HSC Geography - Ecosystems at Risk Notes PDF

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HSC Geography Complete Ecosystems at Risk Notes
Topic 1 Geography...

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Anson Tong

Ecosystems at Risk Syllabus Points Ecosystem and their Management   -

Biophysical interactions which lead to diverse ecosystems and their functioning Vulnerability and resilience of ecosystems Impacts due to natural stress

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Impacts due to human induced modifications to energy flow, nutrient cycling, and relationships between biophysical components

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The importance of ecosystem management and protection Maintenance of genetic diversity

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Utility value

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Heritage value

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Need to allow natural change to proceed

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Evaluation of traditional and contemporary management strategies

Case Studies of ecosystems 

TWO case studies of different ecosystems at risk to illustrate their unique characteristics including: -

Spatial patterns and dimensions: location, altitude, latitude, size and continuity

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Biophysical interactions including o The dynamics of weather and climate o Geomorphic and hydrologic processes such as earth movements, weathering, erosion, transport and deposition, soil formation o Biogeographical processes: invasion, succession, modification, resilience o Adjustments in response to natural stress

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The nature and rate of change which affects ecosystem functioning

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Human impacts (both positive and negative)

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Traditional and contemporary management practices

* - refers to actual syllabus points

Biophysical Interactions 

Biophysical interactions which lead to diverse ecosystems and their functioning

Ecosystems are systems which convert incoming solar radiation through photosynthesis into energy which is then channeled through a hierarchy of life forms. Each ecosystem has its own characteristic flora and fauna which follow its own set of rules. However, even though all ecosystems are unique they are all a direct result of the biophysical components of their given location.

Four Spheres Ecosystems are the resultant product of the interaction between the four spheres:    

Atmosphere (Air) Hydrosphere (Water) Lithosphere (Soil) Biosphere (Life)

Atmosphere The atmosphere is effectively the air surrounding the Earth’s surface. It is the main source of climatic factors that influence an ecosystems functioning. Temperature and the amount of rainfall determine the characteristics of all elements within the ecosystems and the speed at which they function (nutrient and energy cycle). The atmosphere is also the main source of nutrients e.g. nitrogen, carbon and oxygen as well as water. Hydrosphere The hydrosphere is all forms of water on the Earth’s surface which include ice. It is closely linked to the atmosphere as the atmosphere determines the water cycle within that area. The hydrosphere can be also influence the biodiversity as with larger volumes of rainfall the speed at which elements cycle within the ecosystem increase thus increasing biodiversity. Lithosphere The lithosphere is the curst or solid part of the Earth. It determines the nature of soils and provides habitats for many of the decomposer organisms that recycle the minerals essential to the plants that form the basis of the food web. The lithosphere also stores mineral nutrients as

Anson Tong well as water between the soil particles. The capacity of the soil to perform these two functions helps to determine the nature of some ecosystems e.g. sandy soil profiles drain water quickly leaving an extremely dry soil. Landforms are also part of the lithosphere and can influence the ecosystem through the altitude as at different altitudes the weather can change dramatically e.g. valleys are often drainage locations due to its low height above sea level. Biosphere The biosphere is the domain on or near the Earth’s surface where environmental conditions enable solar energy to produce the chemical processes necessary for life. It comprises the biotic (living and dead organisms) components found near the Earth’s surface. Nearly all life on Earth exists which the narrow zone that extends from about 200metres below the surface of the sea to about 9000 metres above sea level. The biosphere is mainly comprised of two types of organisms: those that can manufacture their own food (autotrophs) and those that cannot (heterotrophs). Ecosphere (Special) The ecosphere is the collection of living and non-living organisms (the biosphere), interacting with one another and their non-living environment. The ecosphere represents the aggregate of the world’s ecosystems. Within the ecosphere there are five levels of organizations: -

Organisms Species – A single type of organism that has the ability to reproduce Populations – A group of organisms of the same species living together Habitats – The area where an organism or population lives Communities – Several populations interactions with each other within a habitat

It is important to consider all four spheres when analysing any ecosystem as they can have impacts that extend throughout the ecosystem and it’s functioning e.g. temperature can change the rate of nutrient cycles. The interactions between the four spheres are unique to each location however generalizations can be made and as a result, familiar biomes can be observed. An example of interactions between the four spheres impacting the ecosystem is best seen through the productivity of ecosystems. The productivity of an ecosystem can be express in two ways: 1.) The amount of biomass produced in an area – mass of living new living matter produced per square metre of land per unit of time

Anson Tong 2.) Energy flow – The amount of energy that is “locked into” all the organisms in an area per unit time

