El Nino coral damage could be worst ever - Scientists

Scientists Thursday warned the world faced mass global coral bleaching next year driven by the warming effects of the El Nino weather phenomenon, and it could be the worst on record.

A study by the University of Queensland and the US National Oceanic Atmospheric Administration said it would be only the third recorded global bleaching event in history, with areas such as Australia's Great Barrier Reef set to be hard hit.

"If conditions continue to worsen, the Great Barrier Reef is set to suffer from widespread coral bleaching and subsequent mortality, the most common effect of rising sea temperatures," said the university's Global Change Institute director Ove Hoegh-Guldberg.

"In the first major global event in 1998, more than half the Great Barrier Reef experienced bleaching with about five to 10 percent of the corals dying.

"Thankfully the Great Barrier Reef was spared during this second global event (in 2010) due to storm activity which alleviated the heat stress. The reef may not be so lucky in 2016."


Workers excavate earth at a residential area in southern Nairobi on October 6, 2015, to create larger drainage channels. Heavy floods and drought expected around East Africa, sparked by the El Nino weather phenomenon in coming weeks, could put thousands of lives at risk, the United Nations warned. AFP PHOTO / TONY KARUMBA

Bleaching is a phenomenon that turns corals white or fades their colours, an event that threatens a valuable source of biodiversity, tourism and fishing.

It occurs when reef symbiosis -- the mutually beneficial relationship between two organisms that inhabit corals -- is disrupted by a surge in ocean warming, although there can also be other causes.

One of the worst episodes on record, which affected reefs in 60 tropical countries, took place in 1998, when the El Nino weather pattern was exceptionally strong.

The phenomenon occurs when trade winds that circulate over waters in the tropical Pacific start to weaken and sea surface temperatures rise.

US government scientists in August said the El Nino currently under way -- the first in five years -- could be among the strongest in 65 years, while authorities in Australia have predicted it would be "strong" and "substantial". 

Hoegh-Guldberg said research he conducted in 1999 predicted mass coral bleaching events would become successively worse over time if the world failed to deal with rising atmospheric gases.

"Unfortunately, 16 years later, these predictions are beginning to unfold," he said.

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