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Event

Great Barrier Reef bleaching

Losing more than a natural wonder

The Great Barrier Reef, a natural wonder, is usually associated with colourful fish and incredible beauty. But beyond its pretty looks, the Great Barrier Reef and coral reefs like it around the world provide essential services to ecosystems and local communities.

Between a quarter and a third of all marine species spend a part of their lifecycle in coral reefs. Nearly a billion people depend on corals for their livelihood and food security, for example through related tourism business and fishing. Corals also protect coastlines and those living in close proximity to the coast. Reefs break waves and reduce current velocities and as such greatly contribute to coastal risk reduction. Approximately 200 million people are estimated to depend on coral reefs for protection from storm surges and waves. But currently we are losing our corals at an unprecedented level around the globe. The Great Barrier Reef experienced the most widespread amount of bleaching in 2020; and this for the third time in only five years.

Key Facts

2,300 km

of reef system affected by bleaching, with one quarter of the Great Barrier Reef suffering severe bleaching

35%

of the surveyed area experiencing moderate bleaching

Great Barrier Reef

Australia

Key Impacts

Biodiversity

loss

Coral

mortality

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.

Wider Picture

Wider context

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.

Future context

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.