Western Indian Ocean coral reefs at risk of collapse: study

The findings warn that reefs along Africa’s eastern coast and island nations like Mauritius and the Seychelles face a high risk of extinction unless urgent action is taken.

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

The results, published in the journal Sustainability of nature Monday, warned that reefs along the eastern coast of Africa and island countries like Mauritius and the Seychelles face a high risk of extinction unless urgent action is taken.

For the first time, researchers were able to assess the vulnerability of individual reefs in the vast western expanses of the Indian Ocean and identify the main threats to coral health.

They found that all of the reefs in this region were facing “a complete ecosystem collapse and irreversible damage” within decades, and that warming oceans meant that some coral habitats were already critically endangered. .

“The results are pretty serious. These reefs are likely to collapse,” lead author David Obura, founding director of CORDIO East Africa, a Kenya-based ocean research institute, told AFP. .

“There is nowhere in the region where the reefs are healthy. They have all shrunk somewhat, and it will continue.”

The study, co-authored with the International Union for the Conservation of Nature, assessed 11,919 square kilometers of reef, representing about five percent of the global total.

Reefs bordering scenic island nations like Mauritius, Seychelles, Comoros and Madagascar – popular ecotourism destinations heavily dependent on their marine environment – were most at risk, the researchers said.

“Double whammy”

Coral reefs cover only a tiny fraction (0.2%) of the ocean floor, but they are home to at least a quarter of all marine animals and plants.

In addition to anchoring marine ecosystems, they also provide protein, jobs, and protection from storms and shoreline erosion to hundreds of millions of people around the world.

Obura said healthy reefs were “very precious” and their loss would be “a double whammy”.

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

Climate change has been the biggest threat to coral health in the entire western Indian Ocean, where scientists say seawater temperatures are warming faster than in other parts of the globe .

The oceans absorb over 90 percent of the excess heat from greenhouse gas emissions, protecting land surfaces but generating huge, long-lasting marine heat waves that push many species of coral beyond their tolerance limits .

But along the east coast of mainland Africa, from Kenya to South Africa, the pressure of overfishing was also identified in this latest study as another major plague on reef ecosystems.

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

“We have to give these reefs the best chance. To do that, we have to reduce the conductors, reverse the pressure on the reefs,” he said.

In October, the largest ever global survey of coral health revealed that dynamite fishing, pollution and above all global warming had wiped out 14% of the world’s coral reefs between 2009 and 2018.


Global warming kills 14% of the world’s corals in a decade


More information:
David Obura et al, Vulnerability to collapse of coral reef ecosystems in the western Indian Ocean, Sustainability of nature (2021). DOI: 10.1038 / s41893-021-00817-0

© 2021 AFP

Quote: Coral Reefs of the Western Indian Ocean at Risk of Collapse: Study (2021, December 6) retrieved December 6, 2021 from https://phys.org/news/2021-12-coral-reefs-western-indian- ocean.html

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