Energy Flows and Nutrient Cycling Energy Flows The sun is the primary source of energy within ecosystems. The energy of the Sun is used by plants to turn carbon dioxide and water into glucose and oxygen via photosynthesis. Plants then use the nutrients within the earth and glucose as an energy source to make other substances. Herbivores consume the plants and obtain their nutrients and energy albeit with a loss of energy through heat and other forms. Due to the loss of energy the higher the trophic level the less organisms within each level. However, after an organism dies decomposers recycle these nutrients back into the soil for producers to use. Carbon Cycle Carbon is the basic building block of the compound necessary for life. Most land plants obtain their carbon by absorbing carbon dioxide directly from the atmosphere. Plants within the water absorb carbon through the CO2 dissolved within the water. Carbon is released through the burning of fossil fuels however is absorbed back by producers that absorb CO2 to create glucose and when they die is decomposed back into the ground where the carbon slowly gets turned back into fossil fuels. Water Cycle The water cycle is the continuous process by which water is evaporated into the air, condensed back into water droplets which is then precipitated back to the ground as rain. This water is run off into ponds, lakes and oceans where it is ready to be evaporated again. Oxygen Cycle Oxygen is released into the atmosphere through the process of photosynthesis conducted by producers. This oxygen is then consumed by animals which release it in the form of CO2 which is then used again by producers to form oxygen. Nitrogen Cycle Nitrogen is by far one of the most common gases within the atmosphere at around 78% however, nitrogen as a gas cannot be directly used by plants and animals. In order to overcome this problem, there are nitrogen fixing bacteria that exist with the soil which convert the atmospheric nitrogen gas into ammonium which through the process of nitrification from other bacteria can turn it into a useful form of nitrogen known as nitrates. These nitrates are assimilated into plants which in turn when decomposed release ammonium back into the soil.

Anson Tong Phosphorus Cycle The most common source of phosphorus is found within rocks. For plants to use this as a nutrient, the rocks become weathered by rain and natural processes and is run of into the water. The water now contains phosphate which can be absorbed into the soil and used by plants.

Bioaccumulation Bioaccumulation is the process by which non-biodegradable toxic substances are released into the environment and make their way up the food chain through accumulation within organisms that have consumed it. This process is very dangerous as it can threaten the survival of many populations within the food chain. Synthetic chemicals and heavy metals when released into the environment are absorbed into the biological tissues of the producers. Once the producer is consumed by it’s predator and the predator is consumed etc. the concentration of the synthetic chemical increases due to the amount of food that the predator must consume to survive. This can devastate populations as it can cause some species to be unable to reproduce or weaken its immune system thus making it more prone to diseases. A common example of bioaccumulation or amplification is the use of the chemical DDT and how it’s initial concentration can be 0.0004 PPM within the water but as it reaches fish eating birds it can increased to 25 PPM. This is a 10 million fold increase in concentration which in some cases can even be passed onto us if we do consume the species that has been infected.

Summary – FINAL PART Overall, it becomes clear that the interaction between the four spheres have a direct impact which often determines the nature of the particular ecosystem. The four spheres also heavily influence the energy flows and nutrient cycling that occurs within the particular ecosystem. An example of this is the colder the location the slower the energy and nutrient flow within the ecosystem. Although the four spheres have a major impact on the ecosystem and its functioning, human impacts such as bioaccumulation can also severely damage an ecosystem original functioning. Ultimately the interactions between the four spheres and the processes that come as a result lead to many diverse ecosystems and their functioning.

Vulnerability and Resilience of Ecosystems All ecosystem function in a state of dynamic equilibrium which means that they are in a continual state of balanced change. The state of dynamic equilibrium is due to the interactions between the four spheres. Due to the fact that the four spheres are interdependent, it results in the vulnerability of ecosystems. If there are changes that occur which are beyond the limit of equilibrium then an ecosystem can not function as it was intended to. All ecosystems are vulnerable however the level of

Anson Tong vulnerability depends on how small a change in any element can upset the equilibrium. This shows that ecosystems are not equally at risk with some being more resilient than others. Vulnerability refers to how susceptible an ecosystem is to stress whereas resilience is how quickly an ecosystem can restore natural functioning after a period of stress.

Causes of Ecosystem Vulnerability All ecosystems have some ability to resist stress. There are a number of factors that can influence and ecosystem’s vulnerability to stress. These main factors are: (BELL)  Biodiversity Biodiversity refers to the variety of plant and animal life within a particular ecosystem. When there is high biodiversity within an ecosystem there are a range of pathways for ecological processes to occur. This means that even if one pathway is damaged an alternative may be found and the ecosystem can continue functioning at normal level. However, if the level of biodiversity is greatly diminished the functioning of the ecosystem can be put at risk. The biodiversity of an ecosystem is often considered at three levels, genetic, species and ecosystem diversity. Genetic diversity is the variety of genetic information contained within all the individual plants and animals. Genetic diversity occurs between species and population of species. A high level of genetic biodiversity favors the survival of a species because it increase the chance that some members of the species will have characteristics that aid their survival if the population experiences stress. Species diversity is the measure of the number of species at each trophic level of the particular ecosystem. The greater the species diversity the more robust the ecosystem. This means that if a population of a producer or consumer declines there are likely other organisms within the ecosystem that can fulfil this role without greatly impacting the functioning of the system. Ecosystem diversity refers to the diversity within an ecosystem in terms of habitat differences, biotic communities and the variety of ecological processes.  Extent Extent (size) of an ecosystem is the result of a variety of factors. Ecosystems that are restricted to small areas or have been extensively disturbed often become more vulnerable. This is due to the fact that the same area is a larger proportion of total land.  Location The location of an ecosystem directly related to its functioning. At a global scale the latitude and distance from the sea play decisive roles on determining the climate within the ecosystem e.g. higher latitude often means areas that are colder than the equatorial

