Every shallow-water coral reef ecosystem in Australia faces an extremely high risk of collapse by 2075 driven largely by projected ocean warming, according to a landmark global assessment.
The assessment, a collaboration between International Union for Conservation of Nature (IUCN) researchers at the University of Melbourne and over 250 researchers around the world,found that 96 per cent of the world’s assessed coral reef ecosystems are now classified as Critically Endangered under the IUCN Red List of Ecosystems.
The study evaluated coral reef ecosystems in 127 tropical and subtropical marine ecoregions, including some of the world’s largest and most biodiverse reef systems such as Australia’s Great Barrier Reef, the Coral Triangle in Southeast Asia and the western Pacific, the Mesoamerican Barrier Reef and the Red Sea.
The findings have classified all 17 Australian coral reef ecosystems as Critically Endangered, with increasing marine heat stress and mass bleaching predicted under future climate scenarios.
Researchers found that climate-driven ocean warming is the most widespread and severe threat to coral reefs globally. Increasing marine heatwaves are causing mass coral bleaching events and widespread coral mortality, placing ecosystems under unprecedented pressure.
University of Melbourne research fellow and scientific lead of the global assessment, Dr Mishal Gudka, said the risk of coral reef collapse is escalating, but this must be a wake-up call rather than a cause for despair.
“Coral reefs have shown a remarkable ability to bounce back from devastating bleaching events. Pockets of surviving, resilient coral reefs can remain in the future –but we must do everything within our reach to set them up for success,” Dr Gudka, from the School of Agriculture, Food and Ecosystem Sciences, said.
“Our assessment shows that much of the risk is driven by projected change that have not yet fully materialised and now is a critical window to scale up conservation and climate efforts to avoid catastrophic loss.”
Oceanwise Australia Director and Adjunct Research Fellow at The University of Western Australia’s Oceans Institute, Dr Ben Fitzpatrick, who led the assessment on Australia’s coral reef ecosystems, said although Australian coral reefs can respond well to local management, these gains are increasingly being overwhelmed by our changing climate.
“Unfortunately, these climate change impacts are only expected to intensify under current climate change trajectories, making the risk of collapse for all our coral reefs exceptionally high,” Dr Fitzpatrick said.
“If we double down on local management, and achieve rapid decarbonation we can avoid this outcome, but the window for action is rapidly closing.”
Despite covering less than one per cent of the ocean floor, coral reefs support around a quarter of all marine species. They provide habitat, food and breeding grounds for thousands of species while supporting fisheries, tourism and coastal protection for millions of people worldwide.
A coral reef ecosystem is considered collapsed when reef-building hard corals largely disappear and are replaced by algae, rubble and other organisms. This transformation fundamentally alters the ecosystem dramatically.
IUCN Director General Dr Grethel Aguilar said coral reefs are among the clearest indicators of the state of the ocean.
“Coral reefs are one of the clearest vital signs of the ocean’s health,” Dr Aguilar said.
“Their decline threatens biodiversity, coastal communities and industries that depend on healthy marine ecosystems. It is not too late to give coral reefs a chance to recover, but that requires decisive action to address climate change and halt further ocean warming.”
The global assessment was coordinated by IUCN, the IUCN Commission on Ecosystem Management, the University of Melbourne and CORDIO East Africa, with contributions from more than 250 experts across more than 80 countries and territories.
The research draws on decades of ecological monitoring, coral reef data and satellite observations of ocean temperatures to assess the long-term outlook for coral reef ecosystems worldwide.
The findings complement a recent reassessment of 892 reef-building coral species on the IUCN Red List of Threatened Species, which found that 44 per cent are threatened with extinction.
