An ecosystem is the dynamic link of flora and fauna and micro-organism communities and their non-living surroundings. Two highly specialised ecosystems are coral reefs and coastal dunes. An example of a coral reef is the Great Barrier Reef which spans roughly 2,300 kilometres making it the largest reef in the world. The reef is home to a range of animals and plants and is known for its diversity. Coastal dunes another specialised ecosystem, is formed through a large accumulation of sand located behind the beach zone. Coastal dunes are known for having very extreme environments with only few flora or fauna being able to survive the conditions.
With reference to both ecosystems, explain the biophysical interactions that lead to diverse ecosystems and their functioning.
Coral Reefs
Atmosphere
Due to the location of the Great Barrier Reef, it faces both positive and negative interactions with the atmosphere. The reef lies in an area classified as Australia’s Cyclone Zone, an area hit by many fierce storms in its past. The degree of impact on the reef is subject to the intensity and extent of the storm. The damage occurs due to the large storm waves that are produced from strong winds and low-pressure systems. The forceful waves rip apart the more fragile coral and create chips and imperfections in the harder coral. In severe cyclone cases the whole reef ecosystem may be put under sediment. Tropical cyclones are known for having heavily-induced rain cycles. The extra volume of fresh water means that the salinity of the reef ecosystem is then distorted, and affects coral growth. The atmosphere can also be a constructive interaction. For example in 2006 Cyclone Larry that hit the shores of North Queensland. The cyclone struck the reef, but instead of causing destructing within the ecosystem, the cyclone prevented mass coral bleaching from occurring by lowering the temperature of the water. Atmospheric pressures lead to greater functioning ecosystems through adaptation.
Lithosphere
The Great Barrier Reef is aided in its functioning and transforming by the lithosphere. The reef itself produces limestone. The limestone is weathered and transported throughout the reef. The limestone is then able to create new landforms like coral cay. The limestone is also used as a defence mechanism by coral against the erosive waves. The death of one coral is used as a platform for life for another coral. Another lithospheric factor affecting coral functioning is sediment. Sediment like sand can have the effect of clouding up the water of the reef resulting in increased turbidity levels of the water. There is then less sunlight penetration into the reef, affecting the process of photosynthesis and coral bleaching is more likely to occur.
Hydrosphere
The Great Barrier Reef tends to have best coral growth when hydrosphere conditions are at their greatest. For example coral reefs tend to have optimal growth when wave energy is high. The wave energy is broken by the reef through the seaward, and produces an area of peaceful, protected water behind the reef. The waters of the Great Barrier Reef tend to flow in a northerly direction most of the year, though during monsoonal seasons the form of the waters change, and there is a reversal in the direction of the waters. The reversal allows the cooler southern ocean current to flow into the reef. The waters that run from the north are warm and high in salinity; they provide the reef with high nutrient levels and are major influences for the diversity of the ecosystem.
Biosphere
The biosphere element of the Great Barrier Reef is how the reef grows and obtains its wonderful features. An important animal for the reef are polyps. Polyps are simple organisms that have a stomach and their exoskeleton. Within the polyp is an interdependent algae called zooxanthallae. The two organisms provide mutual benefits with one providing sugars and oxygen through photosynthesis and the other supplying nutrients. Polyp regrowth occurs with the use of the deceased polyp’s exoskeleton. Though coral reproduction is different, where the coral will release their eggs into the summer waters, and instantaneously they release mass amounts of sperm as well. The process of evolving occurs and the larvae grow on the exoskeleton of coral. The diverse range of species within the Great Barrier Reef also has an impact on its functioning. For example crustaceans are great at executing the nutrient recycling role, while the crown of thorn star fish is known for attaching itself to coral and eating it to death. (Appendix A Figure 1.1) shows a Crowns of Thorns starfish preying on coral.
