detritus which feeds the smaller organisms in
the ecosystem, which are in turn eaten by increasingly larger organisms.
Mangroves in Towra Point Nature Reserve perform a number of important functions:
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Reduce water pollution.
Provide shelter, refuge and food for many forms of wildlife.
Prevent bank erosion.
Act as nurseries for fish species.
A number of forms of wildlife can be found in the mangroves of Towra Point Nature Reserve:
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Shore crabs (which are abundant in the mangroves and live in complex networks of
tunnels buried in the sand)
Birds (such as herons, egrets, spoonbills and ibises)
ii.
Salt Marshes
There are over 10 species of salt marsh plant in Towra Point Nature Reserve, existing in areas that
are subjected to both tidal and freshwater inundation. Glasswort is the most common of these
plants. The terrestrial boundaries of the salt marshes are covered in the brackish water reed
Juncus krausii.
Salt marshes appear as open plains dotted with the occasional mangrove. The tidal inundation
and rainfall help to form standing pools of water. Some areas are inundated regularly whilst
others are only inundated occasionally
Salt marshes cover 100 hectares of Towra Point Nature Reserve and are the last remaining in the
Sydney region.
iii.
Rainforests
Rainforests in Towra Point Nature Reserve are home to a number of plant species including:
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Magenta brush cherry (Syzygium paniculatum), a vulnerable species found in small
groves of littoral (relating to or situated on the shore) rainforest.
Lilli Pilli (Acmena smithii) which supplies food to a number of birds such as rosellas and
lorikeets.
Ferns can be found in the understorey layer.
An invasion of lantana is making it a struggle for seedlings to grow.
[49]
Geography
Ecosystems at Risk
iv.
Sand/Mud Flats
The sand flats are of particular importance for a number of species of waterfowl and migratory
birds and have large numbers of molluscs, polychaetes (segmented worms) and small
crustaceans.
The mud flats of Quibray Bay are also popular as a feeding area for birds.
v.
Freshwater Wetlands
The Reserve has a number of freshwater wetlands and ponds including Weedy Pond and Towra
Lagoon.
Weedy Pond is a small attractive pond which is fringed by casuarinas and often remains dry for
long periods, filling after periods of heavy rain. Weedy Pond is also surrounded by a pocket of
littoral (relating to or situated on the shore) rainforest.
Towra Lagoon is the largest fresh water wetland in the Reserve and once supported three
species of dabbling duck and the endangered green and golden bell frog. However, due to
saltwater incursions from Botany Bay, these birds are rarely seen in the lagoon. The eastern-long
necked tortoise was also an inhabitant of this lagoon but is intolerant of any salt and has also
disappeared (along with the frog).
vi.
Seagrasses
The waters around Towra Point support meadows of seagrasses predominantly:
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Eelgrass (Zostera)
Strap weed (Posidonia)
Paddle weed (Halophila).
Seagrasses grow below the low tide level in the sheltered shallow waters of estuaries and are
flowering plants that generally prefer soft sediments like sand or mud. Seagrasses are restricted
to waters no deeper than two metres due to their need for light.
Seagrasses are important as habitats for small aquatic animals and also provide feeding and
nursery grounds for fish and give shelter to juvenile and small adult fish and invertebrates such as
prawns and crabs. Seagrasses provide nutrients in the form of detritus, which contributes to the
nutrient cycling of Botany Bay.
vii.
Forests
1. Casuarina Forest
Another plant community found at Towra Point Nature Reserve is the Swamp Oak forest which is
characterised by tall Casuarina glauca (swamp she-oak) trees as well as a species of Melaleuca
ericifolia (swamp paperbark). Casuarinas have fruits which attract seed-eating parrots. The
casuarina forest is the first above the influence of the tide.
2. Dune Sclerophyll Woodlands
These forests occur on the shoreline and are characterised by Teatree and Coast Banksia. The
woodlands are inhabited by a number of weeds which inhibit the regrowth of these forests.
HSC
[50]
Geography
Ecosystems at Risk
viii.
Importance
Towra Point Nature Reserve was listed as a Ramsar site under the Ramsar Convention in 1984 as
it meets a number of the nomination criteria:
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Towra Point Nature Reserve supports three threatened species – grey headed flying fox,
magenta Lilli Pilli and green and golden bell frog.
