About 96% of hot, shallow-water coral reef ecosystems evaluated worldwide face an “extremely high” risk of collapse by 2075, largely due to ocean warming caused by climate change.
An analysis released on Thursday in the IUCN Red List of Ecosystems classifies as “critically endangered” some of the planet’s most extensive and biodiverse coral systems, such as the Australian Great Barrier Reef, the Western and Central Pacific Coral Triangle, the Mesoamerican Barrier Reef System, and the Red Sea reefs.
The study covers 127 tropical and subtropical ecoregions and 188,362 square kilometres of reefs in more than 80 countries and territories.
“Thermal stress resulting from climate change is the most significant ongoing threat driving the decline of coral reefs worldwide,” warned the IUCN.
The assessment uses the IPCC’s mid-range climate scenario, which projects global warming of 2.7 degrees Celsius by the end of the century, with a continued rise in sea surface temperatures.
“Its decline is depriving numerous species of food, shelter and breeding areas they depend on, while threatening the security and livelihoods of coastal communities,” said the IUCN Director General, Grethel Aguilar, quoted in the report.
According to the study, this situation will also have consequences for economic activities such as fishing, aquaculture and coastal tourism.
The organization also warns that the proportion of ecosystems in critically endangered status would be even higher if data were available for four ecoregions for which information is lacking.
On the other hand, the reefs of the western Galápagos Islands have already been considered collapsed since the El Niño episode of 1982-1983.
A reef collapse occurs when it loses the characteristics that define it as an ecosystem, with the near-total disappearance of hard corals that make up its structure and the predominance of algae, detritus and sponges, factors that alter food webs and reduce the reef’s capacity to sustain a diverse marine life.
Despite the gravity of the projections, the assessment underscored that reefs may still recover if climatic and local pressures are reduced.
The study also highlighted the difference between the deterioration observed so far and the future risk linked to global warming.
If only the trends recorded over the last 50 years were considered, 24% of the assessed ecoregions would be in critically endangered status. That figure rises to 96% when climate projections are included.
“The risk of coral reef collapse is increasing, but this should serve as a warning, not as a reason for despair,” said Mishal Gudka, Director of Research at CORDIO East Africa and scientific lead for the study, who highlighted the capacity of some reefs to recover.
