All Coral Will Suffer Severe Bleaching When Global Heating Hits 1.5C, Study Finds

Almost no corals on the planet will escape severe bleaching once global heating reaches 1.5C, according to a new study of the world's reefs. From a report: Reefs in areas currently regarded as cooler refuges will be overwhelmed at 1.5C of heating, and just 0.2% of reefs will escape at least one bleaching outbreak every decade, according to the research. The team of scientists from the University of Leeds, Texas Tech University and James Cook University used the latest climate model projections to confirm that 1.5C of global heating "will be catastrophic for coral reefs." Corals bleach when ocean temperatures are too high for too long. Algae that provide corals with much of their food and colour separate from the coral during heat stress. Severe bleaching can kill corals, but they can recover from milder outbreaks if there are several years with no further heatwaves. The world's oceans are heating due mostly to the burning of fossil fuels. The study comes as the world's biggest coral reef system, the Great Barrier Reef off Australia's Queensland coast, is on the verge of another mass coral bleaching event. In the study, the team analysed climate projections across all of the world's shallow-water coral reefs, which constitute the vast majority of reefs and provide habitat, tourism revenue and coastal protection. About 84% of the world's corals exist in areas that are expected to bleach less than once a decade and are regarded as "thermal refugia," the study said. But the analysis suggests at 1.5C of global heating, only 0.2% of the area covered by reefs is in water cool enough to avoid bleaching at least once every five years -- a frequency considered too short to allow corals to recover.

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