CS: The Great Barrier Reef (Threats + Possible Management Strategies)

Question 1

General

Answer 1

• located off NE coast of Queensland, Australia
• world’s largest coral reef system, stretching >2,300km, w >2,900 individual reefs + 900 islands

Question 2

What are the threats to coral reefs?

Answer 2

• global warming
• sea lvl rise
• pollution
• physical damage

Question 3

Describe global warming as a threat to coral reefs.

Answer 3

• a rise in global T°Cs has led to coral bleaching, which occurs when sea T°Cs become too high for zooxanthellae to survive in coral, so leaves coral, making them more susceptible to disease, + causes an energy deficit, preventing coral from growing
  
  • e.g. between 2016 + 2020, the GBR suffered 3 mass bleaching events, caused by prolonged ocean heat waves, in which 30% of corals died in 2016 alone

Question 4

Describe sea lvl rise as a threat to coral reefs.

Answer 4

• as global T°Cs rise, glaciers + ice sheets melt, resulting in rising sea lvls, which dec light availability if sea lvls rise faster than upward growth of coral

Question 5

Describe pollution as a threat to coral reefs.

Answer 5

• pollutants (e.g. CO2 emissions from atmo) are dissolved into ocean, leading to ocean acidification, which breaks down the calcium carbonate skeleton making up the coral reef
• also, sediment + land based pollutants can wash into ocean + block light, affecting photosynthesis of zooxanthellae
  
  • e.g. 80-90% of pollution entering the GBR comes from agri runoff from sugarcane + cattle farming, + contains excess nutrients, pesticides + sediment
  • the excess nutrients support COTS, in which COTS outbreaks caused 42% of coral loss on the GBR between 1985 + 2012, bc feed on coral. 1 COTS can eat up to 6m2 of coral per yr

Question 6

Describe physical damage as a threat to coral reefs.

Answer 6

• destructive fishing practices can damage + destroy coral reefs, + inc bottom trawling which involves a large net being dragged on sea floor
  
  • also, overfishing of species (e.g. parrotfish) in the GBR has disrupted ecosystem + allowed algae to overgrow on corals

Question 7

What are the possible management strategies for global warming?

Answer 7

• Reef 2050 LT Sustainability plan (supported by Australian gov): emphasises dec CO2 emissions to limit global warming + aims for net-0 emissions by 2050
• projects like Coral IVF collect coral spawn, focus on breeding heat-tolerant species (inc resistance to coral bleaching), + replant baby corals on damaged reefs
  
  • 2018: >1M coral larvae replanted on parts of reef near Heron Island = helped speed recovery of damaged reefs

Question 8

What are the possible management strategies for sea lvl rise?

Answer 8

• Coral IVF also aims to plant fast-growing coral species that can keep up w rising sea lvls
  
  • inc branching corals, like Acropora = grows vertically more quickly than massive coral types = inc light availability

Question 9

What are the possible management strategies for pollution?

Answer 9

• Reef Water Quality Protection Plan (part of Reef 2050 plan): aims to dec sediment runoff by 25% + nitrogen runoff by 60% by 2025
  
  • achieving this by promoting Best Management Practice (BMP) Programs = work directly w farmers to dec fertiliser + chemical use (e.g. in 2019, ab 65% of sugarcane growers implemented BMPs for nutrient management)
• COTS Control Program: employs divers to manually inject COTS w bile salts = kills them w/o harming other marine life
  
  • from 2013-2021, >1M COTS were killed in key reef zones

Question 10

What are the possible management strategies for physical damage?

Answer 10

• Marine Zoning plan (2004): no-take (green) zones cover + protect ab 33% of reef (prohibits all fishing) + habitat protection (yellow) zones cover 30% of reef (allows some low-impact fishing but bans destructive gear)
  
  • helps protect sensitive reef habitats + allow fish pop to recover

Question 11

Conclusion/evaluation on threats

Answer 11

• threats prove to sig damage reefs + must be banned or carefully controlled + monitored to successfully, sustainably manage reefs

Question 12

Conclusion/evaluation on possible management strategies

Answer 12

• many threats can be successfully mitigated + managed, but bc most effective ways limit eco activities, it may not be considered v sustainable
• also, most methods are ST, so in order to successfully mange reefs in LT, stricter gov policies (esp on CO2 emissions) must be implemented globally