Higher Sea Temperatures
The Great Barrier Reef is a delicate and sensitive ecosystem which will respond negatively to minimal temperature changes. The average temperature range for the Great Barrier Reef is from 22°C to 27°C. A deviation in these temperatures ranging from 1 - 2 °C (see Figure 1.3 below) for a time bracket of 5 – 10 weeks could start a bleaching event on the Great Barrier Reef.
Coral Bleaching
Coral bleaching is a stress condition within corals that involves the breakdown of the symbiotic relationship consisting between the coral and zooxanthellae. Zooxanthellae are microscopic plants that live in the coral and provide the coral with food for growth and for healthy colour. Coral bleaching involves the expulsion of the zooxanthellae from the coral thus resulting in unhealthy and bone-white coral; hence the term ‘bleaching’.
Coral bleaching can be brought on by a number of factors. For example:
- High light intensity
- Increase in water pollution
- Low water salinity
- Changes in water temperature
Although there are many factors that lead to the bleaching events, climate change and changing temperatures are considered the primary cause. The ultimate consequence of coral bleaching is death of the coral. This can cause unbalances in the delicate ecosystem of The Great Barrier Reef. This unbalance can cause a chain reaction where many species in the vast affected communities can also become deceased.
In 2002, The Great Barrier Reef recorded its worst ever bleaching event where 65% to 90% of the reef were affected. Some locations on the reef had up to 90% of their corals perish due to bleaching; however only 5% (17,400km2) of the reefs corals actually perished. There since have been many coral bleaching events observed (see Figure 1.4 below).
Changes In Weather Conditions
Climate change has caused rapid changes in what is considered to be the normal weather patterns. Massive storms, cyclones and heavy rain fall has followed years of severe drought and has left its mark on The Great Barrier Reef.
Tropical Cyclones
In 2006, a category five cyclone (cyclone Larry) ripped through The Great Barrier reef just north of Cairns. As a path of destruction was left, corals were ripped from their communities leaving big, gaping holes where they used to reside (see Figure 1.5 below). There was an immediate imbalance in the reef and a decrease in the overall species in some areas decline. It was estimated that it would take up to 20 years for the reef to repair itself and overcome the damage made. However; this cyclone came just after a spike in the sea temperatures on the reef and did save the reef from a major bleaching event.
If you refer below to Figure 1.6, approximately 33.8% of all coral mortality over the past 16 years has been because of storms. This has been caused by a major deviation of the weather patterns due to climate change.
Management Strategies
There are many management strategies put in place to minimize the effect climate change has on the world. Many of the strategies you might be familiar with are:
- Electric vehicles (see Figure 1.7 below)
- Renewable energy sources (see Figures 1.8, 1.9, 1.10 below)
- The Carbon tax
- Reducing waste and recycling
- Increased public transport (see Figure 1.11 below)
Effectiveness
Climate change is a threat imposed not only to the Great Barrier Reef, but to the entire world. These management strategies (listed above) are strategies you will see around the world but just how effective are they? (Due to a rising population, a measurement of year-to-year greenhouse gas emissions would not be accurate.)
Electric Vehicles
Electric vehicle technology is advanced and commercialised, meaning that anyone who has the money can invest in an electric car. But there lies the problem. Only people who have the money can purchase the vehicle and many people can’t afford to. The Toyota Prius (see Figure 1.7 above) has a starting price of $39,990 excluding on road costs (according to Top Gear magazine November 2011). That is an expensive price to pay for a vehicle that car that can only drive 60km on electric power.
Until electric vehicles become more effective and cheaper, they will remain ineffective; However, I suggest they invest more time into the concept of hydrogen cell-powered cars.
Renewable Energy
Whether it’s solar, hydro or wind, renewable energy is a pollution-free method of producing electricity. It is used in many countries today and is a minor source of energy for all countries in the G20 (see figure 1.12below).
Effectiveness
Renewable energy is a clean source of energy but is costly at commercial prices (approximately $18,000 for 18 solar panels installed on your house) and is costly and wholesale prices. On a large scale, it would be a very costly investment and as it depends on the weather conditions to prove how effective it is; renewable energy isn’t a reliable source of energy.
Traditional Management Strategies
To protect the Great Barrier Reef of Coral Bleaching, Indigenous Australians often did not pollute the waterways and oceans as they believe this affected their land. Indigenous Australians had a deep and religious connection with their land and did not wish to pollute it in any way that was avoidable.
Overfishing
Overfishing, as defined by Wikipedia, is when “fishing related activities reduce the stock levels of fish below acceptable levels.” This, again, is mainly human induced and the effects are as follows:
- Increases in unwanted organisms EG jellyfish
- Possible extinction of species (see below)
- Habitat loss
- Food chain disruption
- Imbalances in species
Possible Extinction of Species
When it comes to overfishing, it is a recurrent issue and is rapidly increasing. The main possibility of overfishing, is the elimination of fish species due to them all being ‘fished out’. If certain species were to become extinct, it could corrupt certain communities that rely on that species and start a chain reaction until that community is completely wiped out.
According to CBC news, fish levels in the North Pacific and Atlantic waters have dropped by 90% since the 1950’s. This is a huge drop in species numbers and if continued, many species will be endangered by 2020.
Figure 1.13 below shows the amount of fish caught from 1950 to 1998 (units in million tonnes). This shows the amount caught in the ocean and the amount that are sustainably removed from ‘aqua farms’. The amount removed from the ocean has reduced and the amount ‘farmed’ has increased.
Management Strategies
When preserving The Great Barrier Reef from overfishing, there are few measures put in place. For Example:
- Licences for fishing in areas
- Minimal zoning
- Shipping routes
These strategies are marginally effective due to the fact they are broad. I suggest they implement more stringent zoning and have the following zones:
- Commercial Zones - for commercial usage
- Tourism Zones – for scuba diving and other tourist activities
- Fishing Zones – for commercial fishing only
- Harvesting Zones – for fish and corals used for non-grocery activities EG fish tanks.
Traditional Management Strategy
Traditionally, overfishing was prevented by partial or complete closure of areas in/surrounding The Great Barrier Reef. This would prove affective as no-one can legally enter the areas; however, closures aren’t practised any more.
Conclusion
The Great Barrier Reef was nominated to become one of the world’s 7 natural wonders of the world. Although it barely missed out, The Great Barrier Reef is an ecosystem of immense beauty and has been recognized so by the heritage listing and the preservation from threats such as oil spills, overfishing and climate change. Further measures will be put in place as these issues progression gets sped up due to increased demand for fish and oil, and increasing fossil fuel usage. As mentioned before, the biodiversity is distinct from any other ecosystem in the world and this glorifies what a beautiful ecosystem it is.
Glossary
Biodiversity – The variety of species and the genetic variability among individuals within each species.
Ecosystem – the dynamic complex of plant animal and micro-organism communities and their non-living environment as a functional unit.
G20 – (Group of 20) the largest 20 producing (economically) countries of the world determined by GDP.
Greenhouse gas – A gas that contributes to the greenhouse effect by absorbing infrared radiation, e.g. carbon dioxide.
Light Intensity - the quantity of visible light that is emitted in unit time per unit solid angle.
Salinity – The level of salt dissolved in water.
Species – All organisms of the same kind that are potentially capable of breeding and producing fertile offspring.
Symbiotic Relationship – A relationship between two entities, which is mutually beneficial to both participants.
Zooxanthellae – A symbiotic algae that lives with coral polyps and created the colours of the coral.
Bibliography
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