Towra Point Nature Reserve is an important area for maintaining the biodiversity of the
Sydney region. It is also one of the most important migratory bird sites in NSW and is a
breeding ground for the endangered little tern
Towra Point Nature Reserve provides critical roosting and feeding habitat for migratory
shorebirds and supports the little tern and a number of species of juvenile species.
Towra Point Nature Reserve is a significant habitat and food source for at least 60 species
of fish.
Towra Point Nature Reserve contains the last remaining tidal wetlands in the Sydney region as
most of the wetlands that existed prior to European settlement have been reclaimed for housing,
recreation and industry.
Towra Point Nature Reserve holds around half of Sydney’s remaining mangroves and most of the
remaining salt marshes.
c. Human Impacts
i.
Erosion
Dredging in Botany Bay has increased wave energy and accelerated erosion along sections of
Towra Beach. Offshore breakwalls and sand nourishment have been suggested as solutions. The
water in Towra Lagoon has become brackish.
ii.
Weeds
The vegetation at Towra Point Nature Reserve has been subjected to clearing and burning for
agricultural and grazing reasons since the 1860’s, leading to extensive invasion by weeds
including lantana, bitou bush and African boxthorn.
iii.
Horse Riding
Horse riding leads to trampling and disturbance of soil and vegetation and the spread of weeds,
as well as causing disturbances to birds. A major management problem is that the horse stables
are located close to the entrance to the Reserve.
iv.
Boating
Boat chains, anchors and jet skis cause damage to seagrasses and disturb wading birds.
v.
Feral Animals
Feral animals, such as foxes, pose a threat to the breeding sites of the Little Tern and all other
fauna found on the reserve. The best Little Tern breeding site on Little Tern Spit may become
connected to the mainland, causing difficulties with the control of feral animals.
HSC
[51]
Geography
Ecosystems at Risk
vi.
Fragmentation
Not all of the Towra Point Nature Reserve is owned or managed by the National Parks and
Wildlife Service. A number of private stakeholders including developers own portions of the
Reserve, as can be seen on the map below (privately owned areas are yellow).
The disjointed land ownership creates problems when horses and trail bike riders gain easy
access to the Nature Reserve and other areas of high conservation significance through nonNPWS land.
vii.
Development and Construction
Development and erosion have caused significant losses to seagrasses and erosion has been
attributed to nearby dredging. Dredging for construction has led to considerable erosion.
d. Traditional and Contemporary Management Strategies
i.
Traditional Management
Towra Point Nature Reserve was of great importance to the Aboriginal Communities who lived in
the surrounding areas. The area was rich in seafood, providing for the needs of the local people
and was also a source of fresh water.
Three middens remain today and show that the local Dharawal people used the area for its
resources.
Captain Cook mapped the Botany Bay area in 1770 and also mapped Towra Lagoon, making it a
key historical site in the reserve.
Towra Point Nature Reserve was used as land for sheep grazing by Thomas Holt, an early
European settler, and was also the home of the first oyster farm. Early settlers copied the
Aboriginal peoples use of plants and also used the area for food.
Industrial land uses adjacent to Towra Point Nature Reserve remove resources from the wetland,
increase turbidity and toxins in the water supplied to mangroves and changes in nutrient and
energy cycles and the food chain.
Adjacent land uses include:
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Airport
Crude oil importing port
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Oil refinery
Container port
These land uses can threaten the ecological character of Towra Point Nature Reserve.
ii.
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HSC
Contemporary Management
As can be seen on the map in the above section, a large portion of Towra Point Nature
Reserve is privately owned and managed. The rest is managed by the National Parks and
Wildlife Service and has been since 1982 for the purpose of conservation of wetlands and
migratory birds.
The National Parks and Wildlife Service have placed restrictions on access to minimise the
amount of damage caused by humans. Horses and dogs are not allowed in the reserve
and a permit is required before entering the reserve.
As well as nature conservation, the Reserve provides opportunities for environmental
education and scientific research and students from a number of institutions regularly
visit the reserve.
