The Dying of the Reefs: Is There Hope?
1,500, plus more than 500 species of living coral: hard, soft, branching, and leafy.
I first dove Australia’s Great Barrier Reef in 1990, having dreamed about it since childhood. It was all I’d hoped for: warm, gin-clear waters vibrant with life, including giant potato cod (grouper), blue-green Napoleon wrasse, sharks, and multihued parrotfish crunching coral and excreting sand. There were canyons and bommies and walls with branching elkhorn, staghorn, plate, and fan corals. There were coral gardens in brown, green, red, pink, and purple, crevices full of moray eels and queen angelfish, and shelves of multiquill geisha-like lionfish along with red and blue spotted coral trout amidst a rainbow confetti of smaller fish, including clowns, damsels, sweetlips, chromis, and Moorish idols. The boulder-sized giant clams with their beautiful soft mantels of purple, green, and red algae-covered mollusk skin that opened like fat lips to the sea seemed to have calmed down considerably since my early TV viewing, when they trapped Sea
Hunt’s Lloyd Bridges by the leg and tried to drown him.
I shared that first boat trip on the Great Barrier Reef with my late love and dive buddy Nancy Ledansky. She died of breast cancer at the age of forty-two in 2002. More than a fifth of the Great Barrier Reef that is 6,000 to 8,000 years old died in 2016. Not coincidentally, that was the planet’s hottest year since modern recordkeeping began in the nineteenth century.
Sixty-seven percent of the reef segment north of Port Douglas is now dead rock. This latest coral die-off is the result of the third and most persistent global bleaching event since 1998; all are linked to fossil-fuel-fired climate disruption.
A new study that recently made the cover of the science journal Nature documents vast coral death along a 500-mile section of the reef. Where we took our dives, some patches are more than 80 percent gone. Other parts of the northern reef have seen less extreme die-offs, averaging 17 to 35 percent. Best estimates are that 22 percent of the total coral cover of the Great Barrier Reef is gone. Most marine scientists now believe 75 percent of the world’s coral reefs will be dead due to accelerating climate change by mid-century. Half are already gone.
“We didn’t expect to see this level of destruction to the Great Barrier Reef for another thirty years,” Terry P. Hughes, a coauthor of the paper, told The New York Times, one of the few U.S. media outlets that have bothered to cover this global catastrophe. He also told the Times that, after reviewing some of their photos taken from low-flying aircraft, he and his graduate students began to cry in mourning. Chasing Coral, a new documentary appearing on Netflix, shows the die-off in stunning time-lapse imagery, including branching corals off New Caledonia that turned luminescent pink, orange, and blue, shining with a radiant light never before seen in the world, just before they died.
I saw my first bleached coral in Fiji in 2002 and my last in Hawaii in late 2015, where about one-third of the corals at Two Steps on the Big Island had turned wedding cake white. The diagnosis, symptoms, and disease mechanisms of coral bleaching are now well understood by science—despite Environmental Protection Agency chief Scott Pruitt’s claim that carbon-dioxide emissions are not a primary contributor to climate change. To understand a statement like that, it helps to know that the oil and gas industry has been a primary contributor not only to climate change and coral bleaching but also to Pruitt’s political career.
Corals, although able to form massive colonies, are counterintuitively delicate, requiring seven specific ocean conditions in which to thrive, including low-nutrient waters of a certain salinity that stay within a particular temperature range.
Ocean warming resulting from climate change, combined with cyclical warming caused by the weather system El Niño, causes the photosynthetic algae that give corals their varied colors and about 70 percent of their nutrients to turn toxic. The coral polyps then expel these zooxanthellae algae and begin turning white even as they continue to grab zooplankton out of the seawater flowing past them (zooplankton provide about 30 percent of their food stock).
“Most marine scientists now believe 75 percent of the world’s coral reefs will be dead due to accelerating climate change by mid-century.”
If ocean thermal conditions change, the coral can recover, but if the bleaching lasts too long, the corals slowly starve to death.
The report in Nature found that repeated exposure to bleaching did not make corals any more resistant to heat stress. Also, while efforts are underway to reduce other threatening impacts, including polluted runoff from coastal development and sugarcane fields, overfishing, and physical damage, the worst bleaching occurred in the least human-impacted northern stretch of the Great Barrier Reef, simply because a series of tropical storms had brought cooler water and relief to the more developed central and southern sections of the reef.
In the Florida Keys, where the coral barrier reef is one-tenth the size of Australia’s but gets ten times the visitors, a combination of all these factors has reduced the live coral cover from about 90 percent when I first snorkeled it at age fifteen to less than 10 percent today.
In more recent years, I’ve seen algae-covered rubble fields where coral gardens once thrived, and intricate fan corals shredded like Irish lace attacked by hungry moths where farm-soil Aspergillus fungus had washed into the sea. Today, Florida’s once common branching staghorn and elkhorn corals are on the U.S. endangered species list.
Yet another challenge for reef survival—along with bleaching, overfishing (which removes grazers like parrotfish that control algae growth), and runoff pollution—is ocean acidification.
When I wrote my first ocean book, Blue Frontier, in 2001, climate scientists still didn’t understand why the atmosphere wasn’t heating up as rapidly as their computer models predicted. It was only in the following years that they realized that as much as a third of our anthropogenic (human-generated) carbon was being buffered by the ocean and converted into carbonic acid, shifting the global pH of the ocean and making it harder for shell-forming creatures, including certain planktons, clams, crabs, oysters, urchins, and, of course, coral, to pull calcium carbonate out of seawater to form their living homes.
Today, the ocean is about 30 percent more acidic than it has been for at least two million years. Among the first to feel the economic impact has been the shellfish industry, including companies like Taylor Shellfish Farms in Washington State and Hog Island Oysters in California, whose spat (baby oysters) can no longer survive in their local breeding waters.
So is there hope?
This past summer, I got to dive in the shark-enhanced (not infested) waters of Palau, which National Geographic Society Explorer-in-Residence Sylvia Earle calls one of the ocean’s “Hope Spots.” Palau, where 80 percent of that nation’s waters have been protected from fishing and other impacts, has avoided the worst of the recent reef bleaching. Its reef remains a healthy, robust ecosystem with most of its living biomass made up of large predators and grazers: schooling sharks, barracuda, sea turtles, jacks, manta rays, pilot whales, and titan triggerfish, one of whom gave me a good nip in the leg. Walking along a seawall in the capital of Koror state, eyeing the tropical fish, clams, and a baby sea snake, I was reminded of my youth in Key West.
Palau’s healthy reefs may also contain corals with genetic traits that help protect them against warming seas. That is why Steve Palumbi and a band of researchers will be visiting this summer. Palumbi is director of Stanford University’s Hopkins Marine Station in Pacific Grove, California, and one of the first marine scientists to use DNA sampling to better understand marine ecosystems. For the past eight years, he’s been sampling corals in American Samoa to see if there are not just physical but genetic differences that distinguish corals capable of tolerating warmer seas.
“Physiologically, your body adjusts to altitude making more red blood cells in Denver than at sea level,” he explains, “but then Tibetans also have the right genes for high elevation. So are there corals that are the Tibetans of the ocean? We found a tabletop coral like that, which is heat tolerant. When we did transplants [from hot spots] to cooler parts of the reef we found they retain about half their heat tolerance.”