With all the alarming news about the Great Barrier Reef and coral bleaching in the past few years, I wanted to see it myself. On my recent trip to Port Douglas, Queensland, I went on a tour with the company Silver Series, and when I got out there, I was surprised by how beautiful it was, which made me want to learn more. I’ve heard about and seen ‘coral bleaching’ on the news, but what is it? Why am I always being told the Great Barrier Reef is dying?
Coral bleaching is one of the most visible and devastating impacts of climate change on coral reefs. While the bleaching process initially affects coral health, it triggers a series of cascading effects that reverberate throughout the reef ecosystem. This chain reaction weakens the coral itself and diminishes the reef's overall biodiversity, threatening the survival of countless marine species.
What is Coral Bleaching?
Coral reefs are made up of colonies of tiny animals called coral polyps. These polyps have a symbiotic relationship with microscopic algae called zooxanthellae. The zooxanthellae provide energy to the coral through photosynthesis and give corals their brilliant colors. When water temperature rises, corals become stressed and expel the zooxanthellae, causing them to turn white or "bleach."
If the water cools soon after bleaching, the corals may recover by regaining their algae. However, if high temperatures persist, the corals will starve and eventually die, triggering a chain reaction that affects the entire ecosystem.
A Rising Trend: Major Bleaching Events
Coral bleaching is not a new phenomenon, but what makes it alarming today is the increased frequency and intensity of bleaching events, driven largely by global climate change. Historically, the Great Barrier Reef experienced occasional bleaching events, but the past few decades have seen a sharp rise in both their occurrence and severity.
In 1998, the world experienced the first mass coral bleaching event, driven by an exceptionally strong El Niño event combined with global warming. During this year, an estimated 16% of the world’s coral reefs were affected, including large portions of the Great Barrier Reef. This marked the first time the world witnessed widespread coral mortality linked to climate change.
The Great Barrier Reef suffered its first large-scale bleaching event in 2002, which affected around 60% of the reef. Water temperatures rose to unprecedented levels, and large sections of coral turned white. While some areas of the reef recovered, others did not, leading to long-term degradation in certain regions.
The year 2016 marked the worst coral bleaching event in recorded history for the Great Barrier Reef. An extreme marine heatwave—again exacerbated by a strong El Niño and climate change—caused mass bleaching across 93% of the reef. The northern part of the reef was hit hardest, with 67% of shallow-water corals dying. The severity of this event underscored the growing urgency of climate action, as the reef showed significant declines in coral cover and biodiversity.
Just one year after the catastrophic 2016 event, the Great Barrier Reef experienced another mass bleaching in 2017. This back-to-back bleaching event was unprecedented, and coral colonies that had barely begun to recover from the 2016 damage were hit again, causing further mortality. In some areas, corals that had managed to survive the previous year’s event died from the cumulative stress, greatly reducing the reef's resilience.
In 2020, the Great Barrier Reef experienced its third mass bleaching event in five years, marking the first time that bleaching occurred during a year without an El Niño event. This signaled that global warming alone was driving the increase in ocean temperatures. In 2020, over 60% of the reef experienced bleaching, with parts of the southern reef—previously spared by earlier events—now being affected (Great Barrier Reef Foundation, 2020). This event confirmed that the reef is experiencing more frequent and widespread bleaching than ever before.
An article from the Australian Institute of Marine Science (AIMS) highlights that the Great Barrier Reef has shown signs of recovery due to cooler La Niña conditions, with record-high coral cover in 2022. The graphs below illustrate the fluctuations in coral cover across the Northern, Central, and Southern Great Barrier Reef over time. In all regions, coral cover exhibits significant declines during mass bleaching events, particularly in the late 1990s and mid-2010s. However, recent trends show some recovery, especially in the Northern and Southern sections. These graphs underscore the reef's vulnerability to environmental stress and its potential for recovery under favorable conditions.