The Towra Point Aquatic Reserve is managed by NSW Fisheries. The establishment of an
Aquatic Reserve was designed to protect the highly significant marine habitats that
surround the Nature Reserve (e.g. seagrasses) by placing restrictions on fishing and
prohibiting bait gathering. More than 200 fish species have been recorded in the Aquatic
Reserve. This diversity can be attributed to the abundance of different habitats,
particularly for juvenile fish
NSW Fisheries have defined two distinct management zones within Towra Point Aquatic
Reserve. These two zones, seen on the map, are the Sanctuary Zone, and the Refuge
Zone. The Sanctuary Zone is for observation only. Disturbing, interfering with vegetation
or removing fish is not allowed in this zone. In the Refuge Zone some fishing is allowed.
[53]
Geography
Ecosystems at Risk
7. The Great Barrier Reef
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A reef is a marine ridge that is located close to the surface of oceans and seas.
It consists mainly of living coral, compacted coral skeletons and other organic material
that consolidate into limestone.
Coral reefs cover only an estimated 0.17% of the ocean floor. However their importance
cannot be underestimated:
o Reefs provide a habitat for approximately 25% of all marine species
o Coral polyps absorb carbon dioxide as part of the carbon cycle
o Reefs act as natural barriers to erosion by reducing wave energy
o Coral reefs build atolls, beaches and islands which are ecosystems
a. Spatial Patterns and Dimensions
i.
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Location and Altitude
They occupy less than 0.1% (284 300km2) of the world’s ocean surface
Though they provide a home for 25% of all marine species
Although corals exist in both temperate and tropical waters, shallow-water reefs form
only in a zone extending from 30° N to 30° S of the Equator
The optimum temperature for most coral reefs is 26-27°C and few reefs exist in waters
below 18°C
The Great Barrier Reef is in the Coral Sea, on Australia’s north-eastern coast
It stretches more than 2300 km from
o 8 S at PNG’s Fly River to
o 24°07’ S at Fraser Island, north of Bundaberg
ii.
Size
 The GBR is composed of 2900 individual reefs including:
o 750 fringing reefs attached to the mainland and offshore islands
o 2150 outer reefs
 The reefs range in size from a few 1000m2 to up to 120km2
 The GBR ecosystem also includes approximately 600 islands
 Of these, 250 continental islands and 70 coral cays are named on maps
 The Great Barrier Reef Marine Park covers an area of 348 700km2
iii.
Shape
 The GBR has many different shaped reefs within it, from narrow ribbon reefs to wide
platform reefs
iv.
Continuity
 The current Great Barrier Reef has existed for approximately 8000 years
 Around 10 000 years ago the polar ice from the most recent ice age began to melt,
causing sea levels to rise
 Coral growth responded to the rise of sea levels and as the sea rose, the reefs grew
 As the sea levels dropped, the coral died off and turned into limestone
 This formed the base for the current coral to develop on
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[54]
Geography
Ecosystems at Risk
b. Biophysical Interactions
i.
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The Role of the Atmosphere
GBR lies within Australia’s cyclone zone
Tropical cyclones have shaped the ecosystem
Cyclones damage corals as a result of large storm waves
Waves rip apart softer corals and chip hard corals
Cyclones may bury the reef system in sediment
They can also alter salinity and turbidity
Cyclones can also remove accumulated sediment and reduce the temperature of the reef
ii.
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The Role of the Lithosphere
Reefs produce solid limestone from the remains of coral polyps
Limestone is weathered and redistributed to create new landforms
Limestone allows reef systems to withstand the erosive power of waves
Sediments can create turbidity and reduce the amount of penetrating light, interrupting
the process of photosynthesis
iii.
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The Role of the Hydrosphere
Coral reefs grow best where there is high wave energy
Reefs are very effective at interfering with wave energy
Water flow tends to be towards the north for most of the year
Summer monsoonal conditions result in a reversal of this pattern
The warm, highly saline waters that flow down bring relatively high nutrient levels
iv.
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The Role of the Biosphere
More than 300 species of coral are found in the GBR
Greatest diversity in the northern section of the reef
Although predominantly rock, made of living polyps
Primitive organisms that consist of digestive sack and outer skeleton of limestone
Within the polyp live a symbiotic algae called zooxanthellae.
