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Great Barrier Reef from above. Photo courtesy Katerina Katopis, Coral Reef Image Bank

The Great Barrier Reef, the world’s largest reef system, has seen half of its coral populations wiped out in the past three decades, said an important new study.

After researching coral colony sizes along the length of the reef between 1995 and 2017, scientists reported that virtually all species showed a decline. Among the worst hit were the Great Barrier Reef’s northern and central regions, where record-breaking extreme temperatures and back-to-back mass coral bleaching events in 2016 and 2017 have had a significant impact. The latest report on the Great Barrier Reef, a system which dates back millions of years and supports a vast array of marine life, is another in the latest round of research reflecting the critical state of the world’s coral reefs. In the last 50 years, half of the world’s corals have died. 

Committed to changing this trajectory, the Paul G. Allen Family Foundation and Vulcan Inc. are working alongside many partners, researchers, technologists and grantees to develop new technologies, revolutionary scientific research, and policies that will tackle the challenges facing the world’s coral reefs. We asked some of our expert partners to weigh-in on what this study means.

‘Climate change is driving a global ecological catastrophe – corals are our last warning to act’

When marine scientists measure coral reef health they often look at how much coral is covering the reef. These scientists took a more detailed look at coral demography – the science of population size structures - to understand how the Great Barrier Reef is changing. Measuring the sizes and types of large, medium, and small corals of different species across 30 reefs revealed not only are there 50% fewer corals today than on those reefs in 1995, but there are far fewer, small, medium and large colonies. This is worrying: disappearances of large colonies means the reef is losing some of its ancient big mamas (who contribute significantly to reproduction) to bleaching and disease. The low number of small colonies suggests that new baby colonies aren’t being established – recruitment isn’t good, which will affect the reefs ability to recover.
There’s largely no doubt that these losses are driven by climate change, which is warming our oceans and essentially cooking the corals in increasingly more frequent and severe bleaching events. The good news is the Great Barrier Reef isn’t dead – the study showed that the southern sector that escaped warming in 2016 and 2017 still had good numbers of corals. But just like a forest after a bushfire, damaged reefs can only recover if there are enough trees left unscathed to establish new seedlings – and if back to back bushfires don’t stop the chance of new seedlings getting established. This study suggests it may be getting harder for reefs to bounce back.
These patterns aren’t unique to the Great Barrier Reef, they are being mirrored in reefs across the globe. The Caribbean is massively degraded and other reefs around the world are following a similar trajectory of coral losses. With over 500 million people worldwide reliant on the fish, tourism and coastal protection that reefs offer, loss of reef structure isn’t just a biodiversity loss issue but a looming humanitarian issue. Unless we act swiftly and decisively on climate change, coral reefs will continue to degrade. 
- Dr. Emma Kennedy is a marine biologist and coral reef expert working on the Allen Coral Atlas project, the first global coral reef habitat map and a revolutionary step for reef conservation.

'The loss of corals is not only an environmental tragedy, but a humanitarian emergency’

The Great Barrier Reef losing half its corals clearly shows the devastating effects of a rapidly changing climate and other human-induced threats, which we must urgently address if we are to continue receiving the valuable benefits that coral reefs provide such as food and economic security, livelihoods, health, and wellbeing for millions of people whether they live near or far from a reef. The loss of corals is not only an environmental tragedy, but a humanitarian emergency. 

This is why we need to protect potentially climate-resilient coral reefs—areas that are less vulnerable to climate change that could help regenerate other reefs in the future. In parallel, we need to build coastal communities’ resilience against climate change while developing sustainably. To give corals a fighting chance, the Coral Reef Rescue Initiative is working with partners to reduce the strain placed on reefs by exploitation and development, employ nature-based solutions, and collaborate with coastal communities, local governments and relevant sectors so that together, we can ensure a better future for both people and nature. 

- Carol Phua leads the Coral Reef Rescue Initiative at WWF. She believes that working closely with communities is key in the conservation of coastal resources. Carol founded Ocean Witness and was the leader of WWF-Malaysia’s Marine Program and the WWF Global Sharks & Rays Initiative. She is also the lead author and editor of the Living Blue Planet Report.

‘We Need Immediate Climate Change Action’

This study highlights we must take immediate action against climate change. Nations need immediate implementation of the 2015 Paris Agreement. We need to both stop burning fossil fuels and implement carbon sequestration through ecosystem restoration.

At the same time we transition to a low-carbon economy, we still need to conserve and restore coral reefs. Conservation to eliminate local stressors such as overfishing, pollution, and habitat destruction. Restoration to jump start destroyed coral reefs and recover ecosystem function.
- Dr. Sarah Frias-Torres is a senior scientist in the Coral Reef Conservation and Restoration Program at Vulcan Inc., managing research on behalf of the Paul G. Allen Family Foundation. In her role, Frias-Torres leads projects and programs that use innovative approaches and reliable data to enhance resilience, scale-up restoration, inform policy, and map the world’s coral reefs.

