 Seychelles Coral
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Sept. 19, 2003 — Several of the Indian Ocean's coral paradises may be wiped out by climate change within the next couple of decades, a study published on Thursday in the British scientific journal Nature said.
Those most at risk include the Seychelles, the Maldives, the Chagos archipelago, the Comoros and parts of the coastline of Tanzania and Mozambique, where fishing and tourism are the main sources of income, it said.
The research, by marine biologist Charles Sheppard at Britain's University of Warwick, was launched after more than 90 percent of shallow corals were wiped out on Indian Ocean reefs in 1998 by a three-month surge of exceptionally warm seas.
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Sheppard's computer model combines past and predicted sea-surface temperatures for 33 sites, including the Red Sea and the Gulf and taking into account the different corals that grow there.
He calculates that most western sites located in a band 10 to 15 degrees south of the Equator face a 20-percent annual risk of experiencing a month as warm as the 1998 surge within the next 10-15 years — and this is a figure that is far more pessimistic than in any previous research.
Corals in these hot-spots may not survive another such attack, Sheppard said.
Five years after the 1998 event, only three to five percent of areas that were bleached at these sites have grown back. Some of the devastated coral was several hundred years old.
It takes some five years for new coral to mature enough to reproduce and about another five to establish a valid eco-system.
That means the coral has no chance of recovering before it is hit by another wave within a few years of the previous one.
By 2020, the most vulnerable sites "are going to see an extinction point," Sheppard said.
A keen diver, he said he felt "devastated" by the sight of bleached corals in some of his favorite dive spots, at depths reaching down to as much as 140 feet in some places.
"Several of the world's poorest countries, for which reefs provide essential resources, will be affected soonest," he added. "The situation is tragic."
The only country that escaped the devastation in 1998 was Mauritius, because by sheer luck the island was smothered by cloud during this time.
The picture is not the same, or so alarming, in northern parts of the Indian Ocean, according to the study.
This is because of differing temperatures and some coral species, such as in the Arabian Gulf, have a better chance of surviving 1998-type temperatures. Much depends on the corals' adaptability.
Overall, if the Indian Ocean's corals become tolerant to temperatures that are just two degrees Celsius (3.6 F) higher than present, this could prolong their survival by nearly a century, according to Sheppard's study.
The UN's top scientific authority on global warming, the Intergovernmental Panel on Climate Change (IPCC), predicted in 2001 that there would be an average temperature rise in the 21st century of 1.4 to 5.8 C (2.5 to 10.4 F).
Sheppard said that his computer model was based on a "medium" figure between these two.
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