An exclusive look inside the largest effort ever mounted to keep the Great Barrier Reef alive

CAIRNS, Australia — “I just got a whiff,” said Peter Harrison, a marine scientist, as he leaned over the edge of the boat and pointed his flashlight into the dark water. “It’s really coming through now.”

It was shortly after 10 pm on a cloudy December night, and Harrison, a coral researcher at Australia’s Southern Cross University, was about 25 miles off the coast of northern Queensland. He was with a group of scientists, tourism operators, and Indigenous Australians who had spent the last few nights above the Great Barrier Reef — the largest living structure on the planet — looking for coral spawn.

And apparently, it has a smell.

A team of researchers and tourism operators try to collect coral spawn above the Great Barrier Reef near Cairns one night in December.

Over a few nights in the Australian summer, shortly after the full moon, millions of corals across the Great Barrier Reef start bubbling out pearly bundles of sperm and eggs, known as spawn. It’s as if the reef is snowing upside down. Those bundles float to the surface and break apart. If all goes to plan, the eggs of one coral will encounter the sperm of another and grow into free-swimming coral larvae. Those larvae make their way to the reef, where they find a spot to “settle,” like a seed taking root, and then morph into what we know of as coral.

Key takeaways

• The Great Barrier Reef, the world’s largest living structure, will likely collapse by the end of the century without immediate and steep cuts to carbon emissions.

• An enormous group of scientists, backed with nearly $300 million, is working tirelessly to delay that decline through an initiative called the Reef Restoration and Adaptation Program.

• At the core of their approach is assisted reproduction — i.e., helping coral have more babies — which they do at sea and in one of the world’s largest research aquariums.

• The broader reef conservation industry in Australia has not fully reckoned with the climate reality it faces, and that undermines efforts to slash emissions, the only long-term solution to save reefs.

Spawning on the Great Barrier Reef has been called the largest reproductive event on Earth, and, in more colorful terms, “the world’s largest orgasm.” Coral spawn can be so abundant in some areas above the reef that it forms large, veiny slicks — as if there had been a chemical spill.

This was what the team was looking for out on the reef, and sniffing is one of the only ways to find it, said Harrison, who was among a small group of scientists who first documented the phenomenon of mass coral spawning in the 1980s. Some people say coral spawn smells like watermelon or fresh cow’s milk. To me it was just vaguely fishy.

“Here we go,” said Mark Gibbs, another scientist onboard and an engineer at the Australian Institute of Marine Science (AIMS), a government agency. All of a sudden the water around us was full of little orbs, as if hundreds of Beanie Babies had been ripped open. “Nets in the water!” Gibbs said to the crew. A few people onboard began skimming the water’s surface with modified pool nets for spawn and then dumping the contents into a large plastic bin.

That night, the team collected hundreds of thousands of coral eggs as part of a Herculean effort to try to keep the Great Barrier Reef alive. Rising global temperatures, together with a raft of other challenges, threaten to destroy this iconic ecosystem — the gem of Australia, a World Heritage site, and one of the main engines of the country’s massive tourism industry. In response to these existential threats, the government launched a project called the Reef Restoration and Adaptation Program (RRAP). The goal is nothing less than to help the world’s greatest coral reef survive climate change. And with nearly $300 million in funding and hundreds of people involved, RRAP is the largest collective effort on Earth ever mounted to protect a reef.

Peter Harrison, a coral researcher at Australia’s Southern Cross University, looks for coral spawn on the ocean’s surface.Nico Briggs, a research technician at the Australian Institute of Marine Science, skims the ocean for coral spawn with a modified pool net.

The project involves robots, one of the world’s largest research aquariums, and droves of world-renowned scientists. The scale is unlike anything I’ve ever seen.

But even then, will it be enough?

The first thing to know about the Great Barrier Reef is that it’s utterly enormous. It covers about 133,000 square miles, making it significantly larger than the entire country of Italy. And despite the name, it’s not really one reef but a collection of 3,000 or so individual ones that form a reef archipelago.

