Great Barrier Reef - Human Impacts
Population pressure
Increased population pressures on mainland North Queensland have resulted in increased levels of pollution and physical activities related to tourism on the reef area.
Tourism
The outstanding beauty of the reef attracts millions of tourists each year. The pressure placed on the reef as a result of tourism includes developments on the shoreline (and associated sewage, rubbish) increase boating activity (including oil spills, coral breakage as a result of boat propellers), and tourist activities (breaking corals while snorkelling, walking on reefs, accessing sensitive areas).
Agriculture (particularly Sugar cane farming)
Agriculture, especially sugar cane farming on the mainland, has resulted in increased sediment and fertiliser run-off from cane farms. In recent years, a downturn in global prices for sugar cane has resulted in farmers using greater amounts of chemicals. These chemicals run off into coastal streams and result in algal blooms and eutrophication in some areas of fringing coral near the mainland.
Sugar cane farmers apply fertilisers containing Nitrogen (N) and Phosphorous (P). Many put on extra fertiliser in case of heavy rain (so it is not all washed away). The introduction of bananas as a crop in the area further increased the use of fertilisers. Of all fertilisers applied, only a third is absorbed by the crops. The rest is either evaporated, enters groundwater or runs off into nearby rivers or canals. Sugar cane crops need water to be drained away quickly. If the crops are left in water the roots will rot. As a result canals were built to drain water away quickly from the crops in case of heavy rain. These canals, or drains, reverse the cycle of how wetlands are meant to function. Rather than regulate and slow the flow of water, the water is quickly moved away from the site and into main river systems. The water rushes off the land carry fertiliser, soil, pesticides, etc. Actually pinpointing the sources of sediment is difficult, but it is believed that most is coming from land which has been tilled and let lie fallow. Sediment is also coming from bank erosion. Since European settlement erosion has accelerated due to clearing of land (less tree to stabilise soil). Due to erosion the river can erode into paddocks. There is believed to be four times more sediment reaching the coast than prior to European settlement, and in some places it is closer to 40 times.
Fishing
Recreational and commercial fishing have had major impacts on the reef. Commercial prawn fishing accounts of a large proportion of Queensland's Fisheries output. Approximately 6 million kgs of prawns area harvested in a good year. Recreational fishing in the General Use zones of the Great Barrier Reef Marine Park (GBRMP) accounts for 75% of the fin fish taken from the reef each year. Commercial fishing includes fishing for crayfish, finfish, reef fish, barramundi and tuna.
An examination of one net which washed ashore showed it contained 14 turtles, a shark and a dugong.
Gamefishing has long been an important industry in North Queensland.
Pisciculture is a trend involving raising fish in fish farms (e.g. tiger prawns and barrmundi).
Dredging
Dredging is removing sediment from the bottom of a river bed, harbour, etc and placing it elsewhere.
Abbot Point: Dredging dumping permitted within Great Barrier Reef waters
Abbot Point approval: Tour operators disappointed by Great Barrier Reef dredge spoil decision
Increased population pressures on mainland North Queensland have resulted in increased levels of pollution and physical activities related to tourism on the reef area.
Tourism
The outstanding beauty of the reef attracts millions of tourists each year. The pressure placed on the reef as a result of tourism includes developments on the shoreline (and associated sewage, rubbish) increase boating activity (including oil spills, coral breakage as a result of boat propellers), and tourist activities (breaking corals while snorkelling, walking on reefs, accessing sensitive areas).
Agriculture (particularly Sugar cane farming)
Agriculture, especially sugar cane farming on the mainland, has resulted in increased sediment and fertiliser run-off from cane farms. In recent years, a downturn in global prices for sugar cane has resulted in farmers using greater amounts of chemicals. These chemicals run off into coastal streams and result in algal blooms and eutrophication in some areas of fringing coral near the mainland.
Sugar cane farmers apply fertilisers containing Nitrogen (N) and Phosphorous (P). Many put on extra fertiliser in case of heavy rain (so it is not all washed away). The introduction of bananas as a crop in the area further increased the use of fertilisers. Of all fertilisers applied, only a third is absorbed by the crops. The rest is either evaporated, enters groundwater or runs off into nearby rivers or canals. Sugar cane crops need water to be drained away quickly. If the crops are left in water the roots will rot. As a result canals were built to drain water away quickly from the crops in case of heavy rain. These canals, or drains, reverse the cycle of how wetlands are meant to function. Rather than regulate and slow the flow of water, the water is quickly moved away from the site and into main river systems. The water rushes off the land carry fertiliser, soil, pesticides, etc. Actually pinpointing the sources of sediment is difficult, but it is believed that most is coming from land which has been tilled and let lie fallow. Sediment is also coming from bank erosion. Since European settlement erosion has accelerated due to clearing of land (less tree to stabilise soil). Due to erosion the river can erode into paddocks. There is believed to be four times more sediment reaching the coast than prior to European settlement, and in some places it is closer to 40 times.
Fishing
Recreational and commercial fishing have had major impacts on the reef. Commercial prawn fishing accounts of a large proportion of Queensland's Fisheries output. Approximately 6 million kgs of prawns area harvested in a good year. Recreational fishing in the General Use zones of the Great Barrier Reef Marine Park (GBRMP) accounts for 75% of the fin fish taken from the reef each year. Commercial fishing includes fishing for crayfish, finfish, reef fish, barramundi and tuna.
An examination of one net which washed ashore showed it contained 14 turtles, a shark and a dugong.
Gamefishing has long been an important industry in North Queensland.
Pisciculture is a trend involving raising fish in fish farms (e.g. tiger prawns and barrmundi).
Dredging
Dredging is removing sediment from the bottom of a river bed, harbour, etc and placing it elsewhere.
