A new IUCN Red List report published at the COP29 climate conference in Baku, Azerbaijan, has found that forty-four per cent of reef-building coral species are at risk of extinction.
The conservation status of 892 warm-water reef-building scleractinia – usually referred to as stony, or hard corals – have been analysed as part of a new global assessment, the first to be carried out on such a scale since 2008, when 33 per cent were adjudged to be threatened.
All species of coral which have been assessed are considered to be in decline.
According to the IUCN Red List of Threatened Species, of the 892 species of reef-building coral so far described, 24 species are now listed as Near Threatened, 56 as Vulnerable, and 251 species as Endangered.
A total of 33 species of scleractinia have now been listed as Critically Endangered, including 23 of the 85 known species of Atlantic coral.
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The report singles out Staghorn coral (Acropora cervicornis) and elkhorn coral (Acropora palmata) in particular, two species endemic to the Caribbean Sea and Gulf of Mexico, which were severely affected by the Caribbean marine heatwave of 2023.
The Caribbean has also been struggling with a widespread outbreak of stony coral tissue loss disease (SCTLD), which has further depleted coral coverage in the region.
The new assessment covers reef-building corals found in the shallow, tropical and sub-tropical habitats commonly visited by scuba divers and snorkellers. Assessments of cold and deep-water corals not dependent on sunlight are ongoing, with just 22 of more than 4,000 species assessed so far.
While deep-water corals are less likely to be affected by changes in surface temperatures, they remain threatened by fishing activity – especially bottom trawling – and may be affected by deep-sea mining for minerals in the future.
Earlier in 2024, coral reefs were subjected to the fourth global mass coral bleaching event recorded since analysis by NOAA began in 1985, and the second in the last decade.
Bleaching, in which coral polyps expel the symbiotic zooxanthellae algae which live inside them providing the coral with nutrients and colour, is survivable if temperatures return to normal and the algae can be reacquired. Sustained exposure to elevated temperatures, however, can cause the coral to die.
The IUCN report places the main threats to reef-building corals squarely at the door of elevated water temperatures caused by climate change, citing computer models published by the Intergovernmental Panel on Climate Change (IPCC) predicting future warming trends as a potential cause of further mass bleaching events.
Other human factors such as pollution, agricultural runoff, and unsustainable fishing practices such as cyanide and dynamite fishing, are also major factors in the degradation of coral reefs.
‘As world leaders gather at the UN climate conference in Baku, this global coral assessment vividly illustrates the severe impacts of our rapidly changing climate on life on Earth and drives home the severity of the consequences,’ said IUCN Director General, Dr Grethel Aguilar.
‘Healthy ecosystems like coral reefs are essential for human livelihoods—providing food, stabilising coastlines, and storing carbon.
‘The protection of our biodiversity is not only vital for our well-being but crucial for our survival.’