Coastal Dunes
Atmosphere
The most pivotal biophysical interaction with coastal dunes is the atmosphere. The atmosphere’s main components are wind, temperature and precipitation. Wind is a major contributor to shaping dunes through aeolion transport, where sand grains are picked up and transported to another location. The amount of sand removed is dependent on the size of sand, velocity of the wind and nature of vegetation cover. The faster velocity of the wind the more likely sand grains will be moved, due to a greater force. The type of local vegetation and amount of vegetation on the sand dunes also impacts aeolian transport, as the vegetation becomes a barrier against the wind for the sand. Temperature plays the role of influencing the rate of sand dryness, and type of vegetation on the dunes. Temperature values also determine the functioning of ocean currents. As temperature increases the dryness of sand increases resulting in only few vegetation’s that are able to live on the dunes, which in turn affects the rate of aeolian transport. Precipitation is also an atmospheric component that impacts coastal dunes, through the level of rainfall. The amount of vegetation on dunes is dependent on the level of rainfall, with regular rainfall meaning a greater variety and denser vegetation.
Hydrosphere
The hydrological processes that have an impact on coastal dune ecosystems include wind-induced waves, longshore drift and rainfall. Wind-induced waves are important for developing coastal dunes. When there are periods of calmness within the ocean, this means sand is able to be transported from offshore deposits to the beaches. This gives greater supply to dunes through wind transportation. On the other hand when there are treacherous conditions in the oceans the waves become powerful, crash into the coastline and remove sand from the beaches and foredunes. Another hydrological process impacting coastal dunes is longshore drift. Longshore drift is the transportation of sediment by currents that are running at parallel to the shoreline. Through longshore drift, sediment is able to be produced in one location and transferred to another. Longshore drift is quite common on the East side of Australia, with many of the islands up in Queensland having been made from sediment that came from New South Wales. The final hydrological process to impact coastal dunes is rainfall. The amount of rainfall has a bearing on the erosion of the sand, with high rainfall eroding the surface and making it vulnerable.
Biosphere
The biosphere influences coastal dunes through flora and fauna. There are three species to flora, primary species, secondary species and tertiary species. The primary species are those that are closest to the sea. These areas are only colonised by vegetation that can handle the conditions. The main role of the pioneer species like Marram Grass is to stabilise any incoming sand. These species of fauna spread at a rapid pace, and so their able to protect much of a sand dune. The secondary species is the foredune vegetation. They are usually comprised of shrubs and small trees like the coastal wattle, and help in maintaining foredune sand mass. The tertiary species are those that go beyond the coastal moorland, like tall trees. This process is known as succession. Fauna on coastal dunes is not very evident. Not many animals live on the dunes closest to the beach, as the conditions are too extreme for them to handle, with only few crabs calling this area home. Towards the back of the dune systems an increasing number of bird species can be found.
Lithosphere
Sand particles are not identical; therefore its mineral and chemical composition will vary from place to place. For example in New South Wales most dunes have sand made of quartzose particles. The particles do not bond easily, resulting in less stable dunes. Dune formation starts with the deposition of sediment and offshore sand bars at the mouths of rivers. Through longshore currents the sediment is relocated then deposited on a beach by wave action. Dry sand is blown inland from the beach. The drift accumulates around obstacles like vegetation and a dune starts to form. Coastal dunes have three types of dunes that could occur, the first being foredunes. The foredune is the first stable dune built. Its main objective is to act as a barrier between the sea and inland. It is located at the back of the beach and usually has pioneer grasses colonising it. As the vegetation matures more sand is trapped creating larger dune systems. (Appendix B Figure 1.1) a foredune has developed with pioneer grasses colonising it. Another type of dune is parallel or transverse dunes. Parallel dunes develop when a foredune has been hit by a storm, and the seaward face has been eroded. When sediment flow restores, a new ridge develops in front of the foredune, with a swale separating them. With the new foredune developing, supply to the old foredune becomes limited and stables. Heath-like shrubs develop on the old foredune once it is stable enough to house them. A diagram of parallel dune is seen in (Appendix B Figure 1.2) where it is shown how a transverse dune develops. The final type of dune is the parabolic dune. Parabolic dunes are the result of blowouts. They are large dunes that are shaped like a horse shoe, and develop in dune systems running parallel to the coast. Their formation is linked to onshore winds. (Appendix B Figure 1.3) shows how parabolic dunes are the resultant of primary wind direction.