John Brewer Reef
Photo courtesy Matt Curnock
Heron Island
Photo courtesy Dr. Emma Kennedy

‘Innovative Coral Reef Approaches Must Be Developed’

The loss of a large proportion of coral colonies of reproductive size from the Great Barrier Reef in combination with an even larger decline in the abundance of small colonies aligns with recent findings of an enormous drop in coral recruitment rates following the 2016 and 2017 mass bleaching events. Today’s rates of natural coral recovery are thus severely impaired. Against the backdrop of increasingly frequent and severe disturbances causing massive coral mortality, this means innovative coral reef restoration approaches must be developed and safely implemented without delay. Unfortunately, without strong action on climate change, even the best restoration methods are unlikely to save coral reefs in the long run.

- Professor Madeleine JH van Oppen and her colleague Dr. Ruth Gates conceived the concept of assisted evolution in corals, a spectrum of laboratory selection approaches which can rapidly generate climate change resilience. Van Oppen is an Australian Research Council Laureate Fellow and is currently working on the development of assisted evolution approaches for incorporation into coral reef restoration initiatives.


‘Let Us Be the Generation That Found the Will to Save the Reefs’

This study highlights the urgency to intervene if we are to continue enjoying the services that coral reefs provide to us. Cutting carbon emissions in half by 2030, enhancing coral reef protection, increasing the scale of coral reef restoration, and fostering stewardship for coral reef conservation are four science-based solutions that can give us a chance to avoid the loss of the world´s coral reefs. We have the knowledge, technology, and intelligence to implement them. Let us be remembered as the generation that found the will to do it.  
- Dr. Phanor H Montoya Maya is the director and founder of Corales de Paz. As part of his role, he develops and manages participatory conservation projects and innovative approaches to building capacity for effective coral reef conservation and restoration. Currently, he is embarked on a mission to increase the scale and effectiveness of science-based coral reef restoration projects throughout the world.  

Ribbon Reefs, Great Barrier Reef. Photo courtesy Matt Curnock with the Coral Reef Image Bank

‘Australia and the World, It's Time to Take Action’

We knew that a major decline was underway on the Great Barrier Reef, but it's still so heartbreaking to see the numbers. 

Imagine losing half of the people in your city, including half of your friends and family. Imagine losing half of all trees on Earth. Dr. Terry Hughes made an important point about this setback: for a long time, Australians thought that the sheer size of the Great Barrier Reef would protect it. But nothing is too big to fail. As we look to the future, what has to happen? 

Climate action. An end to overfishing. Serious reforms to the status quo in dredging, fertilizer use, and coastal development. We have reason for hope, because we've seen coral reefs bounce back after the worst stressors are removed. We've seen smaller islands and nations establish and enforce comprehensive ocean zoning plans to protect their reefs. We've even seen whole reef sites restored to function through coral restoration. I still believe the Great Barrier Reef can regrow and recover its corals. Australia and the world, it's time to take action.
- Dr. Kristen Marhaver is an Associate Scientist at CARMABI Foundation in Curacao and Director of the Marhaver Lab, a laboratory focused on science and science communication for coral reef recovery. Marhaver is an expert on coral breeding and larval propagation, especially in rare and understudied species. Under support from the Paul G. Allen Family Foundation, Marhaver and collaborators established the first permanent coral gene bank in the Caribbean and conducted the first Assisted Gene Flow in Caribbean corals using cryopreserved sperm. Marhaver and her colleagues at CARMABI were also the first to successfully raise a variety of Caribbean coral species from spawned eggs, including the endangered Pillar coral Dendrogyra cylindrus and the disease-threatened Pineapple coral Dichocoenia stokesii.

'This Further Demonstrates the Long-Term Consequences of Major Bleaching Events’

News of the loss of corals across all size ranges along the northern and central regions of the Great Barrier Reef further demonstrates the long-term consequences of the 2016 and 2017 major bleaching events and the challenges for reef recovery with repeated reef disturbances. As a coral reef scientist for many years, it is challenging to stay hopeful about the world’s coral reefs as we watch them disappear before our eyes. In the Caribbean, in addition to bleaching we have a devastating disease outbreak, stony coral tissue loss disease, that is destroying corals across Florida and many Caribbean nations. I stay positive by observing so many coral reef scientists and managers working together to apply scientific knowledge and emerging technologies to better understand coral bleaching and disease, develop ways to treat corals and restore reefs, and better manage, and protect coral reef ecosystems. I hope this buys us time as we collectively learn to mitigate climate change and other damaging impacts to coral reefs.    
- Dr. Valerie J. Paul is the Head Scientist at the Smithsonian Marine Station at Fort Pierce where she explores the chemical ecology of reef organisms and the role of chemical defenses in ecological interactions. She’s currently conducting research on coral diseases, including black band disease and stony coral tissue loss disease. As part of a team of researchers, Paul is working to better understand the microbiology and biochemistry of stony coral tissue loss disease and to develop probiotics for treating this coral disease.