However, this recovery remains fragile, with threats from marine heatwaves, coral bleaching, cyclones, and crown-of-thorns starfish outbreaks continuing. The prognosis for the reef is uncertain, particularly as global warming could lead to annual bleaching events in the future.
The increased frequency and intensity of coral bleaching events—highlighted by the devastating occurrences in 1998, 2002, 2016, 2017, and 2020— paints a stark picture of the future of the Great Barrier Reef. Each event sets off a chain reaction that weakens coral health and reduces biodiversity.
The Chain Reaction: How Coral Bleaching Reduces Biodiversity
Each of these bleaching events sets off a series of devastating consequences that affect not just the corals, but the entire reef ecosystem. The more frequent and severe these bleaching events become, the more difficult it is for the reef to recover, leading to long-term declines in biodiversity. Here’s how the process unfolds:
Loss of Coral Species Diversity
Coral species vary in their sensitivity to temperature stress. When bleaching occurs, the most sensitive species, such as branching corals (e.g., Acropora), are often the first to die. These corals provide essential habitat that supports a wide variety of fish and invertebrates. As these species die off, the reef loses its structural diversity, leaving fewer safe havens for smaller fish and other marine creatures.
Impact on the ecosystem: The loss of complex coral species reduces the availability of habitats for reef-dwelling species, such as damselfish, butterflyfish, and invertebrates like crabs and shrimp. Without these critical structures, many species lose their breeding grounds and places of refuge, leading to population declines and a reduction in species diversity.
Algal Overgrowth and Ecosystem Imbalance
When corals die, the dead coral skeletons become overgrown with algae. Normally, herbivorous fish such as parrotfish and surgeonfish help control algal growth, but when coral cover declines, the balance between algae and coral is disrupted. Algae can outcompete corals for space and resources, particularly after bleaching events when coral health is compromised.
Impact on reef recovery: Algal overgrowth prevents new coral larvae from settling and regenerating the reef. If the algae are not controlled, the reef can shift from being a coral-dominated ecosystem to an algae-dominated system, which supports far less biodiversity and reduces the overall productivity of the ecosystem.
Bleaching Events Are Becoming More Frequent—and More Devastating
The reef has an amazing resilience to recover from such large-scale damage caused by bleaching. I was surprised when I jumped into the ocean and saw the beauty of the recovered reef with my own eyes. But knowing it can’t sustain this level of trauma forever means we need to do something about it now. Recovery requires more frequent reprieves, which are diminishing as climate change accelerates. If climate change continues unchecked, these bleaching events will become even more common, leading to the permanent loss of coral species and a collapse of the ecosystem.
Organizations to look out for:
Several organizations are working tirelessly to protect and restore the Great Barrier Reef, focusing on conservation, research, and policy advocacy. Here are some key organizations and the efforts they’re making to safeguard the reef:
The Great Barrier Reef Foundation is at the forefront of reef conservation, funding large-scale projects aimed at protecting and restoring the reef. They focus on initiatives such as coral restoration, tackling climate change impacts, and improving water quality. The foundation also supports scientific research to build resilience in the reef against climate change.
Australian Marine Conservation Society (AMCS)
The AMCS is a leading advocacy group that campaigns for stronger environmental laws and protections for the reef. Their efforts focus on reducing industrial pollution, stopping coal mining near the reef, and addressing climate change. They also engage the public in actions to protect marine biodiversity and advocate for sustainable fisheries.
Reef Restoration and Adaptation Program (RRAP)
RRAP is a collaborative initiative between researchers, government agencies, and businesses that focuses on large-scale coral restoration. They are developing new technologies and methods to assist coral adaptation to climate change, such as coral breeding and methods to cool the water during heatwaves.
Citizens of the Great Barrier Reef
Citizens of the Great Barrier Reef is a global movement that encourages individuals to take part in protecting the reef. Through community-driven actions, the group promotes reef-friendly behaviors, citizen science projects, and educational campaigns to raise awareness of reef conservation.