Question 2. Analyse the impacts due to both human-induced modifications and natural stress on both ecosystems at risk. How does each ecosystem adjust in response to natural stress?
Coral Reefs
Human Modifications
Human dependence on the Great Barrier Reef has been for many thousands of years. As human populations grow the demand for coral reef resources will increase as well.
Over-fishing of the coral reef often occurs when there is an increase in the human population, as there is a greater demand for seafood. Fishermen usually target those fish that are closely connected with the coral, like snappers. When these species decrease in population fisherman target all fish using methods like spears and nets. Through observation it has been proven that coral with no fish near are more prone to overgrowth by macro-algae and increases in coral diseases. There is also physical damage sustained by the coral, through the anchors and nets.
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Tourism is an additional human induced factor impacting coral reefs, and especially the Great Barrier Reef. One of tourisms foremost asset the Great Barrier Reef brings in $4 billion a year. Research performed by James Cook University of Cairns found several comprehensive impacts of tourism on the reef. The first being coastal tourism development, where many people visiting the reef want to stay as close to the reef as possible. The coastal developments near and around the Great Barrier Reef disrupt currents and gravitate to the displacement of sediment. There is also increase tourism on the islands near the reef causing problems linked with sewage and rubbish. Marine based tourism also occurs in the Great Barrier Reef with the anchor chains of boats having catastrophic effects on the coral. Although operators are very careful when it comes to tourist interaction with coral animals, some tourists negatively interact with the wildlife causing complications in the breeding cycles and natural interactions. (Appendix A Figure 1.2) reveals how close some tourist get to the coral.
Climate change is another contributor of human-induced modification to the Great Barrier Reef. Some of the effects of climate change include changes in rainfall patterns, changes to ocean currents and circulation and increase in sea surface temperature. Especially a rise in sea surface temperature will mean coral bleaching events will occur, creating mass damage through the reef. (Appendix B Figure 1.4) depicts the linkage between average temperatures and bleaching events (one being in 1998 and the other being in 2002). The chemical structure of the water is also changed with greater amounts of carbon dioxide dissolved in the water. Added on with rising sea levels could spell the destruction of coral reefs. An example of climate change affecting the fauna of reef is through the turtle. Turtle gender is determined through the temperature of the water, with warmer temperatures resulting in greater numbers of female turtles, creating a gender imbalance. (Appendix B Figure 1.5) shows the extent to which coral bleaching occurred in 2002, in accordance with the sea temperature.
Natural Stresses
Natural stresses are dangerous to reefs but the reef ecosystem can usually recover and adapt to the change. This is because natural change usually occurs over a long period of time, allowing the ecosystem to adapt. One natural stress is the Crown of Thorns Starfish. Crown of Thorns Starfish are known for eating the coral polyps. Coral reefs can only withstand a low population of these starfish. When the conditions are right for the starfish they can grow in numbers to plague proportions and have harmful consequences on the hard coral population. It could take the reefs up to many years to recover from plague numbers of starfish.
Weather is another natural stress that inflicts damage to coral reefs. Coral thrive best in warm, salty waters. They are generally found in shallow clear waters, which help the zooxanthaelae algae to undertake photosynthesis. When there are changes in temperature and salinity, due to excessive rain, stress is placed on the coral polyps. This stress causes the coral polyps to eject the algae, which results in coral bleaching. For example it was reported in 2010 of mass coral bleaching occurring throughout South-East Asia, the Indian Ocean and the Pacific. The reason behind the bleaching was increased water temperatures. Low levels of water also impact coral, through being exposed to the sun for long periods of time the coral polyps consequently dry up. (Appendix B Figure 1.6) demonstrates the future implications to current scenarios facing the reef ecosystem.
Coastal Dunes
Human Modifications
The main reasons to human induced modifications on dunes are the ever growing desires of humans to live on the coasts, and the increase in human population.