Mutually beneficial to each other
Zooxanthellae algae give corals their brilliant colours
Polyps reproduce to create a colony
The colony expands the reef upwards and outwards
Polyps die, limestone remains to form base for new coral
Coral release eggs in spring
Constant recycling of nutrients
Thousands of species of fish
Predators attracted by fish
Large numbers of cnidarians (invertebrates – coral and jellyfish), molluscs and
crustaceans
Echinoderms
Sea birds are important
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[55]
Geography
Ecosystems at Risk
The Environmental Requirements for Optimum Growth of Corals:
Depth of Water
Corals thrive in water 2-30
metres deep. This allows
photosyntehsis by the
zooxanthellae
Warm Water
Low Sediment Levels
20-35°C
26-27 is optimum for
limestone build up.
If corals are blanketed by
sediment they will die
High Oxygen Levels
Clear Water
Corals like areas where
water is continually
oxygenated by waves e.g.
on the outer edges of the
reef
With low nitrogen,
phosphate and ammonium.
Phosphates interfere with
skeletal development.
Constant High Salinity
They will die with
fluxtuations in salinity
HSC
[56]
Geography
v.
1.
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Ecosystems at Risk
Biogeographical Processes
Rates of Reef Growth
In the southern section of the GBR the reefs grow slowed due to the colder water
Slow growing corals often use chemical warfare against fast growing corals to ensure
their existence
Vertical zones exist:
o Some species tolerate low light conditions and are found in deeper water
o At depth growth rates are slower
2. Resilience
 The high rate of biodiversity in the Great Barrier Reef ecosystem allows the reef to cope
with significant change e.g. cyclones
 Some changes cannot be adjusted to because of the high rate of specialization in the GBR
ecosystem e.g. rise in water temperatures
 All corals are adversely affected by an increase in temperature
 Its low elasticity means it may not return to pre-stress levels for a long time
3.
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Coral Spawning
They spawn in late summer on the night after the full moon
Water temperature, light, moon cycle and tidal cycle have to be right
The annual synchronised mass spawning of corals is considered an amazing biological
event.
The polyp larvae depend on tides and currents Towra Point Nature Reserve distribute
them in favourable colonisation areas
4. Ecological Succession
 Every 15 years a cycle has developed that the Crown of Thorns starfish has a population
explosion
 This is a result of many factors:
o Increase in algae blooms because of use of fertilisers
o Collection of predators (notably the Giant Triton)
o Cyclones
 This predator when in plague proportions can wipe out entire reefs
 When not in plague proportions the Crown of Thorns promotes biodiversity and
ecological succession
c. Nature and Rate of Change Affecting the Ecosystem Functioning
i.
Natural Impacts
1.
Impact of Sea Levels on The Great Barrier Reef
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a. The Nature of Change
Reefs grow when sea levels are high and die when sea levels are so low that they are
exposed
Historically, sea levels stabilised at the present level around 6200 years ago.
[57]
Geography
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Ecosystems at Risk
The modern Great Barrier Reef started growing between 8000 and 8500 years ago over
older reef structures.
Scientists have drilled and have discovered that periods of reef growth and decline are
linked to the rise and fall of sea levels.
b. The Rate of Change
Over the past hundred years, Australian seas appear to have risen an average of 12 to 16
centimetres.
Global warming may be a cause, but earth movements can also cause rises and falls in sea
levels.
If the rate of sea level change occurs slowly in the Great Barrier Reef, its corals may be
able to keep growing to keep pace with the rising water levels.
But if the sea level changes occur rapidly in the Great Barrier Reef, its coral may not be
able to grow fast enough and there may be destruction in some areas
2. Crown-of-thorns Starfish Infestations
a. The Nature of Change
 The crown-of-thorn starfish is considered a boom or bust organism (i.e. an organism that
is either found in small numbers or plague numbers).
 The crown of thorn starfish alters the reef by eating the coral polyps.
 When it is in plague proportions it severely alters the Great Barrier Reef by damaging it
and creating conditions for other organisms to invade the reef
b. The Rate of Change
 Scientists have found that there have been periodic infestations of crown-of-thorn
starfish during the past 6000 and 8000 years.
 Therefore some see the outbreaks as a natural phenomenon.
 Some believe that the starfish help regulate the overgrowth of coral.
 However, in recent times the outbreaks have occurred more frequently.
