Coral reefs of western Indian Ocean at risk of collapse: study

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Nairobi (AFP) – Rising sea temperatures and overfishing threaten coral reefs in the western Indian Ocean with complete collapse in the next 50 years, according to a groundbreaking study of these marine ecosystems.

The findings, published in Nature Sustainability on Monday, warn that coral reefs along the east coast of Africa and island nations such as Mauritius and the Seychelles are at risk of extinction unless urgent action is taken.

For the first time, researchers have been able to assess the vulnerability of individual reefs across the vast western reaches of the Indian Ocean, and identify major threats to coral health.

They found that all coral reefs in this region faced “complete ecosystem collapse and irreversible damage” within decades, and that warming oceans meant that some coral habitats were already in grave danger.

“The results are very serious. These coral reefs are vulnerable to collapse,” lead author David Obura, founding director at CORDIO East Africa, an ocean research institute based in Kenya, told AFP.

“Nowhere in the region is coral reefs in perfect health. They have all degraded to some extent, and that will continue to be so.”

The study, co-authored by the International Union for Conservation of Nature, estimated 11,919 square kilometers of coral reefs, which represents about five percent of the global total.

The coral reefs that surround picturesque island nations such as Mauritius, Seychelles, Comoros and Madagascar – eco-tourism destinations that rely heavily on their marine environment – were most at risk, researchers said.

“double whammy”

Coral reefs cover only a small portion – 0.2 percent – of the ocean floor, but they are home to at least a quarter of all marine animals and plants.

Besides solidifying marine ecosystems, they also provide protein, functionality, and protection from storms and coastal erosion to hundreds of millions of people around the world.

Abora said healthy corals are “extremely valuable” and losing them would be a “double whammy”.

“For biodiversity, but also all kinds of coastal economies that depend on coral reefs,” he said.

Climate change poses the biggest threat to coral health overall in the western Indian Ocean, where scientists say sea water temperatures are rising faster than in other parts of the world.

Oceans absorb more than 90 percent of the excess heat from greenhouse gas emissions, protecting Earth’s surfaces but generating huge, long-lasting marine heat waves that push many coral species beyond their tolerance limits.

But along the eastern coast of mainland Africa from Kenya to South Africa, pressure from overfishing has been identified in this latest study as another major scourge on coral reef ecosystems.

This underscores the need to urgently address global threats to coral reefs from climate change, and local threats such as overfishing, Obura said.

“We need to give these reefs the best chance. In order to do that, we have to reduce drivers and reverse the pressure on the reefs,” he said.

In October, the largest global survey on coral reef health revealed that mainly dynamite fishing, pollution and global warming wiped out 14 percent of the world’s coral reefs from 2009 to 2018.

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