Coastal development is occurring all over the world, due to the demand of humans to live near water. Most coastal development involves the process of flattening the parallel dunes to build. These actions result in the flow of sand inland being disrupted, and the protective barrier situated between the land and the sea vanishes. Another form of coastal development affecting coastal dunes is reclamation. Reclamation involves building a wall that is some distance off the coast. It is done to extend the land out into water, and is extremely harmful to dune ecosystems, as it alters the movement of sediment along the coast. The areas that are reclaimed usually provide sand for dune development and growth.
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Humans also destroy the coastal dunes through the recreational practices that take place. When people try to make their way to beaches they usually trample along plants. This creates holes in the dunes and invites resilient weeds to grow. Most vegetation degradation occurs in the foredune, which happens to be the most important part of the dune system. The weight of vehicles and other means of transport compact the sand, resulting in the sand having less oxygen and therefore less plant growth. For example in Lake Huron, Ontario, Canada research has found that the number of vehicles having access to the dunes has caused the deeper sand to become compact and surface sand to loosen. The loosened sand becomes vulnerable to wind erosion, and causes a decrease in the rate of organic decay.
Coastal dunes are very specialised and tenuous. When there is an introduction in a flora and/or fauna species, this creates havoc in the dune ecosystem. One species that has caused major dune damage is the rabbit. The rabbits were introduced to Australia by the First Fleet and have been destructive ever since their introduction. Rabbits impact coastal dunes through eating the grasses and other vegetation, reducing the ground cover and they expose sand to wind erosion. An example of floral impact on the coastal dunes is the detrimental bitou bush. Once the bitou bush has entered the dune system it quickly takes over and kills all the native plants. The bitou bush is so successful due to its high-volume of seed production, large root systems and having no predators in Australia. (Appendix A Figure 1.3) An example of bitou bush monoculture on dune systems.
Natural Stresses
The major natural factor impacting dunes is storm damage. Storm-induced waves are able to cause a great deal of damage to the structure of the dune system. The ferocious power of the storm can leave the beaches degraded with little sediment, for dune reconstruction. Structural damage comes in two main forms, washovers, and washouts. An example of a major storm damage that has happened was in 1999 on the coastline of Byron Bay, New South Wales. The waves were as high as 3-metres, with the storms created mass coastal erosion. A further example of storms impacting coastal dunes was in Stockton Beach, Newcastle in 2007. The storms occurred over the June long weekend and resulted in approximately 100,000 cubic metres worth of sand being lost, as well as structural damage like erosion around sea walls. This caused major disturbance to the coastal dune functioning, as will take a long time to recover.
Dune systems don’t have perfectly shaped surfaces. The dunes often have recessions and elevations. When a storm-wave height surpasses the height of a recession in the dune, water seeps into the dune creating a washover. With consecutive storm-induced waves the washover impression deepens and widens, causing major damage. Recurring, powerful storms also cause damage to the flora of the dune, further decelerating the process of regeneration. (Appendix B Figure 1.7) makes evident how washovers make rifts in the dune tops. An example of how washovers have caused damage to dunes was the major storm damage that occurred at the Newcastle Port in 1974. The storm had wind gusts up to 165 kilometres/per hour, and swells were over 17 metres high. The impact of the storm on the dunes was the well-built foredunes had been completely flattened.
Washouts are linked with the penetration of sand barriers like those that segregate coastal lagoon from the open sea, after there has been a period of substantial rainfall. Washouts can also occur in dune systems, when there is a build-up of water in the swales that separate dunes. When there are slumps in the dunes surfaces, the water gets directed through the low points and overspills onto the beach, sometimes transport sand with it.
Most if not all ecosystems are affected by both human and natural stresses. Though the difference between the stresses is that ecosystems are able to adapt and overcome natural stresses, while human stresses cause great damage to ecosystems. An example of a natural stress impacting coastal dunes is a washover. Washovers can have significant damage to the dune system, and the dune system must adjust. One form of adjustment is through the accretion cycle. Constructive waves bring sand to the beach from the sea. The sand is dried from the wind and sunlight, and is then able to be transferred to the dunes. Like washovers coastal dunes adapt to washouts in a similar fashion. One way in which coral reefs especially the Great Barrier Reef responds to natural stresses like currents is by taking the shape of the stress. This helps the ecosystem in adapting to the stress and alleviating the consequences of the stress.
