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.”



Above / Ar­riba: A be­fore and af­ter im­age of the bleach­ing in Amer­i­can Samoa. The first im­age was taken in De­cem­ber 2014. The se­cond im­age was taken in Fe­bru­ary 2015. Una im­a­gen del antes y de­spués del blan­queamiento del coral, en Samoa Amer­i­cana. La primera im­a­gen fue tomada en di­ciem­bre de 2014. La se­gunda im­a­gen fue tomada en febrero de 2015. Right / Derecha: Images from a healthy reef in Palau, one of the largest marine re­serves on the planet. Imá­genes de un ar­recife salud­able en Palau, una de las may­ores reser­vas mari­nas del plan­eta. XL CATLIN SEAVIEW SUR­VEY

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