of reef system affected by bleaching, with one quarter of the Great Barrier Reef suffering severe bleaching
of the surveyed area experiencing moderate bleaching
Great Barrier Reef
Increasing carbon dioxide emissions around the world have led to ocean warming with record sea surface temperatures that contribute to coral heat stress, resulting in bleaching. When water is too warm, corals expel the algae (zooxanthellae) living in their tissues, causing the coral to turn completely white. Corals can survive a bleaching event, but they are under more stress and are subject to mortality. If the ocean remains warm or turns even warmer, corals will no longer be able to recover and we would face a future without them. In a world where sea temperatures have risen 1.5°C, coral reefs will be seriously threatened; with a 2°C rise they will virtually no longer exist.
Third mass bleaching in five years. Global coral cover has declined 50−75 per cent over the past 30−40 years, and since the 1990s the number of corals on the Great Barrier Reef have already declined by more than 50 per cent. The last global bleaching event, 2014−2017, spread across the Pacific, Indian and Atlantic Oceans; it was the longest, most pervasive and destructive coral bleaching incident ever recorded.
Risk of a ‘no-coral future’. Corals take about 10 years to recover fully from bleaching events and can’t recover if they remain under continuous stress by e.g. ocean warming. We could lose these wonderful habitats as we know them, and all the essential services we derive from them, potentially leading to loss of food security and biosphere integrity.
At present rates, 60 per cent of coral reefs are expected to be endangered by 2030. Reefs are on a trajectory to collapse and could possibly be lost around the world by 2050, or soon after.