Question 3. Compare and contrast the vulnerability and resilience of the two ecosystems at risk.
All ecosystems have vulnerabilities and resilience. Location is one vulnerability. Coral reefs tend to be greater impacted by location than coastal dunes, as coral reefs are more specialised than coastal dunes. For example for coral reefs to thrive they need a certain water temperature. The temperature should be between 25 Degrees Celsius and 29 Degrees Celsius. An increase in temperature in the summer months has devastating consequences. As seen in the 2010 mass bleaching in the South-East Asian region which came with increased temperatures. On the other hand coastal dunes are more resilient to temperature changes. Coastal dunes are able to better adapt to temperature changes and only with a great increase in temperature change will coastal dunes become less resilient.
On the other hand a loss of land has more impact on coastal dunes than coral reefs. Coastal dunes have greater vulnerability to a loss of land because they are not large in size. If dune land is taken for human uses like parkland or parking spaces, unwanted competition is created within the dune flora and fauna. For example at Long Beach, Collaroy a large amount of the dune system was replaced with a car park area and grass land. This reduced the area of the dune system and created competition within the ecosystem. (Appendix A Figure 1.4) Long Reef Beach were has been redeveloped to fit human wants. In contrast the Great Barrier Reef is more resilient to reef area being taken. The reef being approximately 2,300 kilometres means that even if a few kilometres of reef area is taken, it will not have a major effect on the reef flora and fauna.
The Great Barrier Reef has a large degree of biodiversity, therefore making it more resilient to changes in diversity than coastal dunes. The Great Barrier Reef has around 1,500 species of fish, species of sea grass in beds, 500 coral species and more, showing great diversity. (Appendix B Figure 1.8) shows the diverse range of fish and coral species within the reef, compared to another reef. If for example one producer being algae is ended then there are other producers like sea plants that secondary consumers can feed on. While coastal dunes have very extreme environments, therefore only few flora and fauna are able to survive. This limits the diversity within the ecosystem, and if one primary consumer for example is killed off then there is competition for food, resulting in disequilibrium. Ecosystems with greater interdependence like the Great Barrier Reef can accommodate for change more easily, while coastal dunes (who have harsh conditions, which lowers there flora fauna populations), are more susceptible to change.
Question 4. Evaluate the traditional and contemporary approaches to management and protection of both ecosystems.
Coral Reefs
Traditional Management Strategies
Traditional management approaches were mostly used by the Aboriginal and Torres Strait Islanders. The Aboriginals focused on preserving the reefs and maintaining equilibrium in the ecosystem. The first traditional management plan was season hunting. Season hunting involved hunting only occurring at specific designated times of the year, for example summer. This strategy guaranteed that there would be flora and fauna available for the future generations. The Aboriginals and Islanders only took what resources they needed from the reef, which helped in maintaining dynamic equilibrium in the reef.
Another impressive traditional management tactic used by the Aboriginals in maintaining the reefs was restrictions on fish sizes. This practice involved only catching fish of a certain length or above. Through this practice the fish of the Great Barrier Reef were given the chance to reproduce at least once before they were caught. This let the ecosystem maintain levels of fauna.
Contemporary Management Strategies
Coral reefs are also maintained through contemporary management strategies, with a startegy being zoning. Zoning involves establishing what can be done and where it can be done. The purpose of zoning is to diminish stress placed on certain areas of the reef. An example of zoning is allowing commercial fishing to occur in some parts of the reef, while tourism developments in other parts.
Another way in which reefs can be preserved is through benchmark data. Benchmark data is comparing the ecosystem that is at risk with the ‘standard’ of that ecosystem. Benchmark data helps in understanding whether the reef ecosystem is at the standard that it should be. For example the standard level globally for the amount of dissolved nitrogen in the water of coral reefs is 0.014ppm. Benchmark data is important in interpreting the risk factor the reef ecosystem has.
