All coral reefs in western Indian Ocean could collapse in next 50 years: Study

Almost all coral reefs in the western Indian Ocean are at high risk of collapsing in the next 50 years due to global warming and overfishing, as per study. 

Reef systems from the Seychelles to the Delagoa region off the coasts of Mozambique and South Africa are on the verge of becoming functionally extinct by the 2070s, endangering hundreds of thousands of people’s livelihoods and food sources. 

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As a matter of fact, coral reefs in ten countries around the western Indian Ocean were studied in the study, which was published today in the journal Nature Sustainability. It used the International Union for the Conservation of Nature’s (IUCN) red list of ecosystems framework to assess the health of 11 sub-regions, similar to the method used to assess the risk of extinction of a plant or animal.

Reefs in island nations, in particular, were found to be in grave danger as a result of increasing water temperatures caused by global warming, which is creating bleaching events – when corals expel algae living in their tissue, turning them completely white – to become more common. Reefs in Madagascar’s eastern and southern regions, as well as the Comoros and Mascarene Islands, have all been designated as critically endangered. 

Overfishing, particularly of top predators, has altered the ecology of reefs in north Seychelles and along the entire east African coast, leaving them prone to collapsing. This is causing a build-up of different algae that can smother coral. 

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While the global fall of coral reefs has been established for some time, region-specific assessments provided better clarity about the causes and magnitude of damage, according to David Obura, chair of the IUCN corals group, who led the study.

“The most urgent threat is from climate change up to 50 years from now. But while we estimate 50 years into the future, whether we can meet the 1.5C [rise] future or not depends on what we do in the next 10 years. So, it’s really a 10-year horizon that we have to be concerned about,” he told The Guardian.

“The collapse of a reef means it becomes functionally extinct as a reef system. You might still find some species there but they won’t be able to construct a reef any more. All of the services we get – coastal protection from sea-level rise, tourism, fisheries, especially for low-income households and communities – are at risk. The tourism sector is huge in east Africa and it depends on heathy reefs.”

Due to global warming, overfishing, pollution, and habitat destruction, the world’s coral reef cover has reduced by half since the 1950s. The global decline of ecosystems, which serve as critical nurseries for juvenile fish, is expected to continue as the climate warms. 

Mishal Gudka, a senior scientist at Cordio East Africa and one of the study’s co-authors, said their analysis revealed overfishing of top predators on all of the reefs studied.

“These results highlight the need to improve local fisheries management to ensure the health of reef systems and secure sustainable fish stocks, which support jobs for a quarter of a million people in the region,” Gudka said.

Obura believes that in addition to reducing greenhouse gas emissions, better enforcement of fishery regulations and greater community involvement in reef management could help to ensure their survival.

“This assessment reaffirms the urgency of the interlinked climate and biodiversity crisis addressed by Cop26 last month in Glasgow, and Cop15[biodiversity summit] in a few months in Kunming. We need to take decisive action to address both global threats to corals from climate change, and local ones, such as overfishing,” he said.