By Chris Mooney
20 April 2016
(Washington Post) – The conclusions are in from a series of scientific surveys of the Great Barrier Reef bleaching event — an environmental assault on the largest coral ecosystem on Earth — and scientists aren’t holding back about how devastating they find them.
Australia’s National Coral Bleaching Task Force has surveyed 911 coral reefs by air, and found at least some bleaching of the vast majority of them. The bleaching was the worst in the reef’s remote northern sector — where virtually no reefs escaped it.
“Between 60 and 100 percent of corals are severely bleached on 316 reefs, nearly all in the northern half of the Reef,” Prof. Terry Hughes, head of the ARC Centre of Excellence for Coral Reef Studies at James Cook University, said in a statement to the news media. He led the research.
Severe bleaching means that corals could die, depending on how long they are subject to these conditions. The scientists also reported that based on diving surveys of the northern reef, they already are seeing nearly 50 percent coral death.
“The fact that the most severely affected regions are those that are remote and hence otherwise in good shape, means that a lot of prime reef is being devastated,” said Nancy Knowlton, Sant Chair for Marine Science at the Smithsonian Institution, in an email in response to the bleaching announcement. “One has to hope that these protected reefs are more resilient and better able to [recover], but it will be a lengthy process even so.”
Knowlton added that Hughes, who led the research, is “NOT an alarmist.” [more]
“This is, by far, the worst bleaching they’ve seen on the Great Barrier Reef,” said Mark Eakin, head of the National Oceanic and Atmospheric Administration’s Coral Reef Watch, which partners with the Australian National Coral Bleaching Taskforce. “Our climate model-based Four Month Bleaching Outlook was predicting that severe bleaching was likely for the [Great Barrier Reef] back in December. Unfortunately, we were right and much of the reef has bleached, especially in the north.” [more]
20 April 2016 (ARC Centre of Excellence for Coral Reef Studies) – Australian scientists have revealed today the full extent of the coral bleaching that is unfolding on the Great Barrier Reef, off the coast of Queensland.
The final results of extensive aerial and underwater surveys reveal that 93% of the reef has been affected. It’s a mixed picture of very severe, moderate and little damage that changes dramatically from north to south along the 2300km length of the Reef.
Meanwhile on the west coast of Australia, researchers are also discovering large-scale bleaching caused by elevated temperatures on both sides of the Australian continent.
“We’ve never seen anything like this scale of bleaching before. In the northern Great Barrier Reef, it’s like 10 cyclones have come ashore all at once,” says Professor Terry Hughes, convenor of the National Coral Bleaching Taskforce that is documenting and studying the event. “Towards the southern end, most of the reefs have minor to moderate bleaching and should soon recover.”
“We have now flown over 911 individual reefs in a helicopter and light plane, to map out the extent and severity of bleaching along the full 2300km length of the Great Barrier Reef. Of all the reefs we surveyed, only 7% (68 reefs) have escaped bleaching entirely. At the other end of the spectrum, between 60 and 100% of corals are severely bleached on 316 reefs, nearly all in the northern half of the Reef.”
Underwater, teams of scientific divers have confirmed the accuracy of the aerial surveys, and are continuing to measure the ongoing impact of the bleaching.
“The bleaching is extreme in the 1000km region north of Port Douglas all the way up to the northern Torres Strait between Australia and Papua New Guinea,” says Prof. Andrew Baird from the ARC Centre of Excellence for Coral Reef Studies, who has spent the past 17 days at sea.
“Tragically, this is the most remote part of the Reef, and its remoteness has protected it from most human pressures: but not climate change. North of Port Douglas, we’re already measuring an average of close to 50% mortality of bleached corals. At some reefs, the final death toll is likely to exceed 90%. When bleaching is this severe it affects almost all coral species, including old, slow-growing corals that once lost will take decades or longer to return.”
More modest bleaching is now reaching its peak in a 600km central band of the Great Barrier Reef, between Cairns and Mackay. According to the scientists, reefs further south have escaped damaging levels of bleaching because water temperatures there were closer to the normal summer conditions over recent months.
“The severity of bleaching in the central section is less, and closer to the intensity of the first two mass bleaching events on the Barrier Reef, in 1998 and 2002,” says Prof. Hughes. “Thankfully, many of the corals there are more moderately bleached, so we expect that most of them will survive and regain their normal colour as temperatures drop over the coming months.”
The scientists have found that the huge footprints of the three mass bleaching events in 2016, 2002 and 1998 are different. “In each case, the location of the most severe bleaching coincides with where the hottest water sits for the longest period,” says Prof. Hughes.
“This time, the southern third of the Great Barrier Reef was fortunately cooled down late in summer by a period of cloudy weather caused by ex-cyclone Winston, after it passed over Fiji and came to us as a rain depression. The 2016 footprint could have been much worse.”
Australia’s tourism industry has a longstanding commitment to protecting its most valuable natural asset, the Great Barrier Reef. Reef tourism generates an annual income of $5 billion, and employs nearly 70,000 people. The Australian government has long recognised that climate change is the biggest threat to the Reef and the people who depend on it for their livelihood.
“Thankfully, many parts of the reef are still in excellent shape, but we can’t just ignore coral bleaching and hope for a swift recovery. Short-term development policies have to be weighed up against long-term environmental damage, including impacts on the reef from climate change,” says Daniel Gschwind, Chief Executive of the Queensland Tourism Industry Council.
On the west coast of Australia, researchers from the national taskforce are now also documenting extensive bleaching on the coastline and on offshore atolls.
“The coastal area that I study north of Broome has huge tides, and we thought the corals there are tough “super corals” because they can normally cope with big swings in temperature,” says Dr. Verena Schoepf from the University of Western Australia. “So, we’re shocked to see up to 80% of them now turning snow-white. Even the tougher species are badly affected”.
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