A pink skunk clownfish stares frightfully at me from its anemone home.A collection of flower-like soft corals on a reef northeast of Port Douglas.Dive guide Will Townshend and me on a reef offshore from Cairns.A pineapple sea cucumber with its characteristic bumpy protrusions nestles inside a sea sponge.

Another important detail is that the reef is still spectacular.

Over three days in December, I scuba dived offshore from Port Douglas and Cairns, coastal cities in Queensland that largely run on reef tourism, a whopping $5.3 billion annual industry. Descending onto the reef was like sinking into an alien city. Coral colonies twice my height rose from the seafloor, forming shapes mostly foreign to the terrestrial world. Life burst from every surface.

What really struck me was the color. Two decades of scuba diving had led me to believe that you can only find vivid blues, reds, oranges, and pinks in an artist’s imaginings of coral reefs, like in the scenes of Finding Nemo. But coral colonies on the reefs I saw here were just as vibrant. Some of the colonies of the antler-like staghorn coral were so blue it was as if they had been dipped in paint.

Staghorn coral often appears in brilliant blue.This type of coral is commonly referred to, fittingly, as cabbage or scroll coral.A pair of iconic clownfish in an anemone on a reef off the coast of Port Douglas.

It’s easy to see how the reef — built from the bodies of some 450 species of hard coral — provides a foundation for life in the ocean. While cruising around large colonies of branching coral, I would see groups of young fish hiding out among their nubby calciferous fingers. The Great Barrier Reef is home to more than 1,600 fish species, many of which are a source of food for Indigenous Australians and part of a $200 million commercial fishing industry.

“The reef is part of our life,” said Cindel Keyes, an Indigenous Australian of the Gunggandji peoples, near Cairns, who was part of the crew collecting coral spawn with Harrison. RRAP partners with First Nations peoples, many of whom have relied on the reef for thousands of years and are eager to help sustain it. “It’s there to provide for us, too,” Keyes, who comes from a family of fishers, told me.

Cindel Keyes, on a boat near Cairns, before spawn collection begins.A school of small fish hides out in a colony of branching coral.

The Great Barrier Reef is not dead, as many visitors assume from headlines. But in a matter of decades — by the time the children of today grow old — it very well could be.

The world’s coral reefs face all kinds of problems, from big storms to runoff from commercial farmland, but only one is proving truly existential: marine heat. Each piece of coral is not one animal but a colony of animals, known as polyps, and polyps are sensitive to heat. They get most of their food from a specific type of algae that lives within their tiny bodies. But when ocean temperatures climb too high, polyps eject or otherwise lose those algae, turn bleach-white, and begin to starve. If a coral colony is “bleached” for too long, it will die.

A dead colony of branching coral in the Agincourt reefs.

The global prognosis is bleak. The world has already lost about half of its coverage of coral reefs since the 1950s, not including steep losses over the last two decades. And should wealthy countries continue burning fossil fuels — pushing global temperatures more than 2 degrees Celsius above the pre-industrial baseline — it will likely lose the rest of it.

Projections for the Great Barrier Reef are just as grim. A recent study published in the prestigious journal Nature Communications projected that coral cover across the reef would decline, on average, by more than 50 percent over the next 15 years, under all emissions scenarios — including the most optimistic. The reef would only later recover to anything close to what it looks like today, the authors wrote, if there are immediate, near-impossibly steep emissions cuts. (The study was funded by RRAP.)

The reef has already had a taste of this future: In the last decade alone, there have been six mass bleaching events. One of the worst years was 2016, when coral cover across the entire reef declined by an estimated 30 percent. Yet recent years have also been alarming. Surveys by AIMS found that bleaching last year affected a greater portion of the reef than any other year on record, contributing to record annual declines of hard coral in the northern and southern stretches of the reef.