The new study shows that, on average, the world's reefs will start suffering annual bleaching in 2043. About 5 per cent of them will be hit a decade or more earlier, while about 11 per cent will suffer annual bleaching a decade or more later than this date.
If emission reductions exceed pledges made by countries to date under the Paris Agreement, coral reefs would have another 11 years, on average, to adapt to warming seas before they are hit by annual bleaching.
If such emissions reductions become reality, many high and low latitude reefs in Australia, the South Pacific, India, Coral Triangle and the Florida Reef Tract will have at least 25 more years before annual bleaching occurs, buying time for conservation efforts. However, reefs near the equator will experience annual bleaching much sooner, even if emissions reductions pledges materialize.
"It is imperative that we take these predictions seriously and that, at the very minimum, we meet the targets of the Paris Agreement. Doing so will buy time for coral reefs and allow us to plan for the future and adapt to the present," said Mr. Solheim.
Predicting when and where annual bleaching occurs will help policymakers and conservationists decide which reefs to prioritize. "Reefs that will suffer annual bleaching later - known as climate "refugia" - are top priorities because they have more time to respond positively to efforts that seek to reduce bleaching vulnerability", said Dr. van Hooidonk. Such efforts include reducing land-based pollution, halting overfishing and preventing damage from tourism.
Coral reefs, which are already under threat from overfishing and tourism, are especially vulnerable to climate change because they are easily affected by warm water. When sea temperatures rise, the algae that give coral its bright colours leave their host, causing it to look white, hence the term 'coral bleaching'. The loss of algae, which provide coral with much of its energy, make corals vulnerable to starvation and disease.
Known as the world's underwater cities, coral reefs provide hundreds of millions of people with food, income and coastal protection. They are home to at least one quarter of all marine life and they generate an estimated $375 billion per year from fisheries, tourism and coastal protection.
"We are going to need to be much more innovative and proactive if we want to see coral reefs thrive into the next century," said World Wildlife Fund (WWF) lead marine scientist and study co-author Dr. Gabby Ahmadia.
"Conventional conservation is not going to cut it against the impacts of climate change. We need to embrace the new climate reality to guide efforts to save our oceans".
About the study
Support for the study, entitled "Local-scale projections of coral reef futures and implications of the Paris Agreement", was provided by UN Environment, the World Wildlife Fund, US National Oceanic and Atmospheric Administration's Coral Reef Conservation Programme, the Atlantic Oceanographic and Meteorological Laboratory and the National Marine Fisheries Service via the Pacific Islands Fisheries Science Center, US Geological Survey via the Pacific Islands Climate Science Center, Total Foundation, and US National Fish and Wildlife Foundation. The study was led by Dr. Ruben van Hooidonk and Dr. Jeffrey Maynard.
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