 Some argue this is due to human induced modifications to the Great Barrier Reef
ecosystem through such things as:
o Shell collectors removing the starfish’s predators (crabs love eating the starfish)
o Sediment runoff from eroded banks caused by humans
o Excessive nutrient runoff from farms that flow into rivers and out to sea.
o Overfishing, trawlers catching many unwanted species as part of their by catch
which may remove many natural predators of the starfish when they are in their
larvae stage.
 The problem with the change of rate is that the coral in the Great Barrier Reef has low
elasticity (rate of recovery) sometimes it takes 12 to 15 years for coral to reach its pre
infestation levels.
 If reinfestation occurs within the elasticity period it could alter the Great Barrier Reef
significantly
HSC
[58]
Geography
Ecosystems at Risk
3. Tropical Cyclones
a.
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The Nature of Change
Cyclones can destroy reefs through the creation of large waves
Can increase sediment and turbidity levels
Can bury corals or remove accumulates sediment
Can decrease salinity
b. The Rate of Change
 Over 142 cyclones occurred between 1909 and 1992
 Cyclones and their effects are in effect immediately
ii. Human Impacts
1.
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HSC
Climate Change
Climate change has a number of impacts in Northern Australia:
o Increase in sea surface temperatures
o Increase in sea levels
o Change in rainfall patter
o Changes to ocean currents and circulation
o Increased El Nino events
o Increased Carbon Dioxide (CO2) levels
Ongoing climate change will have many different consequences for the Great Barrier
Reef
Climate change directly impacts:
o Fish
o Invertebrates
o Birds
o Mammals
o Aquatic and Terrestrial Plants
o Root functioning
Climate change alters sea temperature and will affect the movement of water in ocean
currents
Ocean currents act as a part of the nutrient cycle in the reef ecosystem
More dissolved CO2 results in a change in the chemical structure of the water
Sea birds are already declining
Failure of eggs to hatch has occurred in a number of rookeries of seabirds
Fish species are also in danger
Climate change will affect location, frequency and timing of nutrient upwellings
Upwelling’s are ocean currents that bring nutrients from the sea floor upwards
They attract fish and in turn attract predators such as sharks and dolphins
[59]
Geography
Ecosystems at Risk
2. Boating and Commercial Shipping
 Recreational boating is a common pastime on the reef.
 On any day of the year thousands of small craft can be observed fishing, sightseeing and
sailing up and down the length of the reef.
 While for humans those waters represent a relatively safe boating paradise the boats
have the potential to damage the reef ecosystem.
 When boats anchor, the heavy metal anchors damage the reef’s coral formations and
dredge up the sea grass beds.
 The boats are also a source of pollution through oil and fuel spills, rubbish and sewage.
Careless boat owners vent their sewerage systems while a sea, releasing raw sewage into
the water.
 When hundreds of boats do this the impact is considerable.
 The Great Barrier Reef Marine Park Authority estimates that around 6000 large
commercial ships transit through the Great Barrier Reef each year.
 These ships carry everything from grain, minerals, bulk cargo (such as cars) and oil.
 Fortunately there has not yet been a major oil spill on the reef. However, with such a
large number of ships the potential for a major spill is very real.
 Ships also bring with them rubbish and small slicks associated with leaks. The ships also
have the potential to introduce feral aquatic species by releasing ballast water.
 This is water used to balance the ship: water is no longer needed. Small animals and plant
species can be transported across the oceans in this way.
3. Overfishing
 Commercial fishing has long been an important economic activity for Queensland’s
coastal communities.
 Unsustainable fishing practices in the past have left many areas with depleted fish stocks
and it is important that these areas are now managed sustainably.
 While many areas of the reef are today off limits to commercial fishers, various areas of
the reef can still be fished.
 Local fishers are no longer a major threat to the reef as they understand the need to
protect the area’s fish stocks.
 However, the reef remains threatened by illegal fishing, which is often carried out by
foreign fishing trawlers, and by unsustainable recreational fishing.
4. Tourism
a. Importance
 Tourism is one of Northern Queensland’s most important industries
 Worth over $4 billion each year, the GBR is a tourist attraction of international importance
b. Impacts of Tourism
 There are six main ways of categorising the impacts of tourism on the reef:
o Coastal Dune Development
 Most visitors stay in hotels and resorts along the coast of the mainland.
