Devastating coral bleaching is expected around the world within the next year

The world’s coral reefs are under threat like never before. According to a new international study led by Professor Ove Hoegh-Guldberg of the University of Queensland, record-breaking marine heatwaves in 2023 will likely cause devastating mass coral bleaching and mortality worldwide over the next 1-2 years.

The study’s findings are alarming and underscore the urgent need for climate change mitigation to save these vital ecosystems.

The researchers analyzed historical ocean temperature data and discovered that the heat stress conditions coral reefs are experiencing this year started much earlier and have been sustained much longer than any previous records. In some regions, the heat stress began up to 12 weeks earlier than normal. This puts immense and unprecedented pressure on coral reefs globally.

The study warns that we should expect widespread mass coral bleaching and mortality events around the world in the coming 1-2 years as a direct result of the record heat levels. This will have potentially catastrophic impacts on the 25% of marine biodiversity that depends on coral reefs.

According to Professor Hoegh-Guldberg, “Our study shows that ENSO is a major determinant of the fate of the world’s coral reefs,” he said. “Rising sea temperatures, coupled with other stressors such as ocean acidification and pollution, have severely weakened their resilience. This puts coral reefs and a quarter of the ocean’s biodiversity at serious risk of annihilation.”

Unprecedented marine heat waves

The extreme ocean temperatures recorded so far in 2023 represent a global marine heatwave event not seen before. The researchers found that the heat stress conditions coral reefs are experiencing started much earlier and have been sustained much longer than any previous records.

In some regions like the Great Barrier Reef, the extreme heat stress began up to 12 weeks earlier than normal seasonal patterns. No coral reefs worldwide have been spared from the record heat.

Additionally, the researchers note that almost all coral reef regions have already endured heat stress conditions for longer in 2023 than during any previous heatwaves. This puts unprecedented pressure on coral reefs that are already weakened from previous bleaching events.

The study concludes that the current record-breaking marine heatwaves are likely precursors to a global coral reef extinction event if urgent action isn’t taken on climate change.

Mass coral bleaching expected in the next 2 years

Given the unprecedented heat levels coral reefs are experiencing globally, the researchers warn that we should expect devastating mass coral bleaching and mortality worldwide over the next 1-2 years.

The extreme heat conditions are perfect scenarios for coral bleaching events. When sea temperatures remain above normal seasonal highs for extended periods, corals become stressed and expel the symbiotic algae that provide them with nutrition. This causes them to turn completely white, resulting in coral bleaching.

Prolonged heat stress ultimately leads to widespread coral death if temperatures don’t return to normal in time for the corals to recover. However, the current global heatwaves show no sign of relenting anytime soon.

According to Professor Hoegh-Guldberg, “The latest environmental information indicates that we’re well off-track when it comes to keeping global surface temperatures from reaching a very dangerous condition by mid to late this century,” he said. “Frankly, we’re hurtling in the opposite direction.”

Urgent climate action needed

The study makes it clear that coral reefs around the world seriously risk annihilation beyond the next few decades if swift climate change mitigation actions aren’t taken immediately.

Coral reefs globally have already declined by 50% since the 1950s. They now face a dire threat from climate change, which previous research shows they will not be able to adapt to fast enough naturally.

As Professor Hoegh-Guldberg explained, their study reaffirms that climate change remains the biggest threat to the world’s coral reefs. Only rapid and deep emissions cuts will give coral reefs a fighting chance of surviving into the middle of the century.

The researchers conclude that the current record-breaking marine heatwaves are likely precursors to a global coral reef extinction event if urgent climate action like emissions reductions aren’t swiftly implemented worldwide.

In summary, with 25% of all marine biodiversity dependent on coral reefs, their loss would be catastrophic. Concerted global efforts are needed immediately to mitigate climate change and give coral reefs a shot at surviving imminent mass bleaching events. Our window of opportunity is rapidly closing.

The full study was published in the journal Science.

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