Coral Reefs and Ocean Warming

Passage

Coral reef ecosystems, which cover less than one percent of the ocean floor yet support approximately twenty-five percent of all known marine species, are currently experiencing an existential crisis driven primarily by the progressive warming of ocean surface temperatures resulting from anthropogenic greenhouse gas emissions. The process of coral bleaching, which occurs when thermal stress causes corals to expel the symbiotic photosynthetic algae known as zooxanthellae that provide them with up to ninety percent of their nutritional requirements, has increased dramatically in both frequency and geographic extent since the 1980s. The Great Barrier Reef, the world's largest coral reef system stretching over two thousand kilometres along the northeastern coast of Australia, has experienced five mass bleaching events since 1998, with the two most recent occurring in consecutive years, a pattern that allows insufficient time for meaningful ecological recovery. Beyond their extraordinary biodiversity value, coral reefs provide critical economic services to hundreds of millions of people worldwide through coastal protection, fisheries support, and tourism revenues estimated collectively at hundreds of billions of dollars annually. Scientists warn that if global average temperatures rise by two degrees Celsius above pre-industrial levels, a threshold current emissions trajectories make dangerously plausible, the functional extinction of the majority of the world's coral reef systems becomes a near-certain outcome within this century.