Global Warming Continues to Damage Coral Reefs

by Duane Nichols on March 19, 2017

Coral Reefs important to ocean life

Coral Reefs’ Only Hope Is Halting Global Warming

From an Article by Nicholas Kusnetz, Inside Climate News, March 15, 2017

PHOTO: The Great Barrier Reef has experienced a series of damaging bleaching events since 2014.

>>> Bleaching events have stressed coral worldwide, particularly the Great Barrier Reef, and research says their survival depends on quickly slowing climate change. <<<

Two doses of bad news for the world’s coral reefs came in the last week. First, Australia’s government confirmed that the Great Barrier Reef is in the midst of a second consecutive year of mass bleaching. It’s the first time the reef has experienced back-to-back events, and it seems to be weakening many of the corals.

Then on Wednesday, leading scientists published a new study about last year’s bleaching—the worst to date—suggesting that when the seas are hot enough for long enough, nothing can protect coral reefs. Their only hope is that we rapidly slow climate change.

The research, published in the journal Nature, looked at data from three bleaching events along the 1,400 mile-long Australian reef system dating back to 1998. By looking at factors including water temperature, water quality and fishing protections, the authors determined that last year’s bleaching was linked almost exclusively to ocean warming.

Conservationists have long hoped that protecting corals from other threats, such as pollution and overfishing, might help shield at least some of them from bleaching, too. While the new paper doesn’t entirely deflate that hope—such protections likely help reefs recover—it shows that such work provides little if any relief from severe bleaching.

“At the level of heat stress that was seen during this event, it just didn’t matter,” said C. Mark Eakin, coordinator of the Coral Reef Watch program at NOAA and a co-author of the paper.

Ilsa B. Kuffner, a marine biologist with the United States Geological Survey who was not involved in the research, said the new paper supports a solid body of evidence suggesting that disease and bleaching are driving coral mortality, while other factors play a more important role in the recovery from those threats. “It’s a distinction that, while it’s subtle, is also very important when you talk about what’s actually causing coral reef decline,” she said.

The paper also found that a reef’s history made little difference. Some studies have suggested that previous bleaching may make reefs more resilient if they are given time to recover, perhaps by killing off weaker corals or driving some adaptive response.

Warmer-than-average temperatures can cause coral to expel the symbiotic algae that live on its surface, turning the reef white. Such bleaching stresses coral and can make it more susceptible to disease and death.

The world’s reefs are in the midst of what scientists consider to be a single, mass bleaching event dating back to 2014. Climate models project that most of the world’s reefs could experience annual bleaching by 2050 without rapid cuts in greenhouse gas emissions.

While coral can survive even extreme bleaching, surveys conducted this month along the Great Barrier Reef are showing evidence that successive hits take a toll. Eakin said the level of heat stress—a measurement of how hot the waters are for how long—is lower than last year, and yet the bleaching appears to be just as widespread.

“They haven’t bounced back yet, so when you hit them with another event a year later, you can see more bleaching at a lower level of heat stress,” he said. “A lot of the corals that have survived last year really are not ready for another event.”

The bleaching has also spread to areas of the reef that escaped last year’s event, according to the recent surveys.

Successive bleaching also appears to be reshaping the makeup of the reef system. Reefs are composed of a rich diversity of coral species, with some particularly sensitive to bleaching and some that recover much more quickly than others. With consecutive years of bleaching, and after four events over 20 years, the new paper said the composition of the reef is changing in areas that have seen recurrent bleaching, perhaps irreversibly.

“The good news is you’ve got some tough corals that are surviving,” Eakin said. “The bad news is, one of the most important things about coral reefs is their diversity, and you’re cutting out some of that diversity.”

The paper’s authors believe that protecting reefs from pollution and overfishing will help them recover from bleaching. But the most important action, they said, lies elsewhere.

“Securing a future for coral reefs, including intensively managed ones such as the Great Barrier Reef,” they wrote, “ultimately requires urgent and rapid action to reduce global warming.”

{ 1 comment… read it below or add one }

Nadia Prupis April 10, 2017 at 11:11 pm

Great Barrier Reef Faces ‘Terminal’ Stage in Climate Change Fight

>>> New aerial surveys show damage has spread to two-thirds of reef, up from one-third last year < <<

From Nadia Prupis, Common Dreams, April 10, 2017

This year's mass bleaching occurred even in the absence of an El Niño event. 

The Great Barrier Reef may be at a "terminal" point after being hit with unprecedented bleaching events in consecutive years, scientists warned Monday.

According to new aerial surveys conducted by the Australian Research Council's Centre of Excellence for Coral Reef Studies, two-thirds of the reef have now been affected, up from one-third last year. This year's mass bleaching occurred even in the absence of an El Niño event.

Professor Terry Hughes, who led the surveys, told the Guardian, "The significance of bleaching this year is that it's back to back, so there's been zero time for recovery."

"It's too early yet to tell what the full death toll will be from this year's bleaching, but clearly it will extend 500km (310 miles) south of last year's bleaching," he said.

Australia now faces a rapidly approaching deadline for saving the reef by addressing climate change, Hughes added. "It takes at least a decade for a full recovery of even the fastest growing corals, so mass bleaching events 12 months apart offers zero prospect of recovery for reefs that were damaged in 2016," said Dr. James Kerry, who also took part in the surveys.

Bleaching occurs when overly warm ocean waters cause coral to get rid of its internal algae, which turns the coral white and erodes its structures. The loss of structure makes shorelines more vulnerable to extreme weather and destroys natural habitats for marine life.

A groundbreaking study published last year found that climate change is the primary cause of coral reef degradation around the world.

Jon Brodie, a water quality expert, told the Guardian that the reef was now at a "terminal stage" and that many scientists have lost hope that it can be salvaged. "We've given up. It's been my life managing water quality, we've failed," Brodie said. "Even though we've spent a lot of money, we've had no success."

Others remained hopeful that the reef had a future, but warned that time was of the essence. "You've got to be optimistic, I think we have to be," said Jon Day, former director of the Great Barrier Reef Marine Park Authority. "But every moment we waste, and every dollar we waste, isn't helping the issue. We've been denying it for so long, and now we're starting to accept it. But we're spending insufficient amounts addressing the problem."

Hughes continued, "The sooner we take action on global greenhouse gas emissions and transition away from fossil fuels to renewables, the better."


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