Unit 8 - Essays - Coral Reefs UPDATED Flashcards
To What Extent Can the Threats to Coral Reefs Be Successfully Managed?
- Climate Change and Coral Bleaching: The Biggest Challenge
Point:
Rising ocean temperatures cause coral bleaching, the most severe threat to reefs.
The GBR has suffered multiple bleaching events (2016, 2017, 2020), affecting 60% of reefs in 2016 alone (GBRMPA, 2021).
If global temperatures rise by more than 1.5°C, up to 90% of the world’s coral reefs could disappear (IPCC).
Management Efforts:
Global efforts: Australia has pledged to achieve net-zero emissions by 2050, but worldwide emissions reductions are slow.
Local adaptation: Marine cloud brightening is being trialed to cool surface waters.
Effectiveness:
Local solutions like cloud brightening may help but cannot stop warming altogether.
Climate action requires global cooperation, meaning that management at a national level is limited.
Judgment:
Local actions provide short-term relief, but only global climate action can prevent large-scale bleaching in the long run.
- Pollution and Runoff: Local Management Successes and Challenges
Point:
Agricultural runoff (fertilizers, pesticides, sediment) from Queensland’s farms harms the GBR.
Runoff leads to algal blooms that smother corals and increase Crown-of-Thorns Starfish (COTS) outbreaks.
Over 80% of land-based pollution affecting the GBR comes from farming.
Management Efforts:
Reef 2050 Plan: Aims to cut nitrogen runoff by 60% and sediment by 25% by 2025.
Progress so far: By 2023, nitrogen runoff had only decreased by 25% (Australian Institute of Marine Science, 2023).
Best practices in agriculture: Encouraging farmers to use buffer zones, better fertilizer techniques, and restore wetlands.
Effectiveness:
Some local improvements have been made, but widespread enforcement remains difficult.
Pollution control works at small scales, but full success is challenging due to spatial variation—some areas are harder to regulate than others.
Judgment:
Partially successful: Progress is slow, and pollution control efforts struggle to keep up with new sources of pollution.
- Overfishing and the Role of Marine Protected Areas (MPAs)
Point:
Overfishing reduces populations of key species like parrotfish, which help keep algae in check.
Removing too many fish makes reefs more vulnerable to bleaching and disease.
Management Efforts:
The GBR has one of the world’s most extensive Marine Protected Areas (MPAs) (344,400 km²).
33% of the reef is a no-take zone, meaning fishing is banned.
Fish populations in MPAs are 50% higher than in non-protected areas (GBRMPA, 2022).
Effectiveness:
MPAs have successfully restored fish populations in protected zones.
However, illegal fishing continues, particularly in remote areas where enforcement is difficult.
MPAs do not address global threats like climate change—fish stocks recover, but the reef is still at risk from warming and acidification.
Judgment:
Successful at a local scale, but MPAs alone cannot save the reef from global environmental changes.
- Tourism and Coastal Development: Can It Be Controlled?
Point:
Tourism is a major part of the GBR’s economy, contributing $6.4 billion annually and supporting 64,000 jobs.
However, poorly managed tourism can damage reefs (anchor drops, trampling, pollution).
Coastal development, such as the expansion of Abbot Point coal terminal, increases risks from sedimentation and pollution.
Management Efforts:
Tourism regulations: Limiting visitor numbers in fragile areas, eco-certification programs for tourism operators.
Enforcement success: 85% of tourism operators follow best practices to minimize damage.
Coastal development laws: Some projects have been blocked due to environmental concerns, but economic pressures continue to allow new developments.
Effectiveness:
Tourism can be controlled, but coastal development remains a challenge due to economic trade-offs.
High-traffic areas (e.g., Cairns, Whitsundays) show more damage than less-visited parts of the GBR, highlighting spatial variation in effectiveness.
Judgment:
Tourism can be successfully managed, but the pressures of coastal development remain an ongoing threat.
- Coral Restoration: A Hope for the Future?
Point:
Scientists are experimenting with coral restoration projects to help reefs recover.
Methods include:
Coral nurseries (growing corals and transplanting them).
Artificial reefs.
Breeding heat-resistant corals.
The Australian government has invested $150 million into these projects.
Early trials of heat-resistant corals show 75% survival rates in controlled environments (Australian Institute of Marine Science, 2023).
Effectiveness:
Restoration is promising, but:
It is expensive and only works in small areas.
