Why revisiting the Great Barrier Reef’s past could protect its future

Our world-first research is investigating how the reef ecosystem’s past responses to climate change – its greatest threat – can help us better understand its capacity to react to future cataclysmic events and survive them.

Led by Associate Professor Jody Webster, the University’s research team uses a suite of high-tech methods to unlock the reef’s history. They drill hundreds of metres below sea level to recover fossil reef cores, use ships and underwater robots to map the seabed and apply 3D modelling to reconstruct reef development over tens of thousands of years.

They are looking at the reef like no one else.

This innovative approach creates an archive of environmental change from the distant past that is then linked to the present and provides invaluable intel for protecting the reef in the future. For example, carbon dating of ancient coral and algae extracted from reef cores helps to determine the historic life-and-death impact of climate change.

This archive gives us a better understanding of the environmental thresholds of the Great Barrier Reef – such as changing sea level, surface temperature and nutrients – so we can better predict where we are going to in the future and how the reef will respond to climate changes.

“A really innovative part of our work is the numerical reef modelling, which no-one in the world is doing in this fashion,” Associate Professor Webster says.

This deep predictive modelling enables his team to pinpoint precisely how reef habitats have grown, died and migrated in response to changes such as melting glaciers and ice caps 25,000 years ago. It is groundbreaking because it encompasses and measures change over larger geological and physical scales than ever before – across many centuries and millennia.

At the same time, Associate Professor Webster’s colleague Associate Professor Will Figueira is using innovative 3D mapping and modelling techniques to assess the effects of modern threats to reefs – such as coral bleaching caused by ocean warming – to develop effective intervention strategies. These threats destroy corals, the structurally complex environments they create and much of the biodiversity that relies on these habitats.

Associate Professor Figueira is the co-lead (along with Professor Maria Byrne) of the 3D Reefs program. The program captures hundreds of photos from individual coral colonies and thousands of photos from large areas of reef and repurposes them into 3D models. These models provide precise data about the impact of losing complex coral reef structures and inform measures to reduce the severity of future damage and conserve reef biodiversity. His research on global warming and coral bleaching was recently published in one of the world’s most influential scientific journals, Nature.

Together, our researchers are an integral part of Australia’s efforts to protect the Great Barrier Reef against long-term climate change – exploring the reef across time and space to better imagine the future.

The data generated are already having an enormous impact, nationally and globally. Australian governments and the Great Barrier Reef Marine Park Authority routinely use the information to determine optimal reef management. Associate Professor Webster’s team’s high-resolution mapping has provided more precise guidance on dividing up reef zones and his environmental thresholds data from the past can help determine how sensitive the reef is to sediment run-off and nutrient delivery from waterways that feed into it. This is a critical part of reef management as debates continue about land use in the reef’s hinterland by primary industries, including agriculture and mining.

The Intergovernmental Panel on Climate Change – the leading global authority on climate science – directly accesses Associate Professor Webster’s results, which were recently published in Nature and Nature Geoscience.

For the Nature paper, Associate Professor Webster and colleagues constructed a new relative sea level ‘curve’ and used it to better understand how ice sheets behaved in the past. Their findings will enable climate modellers to make more accurate predictions about sea level rise. Being able to determine how fast and high sea level will rise also has implications for coastal erosion.

His Nature Geoscience paper focused on how the Great Barrier Reef has evolved over tens of thousands of years. His findings show that the entire reef ecosystem has survived at least five near-fatal ‘death’ events over the last 30,000 years and created its own defence mechanisms, such as migrating backwards and forwards across the sea floor as ocean levels have fallen and risen.

While the reef ecosystem has proven to be remarkably resilient to the ravages of climate change, the threat is greater than ever before, because changes such as water temperature rises are happening much faster than they did since the last ice age 20,000 years ago. The reef is also highly sensitive to increased sediment and poor water quality, his research shows.  

The University of Sydney will continue to be at the forefront of protecting the Great Barrier Reef threats at our research station, One Tree Island­­­­­­­­­­. By reconstructing the past and repairing the damage from the present, our researchers are helping to safeguard the survival of reef habitats for 1600 species of fish, 215 species of birds and many other animals for the long term.

They are also ensuring that the estimated 2 million people who visit the Great Barrier Reef each year can enjoy it for decades to come.

Want more research news? Sign up here.

Generous donors have made much of Associate Professor Figueira’s work possible, in particular the mapping of reefs across the Great Barrier Reef and Coral Sea to create structures for biodiversity regeneration. Find out more about the campaign.