High-resolution predictions of annual coral bleaching under climate change…

New research predicts the future of coral reefs under climate change and the fate of one of Earth’s most important ecosystems. High-resolution projections predict that Taiwan and the Turks and Caicos islands will likely be among the world’s first areas to experience annual bleaching events. In the past, severe bleaching events usually coincided with the El Nino Southern Oscillation, an event that occurs roughly every couple years. In the future, annual events will become more common.

“These predictions are a treasure trove for those who are fighting to protect one of the world’s most magnificent and important ecosystems from the ravages of climate change,” said Erik Solheim, head of UN Environment. “They allow conservationists and governments to prioritize the protection of reefs that may still have time to acclimatize to our warming seas. The projections show us where we still have time to act before it’s too late.”

The Paris Agreement, which set a target of limiting global temperature increase to only 1.5 degrees Celsius, provides a good start for saving coral reefs, however, the danger is still imminent. Even if emission reductions exceed the pledges made by the countries under the Paris Agreement, more than three quarters of the the world’s coral reefs will bleach annually before the year 2070.

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However, under current trends, severe bleaching events will occur every year on 99% of the world’s reefs in the next 100 years.

Roughly 5 years is how long it takes for a single reef to recover from a bleaching event.

“Bleaching that takes place every year will invariably cause major changes in the ecological function of coral reef ecosystems,” said study leader Dr. Ruben van Hooidonk of NOAA and the University of Miami. “Further, annual bleaching will greatly reduce the capacity of coral reefs to provide goods and services, such as fisheries and coastal protection, to human communities.”

Between 2014 and 2016, the longest global bleaching event ever recorded killed coral on an unprecedented scale. In 2016, bleaching affected 90% of the Great Barrier Reef and killed more than 20% of the reef’s corals.

Many reefs near the equator will begin experiencing annual bleaching in less than 25 years, even if pledges under the Paris Agreement are fulfilled. Coral reefs are already threatened by numerous other factors, such as pollution, smothering, destructive fishing practices, diseases, and warming, more acidic ocean waters.

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Sequence of coral bleaching and mortality in American Samoa.

“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”.

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