Coral reefs in the Indian Ocean have partly recovered from the 1998 spike in sea temperatures, but climate change will probably hamper future conservation, a coral expert said on Wednesday.
An unusual spike in sea temperatures a decade ago killed coral throughout the Indian Ocean, dropping the average healthy, hard coral cover to 15 percent of reefs from 40 percent before.
Tim McClanahan, a coral expert with the Wildlife Conservation Society (WCS) said hard coral cover had recovered to 30 percent by 2005, although the data masked big variations.
"We have a double whammy -- we have heavy usage for food and now we have climatic disturbances," he added.
Reefs in northern Kenya, the Maldives and the Seychelles were hardest hit by the 1998 temperature spike, while those to the south, in Tanzania, Mauritius and Madagascar, were less affected, he told Reuters by e-mail and phone.
1998 and 2005 were the warmest years since records began in the mid-19th century, according to the U.N. World Meteorological Organization, with a strong El Nino warming of the Pacific Ocean adding to the impact of climate change in 1998.
Based in Mombasa, Kenya, McClanahan has been working on coral reefs for 30 years, mostly in the Indian Ocean. Like other seas, the Indian Ocean's waters are warming by about one degree Celsius every century, he said.
"It doesn't sound like it is warming a lot ... but that is fast enough that the genetics of corals will have a very hard time adapting."
RESILIENCE
Coral reefs, delicate undersea structures resembling rocky gardens that are made by tiny animals called coral polyps, are important nurseries and shelters for fish and other sea life.
They are also considered valuable protection for coastlines from high seas, a critical source of food for millions of people, important for tourism and a potential storehouse of medicines for cancer and other diseases.
The key problem for reefs around the world has traditionally been over-fishing, removing too many fish from the fragile ecosystems and allowing algae to flourish at coral's expense.
But climate change has emerged as a greater threat and one of the lessons learned from the past decade is that, up to a certain point, reefs impacted by human activity have been more resilient than others, McClanahan said.
McClanahan said he had found mixed success with coral transplants and had been interested to see the re-emergence of different types of coral on some reefs.
"In the Maldives the cover of coral has increased from one to 20 percent ... but the dominant species are not the same as what used to be there before 1998," he said.
The region's reefs are in better shape than the Caribbean's, but less resilient to temperature change than Australia's Great Barrier Reef, McClanahan said.
His organisation, WCS, consists mostly of terrestrial projects, but conducts marine work in Kenya, Madagascar, Papua New Guinea, Indonesia, Fiji, and Belize, including either fishing bans or the use of non-destructive fishing methods.
Destructive methods include dragging nets across the coral and to a lesser extent trampling the coral while wading through the water. Dynamite is still widely used in Tanzania, he said.
Some observers say agricultural and industrial pollution are key risks to Mauritius's coral, but McClanahan said much of the island nation's pollution was washed away by ocean currents.
McClanahan said there was no single solution for protecting coral reefs, adding a diversity of solutions was probably best.
"No matter how well they are managed by people, climatic effects are probably going to override that management." (Editing by Catherine Evans)
Source: http://africa.reuters.com
