Stretching 2,300 kilometres along the Queensland coast, the Great Barrier Reef is the world’s largest coral reef system and one of the most complex natural ecosystems on the planet. It is home to over 1,500 species of fish, 4,000 types of mollusc, and more than 200 species of birds. It has been a UNESCO World Heritage Site since 1981.
It is also in serious trouble.
Mass Bleaching Events
Coral bleaching occurs when water temperatures rise above the corals’ tolerance threshold, causing them to expel the symbiotic algae that give them colour and nutrition. Without these algae, corals turn white and, if temperatures remain elevated, die.
The Great Barrier Reef has experienced six mass bleaching events: 1998, 2002, 2016, 2017, 2020, and 2022. The frequency is accelerating. The 2022 event was the first to occur during La Niña conditions — a period that historically brings cooler waters — suggesting that even “cool” years are now too warm for the reef’s corals.
🌡️ Fact: The Great Barrier Reef Marine Park Authority’s 2024 outlook report rated the reef’s overall condition as “critical.”
Other Threats
Water Quality
Agricultural runoff carrying sediment, nutrients, and pesticides from Queensland’s coastal farms smothers corals and fuels algae growth. Improving water quality in reef catchments is one of the most tractable local interventions available.
Crown-of-Thorns Starfish
Outbreaks of this coral-eating starfish are a natural phenomenon, but they become more destructive when nutrients from agricultural runoff boost juvenile starfish survival rates. Control programs involving manual removal and injection with bile salts are ongoing.
Coastal Development
Dredging, port expansion, and coastal construction threaten inshore reef areas through increased turbidity and direct physical disturbance.
Signs of Resilience
Despite these threats, the reef shows remarkable resilience in areas where local pressures are managed. Northern sections that escaped the worst bleaching have seen coral recovery. Coral gardening programs — where fragments of heat-tolerant coral varieties are grown in nurseries and transplanted — offer genuine hope for assisted evolution of the reef ecosystem.
What You Can Do
- Support the Great Barrier Reef Foundation
- Choose reef-safe sunscreen when swimming in reef waters
- Reduce your carbon footprint — climate change is the reef’s biggest long-term threat
- If visiting the reef, choose operators who follow GBRMPA best practice guidelines
- Support stronger agricultural runoff regulations by engaging with your state MP