Fighting Coral Loss on the Great Barrier Reef

The Great Barrier Reef, one of the world’s most iconic natural wonders, faces multiple threats ranging from climate change to overfishing. Among these threats, outbreaks of the crown-of-thorns starfish (CoTS) have long posed a significant risk to coral health. These starfish consume coral at alarming rates, and repeated outbreaks over the past four decades have devastated large sections of the reef. Recent research led by CSIRO and the Australian Institute of Marine Science (AIMS) provides new evidence that large-scale conservation measures and improved fisheries management are helping to reduce the frequency and intensity of these outbreaks, offering hope for the reef’s long-term resilience.
The Threat of Crown-of-Thorns Starfish
Crown-of-thorns starfish are native to the Indo-Pacific region and are a natural part of coral reef ecosystems. However, under certain conditions, their populations can explode, leading to widespread coral destruction. Outbreaks are often exacerbated by human impacts, such as overfishing, which reduces populations of predatory fish that naturally keep CoTS numbers in check.
“These starfish remain one of the most significant natural threats to Reef health,” says Dr. Scott Condie, CSIRO researcher and lead author of the study. “Multiple outbreaks over the past 40 years have shown how quickly they can damage coral if left unchecked.”
The consequences of unchecked CoTS outbreaks are severe. Large-scale coral loss reduces biodiversity, weakens reef structure, and diminishes the reef’s ability to support fisheries and tourism. Moreover, coral degradation has broader implications for coastal protection and carbon cycling, highlighting the reef’s global ecological importance.
Conservation Initiatives: Zoning and Fisheries Management
In response to these threats, the Australian Government implemented significant conservation reforms in 2004. The reforms included expanding no-take zones to cover 33% of the Great Barrier Reef Marine Park and introducing tighter fishing regulations. These measures aimed to protect key fish species, such as emperors and groupers, which prey on crown-of-thorns starfish.
Using advanced ecosystem modelling, the research team demonstrated that these strategies likely played a pivotal role in rebuilding predatory fish populations. By supporting these natural predators, the measures help to keep CoTS numbers under control, reducing the risk of widespread coral loss.
“Our model shows that these initiatives likely averted a catastrophic tipping point,” Dr. Condie explains. “Without these protections, we could have seen continuous CoTS outbreaks and far greater coral loss.”
Long-term monitoring supports this conclusion. Reefs within protected zones consistently experience fewer outbreaks, indicating that these conservation strategies are effective in practice, not just in theory.
The Role of Direct CoTS Management
In addition to protecting predatory fish, direct management of crown-of-thorns starfish has evolved over the decades. Early efforts in the 1980s involved manually removing starfish from individual reefs, a labor-intensive process with limited impact. Today, the CoTS Control Program, led by the Great Barrier Reef Marine Park Authority, operates on a much larger scale.
Each year, specialist vessels target over 200 priority reefs, focusing efforts where outbreaks are most severe or where tourism and biodiversity are highly valued. The program combines cutting-edge monitoring techniques with targeted culling, effectively reducing starfish populations and minimizing damage to coral. Evidence from recent studies confirms the program’s effectiveness, particularly when paired with broader reef protection strategies.
Dr. Daniela Ceccarelli, AIMS researcher and co-author of the study, emphasizes the importance of integrating fish protection with direct CoTS control: “Without intervention over the past 20 years, grouper and emperor populations would have steadily declined under mounting fishing pressure. Our modelling shows that fish-protection strategies are crucial for buffering the Reef against future outbreaks.”
Projected Impacts and Future Implications
Model projections to 2050 indicate that without continued conservation and fish protection strategies, the proportion of reefs experiencing CoTS outbreaks could increase four-fold. This scenario underscores the importance of sustained management in the face of escalating climate pressures, such as ocean warming and acidification, which further stress coral ecosystems.
The study highlights that maintaining healthy fish populations is not only critical for controlling starfish but also for preserving overall reef resilience. Predatory fish help maintain balanced ecosystems, allowing coral communities to recover from disturbances and adapt to changing environmental conditions.
Additionally, the research provides a roadmap for refining conservation strategies in the future. By combining zoning reforms, fisheries management, and direct CoTS control, policymakers and marine managers can implement a multi-layered approach that addresses both immediate threats and long-term ecological stability.
Conclusion
The Great Barrier Reef continues to face complex and interconnected challenges, from climate change to invasive species outbreaks. However, the latest research demonstrates that well-designed conservation measures can make a meaningful difference. By expanding protected zones, regulating fisheries, and actively managing crown-of-thorns starfish populations, Australia has taken significant steps to safeguard the reef’s biodiversity and resilience.
The findings from CSIRO and AIMS underscore a vital message: long-term, science-driven management works. Rebuilding predatory fish populations and controlling starfish outbreaks has not only reduced immediate threats to coral but also strengthened the reef’s capacity to withstand future environmental pressures.
As the Reef faces increasing climate-related stressors, continued monitoring, research, and adaptive management will be critical. This study offers a hopeful example of how targeted conservation efforts, informed by rigorous scientific modelling, can help protect one of the planet’s most precious ecosystems for generations to come.