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regions. Locational factors can even refer to microclimatic features such as the slope of a hill affecting the amount of sunlight the area receives in comparison to a flat area. Another factor that must be considered when analyzing the effect of location on ecosystems is the ecosystem’s proximity to human activities. This is due to the fact that as the human population grows the importance of land increases thus pushing into previously natural areas. Linkages Linking refers to the interdependence within the ecosystem which is related to species diversity. The greater the level of interdependence within an ecosystem the greater its ability to absorb change within affecting the functioning of the ecosystem. Ecosystems that have less interdependence are more vulnerable to change e.g. if there were only one species of krill and they were to become extinct the whales in the region would suffer a lot more than if there were more than one species of krill. These links however obvious or subtle can create the very foundation of the ecosystem.

Impacts of Natural Stress * Natural stress is the natural environmental factors such as extreme temperatures, winds, drought and salinity which make it difficult for plants and animals to survive. However, these changes within the natural environmental usually occur over a prolonged period of time meaning that while natural stress does occur necessary evolutionary changes also happen in order to balance this out. The delicate balance between natural stress and natural evolution can be easily broken as a result of human interference. Resilience is an ecosystems ability to recover from episodes of natural stress whether they be human-induced or natural. Ecosystems rich in biodiversity usually have greater resilience due to the fact that they have more linkages and therefore have other pathways if a certain species were to become endangered. The more successful a species is at regeneration and adaptation the less vulnerable it is to change within an ecosystem. However, stress isn’t always a bad thing as some species rely on natural stresses in order to stimulate growth within their system e.g. some species of eucalypt rely on fire to initiate a stage in their reproductive cycle. Other factors such as intensity and duration of the stress also effects the ecosystems resilience. Elasticity represents the rate that an ecosystem can recover after a disturbance whereas amplitude is the maximum level of stress before it becomes impossible for the ecosystem to recover. Malleability is the difference between the ecosystem’s final recovery level and the pre-stress level. The greater the difference the less resilient the ecosystem.

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Impacts due to human induced modifications to the energy flow, nutrient cycling, and relationships between biophysical components * As mentioned before stress can be induced by both humans and nature. However, human induced modifications to the ecosystem are usually more harmful as these process were never intended to occur making it difficult for many species to cope with the changes. Many naturally occurring changes take place slowly and allow ecosystems to slowly adapt and plant and animal species with characteristics not suitable for the new environment slowly die out. This process is known as natural selection. Human initiated stress can e.g. damming of a river, draining of a wetland or clearing vast natural vegetation cause such drastic changes that the can result in habitat destruction and even the extinction of a species. The ability to induce large-scale environmental change means that people are able to push the state of dynamic equilibrium beyond its limits thus damaging ecosystems beyond point of return. Due to this many people have created situations where they are required to maintain a state of equilibrium through the use of resources found elsewhere e.g. fertilizers and pesticides. Without the management of the state of equilibrium some ecosystems would collapse e.g. monoculture without fertilizers and pesticides. This shows that overall human activities often have the capability to seriously threaten species and degrade their habitats. Environmental Impacts of human activity Humans have changed the way many ecosystems operate and threaten the existence of many species and habitats. There are many ways humans have changed the way ecosystem function with the following being the main ones: 

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Species introduction Species introduction is the process where nonnative species are introduced to an ecosystem whether it was deliberate or on accident. These introduced species can devastate the native flora and fauna by disrupting the flow of energy within the ecosystem. This can come in various forms e.g. preying on or out-competing other species for food and space. These effects are magnified throughout the food chain. Habitat destruction The destruction of habitat is considered a major threat to biodiversity. Habitat loss can be seem in several forms including outright loss as it is converted to human use, as well as degradation and fragmentation where native species are deprived of food, shelter and breeding areas and are squeezed into smaller and smaller areas of undisturbed land. Hunting

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Hunting of animals can lead to the uncontrolled exploration of and trade in wildlife. It has decimated some species like the Amur Tiger and African elephants. Overfishing is a common example which has destroyed the herring and cod fisheries around the world. Black markets often appear and can lead to additional problems that hunting causes. Pollution Pollution is a major threat in aquatic and land-based ecosystems. These pollutants can come from a large range of places e.g. fertilizer run-off from farms to factories dumping pollutants into the waterways and the atmosphere. This can result in serious decline in ecosystems all around the world as pollutants aren’t just restricted to a local area.

Human-induced modifications to ecosystems Humans are part of the biosphere and play a role in maintaining or disturbing the dynamic equilibrium of any ecosystem. Humans have been modifying ecosystems since as early as 40,000 years ago when the Australian Aboriginals used fire-stick faming to gradually change forest ecosystems so that fire-resistant species now dominate. Other common modifications include the domestication of animals and the cultivation of crops which has changed the way humans live on the planet and caused the beginning...