6 July 2018: A scientific assessment by the UN Educational, Scientific and Cultural Organization (UNESCO) World Heritage Centre found that 21 of 29 World Heritage reefs have been subjected to severe or repeated heat stress. Such conditions, the assessment notes, can cause coral bleaching and annual economic losses upwards of US$500 billion by 2100.

Published under the title, ‘Impacts of Climate Change on World Heritage Coral Reefs: A First Global Scientific Assessment,’ the analysis finds that, under a business-as-usual scenario, all 29 World Heritage reefs, including Australia’s Great Barrier Reef, “would cease to exist as functioning coral reef ecosystems” by the end of the century.

Coral reefs are set to disappear unless GHG emissions are reduced in line with goals set by the Paris Agreement.

A UNFCCC article emphasizes reefs’ fragility, noting that a global average surface temperature spike of 1-2°C above preindustrial levels is enough to cause bleaching. Global surface temperatures have not only risen by 1°C, the article notes, but the effect is further amplified by ocean acidification due to oceans’ absorption of carbon dioxide (CO2) from the atmosphere and weather events such as El Niño, where warmer waters trigger shifts in weather patterns.

The article underscores that bleached corals are still alive, and that the trend is triggered as a stress response. However, it notes that even temporary bleaching has negative impacts, and that if the conditions remain for several weeks, the coral will die, reducing both the physical structure and biodiversity of the reef.

Echoing UNESCO’s assessment, the UNFCCC notes that unless greenhouse gas (GHG) emissions are reduced in line with goals set by the Paris Agreement on climate change, coral reefs are set to disappear. [Impacts of Climate Change on World Heritage Coral Reefs: A First Global Scientific Assessment] [UNFCCC News Article] [UNESCO News Story]