 This places stress on coastal environments e.g. estuarine ecosystems
o Island-Based Tourism
HSC
[60]
Geography
Ecosystems at Risk

o
o
o
o
5.
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The encroachment of tourism and associated development onto the
reef’s surrounding islands poses risks, especially those associated with
sewage and rubbish discharges
Marine-Based Tourism
 Tourist boats make thousands of journeys out to the reefs each year
 These boats bring with them rubbish and the potential for oil spills
 They also require mooring areas, usually located on outer reefs, which
destroy the coral as does the dropping of anchors
Water-Based Activities
 Diving and snorkeling are popular and most divers are careful
 A small proportion of divers break coal as the fragile branches are
especially susceptible
Wildlife Attractions
 Most operators do not allow their customers to get too close to wild
animals
 Some careless operators and tourists disrupt wildlife and impact on
breeding and natural interactions
Other Impacts
 Trampling of coral (walking along reefs at low tide is now illegal)
 Taking souvenirs of coral, shells etc. (also illegal)
Land Clearing
There are 26 major river systems that flow from mainland Queensland to the GBR
25% of the land area of QLD is drained onto the reef
This runoff represents urban and agricultural development and aquaculture
Development of urban zones adjacent to coastal areas is expanding rapidly
This places pressure to clear land in order to accommodate the expansion
Due to this, surface runoff is increased dramatically
The GBRMPA noted that the clearing of wetlands has encroached on the sustainability of
the reefs
Estuaries provide nursing for many reef species
6. Agriculture
 Aquaculture is a popular commercial farming activity in ponds near the GBR
 It includes the commercial manufacture of:
o Several fish species
o Pear
o Edible oysters
 The aquaculture farms can release chemicals and diseases impacting on natural species
 Conventional agriculture: The coastal plain adjacent to the reef has been of a constant
concern for reef and marine biologists
 Use of chemical fertilisers increases nutrients that lead to algal growth
 Algae smothers the reef and reduces light penetrations
 Land clearing removes vegetation cover resulting in erosion, increasing turbidity and
smothering corals
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[61]
Geography
Ecosystems at Risk
d. Human Impacts
Climate
Change
Boating and
Commercial
Shipping
loss of
species
oil spills
Overfishing
HUMAN
THREATS
TO THE
GBR
dredging
and
sandmining
Tourism
land
clearing
sewage
agriculture
Human
Impact
Climate Change
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Effect
The El Nino effect is considered to be the primary culprit in the increase in water
temperatures that have begun to strike the Great Barrier Reef with increasing frequency.
The impact of coral bleaching is just one of the ways in which higher temperatures affect the
reef. Climate change in general is believed by many prominent biologists to be a massive
threat to the reef’s future, predicting its gradual decline until it becomes practically extinct
by the year 2030.
A temperature rise of 2-3 degrees is believed to put 97% of the reef in the danger zone of
bleaching every year. The rise in levels of atmospheric greenhouse gases are believed to be
another significant factor – particularly carbon dioxide, which if it rises to a level of 450ppm,
[62]
Geography
Boating &
Commercial
Shipping
Overfishing
Tourism
Land Clearing
Agriculture
Sewage
Dredging &
Sandmining
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Ecosystems at Risk
will put coral and reef habitats in an extremely vulnerable position.
Recreational boating is a common pastime on the reef. The reef represents a safe boating
paradise, though the boats have the potential to damage the ecosystem. Anchoring
damages coral formations and sea grass beds.
The occurrence of collisions and groundings leave an immediate and drastic effect on the
ecosystem as debris and other objects enter the water and remain there for a long period of
time. 6000 large commercial ships transit through the Great Barrier Reef every year.
Reefs are suffering directly and indirectly from the increasing pressure of man’s resource
exploitation. Overfishing is one driving pressure that has had devastating impacts on coral
reefs. Aggressive fishing methods have hurt coral reefs sometimes beyond repair. However,
over-fishing in general is also a damaging problem to many coral reefs around the world.
Specifically to the Great Barrier Reef, overfishing has caused a shift in the reef ecosystem.
Overfishing of certain species near coral reefs can easily affect the reef’s ecological balance
and biodiversity.