Given the GBR’s massive size (2,300 km long), restoration alone cannot protect the entire reef.
Timescale limitation: Climate change is happening faster than restoration can keep up.
Judgment:
Useful as a short-term solution, but restoration cannot replace global climate action.
Conclusion
The threats to the GBR are managed with mixed success.
Local strategies such as MPAs, pollution controls, and tourism regulations have helped, but they do not address larger-scale threats like climate change.
Coral restoration offers hope, but it is not enough to save the reef at a global scale.
Most major threats require global action, especially reducing carbon emissions.
Final judgment: While local efforts help mitigate damage, they cannot prevent large-scale coral decline unless there is urgent international climate action. The future of the GBR depends on both local and global efforts working together.
Assess the significance of different threats to coral reefs.
- Global warming and coral bleaching – Most significant threat
Point:
Global warming causes sea temperatures to rise, leading to coral bleaching
Explanation:
Coral polyps eject zooxanthellae (algae) when stressed by heat → lose colour and energy source
Frequent and intense bleaching weakens coral health, lowers reproduction, and increases mortality
Evidence:
GBR has had 5 mass bleaching events since 1998 (notably 2016, 2017, 2020, 2022, 2024)
2016: 91% of northern GBR reefs bleached; 67% severely affected overall
Sea surface temps are increasing; events now occur every ~5 years instead of 27 years
Spatial & Temporal Impact:
Widespread: Affects the entire reef system
Long-term: Frequent events reduce recovery time
Evaluation (Significance):
High severity, huge spatial impact, and worsening over time
Climate change also worsens other threats, e.g. acidification
🟦 2. Ocean acidification – Long-term, global threat
Point:
Ocean acidification results from CO₂ dissolving into oceans, lowering pH levels
Explanation:
Reduces availability of carbonate ions → corals struggle to build skeletons
Slower reef growth, weaker structures, more erosion and breakage
Evidence:
Ocean acidity up 30% since 1800s
GBR calcification rates dropped 14% since 1990 (AIMS)
IPCC predicts pH could drop 0.3–0.4 units by 2100
Spatial & Temporal Impact:
Global and uniform across reef systems
Long-term, irreversible damage unless global emissions are reduced
Evaluation (Significance):
Less visible than bleaching, but serious structural consequences
Slower impact but highly damaging over decades
- Sea level rise – Medium threat with varied impact
Point:
Rising sea levels due to melting ice caps and thermal expansion affect reef ecosystems indirectly
Explanation:
Deeper water reduces sunlight → weaker photosynthesis
Coastal erosion increases → more sediment washed into reef system
Evidence:
IPCC projects up to 1m rise by 2100 under high-emissions
Burdekin River sediment plume: increased sedimentation in nearby inshore GBR reefs
Turbidity harms coral health and promotes algal overgrowth
Spatial & Temporal Impact:
Inshore areas most affected
Slow onset, but growing concern
Evaluation (Significance):
Not as dramatic as bleaching, but contributes to long-term decline
Uneven impact across reef zones
Linked to land use + climate change
- Pollution and agricultural runoff – Serious but localised
Point:
Pollution from agriculture adds nutrients and chemicals to reef waters
Explanation:
Excess nitrogen and phosphorus → algal blooms → compete with coral for light
Pesticides reduce coral resilience and damage nearby seagrass beds
Evidence:
2019 Reef Water Quality Report Card: only 2% of sugarcane land uses best practices
Fitzroy and Burdekin Rivers bring 90% of sediments to central GBR
Crown-of-thorns starfish outbreaks linked to high nutrient levels
Spatial & Temporal Impact:
Localised (mainly inshore reefs near river mouths)
Ongoing, especially during rainy seasons and floods
Evaluation (Significance):
High in specific locations but not reef-wide
Manageable with stricter regulations, making it less permanent than climate threats
- Physical damage from tourism and fishing – Manageable but cumulative
Point:
Direct human activities like anchoring, walking on reefs, or fishing damage coral structures
Explanation:
Broken coral = slow recovery
Overfishing of key species (e.g. parrotfish) → imbalance in reef ecosystems
Tourism brings boats, snorkellers, divers — accidental damage
Evidence:
2 million+ visitors/year to GBR
Whitsundays: one of most impacted zones
Anchoring and trampling damage coral branches; boat strikes hurt turtles and dugongs
Spatial & Temporal Impact:
Highly localised near tourism hotspots
Short-term but repetitive → adds up over time
Evaluation (Significance):
Less severe than climate threats, but adds pressure to already weakened reefs
Good regulations can limit damage (e.g. designated mooring zones)
Conclusion (Judgement)
Judgement Summary:
The most significant threats to the GBR are climate-related: warming and acidification
These threats are widespread, long-term, and difficult to reverse
Pollution and human activity are also serious, but more localised and easier to manage through laws and behaviour change
Action is needed at both local (pollution control, reef protection zones) and global (emissions reduction) levels
Overall, climate change is the biggest threat due to its scale, severity, and ability to make other problems worse
‘The characteristics and formation of fringing reefs, barrier reefs, and atolls are very different.’ How far do you agree with this view?
