Fish swimming on a coral reef in the Maldives

The coral reefs of the western Indian Ocean are some of the most pristine in the world. Image © Andrea Izzotti/Shutterstock

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Coral reefs at risk of being wiped out in western Indian Ocean

Some of the world's most picturesque coral reefs are at risk of being wiped out in the next 50 years.

A combination of overfishing and climate change threatens these ecosystems of the western Indian Ocean, putting species, economies and human lives on the line. 

A swathe of the world's coral reefs are at high risk of collapse as climate change and overfishing take their toll. 

A team of international scientists found that all the reefs of the western Indian Ocean, an area covering Africa's east coast as well as islands such as the Maldives, are at risk of ecosystem collapse and irreversible damage in the coming years. 

As well as being an ecological catastrophe, a collapse of these reefs would also be a humanitarian disaster for the region, with many residents dependent on the reefs for their food and income. 

Dr David Obura, the lead author of the study, says, 'We've known for some time that coral reefs are in decline, but now we know more precisely to what degree, and why. This assessment reaffirms the urgency of the interlinked climate and biodiversity crises addressed by COP26 last month in Glasgow, and COP15 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.' 

The study, led by scientists at Coastal Oceans Research and Development in the Indian Ocean (CORDIO) was published in Nature Sustainability.

A group of pontoon houses surround a coral island in the Maldives

Coral reefs in countries such as the Maldives are a draw for tourist, boosting local economies. Image © Sven Hansche/Shutterstock

The ocean's bounty 

The Indian Ocean is the world's third largest ocean, spanning from the east coast of Africa to the western shores of Australia. 

Due to its position along the equator, it is home to almost half of the world's coral reefs, primarily around Indonesia, Australia and India.  

However, the western half of the ocean still has a significant amount of biodiversity, with countries such as Madagascar, Mozambique and the Seychelles estimated to each have hundreds of species of coral.

These support a wealth of fish, with island nations like the Maldives having over a thousand species found in their waters. Fisheries are incredibly important to the region's economy to such an extent that if these seas were a country, they would represent the fourth-largest economy in the western Indian Ocean. 

The reefs also provide food security for the people that live in the region and provide added benefits as a draw for tourists. 

However, the exploitation of the ocean has led the fragile ecosystems found there to the brink of collapse. Fishing from both countries within and outside the region is one of the leading causes, followed by oil extraction and climate change. 

To assess the state of these corals, they were assessed using the International Union for the Conservation of Nature's (IUCN) Red List of Ecosystems. While similar to the red list for animal species which assesses their vulnerability to extinction, it instead asks how close the ecosystem is to collapse. 

The answer was that the region's reefs are perilously close to the edge. 

A net floats in the water above a dead coral reef

Overfishing is one of the leading threats to the survival of coral reefs. Image © Ryan Janssens/Shutterstock

Fishing threat 

The scientists compiled their report by splitting the reefs across the western Pacific into 11 sub-regions, running north up the east coast of Africa from Kenya to South Africa and east to the island states of the Seychelles and Mauritius. 

Each area was assessed individually for its status, allowing the researchers to know the state of around 5% of the world's reefs. 

They found that all sub-regions were at risk of collapse, with reefs around island nations with unique biodiversity, such as the Comoros and the Mascarene Islands, assessed as Critically Endangered. 

The same assessment was given for east and south Madagascar, though its north and west coasts were found to be less threatened and judged instead to be Endangered.  

The greatest threat to these island reef systems was climate change, which is causing ocean temperatures to rise in the shallow waters in which tropical corals thrive. Rising temperatures put the corals more at risk of bleaching and being unable to recover. 

The situation was better on the continental African coast, where the entire stretch was assessed to be Vulnerable. Here, overfishing was found to pose the greatest threat to the reefs.  

'We detected overfishing of top predators on all the reefs from which we had data,' said co-author Mishal Gudka. '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.' 

The scientists hope that similar assessments will be carried out for the rest of the world's reefs using the same framework they have, providing a stocktake of the world's coral. By knowing the state of these ecosystems, the scientists hope that politicians will take the necessary steps to pull coral reefs back from the brink.