Abbot Point: Dredging dumping permitted within Great Barrier Reef waters
Abbot Point approval: Tour operators disappointed by Great Barrier Reef dredge spoil decision
Approval of Galilee mega mine leaves Reef strategy in tatters.
Landuse impacts on Great Barrier Reef water quality and ecosystem condition
Dredging set to swamp decades of Great Barrier Reef protection
WWF - Queensland resources sector needs leadership
Landuse impacts on Great Barrier Reef water quality and ecosystem condition
Dredging set to swamp decades of Great Barrier Reef protection
WWF - Queensland resources sector needs leadership
Hughes described some of the main drivers of degradation of coral reefs: pollution, overfishing and climate change. He explained how overfishing had resulted in the reduction of stock sizes for different species in the past century, how pollution from inland activities resulted in coral mortalities and encroachment of different ecosystems like mudflats in areas previously thriving with corals. He went on to say that the scale and extent of these changes were being dwarfed by the immediate and irreparable changes being wrought by back to back bleaching events.
Mass bleaching events have occurred in both 2016 and 2017 as a result of increased ocean temperatures. The bleaching is as a result of corals expelling their symbiotic algae. Coral bleaching tends to occur after the summer temperature maximum, and relates to where the hottest water is. In 2016 coral bleaching severely bleached the northern third of the Great Barrier Reef, the middle section was bleached to a lesser extent, but still quite severely, while the bottom third of the reef largely escaped bleaching in 2016. This was established by the surveying of 1160 reefs through 9000km of aerial surveys, and 75 hours of flying. The 2017 bleaching event impacted the central section of the GBR, while the bottom third is again largely unbleached. Cycle Debbie, a chance weather event, lowered temperatures in the southern part of the reef, which contributed to reducing bleaching in this section. The combination of both the 2016 and 2017 bleaching events has been extremely damaging.
There have been reports that the recent cyclone that affected Queensland, Cyclone Debbie may play a role in reducing the impact of coral bleaching. It was reported in the Cairns Post that the cyclone would reduce ocean temperatures, bring cooler waters to the surface and increase cloud cover, thus reducing bleaching, providing stressed corals with an opportunity to recover. The Cairns Post reported that temperatures off Lizard Island had dropped by three degrees and that this would reduce the severity of bleaching. It also provided quotes from a free diver describing the amazing colours and marine life of the outer reef. In reality, as already stated Lizard Island and the top third of the Great Barrier Reef were already severely affected by bleaching in 2016 (well before Cyclone Debbie) and were again affected in 2017. In any case, the path of the cyclone was too far south to have any real impact on areas severely affected by bleaching.
Will the Great Barrier Reef recover?
There is a narrow opportunity for limited recovery, but the Great Barrier Reef as we know it (complexity, extent, etc) is already dead in many areas. It will continue to exist but with reduced biodiversity.
Any real opportunities to protect the reef as it remains is reliant on halting temperature increases and stabilising the climate through reducing reliance on fossil fuels. With negotiations underway between the Australian Government and Adani for for the creation of the Marmichael mines this seems highly unlikely.
For more detail on coral bleaching see my article in this term's GTA NSW HSC edition of the Bulletin.
http://www.gtansw.org.au
Will the Great Barrier Reef recover?
There is a narrow opportunity for limited recovery, but the Great Barrier Reef as we know it (complexity, extent, etc) is already dead in many areas. It will continue to exist but with reduced biodiversity.
Any real opportunities to protect the reef as it remains is reliant on halting temperature increases and stabilising the climate through reducing reliance on fossil fuels. With negotiations underway between the Australian Government and Adani for for the creation of the Marmichael mines this seems highly unlikely.
For more detail on coral bleaching see my article in this term's GTA NSW HSC edition of the Bulletin.
http://www.gtansw.org.au
Coral Bleaching - student activities
Students should define the following key terms:
- acclimatise
- connectivity
- recruit
- adaptation
- natural selection
- symbiotic
- zoozanthallae
- parasite
- photosynthesis
Answer the questions below. Conduct internet research to find articles and reports which support your answers.
Resources:
Coral bleaching - GBRMPA
Coral bleaching and the Great Barrier Reef - ARC CoE
Coral bleaching: Extreme heat pushes parts of the Great Barrier Reef beyond recovery - ABC
Coral bleaching events - AIMS
Great Barrier Reef: a "hopping hotspot" - Australian Geographic
- acclimatise
- connectivity
- recruit
- adaptation
- natural selection
- symbiotic
- zoozanthallae
- parasite
- photosynthesis
Answer the questions below. Conduct internet research to find articles and reports which support your answers.
- Describe the causes of mass coral bleaching events.
- How has coral bleaching affected different geographical areas of the Great Barrier Reef? Find or create a graphic that represents the geographic distribution of coral bleaching.
- Describe the ways that coral bleaching has changed the nature of coral reefs (refer to the Great Barrier Reef, but also try to refer to reefs globally)?
- How has coral bleaching impacted on the vulnerability and resilience of coral reef ecosystems in various parts of the Great Barrier Reef?
- Develop a range of strategies to manage the causes and impacts of coral bleaching. For each strategy make a judgement about how effective it is likely to be (start by giving it a rating out of 5 - 5 being extremely effective, 3 being somewhat effective and 1 being completely ineffective). For each strategy write several sentences which justify your decision about how effective/ ineffective it will be.
Resources:
Coral bleaching - GBRMPA
Coral bleaching and the Great Barrier Reef - ARC CoE
Coral bleaching: Extreme heat pushes parts of the Great Barrier Reef beyond recovery - ABC
Coral bleaching events - AIMS
Great Barrier Reef: a "hopping hotspot" - Australian Geographic