Coral disease is wiping out entire reefs, and it’s about to get worse

Deadly coral reef disease continues to spread as temperatures rise globally — and it’s likely to become endemic to reefs worldwide by next century, new research shows.

The study, published in Ecology Letters and conducted by researchers at the University of New South Wales in Sydney, Australia, shows the looming damage coral reefs will suffer from climate change. 

The research demonstrated how rising temperatures exacerbated coral reef disease over time. In the last 25 years, coral reef disease tripled — with nearly 10% of coral reefs suffering from the illness worldwide. 

The disease has the potential to wipe out entire reef systems and devastate coastal communities. 

Should temperatures continue to rise at the current trajectory, the research estimates that disease prevalence could increase to 76.8% in 2100, which is the most conservative worst-case scenario. This means three-quarters of the world’s reefs could fall ill by that time.

Lead author of the study Samantha Burke said that mitigating climate change is crucial. “Coral disease is a serious cause of coral mortality globally and reef decline, and our modeling predicts it will only continue to worsen — even if ocean temperatures remain conservative,” Burke said in a statement. 

The research showed that the Pacific Ocean is more at risk of worsening coral disease than the Atlantic or Indian Oceans, as things stand now. But it is important to note that while a factor, temperature may not be the only contributor in coral disease threats. 

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“Particular oceans are more at risk, but it’s difficult for us to know whether that is solely from warming ocean temperatures or combined with the many other stressors coral face,” said Burke. “But what is clear is that coral disease prevalence is climbing across the globe, and without urgent action to address warming temperatures, more coral will become diseased.” 

Coral reefs are vital to a marine ecosystem and support about a quarter of the world’s fish. Because of this, they are critical to coastal communities relying on fisheries and tourism, in addition to protections from storms and erosion, the study said. 

“They are the habitat builders. Without coral, there is no reef environment and no coastal industry,” Burke said. 

Coral disease spreads when the immune system of a coral is compromised. This can happen through the infection of a pathogen like a bacteria or fungus. But the disease is not to be confused with coral bleaching, which is when corals turn white while under stress and expel the zooxanthellae algae responsible for their coloring. 

Rising temperatures can increase the growth rate of the disease-causing organisms that infect the coral, the research explained. 

Corals are sensitive. They require a specific set of conditions to sustain life, such as a certain water temperature, salinity and quality. Because of this, the corals that become diseased typically end up dying. Entire sections of a reef could be lost. 

“The solution to coral disease is likely complex and needs action on a large and small scale. We can’t just wait around and hope for a silver bullet like a universal antibiotic,” Burke said. 

“Given what’s at stake, we need to take many steps forward to develop effective mitigation strategies, and addressing increasing temperatures would be a great place to start,” she continued.