The Role of People in Protecting the Reef
Individuals can play a crucial role in helping to protect the Great Barrier Reef. While large-scale solutions are needed to combat climate change, personal actions can make a significant impact:
Reduce Carbon Footprint
Climate change is the primary driver of coral bleaching, so reducing your personal carbon emissions is key. Simple actions like using renewable energy, reducing single-use plastics, conserving water, and using public transport can help lower the amount of greenhouse gases contributing to global warming.
Support Reef-Friendly Products
Avoid purchasing products that harm marine life or contribute to pollution. Choose sustainable seafood, use reef-safe sunscreens, and avoid plastics that can end up in the ocean. Being a conscious consumer helps reduce the environmental pressure on reefs.
Donate or Volunteer
Supporting organizations that work to protect the reef through donations or volunteering can make a direct impact. Many reef conservation groups offer citizen science projects where individuals can contribute to reef monitoring efforts.
Advocate for Climate Action
Push for stronger environmental policies by supporting legislation that aims to reduce emissions, protect marine habitats, and limit industrial activities near sensitive ecosystems like the Great Barrier Reef. Signing petitions, joining climate campaigns, and voting for eco-conscious leaders are all ways to support reef protection efforts.
Final thoughts
Visiting the Great Barrier Reef was truly an eye-opening experience. While I had heard about coral bleaching before, seeing both the vibrant life and the bleached sections firsthand made the crisis feel more immediate and personal. The beauty of the reef is breathtaking, and being there, I saw its fragility—a delicate ecosystem that’s now under severe threat. As a lover of nature, I understand the interconnection we have with it and the pressing need for urgent action to protect it.
The experience deepened my understanding of the devastating effects of climate change, and it left me with a strong sense of responsibility. It's no longer just about what governments or organizations can do—it’s about the choices we make every day. I left the reef with hope, but also with the knowledge that without a collective effort, the future of the reef, and the countless species that depend on it, is uncertain. We all have a role to play and any small action makes a difference.
References
ARC Centre of Excellence for Coral Reef Studies. (2016). Great Barrier Reef suffered worst bleaching on record in 2016. Coastal Care. Retrieved September 18, 2024, from https://coastalcare.org/2016/11/great-barrier-reef-suffered-worst-bleaching-on-record-in-2016/
Australian Institute of Marine Science. (n.d.). Coral bleaching events. AIMS. Retrieved September 18, 2024, from https://www.aims.gov.au
Great Barrier Reef Foundation. (2020). Great Barrier Reef faces most widespread bleaching on record. Great Barrier Reef Foundation. Retrieved September 23, 2024, from https://www.barrierreef.org
Hughes, T. P., Kerry, J. T., Baird, A. H., Connolly, S. R., Dietzel, A., Eakin, C. M., Heron, S. F., Hoey, A. S., Hoogenboom, M. O., Liu, G., McWilliam, M. J., Pears, R. J., Pratchett, M. S., Skirving, W. J., Stella, J. S., & Torda, G. (2018). Global warming transforms coral reef assemblages. Nature, 556(7702), 492–496. https://doi.org/10.1038/s41586-018-0041-2
International Coral Reef Initiative. (2000). Status of coral reefs of the world: 2000. Retrieved September 21, 2024, from https://www.icriforum.org/
James Cook University. (2017). Two-thirds of Great Barrier Reef hit by back-to-back mass coral bleaching. JCU. Retrieved September 18, 2024, from https://www.jcu.edu.au
Status of Coral Reefs of the World: 2004. (n.d.). ICRI. Retrieved September 21, 2024, from https://icriforum.org/documents/status-of-coral-reefs-of-the-world-2004/
Is the Great Barrier Reef reviving - or dying? Here’s what’s happening beyond the headlines. (2023, August 9). AIMS. Retrieved September 18, 2024, from https://www.aims.gov.au/information-centre/news-and-stories/great-barrier-reef-reviving-or-dying-heres-whats-happening-beyond-headlines