The managing of tourism on the reef is also a significant factor of contemporary management strategies. Tourism generally has a negative impact on the reef, so it’s important that these tourists learn more about the reefs and the need to manage them. The Great Barrier Reef Marine Park Authority (GBRMPA) makes all tourists pay a certain fee when visiting the reefs, so they can reinvest the money into the reef. One of the major issues regarding tourism in reefs is the concentration on certain areas. For example, around 85% of all Great Barrier Reef tourism occurs in the areas of Cairns and Whitsunday Islands. Though they only make up 7% of the entire Great Barrier Reef putting immense risk on these areas. Over the years there have been many pontoon accidents in the reef and so the GBRMPA decided to ban all pontoon activity unless granted otherwise. Tourism also impacts the wildlife and breeding cycles. Fauna have certain places and times when they are breeding and sometimes humans disturb their cycles. For example research found that many bird species that regularly bred on Michaelmas Cays had stopped breeding due to the growing tourist activity on the island.
Coastal Dunes
Traditional Management Strategies
Very little is known on the traditional Aboriginal ways of the management of coastal dunes. The findings of middens, which are mounds of shells, are indicators to the type of marine environment in the area, and the time that the Aborigines used the resources. Totems were also used by Aboriginals. Totems are animals assumed as an emblem to an individual or family. For many Aborigines the totems were an animal ancestor of theirs. They were not allowed to eat their totem animals or harm it in anyway. This management strategy helped in making sure species were not overhunted. The most known form of Aboriginal management of coastal dunes was back-burning. Back-burning occurred through fires or fire stick farming, and would occur during cool periods so the fires would not get out of hand and kill the whole ecosystem.
Contemporary Management Strategies
For successful dune protection to occur, the natural functioning of the dune must be sustained, while allowing humans to use the coastal dune ecosystem in a sustainable manner.
As dune restoration is extremely costly many bodies of power have used strategies that protect the current dunes, and keep them in the best possible condition. One strategy imposed is land-use controls. Through state and local governments there is the ability to have stricter planning laws on human activities on dunes. Local governments have the power to accept or decline any development applications on the dunes. This would help the dune system function in a more natural state.
Dune stabilisation is also an important feature to management and involves securing exposed sand and stopping it from blowing away. One way of doing this is through reshaping the dunes. Reshaping transpires through the use of earthmoving equipment that makes the dunes more aerodynamic shaped. Reshaping is able to create the needed form of the dune for vegetation and organisms to become established on the dunes. Dune reconstruction usually occurs on dunes that lack in sand. As it is expensive to import sand, chemicals and other inorganic fertilisers are used. If dune reconstruction is applied with other efficient management methods like revegetation, then it is extremely positive for the dune, as seen in Texas, USA where sand dunes using this method have grown by 2 or 3 metres in only 2 years.
The most successful method for dune stabilisation is revegetation. Revegetation is proven to be the least expensive, most durable and is able to self-maintain. The main role of dune plants is to trap and hold wind-borne sand. The leaves of vegetation also play a part, as they disturb the movement of sand by saltation and surface creep. Revegetation usually takes on the form of developing a plant succession on the dunes. If the dune is somewhat degraded then pioneer dune grasses, like sand spinifex, are brought in to stabilise the dune, then introduced are the secondary vegetation like she oaks and finally tertiary species like coastal trees. As coastal dunes are extremely harsh and specialised ecosystems it is preferred that the seedlings of the revegetation come from neighbouring areas, as the vegetation has experienced the conditions. Revegetation does not come cheap and is particularly labour-intensive. Through the actions of volunteers like Dune Care, dune revegetation is able to occur more often and with fewer expenses. (Appendix A Figure 1.5) an example of successful dune revegetation occurring on coastal dunes.
Conclusion
Both coral reefs and coastal dunes are extreme environments in their own ways. They face common problems in terms of the biophysical interactions and human stresses, but also contrasting difficulties with one being more vulnerable than the other. Much importance must be placed on preserving both ecosystems as they offer us many resources. Efficient management approaches must also be used to sustain them for future generations. These environments offer humans an insight into the power and ferocity that is instilled in Mother Nature. The ecosystems have adapted to the many conditions they have faced, and will continue as long as we can help preserve them.
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