According to a report by the Global Coral Reef Monitoring Network (GCRMN) covering 40 years of data and over 12,000 sites, 14 percent of the world's coral died off between 2009 and 2018. When you take the whole data range into consideration, some regions are hardly effected, others are hit even harder as our chart shows.
In the South Asia region, live coral cover saw a mean absolute decline of almost 21 percent between the first and the most recent survey, most likely attributable to commercial fishing and pollution. Australia, home to the Great Barrier Reef spanning 344,000 km² of islands and individual reefs, had only the third largest pure coral reef area with 41,000 km² in 2019 but was dealing with ten percent absolute mean decline in live corals. As indicated by the GCRMN's report, corals can be resilient when granted the chance to recover from external stress factors: In 2019, live coral growth on reefs increased by two percent.
Even though coral reefs only cover 0.2 percent of the ocean floor, they provide sustenance and habitats for 25 percent of marine life, which makes the decline of these ecosystems even more impactful. One of the key reasons for the death of corals is coral bleaching caused by a rise in water temperature most often attributed to climate change. In this process, the corals expel the algae serving as the main source of food and the coral's color, leading to increased susceptibility to disease and death.