Back-to-back severe bleaching events, caused by warming oceans, have affected two-thirds of Australia’s Great Barrier Reef, new aerial surveys have found. Climate change is not the only challenge – runoff-affected water quality, reef-killing crown of thorns starfish and the destruction of Cyclone Debbie also threaten the reef’s health. Scientists are warning that Australia has little time left to act on climate change and save the world’s largest living structure.

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