While many areas, techniques and species of marine life in the reef are protected by law,
trawling for various types of permitted sea life inevitably leads to other species getting
caught in the nets as a side effect.
Tourism has five broad impacts on the reef:
 Coastal tourism development – Most visitors stay in hotels and resorts, which strain
coastal environments including estuaries.
 island based tourism – The encroachment of tourism and associated development
on the reefs islands poses risks
 marine based tourism – Boats make thousands of journeys on the reef each year,
bringing rubbish and potential oil spills
 water based activities – A small proportion of divers break corals, especially fragile
branching corals
 Wildlife interactions – A small proportion of careless operators and tourists interrupt
wildlife, impacting natural interactions
 Other impacts – Trampling of coral and souveniring of coral are both illegal, though
still performed
26 major river systems flow from mainland Queensland into the Great Barrier Reef, covering
25% of the area of Queensland. This runoff represents a major threat to the reef as
agriculture, urban development and aquaculture all affect the quality of the water that
flows into the Coral Sea. Expanding coastal developments have an increased surface runoff
which brings more nutrients and sediments to the reef and increase sewage and pollution.
80% of the land adjacent to the Great Barrier Reef is farmland that supports agricultural
production, intensive cropping of sugar cane and major beef cattle grazing. Fertilisers
contain high levels of phosphates and nitrates which promote algal growth. Runoff carries
this into the Great Barrier Reef ecosystem.
Pesticides used by farmers are made of heavy metals such as lead, mercury, arsenic and
other toxins which are dangerous to aquatic plant and animal species.
Nutrient runoff from agricultural land has promoted growth of the Crown of Thorns starfish,
which eat coral polyps in plague proportions.
Boats venting their on board sewerage system release raw sewage into the water. The
sewage from a single boat is not damaging in itself, though the impact of numerous boats is
considerable.
The sewerage systems of residents can be transported through runoff into the Great Barrier
Reef ecosystem. Agricultural waste can cause increase in phytoplankton levels, resulting in
outbursts of the threatening Crown of Thorns Starfish.
Dredging and material placement (also called spoil dumping) have relatively well-known
potential impacts such as degradation of water quality, changes to hydrodynamics,
[63]
Geography
Oil Spills
Loss of Species
Ecosystems at Risk
smothering of benthic fauna and flora, damage to marine wildlife through the dredge
mechanism, translocation of species and removal of habitat. If inappropriately managed,
dredging activities may impact areas of conservation value. Dredging and material
placement processes need to be carefully managed to ensure any adverse effects are
prevented or confined to areas of low conservation value.
Despite the best efforts of government agencies to keep the Great Barrier Reef in the best
condition possible, there have been a huge number of oil spills over the last few decades
that gave directly affected the reef and its marine life.
While the act of oil drilling is banned on the reef, spills caused by passing oil container ships
have still continued to occur. A recent spill created a massive grounding scar over 3
kilometres long. As a result, some of the damaged areas have become uninhabitable for
marine life and there are estimates from experts that the reef may take 10 to 20 years to
recover from the incident.
Six of the seven species of marine turtles in the world are found on the Great Barrier Reef.
All six species are threatened. An estimated 1750 turtles are caught in trawl nets each year.
 The Queensland population of loggerhead turtles are facing extinction
 70-90% population decline caught in numbers over the last 30 years
 14% of turtles caught in trawl nets are loggerhead turtles
 Average size of nesting female green turtles has been reducing over the last 20 years
 Analysis of 10 years nesting data of hawksbill turtles shows a downward trend in
numbers of breeding females
Over 90% decline in Dugong numbers south of Cooktown since the 1960’s. Dangerous
organo-chlorine pesticide residues have been found in dugongs and dolphins. The Great
Barrier Reef remains one of the last areas in the world with viable populations of dugongs.
Michaelmas Cay has seen a 25% decline in population of Crested Tern and Sooty Tern and a
45% decline in Common Noddy tern population since the 1980’s.
e. Traditional and Contemporary Management Strategies
i.
Contemporary Management Strategies
1.
Tourism
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a. The Role of Education
Tourism plays an important role in educating people about this fragile ecosystem and
why it needs to be protected.
One of the aims of the World Heritage Conventions is to promote education about
environmental protection and the impact of human activities on ecosystems.
