All of Australia’s shallow-water coral reef ecosystems face an extremely high risk of collapse by 2075, mainly due to the projected rise in ocean temperatures. The conclusion is part of an international assessment coordinated by the International Union for Conservation of Nature (IUCN), the University of Melbourne and other entities, which involved more than 250 researchers from over 80 countries and territories. Worldwide, 96% of the coral reef ecosystems assessed were classified as “Critically Endangered” on the IUCN Red List of Ecosystems.
The analysis covered reefs from 127 tropical and subtropical marine ecoregions, including the Australian Great Barrier Reef, the Coral Triangle in Southeast Asia and the Western Pacific, the Mesoamerican Barrier Reef System, and the Red Sea reefs. In Australia, the classification covers the 17 ecosystems evaluated. The increase in marine heatwaves is triggering mass bleaching events and contributing to widespread coral mortality, placing these ecosystems under increasing pressure.
Mishal Gudka, a researcher at the University of Melbourne and the scientific lead for the global assessment, considers that the worsening risk should serve as a warning, but it does not mean recovery is impossible. “Coral reefs have demonstrated a remarkable capacity to recover from devastating bleaching events. There may continue to be areas with surviving and resilient corals, but we must do everything in our power to give them conditions to thrive,” he says.
The researcher adds that part of the identified risk results from projected climate changes that have not yet fully materialized, so there is an opportunity to strengthen conservation and climate action. Ben Fitzpatrick, the lead for the Australian reef assessment, warns, however, that the benefits of local management are being progressively overtaken by the effects of climate change. “If we strengthen local management and achieve rapid decarbonization, we could avoid this scenario, but the window of opportunity to act is closing rapidly,” he warns.
Although they occupy less than 1% of the ocean floor, coral reefs support around a quarter of marine species. They provide habitat, food and breeding sites for thousands of species, and contribute to fishing, tourism and coastal protection for millions of people. The collapse of a reef occurs when the hard corals that build the ecosystem’s structure largely disappear and are replaced by algae, debris and other organisms, profoundly altering its functioning.
Grethel Aguilar, the IUCN Director-General, emphasizes that the decline of reefs threatens biodiversity, coastal communities and economic activities that depend on healthy marine ecosystems. The assessment also follows a reassessment of 892 reef-building coral species, according to which 44% are threatened with extinction. The researchers argue that limiting global warming and strengthening conservation will be decisive in reducing the risk of irreversible losses.
