Rising water temperatures and overfishing threaten coral reefs in the western Indian Ocean, which could collapse in the next 50 years, according to the very first study of these ecosystems published on Monday 6 December.
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Its findings, published in the journal
Nature Sustainability
, warn that corals along Africa's east coast face a high risk of extinction if urgent action is not taken.
For the first time, researchers were able to assess the vulnerability of several reefs across the western Indian Ocean, and identify the main threats to coral health.
Scientists estimate that all corals in this region face "
total ecosystem collapse and irreversible damage
" in the decades to come.
Several coral habitats are already critically endangered.
The reefs "have all already declined"
“
The conclusions are quite serious. These reefs are in danger of collapsing,
”David Obura, founder of the Kenya Ocean Research Institute CORDIO East Africa and lead author of the study, told AFP. “
The reefs are not healthy anywhere in the region. They have all already declined, and it will continue
”. The study, co-signed by the International Union for the Conservation of Nature, covered nearly 12,000 km2 of reefs, which represent about 5% of the world total.
Reefs near islands like Mauritius, Seychelles, Comoros and Madagascar - popular tourist destinations for their marine ecosystems, including reefs - are most threatened, researchers say. Coral reefs cover only a tiny portion (0.2%) of the ocean floor, but are home to at least a quarter of all marine flora and fauna. They also offer protection against storms and coastal erosion but also jobs for millions of humans. For David Obura, the health of reefs is "
very precious
" and their loss would be "
a double test
": "
for biodiversity, but also for all kinds of coastal activities that depend on reefs.
"
Global warming poses the greatest threat to coral health in the western Indian Ocean, where scientists say water temperatures are rising faster than elsewhere on the planet.
The oceans absorb over 90% of the excess heat from greenhouse gases, which helps cool the land but generates intense and long marine heat waves.
From Kenya to South Africa, the pressure from overfishing is also identified as another risk.
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The study underlines the need to respond as quickly as possible to these two threats, global and local, says Obura: “
We have to give these corals the best possible chance.
To do this, we must reduce these factors, alleviate the pressure on the corals
”.