Paragraph 1: Fringing Reefs – Characteristics & Formation
Key Features
Found close to the coastline – no wide lagoon.
Simple structure: reef flat, boat channel, and reef crest.
Most common reef type globally.
Formation Process
Coral larvae settle on shallow coastal platforms.
Grow seaward over time.
Little dependence on sea-level change or land movement.
Development
Tend to form first in Darwin’s sequence.
Spatial example: Philippines, Indonesia, Caribbean.
Contrast
Simpler structure and faster formation compared to barrier reefs and atolls.
Paragraph 2: Barrier Reefs – Characteristics & Formation
Key Features
Located farther from the coast than fringing reefs.
Separated from land by a wide, deep lagoon (can be over 100 m deep).
Often very large and continuous.
Formation Process
Begin as fringing reefs.
As land subsides or sea level rises, corals keep growing upward.
Creates deep lagoon between reef and land.
Case Study: Great Barrier Reef
Largest reef system in the world: 2,300 km long.
2,900 individual reefs, up to 250 km offshore.
Started forming 500,000 years ago; current structure around 6,000–8,000 years old.
Rich biodiversity: 1,500 fish species, 400 coral types.
Development
Takes thousands of years.
Highly dependent on long-term sea level change.
Paragraph 3: Atolls – Characteristics & Formation
Key Features
Ring-shaped reef with a central lagoon, no central landmass.
Only found in open ocean (often on old volcanic island sites).
Very fragile ecosystems.
Formation Process
Follows full Darwin-Dana model:
Starts as fringing reef around volcanic island.
Island subsides slowly.
Reef grows upward; island eventually disappears, leaving lagoon.
Examples
Bikini Atoll (Marshall Islands), Maldives.
Development
Takes millions of years.
Coral must keep up with subsidence and sea-level rise.
Very vulnerable to climate change: sea level rise of 0.5 m could cause flooding.
Paragraph 4: Similarities Between Reef Types
Shared Environmental Conditions
All require:
Warm water (23–29°C).
Shallow depths (<50 m).
Clear, sunlit water (for zooxanthellae photosynthesis).
Stable salinity and low sediment.
Found in tropical belts (30°N–30°S).
Biological Similarities
All built by coral polyps using calcium carbonate.
All support high biodiversity (e.g., Great Barrier Reef = 1,500 fish species).
Shared Formation Triggers
Coral growth rate: 1–10 mm/year.
Affected by temperature, light, wave energy, and sediment.
Paragraph 5: Reef Formation Theories – Showing Links and Differences
Darwin-Dana Hypothesis
Reefs develop in sequence: fringing → barrier → atoll.
Based on subsiding volcanic islands.
Helps explain differences as stages in evolution.
Murray Hypothesis
Emphasizes outward growth of reefs from coral debris.
Not dependent on land sinking.
Could apply to all types – suggests similar formation processes.
Daly Hypothesis
Focuses on post-glacial sea-level rise (after last ice age).
Coral colonised submerged wave-cut platforms.
Explains atoll formation.
Evaluation
Theories suggest some overlap in reef development.
In some places, different reef types may be linked through time.
However, local conditions (e.g. no volcanic islands) may stop this sequence.
Conclusion (Clear Judgement)
Overall, reef types show major differences in structure, location, and formation timescales.
Fringing reefs are simple and coastal, barrier reefs are large and offshore, and atolls are ring-shaped and oceanic.
However, all depend on similar environmental needs and are shaped by related processes.
Therefore, I mostly agree with the view: while some similarities exist, the differences between reef types are significant and meaningful
