Apr 4, 2019

Global warming is pushing the Great Barrier Reef to the brink

Bleached coral on Lizard Island in the Great Barrier Reef in 2016. Photo: Underwater Earth/XL Catlin Seaview .

Repetitive, severe marine heat waves are disrupting the Great Barrier Reef's ability to regrow with a similar abundance and mix of species as before, a new study warns. The paper, published in Nature Wednesday, depicts a vast, complex reef ecosystem that is on the verge of "ecological collapse."

Why it matters: The Great Barrier Reef is the word's largest coral reef ecosystem, spanning 1,400 miles from north to south off the eastern coast of Australia. The reef is a haven for biodiversity and a major driver of tourism for Australia. The new results add to a series of grim findings about just how susceptible this reef community, long viewed as too big to fail, is to warming ocean waters.

What they did: For the study, researchers in Hawaii and Australia examined how corals reproduce, or spawn, from one year to the next, by taking in situ measurements out on the Great Barrier Reef. Researchers compared spawning behavior in years prior to the marine heat waves that struck two-thirds of the reef in 2016 and 2017 against what happened immediately following the heat waves, also referred to as coral bleaching events for their tendency to turn corals a ghostly white as heat stress causes organisms to kick out symbiotic algae that gives corals their vibrant colors.

What they found: By comparing coral spawning behavior in years without marine heat waves with what followed the devastating marine events of 2016 and 2017, the study found that such heat events compromise the reef's capacity to recover by causing a sharp plunge in coral reproduction rates.

  • By killing adult corals, the heat waves slashed the rate of reproduction and the balance between coral species. According to the study, the number of new corals settling on the Great Barrier Reef declined by 89% following the assault on adult corals in 2016 and 2017.

One species, Acropora, which establishes branching and table coral, declined by 93% compared to prior, non-heat wave years.

What they're saying: There are more reasons for pessimism about the reef's future than optimism, scientists tell Axios, but all is not lost, at least not yet.

The increased frequency of bleaching events means that more corals will die before they can recover. "One more large scale bleaching event in the next few years and it could be curtains" for many parts of the Great Barrier Reef, study co-author Andrew Baird, of James Cook University in Australia, tells Axios via email.

But the new study is just one snapshot of the reef's damage right after a massive shock. "The drop in coral recruitment is what we would expect after such severe bleaching events that result in high mortality of adult reproductive corals," says Sarah Lester, who studies corals at Florida State University.

“I think extrapolating that to say that we could understand how these systems are going to respond or compensate potentially over the longer term, that’s a bit harder, that still would remain to be observed because we’re still trying to extract these lessons from these sort of life after death moments,” says Kim Cobb, a coral expert at Georgia Tech.

But, but, but: However, the severe bleaching events mean that the surviving corals were able to withstand the extreme heat, and that they may prove more resilient to future events as well.

Madhavi Colton, program director with the nonprofit Coral Reef Alliance, says she''s interested in seeing what happens with coral recruitment (the term that describes the process by which coral larvae attach themselves to existing coral) beyond just a single year following the bleaching event.

“I would be interested in seeing if this trend holds up, then we should be more alarmed than we are with one very bad year,” she tells Axios.

Be smart: Colton says in looking at these results, one could focus on the high percentage of corals that died, which previous studies have pegged at about75% of all the corals in the northern two-thirds of the reef. Or, as she put it, "Oh my gosh, 25% of the corals survived! They made it through that! And that’s where the future lies," Colton says.

The bottom line: According to Cobb, the future of the world's reef ecosystems will look nothing like what we've known in the recent past.

“It’s worth remembering that we kind of think about will they ever get back to where they were before these events happened? Probably not," she says.

"Will they look very, very different? Will there just be a different kind of reef there, will they have a different functionality? Maybe yes.”

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In photos: Americans venture out for Memorial Day weekend

Venice Beach in Los Angeles on May 24. Photo: David McNew/Getty Images

Authorities warned Americans to take precautions against the coronavirus pademic amid reports of packed beaches and bars during the Memorial Day weekend.

The big picture: Law enforcement stepped up beach patrols, authorities on Florida's Gulf Coast closed parking lots because they were full and there were crowded scenes at Lake of the Ozarks bars in Missouri, per AP, which reports a shooting injured several people at a packed Daytona Beach in Florida.

Coronavirus dashboard

Illustration: Aïda Amer/Axios

  1. Global: Total confirmed cases as of 9:30 p.m. ET: 5,405,029 — Total deaths: 344,997 — Total recoveries — 2,168,408Map.
  2. U.S.: Total confirmed cases as of 9:30 p.m. ET: 1,642,021 — Total deaths: 97,698 — Total recoveries: 366,736 — Total tested: 14,163,195Map.
  3. World: White House announces travel restrictions on Brazil, coronavirus hotspot in Southern Hemisphere Over 100 coronavirus cases in Germany tied to single day of church services — Boris Johnson backs top aide amid reports that he broke U.K. lockdown while exhibiting symptoms.
  4. Public health: Officials are urging Americans to wear masks headed into Memorial Day weekend Report finds "little evidence" coronavirus under control in most statesHurricanes, wildfires, the flu could strain COVID-19 response
  5. Economy: White House economic adviser Kevin Hassett says it's possible the unemployment rate could still be in double digits by November's election — Public employees brace for layoffs.
  6. Federal government: Trump attacks a Columbia University study that suggests earlier lockdown could have saved 36,000 American lives.
  7. What should I do? Hydroxychloroquine questions answeredTraveling, asthma, dishes, disinfectants and being contagiousMasks, lending books and self-isolatingExercise, laundry, what counts as soap — Pets, moving and personal healthAnswers about the virus from Axios expertsWhat to know about social distancingHow to minimize your risk.
  8. Other resources: CDC on how to avoid the virus, what to do if you get it, the right mask to wear.

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Updated 56 mins ago - Politics & Policy

Republicans sue California over mail-out ballot plan

California Gov. Gavin Newsom during a February news conference in Sacramento, California. Photo: Justin Sullivan/Getty Images

President Trump accused Democrats of trying "Rig" November's general election as Republican groups filed a lawsuit against California Sunday in an attempt to stop Gov. Gavin Newsom (D) from mailing ballots to all registered voters.

Driving the news: Newsom signed an executive order this month in response to the coronavirus pandemic ensuring that all registered voters in the state receive a mail-in ballot.