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For 500,000 years, the Great Barrier Reef has grown steadily in the fresh, clear waters of Australia. But after surviving five glacial periods, the billions of reef inhabitants may not survive humanity.
On March 26, The Reef endured its third major whitening event in five years. According to the Australian government, many of its corals suffered massive bleaching, even in the relatively intact southern part during previous events. Wave-warming climate has sent wave after wave of hot water bathing the 3,000 individual coral reefs that make up the massive living structure, which stretches across 2,300 km (1,429 miles).
When the water temperature rises only a few degrees above normal, stressed corals can expel their symbiotic algae, leading to bleaching events. Off-white corals are left without their life-giving algae. Some recover. But if bleaching occurs too frequently and intensively, reefs die along with their ecosystem, often comparable to a destroyed tropical forest.
Sea surface temperatures, which are already 0.4 degrees Celsius higher than historical averages, will reach 2.5 degrees Celsius above normal by the end of the century. “Climate change remains the biggest challenge for the Reef,” says Australia’s marine park agency.
Andrea Dutton, a paleoclimatologist at the University of Florida, has spent her life studying this phenomenon. She drills through fossilized corals to see what they can tell us about the past hundreds of thousands of years of sea levels and ice sheets during episodes of global warming.
She spoke to Quartz twice in the past year to detail what current corals portend about climate and the importance of bleaching in the world’s largest coral system. Change, she knows, is part of life on the reef. But the rhythm now dwarfs anything that has happened before. “It’s not that life can’t adapt,” she says. “But the question really is, can we continue to support human civilization in a sustainable way on this planet? To do this, we need a healthy ecosystem around us … Not having healthy oceans is a profound risk to human civilization. “
This generation is likely to be the last to see the Great Barrier Reef as such an ecosystem. Dutton, who is in New Zealand for a Fulbright scholarship, planned to take his children to see the Reef for the first time this year, especially in the relatively pristine southern section. But the coronavirus pandemic canceled his plan, and the bleaching struck a few weeks later. “I was hoping to show my two Australian children the Great Barrier Reef this month in all its glory, before it was too late,” she says. “Now, I’m not sure if they will ever have that opportunity.” The hope now, he adds, is to slow down the rate of global warming.
This interview was edited for its length and clarity.
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Quartz: What can you discover about the weather by trying these corals?
Dutton: It is surprising how much information we can extract. I always tell people who pick up a rock, any rock, they can tell you a full story about what happened to make that rock emerge the way it is. What we are seeing is not only how sea levels change, but also how the reef responded to sea level and climate change.
Are corals a kind of canary in the coal mine for climate change?
This is one of them. What we are seeing now with reef bleaching globally is really scary because most reefs don’t really recover from bleaching. Or if they do, the coral could take 15 years or more. This is not a small thing we are seeing.
Can you describe exactly what is going on?
When the ocean warms up, the symbiotic algae, the zooxanthellae [a yellowish-brown symbiotic dinoflagellate that lives in the coral and gives it color]I can no longer stay there. And so they go. And what remains is just the coral skeleton, which is white. If you look at it from above, it completely changes the reef. All the color would be gone. Things that depend on coral for food also begin to struggle.
And this is what corals look like in the fossil record. It is just these white carbonate skeletons that I work with to try to understand what happened in the past.
If you had to make an analogy of what happens to reefs as if they were a human city, how would you describe that?
When a hurricane hits and kills everything you need to live, it is left in ruins. Things start to grow above. You can no longer imagine life there. That is what is happening to coral reefs, which host so many different organisms in the oceans.
When these corals do not survive, they are covered with algae. These really slimy green disgusting things. I have been diving in reefs covered with algae. It smells of all dead organisms on the reef after the bleaching event. It was so annoying that I had to get out of the water. I couldn’t stay there. It was absolutely horrible to experience in person when you see what is happening.
The problem is that if you want to rebuild the reef, it is not like rebuilding a city. If I had a lot of money, I could go in there and build new buildings, and people could move out immediately. For reefs, you could try to recruit small recruits, small colonies of small corals there, and it would be very difficult to repopulate the entire reef. We would have lost species. Many of those coral recruits would not survive anyway.
It is not that we can simply flip a switch and rebuild in the same way that you can rebuild a city.
So are coral reefs a lost cause? You mentioned that things will get worse before they get better. Why is that?
Therefore, it is not a lost cause. The reason I said it would get worse before it got better is that even if we stopped all greenhouse gas emissions today, we would still get some residual warming. Ice sheets will already start to melt just from the amount of heat in the ocean. There will still be some continuing effects of climate change.
But we could start to stabilize. Not that there is no hope. Because our actions can and do make a difference. That doesn’t mean there won’t be some pain and suffering along the way, but that could mean there is less.
REUTERS / Susannah Sayler
You have studied corals for long periods of history. The last time we saw such high atmospheric CO2 concentrations was about 3 million years ago. From today’s coral reef perspective, have you ever been in these conditions before?
Earth has been warmer before. But again, I must reiterate, one of the challenges here is that change occurred much slower than what we are seeing today. It is not a perfect analogy in that regard.
People in Australia are studying how fast coral larvae can disperse to escape warmer waters and migrate fast enough compared to the speed at which temperatures change. And the answer in one of those studies I saw was “no”.
That is the great challenge now in terms of trying to adapt. The pace of these changes. Earth and its natural mechanism (negative feedback, checks and balances) is happening too fast now.
If you were to describe what we know today that we didn’t know 20 years ago, five years ago, and even a year ago, what would it be? Can you break that
One focus of my research is to observe the change in sea level. For a long time, we thought that the ice sheets in Antarctica and Greenland were so large that it would take a huge change in temperature for them to respond. It turns out that we have learned by looking at warm past periods that this is not the case.
In fact, they are sensitive to small changes in temperatures of one or two degrees. We used to think of them as sleeping giants. But those giants have woken up to the amount of warming we’ve already seen. That is one of the main focuses of research now: how fast it will happen and how fast it will melt and retreat.
The problem is that humans have never been present to witness this dynamic and rapid withdrawal of an ice sheet like that. There are too many unknowns in the physical models of these ice sheets. We don’t fully understand physics there.
And that’s where my work comes in. We can observe these past warm periods and calibrate the ice sheet models to the data we have obtained in the past. So those models will be better calibrated when we run them in the future trying to predict how fast that recall will happen.
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You also mentioned that you have children. When you talk about your work, what do you tell them about what is happening?
Well, I am telling you the truth. We sat down and watched that movie Chasing Coral. It’s on Netflix for free.
I had to see him at work. We had a panel afterwards. We’ve alredy talk about that. And I went home to see him with my children. It was a totally different experience because we were sitting there and I was looking at him through his eyes. They were watching their future and the Great Barrier Reef disappearing. My children were born in Australia and it really came home to them.
The three of us were sitting on the couch with tears streaming from our eyes watching this documentary about what was happening to the coral reefs. And it was so deeply moving.
When I think about the future, do my children motivate me and the work I do? Yes. I see our legacy in his eyes every day. It is absolutely motivating.