Every visitor to the reef pays a small fee which is used by the Great Barrier Reef
Marine Park Authority to run educational programs
b. The Impact of Geographical Concentration
85% of visitors visit the reef around Cairns and the Whitsundays
These two regions represent 7% of the total area of the reef
In excess of 1 million people visit the reef in these tiny areas and consequently, the
potential impact is enormous and careful management is essential.
[64]
Geography

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Ecosystems at Risk
c. Pontoons
Most visitors to the reef are day-trippers and most of these spend their day on
floating pontoons
There have been a number of accidents involving pontoons including sinking
As a result, pontoon operators need to complete a detailed environmental impact
statement
d. Recreational Boats
Management of
tourist boats is a
key issue for the
GBRMPA
Speed limits are
enforced to reduce
the impact of wake
from boats
GBRMPA runs a
massive education
program about
boat pollution
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This is particularly
important when
boats travel close
to shore
Advertisements are
used along with
signs at boat ramps
e. Disturbance to Wildlife and Breeding Cycles
Breeding cycles with some bird colonies were being affected by tourists
Seabirds on Michaelmas Cay had stopped breeding
Bird breeding islands are controlled by the Queensland Parks and Wildlife Service
The service regularly assesses colonies for danger
Many islands are now permanently closed to humans
The QPWS is working closely with tourist operators to limit but allow tourist access
f. Whale Watching
Whale watching has become a popular tourist activity on the reef
Commonwealth and Queensland laws prevent operators from steering too close to
whales
A small number of operators allow tourists to swim near whales
A code of conduct ensures that this is not adverse for the whales
This includes fully briefing swimmers about correct conduct with whales
g. Turtles
The most common interaction between humans and turtles is on the beaches where
they lay their eggs
[65]
Geography

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


Ecosystems at Risk
Nesting turtles can be easily disturbed so a code of conduct was established
The Commonwealth Government has protected turtles through legislation
h. Role of the Tourism and Recreational Reef Advisory Committee
The Tourism and Recreational Reef Advisory Committee acts as a liaison between the
authority and the tourism industry
The TRRAC meets several times a year and has representative members from a broad
cross section of the GBR tourism industry
Through the TRRAC the tourism industry plays an important role in managing the GBR
It is in the best interests of the industry to protect the reef
2. Improving Water Quality
 Research by the Commonwealth and Queensland governments discovered that many
of the inshore and fringing reefs are being degraded by poor water quality
 These findings led to the creation of the Reef Water Quality Protection Plan which
aims to reduce the decline in water quality of water entering the GBR system
Reef Plan Goals
To reduce the
To rehabilitate the
amount of water
river catchments
pollutants entering and better manage
the GBR
them


The Reef Plan recognises the need for cooperation
Some recent initiatives include:
The development of regional plans to better manage river
catchments
Farm Management Systems initiative launched to identify and deal
with environmental risks
The Queensland Wetlands Program designed to research, protect
and
HSC rehabilitate wetland ecosystems
[66]
Geography
Ecosystems at Risk
3. Anchoring and Mooring
a. Public Mooring
 At many of the most popular boating destinations, the GBRMPA has installed public
moorings
 These are permanently fixed to the seabed and remove the need for anchors
 This removes the damage caused by anchors
b. Restrictions to Anchoring
 The zoning plan forbids anchoring in many parts of the reef
 This is difficult to police due to the sheer size of the reef and many careless skippers
still use anchors in a damaging way
ii. Traditional Management Strategies
 Aboriginal and Torres Strait Islander believed that they were not above nature but part of
it thus they approached their management of the GBR by being stewards as there is an
obligation to look after one's country because of the deep spiritual links with the land.
 Thus, traditional management strategies focus on using marine and terrestrial resources
in a sustainable way.
 They did this through a detailed practical knowledge of the ecosystem, its natural history
and habitats, animal migration patterns and seasons.
 This detailed knowledge and connectedness led to strategies such as:
o Setting size limits on the fish they caught, some local Aboriginal people believe
the sizes allowed these days are too small
o Seasonal hunting, ensured that species could recover and be plentiful for the
future
o Assigning sacred animal totems so that person or group was responsible for its
survival
o Maintaining relatively small population levels and relatively low-level technology
so it did not place stress on the ecosystem.
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[67]